the granulin gene family: from cancer to dementia
TRANSCRIPT
DOI 10.1002/bies.200900086 My favorite molecule
The granulin gene family: from cancerto dementiaAndrew Bateman* and Hugh P. J. Bennett
Endocrine Research Laboratory, McGill University Health Centre, Royal Victoria Hospital, Montreal, Canada
The growth factor progranulin (PGRN) regulates celldivision, survival, and migration. PGRN is an extracel-lular glycoprotein bearing multiple copies of thecysteine-rich granulin motif. With PGRN family membersin plants and slime mold, it represents one of the mostancient of the extracellular regulatory proteins still extantin modern animals. PRGN has multiple biological roles.It contributes to the regulation of early embryogenesis,to adult tissue repair and inflammation. Elevated PGRNlevels often occur in cancers, and PGRN immunotherapyinhibits the growth of hepatic cancer xenografts inmice. Recent studies have demonstrated roles for PGRNin neurobiology. An autosomal dominant mutation inGRN, the gene for PGRN, leads to neuronal atrophy inthe frontal and temporal lobes, resulting in the diseasefrontotemporal lobar dementia. In this review we willdiscuss current knowledge of the multifaceted biologyof PGRN.
Keywords: carcinogenesis; evolution; frontotemporal lobar
dementia; inflammation; wounds
Introduction
Our laboratories began to investigate the function of the
granulins (GRNs) while looking for peptides of the innate host
response. While purifying members of the defensin family of
anti-microbial peptides from extracts of human leukocytes,
using a protocol we devised to screen for fractions containing
cysteine-rich peptides, the GRNswere identified in minor side
fractions.(1) Members of the GRN family were also shown to
be significant components in extracts of carpmyeloid tissue.(2)
Sequence analysis of human and carp GRNs revealed a
unique 12-cysteine motif consisting of four pairs of cysteines
flanked by two single cysteines at the amino and carboxyl
termini (Fig. 1A). All cysteines were found to be fully crossed-
linked to form six disulfide bridges. Two-dimensional nuclear
magnetic resonance analysis of purified carp GRN-1 revealed
that the peptide backbone adopts a unique conformation of a
parallel stack of beta-hairpins in the form of a left-handed
*Correspondence to: A. Bateman, Endocrine Research Laboratory, McGill
University Health Centre, Royal Victoria Hospital, 687 Pine Ave West,
Montreal, Canada H3A1A1.
E-mail: [email protected]
BioEssays 31:1245–1254, � 2009 Wiley Periodicals, Inc.
helix.(3) Recombinant mammalian GRN modules show a
similar, but less rigid structure(4) (Fig. 1B). Subsequent work
showed that the mammalian GRN peptides were fragments
of a larger protein, progranulin (PGRN), bearing seven and
one-half GRN repeats (Fig. 1A). While both PGRN and its
constituent GRN peptides have biological activity, most
research has focused on the function of the larger PGRN
protein.
Initially the function of the GRNs was obscure, and our
continued interest in them was based more on the concept
that their unusual chemical structures strongly suggested that
they would prove biologically interesting, than on a clear idea
of function. Slowly work from a number of groups including our
own began to elucidate tentative roles and about 10 years ago
we wrote a review called, optimistically, ‘‘Granulins: the
structure and function of an emerging family of growth
factors.’’(5) In the intervening years, members of the GRN
gene family (GRN) have indeed emerged as significant
players in the extracellular regulation of cell function, although
often in surprising contexts that we had not predicted 10 years
ago. We know now, for example, that the human family
member PGRN is critical in maintaining neuronal survival,
since mutations of the GRN gene lead to cell death in the
frontal and temporal lobes of the brain.(6,7) The role of PGRN
in cancer has been repeatedly demonstrated.(8–26) PGRN has
been invoked in early embryogenesis,(27) wound repair, and
inflammation.(28–30) These are diverse roles, extending from
control of embryonic development during the first days of life
to the survival of long-lived post-mitotic neurons of the adult
brain. In this article we wish to identify unifying themes in the
biology of PGRN and other members of the GRN family that
would help rationalize this complexity.
Evolutionary origins and structure
The unique nature of the 12-cysteine GRN motif makes
unambiguous identification of homologous structures possible.
AGRNmotif is found at the carboxyl terminus of the cathepsin
K family of cysteine proteases found in numerousmembers of
the plant kingdom whose expression is up-regulated by
environmental stressors(31) (Fig. 1A). A form of GRN is found
in the slime mold Dictyostelium discoideum,(32) a social
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amoeba that is a modern representative of a primordial
organism that is thought to have predated the divergence of
the plant and animal kingdoms. Fungi do not have a GRN
gene. In fish, andmany invertebrate organisms, multipleGRN
Figure 1. The structure of PGRN. A: A comparison of GRN family mem
The circles represent the complete GRN modules of 12 cysteines, while
GRNs are always found at the carboxyl terminus of a cysteine protease.B:
dimensional nuclear magnetic resonance.(4) The two images are identical b
(yellow) form an axial ‘‘rod’’ through the center of themolecule. The beta-str
is violet, oxygen atoms are red, and nitrogen atoms are blue (from NCB
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genes are found, whereas mammals possess only one known
member of the GRN gene family. The zebrafish genome, for
example, harbors four GRN genes.(33) zPGRN-A and
zPGRN-B are co-orthologs of the human gene bearing
bers in humans, zebrafish, the slime mold Dictyostelium, and plants.
semi-circles are partial GRN domains of only six cysteines. The plant
The three-dimensional structure of humanGRN-A determined by two-
ut turned approximately 908 in the vertical plane. The disulfide bridgesands are represented by the broad gold arrows. The peptide backbone
I structure database MMDB: 63884 viewed using Cn3D).
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A. Bateman and H. P. J. Bennett My favorite molecule
multiple copies of the GRN motif (Fig. 1A). Two smaller forms
(zPGRN-1 and zPGRN-2) are also present (Fig. 1A). Syntenic
conservation of gene location shows that zPGRN-A is the
ortholog of mammalian GRN. Why only one family member
was retained in mammals and other land vertebrates is not
known.
The phylogenetic distribution of the GRN motif suggests
that it evolved only once about 1.5 billion years ago. Has it
always functioned as a signaling factor? The appearance of
complex life forms was concomitant with the evolution of a
multiplicity of cell signaling and cell-cell adhesion proteins
responsible for the complexity and diversity of multicellular
organisms. The sponge Oscarella carmela has a simple
branching body plan but surprisingly has nearly all the
classical growth factor signaling mechanisms including
the Wnt, Hedgehog, and TGF-beta pathways.(34) In contrast,
Monosiga brevicollis, an example of the Choanoflagellates,
which are the closest known unicellular relatives of metazo-
ans, lacks all these critical pathways.(35) However, GRN
genes are found in O. carmela (EC372216), M. brevicollis
(XP_001748993), and D. discoideum (XP_638956), suggest-
ing that the GRN signaling system evolved before most other
contemporary growth factor pathways.
The mammalian GRN gene encodes a multifunctional
secreted glycoprotein with tandem repeats of cysteine-rich
GRN modules(1,36–39) (Fig. 1A). It is known synonymously as
PGRN,(8) granulin-epithelin precursor (GEP),(40) proepithe-
lin,(38) PC cell-derived growth factor (PCDGF),(10) acrogra-
nin,(39) and epithelial transforming growth factor (TGFe).(41)
This rather dense nomenclature for a single gene is revealing
since it captures many of the essential features of the biology
of PGRN. TheGRN nomenclature emphasizes its association
with granulocytes and the cells of the innate immune
system, while the epithelin nomenclature emphasizes its
association with epithelial cells. The PCDGF and TGFe
designations emphasize the functional aspects of the protein
as a growth modulator, while acrogranin (from acrosome, a
compartment of the sperm head) brings out the likely roles of
PGRN in reproduction and early development.
Tissue remodeling and development
PGRN is often expressed under conditions of tissue
remodeling where cells are dividing and actively migrating.
For adult epithelia it is abundant in regions that are
rapidly turning-over, notably in the intestinal deep crypt and
epidermal keratinocytes.(42) Other less mitotically active
epithelia usually express PGRNat far lower levels. Fibroblasts
and endothelial cells, which are normally mitotically quies-
cent, show corresponding low levels of PGRN.(43) However,
these cells can rapidly deploy very active tissue remodeling
programs of increased proliferation and migration following
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wounding, for example. As they do so, their expression of
PGRN increases dramatically.(28) The increased expression
of PGRN in wounds is likely to contribute to the repair
process,(28) since adding PGRN to skin wounds in mice
increases the number of fibroblasts and capillaries that enter
the wounds in the early stages of healing.(28) In tissue culture
PGRN stimulated the proliferation and migration through
collagen of dermal fibroblasts and endothelial cells, recapi-
tulating the effects that were observed in the intact
wounds.(28) The actions of PGRN in injury extend to regulating
inflammation, since PGRN is a potent inhibitor of the
inflammatory cytokine tumor necrosis factor-a (TNF-a).(29,30)
Tumors exhibit pathologically disordered tissue remodeling
and PGRN expression is often highly elevated in cancers of
many types including carcinomas,(11,22,44–47) gliomas,(26)
multiple myelomas,(13) and uterine smooth muscle sarco-
mas.(12) In most cases there is a relationship between
the cancer progression and the expression of PGRN, the
higher-grade tumors being more likely to express elevated
PGRN.
PGRN is intimately involved in early embryogenesis and,
importantly, shows specificity of both expression and effect. In
the blastocyst (the fluid-filled form of the embryo prior to
implantation into the uterus), PGRN immunoreactivity is
located in the trophoblast,(48) the outermost shell of cells
around the inner cell mass that expand after implantation to
create the fetal compartment of the placenta. PGRN becomes
detectable in the inner cell mass only after the conceptus has
attached to the uterus.(49) This is consistent with biological
studies in which PGRN was found to stimulate cavitation, the
process whereby the solid ball of cells of the morula becomes
the fluid-filled blastocyst, and shown to have growth-
promoting activity on trophoblasts, but not the inner cell
mass.(48,49) In addition, PGRN stimulates the hatching,
adhesion, and outgrowth of the blastocyst in experimental
models of implantation.(48) PGRN continues to be expressed
in the placenta after implantation(50) and in the embryo,
particularly in the epidermis and developing nervous
system,(51) which may be significant given the recent
discovery of the role of PGRN in neurodegenerative diseases.
Progranulin and neurodegenerativediseases
Although the relationship between PGRN expression and
tissue remodeling is compelling, there are cases where this
evidently does not apply, perhaps the most obvious being in
the post-mitotic cells of the brain and spinal cord, many of
which express PGRN very strongly,(42,51) but are neither
proliferating nor migrating. Recent evidence, mostly from the
genetics of neurological disease, reveals that PGRN protects
neurons from premature death. Mutation of a single copy of
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Figure 2. Different facets of the biological activity of PGRN. A: The partial loss of PGRN causes severe neurodegeneration. The images show
the gross appearance of the brain from a patient carrying a mutation in the PGRN gene (IVS709-2A4G). Note the extensive asymmetric
degeneration with temporal atrophy on the left (L) being more extensive than on the right (R).(99) B: Elevated PGRN levels stimulate proliferation
and tumorigenesis. In murine embryo fibroblasts two growth factors are required to complete the cell cycle, a competence growth factor such as
PDGF and a progression growth factor such as IGF-I. PGRN stimulates cell division but, unlike the classic growth factors, it does so
independently and does not require priming with a competence factor.(16) C: Athymic nude mice were injected subcutaneously with SW13
cells that are normally not tumorigenic in vivo (lower panel), and SW13 cells that over-express PGRN (upper panel). The SW13/PGRN cells
formed large tumors.(8) D: The activity of PGRN is regulated by proteolytic enzymes. In the upper panel (1) PGRN binds SLPI; this prevents the
cleavage of PGRN by neutrophil-derived proteases such as neutrophil elastase (NE) and proteinase-3. The intact PGRN inhibits the activation of
neutrophils by TNF-a and is therefore anti-inflammatory. In the lower panel (2) there is insufficient SLPI to protect PGRN from elastase digestion
and PGRN is broken down to its 6 kDaGRN fragments. The fragments no longer regulate the activity of TNF-a, but instead stimulate the secretion
of interleukin-8, and may therefore be pro-inflammatory.(29,30)
My favorite molecule A. Bateman and H. P. J. Bennett
the humanGRN gene results in neuronal atrophy of the frontal
and anterior temporal lobes (frontotemporal lobar degenera-
tion, FTLD)(6,7) (Fig. 2A).
Clinically, this manifests as a disease called frontotemporal
dementia (FTD). FTD is often a familial disease, and typically
appears at a relatively young age, being the second most
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common dementia for people under 60 years. The frontal and
temporal lobes have key roles in regulating behavior, empathy,
and social understanding as well as language and this is
reflected in the initial clinical presentation of the disease.
Generally speaking, three variants of FTD are recog-
nized,(52,53) a behavioral variant (bvFTD), and two forms that
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A. Bateman and H. P. J. Bennett My favorite molecule
are associated with language problems, namely progressive
non-fluent aphasia, which is characterized by loss in the ability
to produce speech, with the individuals eventually becoming
effectively mute, and semantic dementia, in which patients
retain the ability to speak but in an increasingly disorganized
and meaningless manner as the disease worsens. GRN
mutations are often associated with bvFTD, but many instances
of language-deficit FTD linked to GRN mutations have been
reported.(54) FTD may be accompanied by motor neuron
disease, although this is rare in individuals with mutant GRN.
FTD is genetically heterogeneous. Other mutations in
addition to GRN cause FTD, most notably the microtubule-
associated protein tau (MAPT),(55) and, more rarely, chromatin-
modifying protein 2B (CHMP2B)(56) and the valosin-containing
protein (VCP).(57) MAPT was the first FTD gene to be
identified, and maps in remarkably close proximity to GRN on
chromosome 17q21.3.(6,7) Presently the Alzheimer Disease
and Frontotemporal Dementia Mutation Database (http://
www.molgen.ua.ac.be/FTDMutations/) records 66 distinct
GRN mutations.(58) Most, if not all the GRN-dependent FTDs
result from a decrease in the amount of PGRN expressed or
secreted, rather than an acquired toxic effect of mutant
protein. Many of these mutations lead to nonsense-mediated
mRNA decay, a process that eliminates the mutant transcripts
and therefore lowers the expression level of PGRN mRNA by
50%.(59) Other mutants may affect the translated protein, for
example, by changing one of the cysteines to another residue
and therefore disturbing disulfide bridge formation, or by
impeding secretion throughmutations of the signal peptide.(60,61)
Insufficient production of PGRN protein as the underlying cause
of disease was confirmed with the identification of FTD
associated with allelic loss of the entire GRN locus.(62)
Although neuronal death is the hallmark of FTLD, theGRN-
and MAPT-dependent phenotypes are strikingly different at
the cellular level. In the GRN-linked condition, the neurons
accumulate cytoplasmic and nuclear inclusions that stain
strongly for ubiquitin and phosphorylated fragments of a
protein called TAR DNA-binding protein 43 (TDP-43).(63,64)
Ubiquitin inclusions are rarely found when FTLD is due to
mutantMAPT, instead the affected neurons display aggrega-
tions of the tau protein, identifying this form of FTLD as a
tauopathy along with other dementias such as Alzheimer’s
disease.(65) Thus far, allGRN-linked forms of FTLD examined
exhibit ubiquitin inclusions. However, inclusions occur in
cases of FTLD that do not arise from mutant GRN. Moreover,
the ubiquitin/TDP-43 inclusions occur in other neurodegen-
erative diseases, such as amyotrophic lateral sclerosis (ALS),
where there is no strong link with GRN mutations.(66)
Given the complex histopathological relationship between
GRN mutations and ubiquitin/TDP-43 inclusions, are there
any functional relationships between PGRN and TDP-43?
The ubiquitin/TDP-43 inclusions do not contain PGRN,(67)
and therefore the direct seeding of ubiquitin inclusions by
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PGRN is highly unlikely. When PGRN mRNA levels were
depleted in cell culture, TDP-43 underwent a partial caspase-
dependent proteolysis.(68) The fragmentation of TDP-43
appears to be an initial step in the formation of ubiquitin/
TDP-43 inclusions, although it should be pointed out that
other investigators found no alteration in TDP-43 localization
or stability following depletion of PGRNmRNA.(61) The 25 kDa
carboxyl-terminal fragment of TDP-43 accumulates in
neurodegenerative tissue, and, when over-expressed in cells,
it was phosphorylated, ubiquitinated, and cytotoxic.(69,70)
Among its several functions, TDP-43 is a specific mRNA-
binding protein for human neurofilament mRNA,(71) and may
be involved in the response to neuronal injury since its levels
increased and it was translocated from the nucleus to the
cytoplasm in injured motor neurons.(72) As TDP-43 increased
in the injured neurons, the cytoplasmic levels of PGRN
dropped in parallel.(72) Assuming that neuronal PGRN levels
also decrease after injury in the brain, the depletion of the
remaining 50% normal PGRN in GRN-mutant carriers
following cerebral stress or trauma may on occasion bring
neuronal PGRN to very low levels compared to non-carriers.
The functional roles of PGRN in neurons and neurode-
generation are only beginning to be explored. PGRN is
neurotrophic for cortical and spinal cord neurons,(73) which
may be relevant in the loss of cortical neurons in FTD;
however, other factors are likely to be at work. Not everyone
with a GRN mutant develops FTD, and some carriers of
pathological variants ofGRN have lived well into their 70s and
beyond with no apparent loss of cognitive function.(59) This
would suggest that there are important biological modifiers of
GRN pathological outcome, but little if anything is known of
what these may be.
In other cell types, PGRN is a potent extracellular anti-
apoptotic factor(16,21,74) and if this is true also for neurons, the
loss of half the normal level of PGRN may sensitize the
affected neurons to a range of traumatic shocks. Similarly,
PGRN has roles in peripheral inflammation.(29,30) The
equivalent neuroinflammatory cells in the brain, the microglia,
express PGRN very strongly in diseased tissue, and an
inflammatory contribution from PGRN to the disease has
been hypothesized.(75) Although PGRN is widely distributed,
the pathology due to GRN mutations is highly restricted.
PGRN is expressed in many neurons outside the cerebral
cortex,(42) but these appear to be far less affected by GRN
mutations.Why the cells of the frontal and temporal cortex are
so much more sensitive to loss of PGRN than others is not
known. The lack of a direct causative influence in other
neurodegenerative diseases does not exclude more subtle
roles. For instance, genetic variants of GRN may be disease
modifiers in ALS,(76) although other investigators have not
been able to reproduce this correlation.(66)
PGRN has other functions in the brain. The male
hypothalamus undergoes a default female developmental
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program until late in embryonic development when it is
masculinized by the actions of circulating androgens. GRN
mRNA was identified as one of the transcripts that were most
strongly up-regulated by androgens in neonatal mouse
hypothalami and in a series of elegant experiments by Suzuki
et al.(77) it was shown that depletion of PGRN blunts many of
the normal masculine reproductive behaviors, particularly
ejaculation.(78,79) Abrogation of the GRN gene in male mice
showed unusual levels of anxiety, which were attributed at
least in part to decreased expression of the serotonin receptor
5HT1A.(79) These findings coupled with the expression of
PGRN in many regions of the embryonic mouse brain(51) hint
at yet further roles for PGRN in brain development.
Intriguingly, comparative studies also support a key neuronal
role for PGRN, since a PGRN-like protein is evident in the
nerve cells of an annelid ragworm, whose last common
ancestor with vertebrates presumably dates very early in
animal evolution.(80)
Progranulin as a somatic growth factor
PGRN is a double-edged sword. Of equal importance to the
problems that accrue when PGRN levels are low is what
happens to cells with increased exposure to PGRN. Elevated
PGRN stimulates proliferation,(8–10,15,16,28,40) survival,(9,21,74)
and motility(9,24,28) of epithelia, fibroblasts, and endothelia.
PGRN activates typical growth factor signal transduction
pathways such as the phosphorylation of shc and p44/42
mitogen-activated protein kinase (p44/42MAPK) in the
extracellular regulated kinase (ERK) pathway as well as
phosphatidylinositol 3-kinase (PI3K), protein kinase B/AKT,
and the p70S6 kinase in the PI3K pathway.(9,15,16) PGRN
promotes tyrosine phosphorylation of focal adhesion kinase
(FAK),(9) which is a cytoplasmic tyrosine kinase in the
signaling pathways associated with clustered integrins.(81)
FAK provides a link between integrin and growth factor
signaling since it is required for epidermal growth factor (EGF)
and platelet-derived growth factor (PDGF) to promote cell
motility.(82) In bladder cancer cells where PGRN is a strong
motogen but a poor mitogen, PGRN promoted the association
of FAK with paxillin and p44/42MAPK,(24) suggesting, at the
very least, a cellular link between PGRN and extracellular
matrix (ECM) signaling machinery.
To appreciate how the growth factor-like properties of
PGRN differ from those of conventional growth factors, it is
necessary to revisit some of the fundamentals of growth factor
biology. In serum-free medium, normal fibroblasts require two
distinct growth factor signals to progress through the
complete cell cycle.(83) One growth factor, the competence
factor, prepares the cell to pass into the S-phase where DNA
synthesis occurs. The second growth factor, the progression
factor, then drives the cell through the S-phase and into the
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M-phase, where cell division takes place. PGRN, unlike
classic growth factors, is simultaneously both a competence
and progression factor, that is, it successfully stimulates
the completion of both S- and M-phase without assistance
from other growth factors.
In murine embryonic fibroblasts, the dominant progression
signal is provided through the insulin-like growth factor-I
receptor (IGFI-R).(83) Disrupting this receptor prevents mouse
embryo fibroblasts from completing the cell cycle not only
in response to IGF-I, the progression factor, but also to
competence factors such as PDGFor EGF.(84) PGRN, however,
circumvented the requirement for the IGFI-R-mediated signal
and supported the traverse of both the S- and M-phase,
allowing the IGFI-R-deficient cells to complete the cell cycle in
serum-free medium(16) (Fig. 2B). PGRN is the only extra-
cellular protein known to do this and appears to achieve this
unusual feat because of the kinetics of its signal transduction
response.(16) Growth factors such as PDGF or EGF elicit
relatively transient signaling responses in IGFI-R-deficient
cells, whereas the PGRN response is considerably more
prolonged.(16) Whether this is due to events at the level of
PGRN receptor-ligand interactions, or to PGRN eliciting
weaker downstream counter-regulatory effects responsible
for turning off the ERK signal after stimulation is unclear.
Frustratingly, identifying the receptors or other PGRN-binding
proteins in cell membranes has proven elusive, making it very
difficult to address questions of this kind.
Progranulin in cancer
Signaling does not prove function. Evidence that PGRN is a
functional growth factor came from work on cancer. Initially
PGRN was found to be an autocrine growth stimulus for an
aggressive murine teratoma.(10) Reducing PGRN mRNA
expression greatly reduced tumor formation by the teratoma
cells,(14) as well as in breast cancer,(17) liver cancer,(46) and
squamous esophageal cancer(18) cell lines in vivo. Clearly
therefore PGRN is required for these cells to be tumorigenic.
To demonstrate whether PGRN is not only necessary for tumor
growth but also actively confers malignancy, it was over-
expressed in a cancer cell line (SW13 adenocarcinoma cells)
that is normally weakly tumor-forming. The PGRN over-
expressing cells then formed substantial tumors in mice(8)
(Fig. 2C).
The potency of PGRN as a tumorigenic agent was
demonstrated using primary human cells from ovarian
epithelia(20) and uterine smooth muscle.(12) Human primary
cells are difficult to transform by gene transfer in culture,(85)
requiring at minimum the increased expression of telomerase
activity, blockade of the retinoblastoma (Rb) tumor suppressor
system, and a strong mitotic drive provided in most
experiments by oncogenes such as mutant RAS. PGRN
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A. Bateman and H. P. J. Bennett My favorite molecule
can substitute for RAS in the transformation process. The
combination of telomerase (Tert) and SV40 T-antigen (to
block the Rb and P53 tumor suppressors) immortalized, but
did not transform primary human ovarian cells(20) or uterine
smooth muscle cells,(12) but when GRN was included with
Tert and SV40, the primary cells became very tumorigenic in
mice.(12,20) It is interesting to speculate whether this is related
to the unusual property of PGRN as a conjoint competence
and progression factor, although at present experimental
evidence neither supports nor refutes this hypothesis.
PGRN supports tumor growth by increased prolifera-
tion,(8,15) decreased apoptosis,(9,29,86–88) and greater inva-
siveness through the ECM.(9,19) Each of these actions
requires the activity of the ERK and PI3K signal transduction
pathways, although the extent to which either pathway
contributes is variable.(16) If PGRN promotes tumor growth
as we propose here, blocking its action should block tumor
growth. As discussed above, attenuating PGRN mRNA
inhibits tumor growth of cancer cells in mouse models, but
this might mean only that losing PGRN prevents the ability of
the cells to seed. Is the depletion of PGRN relevant when
dealing with large established tumors?
When liver cancer cells were transplanted into mice,
allowed to form tumors and then exposed to injections of a
PGRN monoclonal antibody, tumor growth was impeded by
approximately 50%.(25) Treating cancers in mice is far from
treating people, but the liver cancer experiments show that
PGRN has potential as a cancer drug target and is an
extremely promising area for future investigation. Interest-
ingly, the PGRN monoclonal antibodies not only inhibited
proliferation of the cancer cells directly, but also had a striking
anti-angiogenic action,(25) possibly due to decreased secre-
tion of the angiogenic growth factor VEGF in the treated
tumors,(19) although given that PGRN stimulated angiogen-
esis in wounds,(28) a more direct effect on tumor vasculariza-
tion can be postulated.
Progranulin interaction withother proteins
Extracellular protein-protein interactions regulate the activity
of many growth factors, and PGRN is no exception. During
inflammation, neutrophils release proteases such as elastase
and proteinase-3 that digest PGRN into its individual GRN
domains, which are then liberated as 6 kDa GRN peptides. In
many instances the GRN peptides oppose the effects of intact
PGRN. Thus while PGRN stimulates proliferation and inhibits
the actions of TNF-a on neutrophils,(29,30) some of the GRN
peptides inhibit cell proliferation,(36) and stimulate inflamma-
tion by eliciting the secretion of interleukin-8.(29) The critical
balance between intact PGRN and the 6 kDa GRN peptides is
maintained by a third party, the secretory leukocyte protease
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inhibitor (SLPI), which binds PGRN, and prevents proteolysis
by neutrophil proteases. The activity of PGRN in a wound, or
other site of inflammation, depends therefore on the levels of
PGRN itself, the protective factor SLPI, and the neutrophil
proteases (Fig. 2D). The significance of the triad effect –
PGRN, SLPI, proteases – has been confirmed in compound
knockouts of neutrophil elastase and proteinase-3(30) and in
slpi knockout mice whose severely disrupted wound repair
could be rescued by treating the wounds with PGRN.(29)
Moreover, the SLPI-PGRN interaction is not limited to
inflammation since it has been implicated in ovarian tumor
progression.(89,90)
The interplay of proteases and PGRN may be a wide-
spread determinant of PGRN activity. Metalloproteinases
such as MMP-14(91) and ADAMTS-7(92) (a disintegrin and
metalloproteinase with thrombospondin-7) digest PGRN, with
ADAMTS-7 inactivating the growth factor-like effects of
PGRN during endochondral bone formation.(92) This interac-
tion has also been implicated in the pathogenesis of
arthritis.(93) PGRN binds the ECM proteins perlecan(94) and
chondrocyte oligomeric matrix protein (COMP);(95) the
perlecan interaction decreases the proliferative activity of
PGRN, whereas the COMP interaction enhances it. In both
cases PGRN binds its partner weakly, with affinities in the
micromolar range,(94,95) and associateswith the target protein
through an EGF-containing module. PGRN reportedly binds
the membrane protein Dlk,(96) which is also rich in EGF
modules, and although not yet tested, an affinity for EGF
modules may prove a recurrent pattern in PGRN-protein
interactions. Interactions of PGRN with intracellular proteins
such as cyclin T havebeen reported, although their physiological
significance is uncertain.(97)
GRN knockout and transgenic models
Grn knockout mice display behavioral abnormalities but few
other recorded phenotypes.(79) Given the biological actions
that have been attributed to PGRN, the mild knockout
phenotype suggests that PGRN is a molecular generalist,
contributing to many tasks but acutely essential for few.
Dissecting the biological functions of PGRN is being revealed
through conditional transgenic and knockout strategies. For
instance, keratinocyte-specific over-expression of PGRN
leads to abnormal hair development, suggesting a role for
PGRN in maintenance of hair follicles.(98)
Conclusion
When we first identified the GRN peptides as minor side
fractions on a chromatogram, there was nothing to suppose
that what would emerge was an extracellular signaling
1251
My favorite molecule A. Bateman and H. P. J. Bennett
gene family that extends back to green plants and slime mold,
or that would be implicated in so many biological functions. In
recent years knowledge of the structure and function of
products ofGRN gene expression has expanded enormously,
particularly in the areas of cancer and neurobiology, but also
in the fields of development, tissue repair, and inflammation.
Much remains to be discovered, and hopefully the next few
years will see breakthroughs that will put the latest insights on
a firm footing through identification of PGRN receptors and
binding proteins, definition of its function in nerve cells, and its
application as a therapeutic target.
Acknowledgments: The research carried out in the labora-
tories of the authors and reviewed in this article was sup-
ported by grants from the Canadian Institutes for Health
Research, the National Cancer Institute of Canada, and
the Canadian Breast Cancer Research Association Ideas
Program. We gratefully acknowledge Dr. Thomas D. Bird,
University of Washington School of Medicine, Seattle, for
permission to use the image in Fig. 2A.
References
1. Bateman A, Belcourt D, Bennett H, et al. 1990. Granulins, a novel class
of peptide from leukocytes. Biochem Biophys Res Commun 173: 1161–
1168.
2. Belcourt DR, Lazure C, Bennett HPJ. 1993. Isolation and primary
structure of the three major forms of granulin-like peptides from hemato-
poietic tissues of a teleost fish (Cyprinus carpio). J Biol Chem 268: 9230–
9237.
3. Hrabal R, Chen Z, James S, et al. 1996. The hairpin stack fold, a novel
protein architecture for a new family of protein growth factors. Nat Struct
Biol 3: 747–752.
4. Tolkatchev D, Malik S, Vinogradova A, et al. 2008. Structure dissection
of human progranulin identifies well-folded granulin/epithelin modules with
unique functional activities. Protein Sci 17: 711–724.
5. Bateman A, Bennett HPJ. 1998. Granulins: the structure and function
of an emerging family of growth factors. J Endocrinol 158: 145–
151.
6. Baker M, Mackenzie IR, Pickering-Brown SM, et al. 2006. Mutations in
progranulin cause tau-negative frontotemporal dementia linked to
chromosome 17. Nature 442: 916–919.
7. Cruts M, Gijselinck I, van der Zee J, et al. 2006. Null mutations in
progranulin cause ubiquitin-positive frontotemporal dementia linked to
chromosome 17q21. Nature 442: 920–924.
8. He Z, Bateman A. 1999. Progranulin gene expression regulates epithelial
cell growth and promotes tumor growth in vivo. Cancer Res 59: 3222–
3229.
9. He Z, Ismail A, Kriazhev L, et al. 2002. Progranulin (PC-cell-derived
growth factor/acrogranin) regulates invasion and cell survival. Cancer Res
62: 5590–5596.
10. Zhou J, Gao G, Crabb JW, et al. 1993. Purification of an autocrine growth
factor homologous with mouse epithelin precursor from a highly tumori-
genic cell line. J Biol Chem 268: 10863–10869.
11. Serrero G, Ioffe OB. 2003. Expression of PC-cell-derived growth factor in
benign and malignant human breast epithelium. Hum Pathol 34: 1148–
1154.
12. Matsumura N, Mandai M, Miyanishi M, et al. 2006. Oncogenic property
of acrogranin in human uterine leiomyosarcoma: direct evidence of
1252
genetic contribution in in vivo tumorigenesis. Clin Cancer Res 12:
1402–1411.
13. Wang W, Hayashi J, Kim WE, et al. 2003. PC cell-derived growth factor
(granulin precursor) expression and action in human multiple myeloma.
Clin Cancer Res 9: 2221–2228.
14. Zhang H, Serrero G. 1998. Inhibition of tumorigenicity of the teratoma PC
cell line by transfection with antisense cDNA for PC cell-derived growth
factor (PCDGF, epithelin/granulin precursor). Proc Natl Acad Sci USA 95:
14202–14207.
15. Lu R, Serrero G. 2001. Mediation of estrogen mitogenic effect in human
breast cancer MCF-7 cells by PC-cell-derived growth factor (PCDGF/
granulin precursor). Proc Natl Acad Sci USA 98: 142–147.
16. Zanocco-Marani T, Bateman A, Romano G, et al. 1999. Biological
activities and signaling pathways of the granulin/epithelin precursor.
Cancer Res 59: 5331–5340.
17. Lu R, Serrero G. 2000. Inhibition of PC cell-derived growth factor
(PCDGF, epithelin/granulin precursor) expression by antisense PCDGF
cDNA transfection inhibits tumorigenicity of the human breast carcinoma
cell line MDA-MB-468. Proc Natl Acad Sci USA 97: 3993–3998.
18. Chen XY, Li JS, Liang QP, et al. 2008. Expression of PC cell-derived
growth factor and vascular endothelial growth factor in esophageal
squamous cell carcinoma and their clinicopathologic significance. Chin
Med J (Engl) 121: 881–886.
19. Tangkeangsirisin W, Serrero G. 2004. PC cell-derived growth factor
(PCDGF/GP88, progranulin) stimulates migration, invasiveness and VEGF
expression in breast cancer cells. Carcinogenesis 25: 1587–1592.
20. Miyanishi M, Mandai M, Matsumura N, et al. 2007. Immortalized ovarian
surface epithelial cells acquire tumorigenicity by acrogranin gene over-
expression. Oncol Rep 17: 329–333.
21. KamravaM, Simpkins F, Alejandro E, et al. 2005. Lysophosphatidic acid
and endothelin-induced proliferation of ovarian cancer cell lines is miti-
gated by neutralization of granulin-epithelin precursor (GEP), a prosurvi-
val factor for ovarian cancer. Oncogene 24: 7084–7093.
22. Davidson B, Alejandro E, Florenes VA, et al. 2004. Granulin-epithelin
precursor is a novel prognostic marker in epithelial ovarian carcinoma.
Cancer 100: 2139–2147.
23. Jones MB, Michener CM, Blanchette JO, et al. 2003. The granulin-
epithelin precursor/PC-cell-derived growth factor is a growth factor for
epithelial ovarian cancer. Clin Cancer Res 9: 44–51.
24. Monami G, Gonzalez EM, Hellman M, et al. 2006. Proepithelin promotes
migration and invasion of 5637 bladder cancer cells through the activation
of ERK1/2 and the formation of a paxillin/FAK/ERK complex. Cancer Res
66: 7103–7110.
25. Ho JC, Ip YC, Cheung ST, et al. 2008. Granulin-epithelin precursor as a
therapeutic target for hepatocellular carcinoma.Hepatology 47: 1524–1532.
26. Liau LM, Lallone RL, Seitz RS, et al. 2000. Identification of a human
glioma-associated growth factor gene, granulin, using differential
immuno-absorption. Cancer Res 60: 1353–1360.
27. Diaz-Cueto L, Stein P, Jacobs A, et al. 2000. Modulation of mouse
preimplantation embryo development by acrogranin (epithelin/granulin
precursor). Dev Biol 217: 406–418.
28. He Z, Ong CH, Halper J, et al. 2003. Progranulin is a mediator of the
wound response. Nat Med 9: 225–229.
29. Zhu J, Nathan C, Jin W, et al. 2002. Conversion of proepithelin to
epithelins: roles of SLPI and elastase in host defense and wound repair.
Cell 111: 867–878.
30. Kessenbrock K, Frohlich L, Sixt M, et al. 2008. Proteinase 3 and
neutrophil elastase enhance inflammation in mice by inactivating antiin-
flammatory progranulin. J Clin Invest 118: 2438–2447.
31. Chen HJ, Huang DJ, Hou WC, et al. 2006. Molecular cloning and
characterization of a granulin-containing cysteine protease SPCP3 from
sweet potato (Ipomoea batatas) senescent leaves. J Plant Physiol 163:
863–876.
32. Eichinger L, Pachebat JA, Glockner G, et al. 2005. The genome of the
social amoeba Dictyostelium discoideum. Nature 435: 43–57.
33. Cadieux B, Chitramuthu BP, Baranowski D, et al. 2005. The zebrafish
progranulin gene family and antisense transcripts. BMCGenomics 6: 156.
34. Nichols SA, DirksW, Pearse JS, et al. 2006. Early evolution of animal cell
signaling and adhesion genes. Proc Natl Acad Sci USA 103: 12451–
12456.
BioEssays 31:1245–1254, � 2009 Wiley Periodicals, Inc.
A. Bateman and H. P. J. Bennett My favorite molecule
35. King N, Westbrook MJ, Young SL, et al. 2008. The genome of the
choanoflagellate Monosiga brevicollis and the origin of metazoans.Nature
451: 783–788.
36. Shoyab M, McDonald VL, Byles C, et al. 1990. Plowman GD. Epithelins 1
and 2: isolation and characterization of two cysteine-rich growth-modulat-
ing proteins. Proc Natl Acad Sci USA 87: 7912–7916.
37. Bhandari V, Palfree RG, BatemanA. 1992. Isolation and sequence of the
granulin precursor cDNA from human bone marrow reveals tandem
cysteine-rich granulin domains. Proc Natl Acad Sci USA 89: 1715–
1719.
38. Plowman GD, Green JM, Neubauer MG, et al. 1992. The epithelin
precursor encodes two proteins with opposing activities on epithelial cell
growth. J Biol Chem 267: 13073–13078.
39. Baba T, Hoff HB, III, Nemoto H, et al. 1993. Acrogranin, an acrosomal
cysteine-rich glycoprotein, is the precursor of the growth-modulating
peptides, granulins, and epithelins, and is expressed in somatic as well
as male germ cells. Mol Reprod Dev 34: 233–243.
40. Xu SQ, Tang D, Chamberlain S, et al. 1998. The granulin/epithelin
precursor abrogates the requirement for the insulin-like growth factor 1
receptor for growth in vitro. J Biol Chem 273: 20078–20083.
41. Parnell PG, Wunderlich J, Carter B, et al. 1992. Transforming growth
factor e: amino acid analysis and partial amino acid sequence. Growth
Factors 7: 65–72.
42. Daniel R, He Z, Carmichael KP, et al. 2000. Cellular localization
of gene expression for progranulin. J Histochem Cytochem 48: 999–
1009.
43. Bhandari V, Giaid A, Bateman A. 1993. The complementary deoxyr-
ibonucleic acid sequence, tissue distribution, and cellular localization of
the rat granulin precursor. Endocrinology 133: 2682–2689.
44. Donald CD, Laddu A, Chandham P, et al. 2001. Expression of progra-
nulin and the epithelin/granulin precursor acrogranin correlates with
neoplastic state in renal epithelium. Anticancer Res 21: 3739–3742.
45. Pan CX, Kinch MS, Kiener PA, et al. 2004. PC cell-derived growth factor
expression in prostatic intraepithelial neoplasia and prostatic adenocar-
cinoma. Clin Cancer Res 10: 1333–1337.
46. Cheung ST, Wong SY, Leung KL, et al. 2004. Granulin-epithelin pre-
cursor overexpression promotes growth and invasion of hepatocellular
carcinoma. Clin Cancer Res 10: 7629–7636.
47. Jones MB, Houwink AP, Freeman BK, et al. 2006. The granulin-epithelin
precursor is a steroid-regulated growth factor in endometrial cancer.
J Soc Gynecol Investig 13: 304–311.
48. Qin J, Diaz-Cueto L, Schwarze JE, et al. 2005. Effects of progranulin on
blastocyst hatching and subsequent adhesion and outgrowth in the
mouse. Biol Reprod 73: 434–442.
49. Diaz-Cueto L, Gerton GL. 2001. The influence of growth factors on the
development of preimplantation mammalian embryos. Arch Med Res 32:
619–626.
50. Desmarais JA, Cao M, Bateman A, et al. 2008. Spatiotemporal expres-
sion pattern of progranulin in embryo implantation and placenta formation
suggests a role in cell proliferation, remodeling, and angiogenesis.
Reproduction 136: 247–257.
51. Daniel R, Daniels E, He Z, et al. 2003. Progranulin (acrogranin/PC cell-
derived growth factor/granulin-epithelin precursor) is expressed in the
placenta, epidermis, microvasculature, and brain during murine devel-
opment. Dev Dyn 227: 593–599.
52. Josephs KA. 2007. Frontotemporal lobar degeneration. Neurol Clin 25:
683–696, vi.
53. Wittenberg D, Possin KL, Rascovsky K, et al. 2008. The early neurop-
sychological and behavioral characteristics of frontotemporal dementia.
Neuropsychol Rev 18: 91–102.
54. Snowden JS, Pickering-Brown SM, Mackenzie IR, et al. 2006. Progra-
nulin gene mutations associated with frontotemporal dementia and pro-
gressive non-fluent aphasia. Brain 129: 3091–3102.
55. Rizzu P, Van Swieten JC, Joosse M, et al. 1999. High prevalence of
mutations in the microtubule-associated protein tau in a population study
of frontotemporal dementia in the Netherlands. Am J Hum Genet 64: 414–
421.
56. Skibinski G, Parkinson NJ, Brown JM, et al. 2005. Mutations in the
endosomal ESCRTIII-complex subunit CHMP2B in frontotemporal demen-
tia. Nat Genet 37: 806–808.
BioEssays 31:1245–1254, � 2009 Wiley Periodicals, Inc.
57. Forman MS, Mackenzie IR, Cairns NJ, et al. 2006. Novel ubiquitin
neuropathology in frontotemporal dementia with valosin-containing pro-
tein gene mutations. J Neuropathol Exp Neurol 65: 571–581.
58. Gijselinck I, Van Broeckhoven C, Cruts M. 2008. Granulin mutations
associated with frontotemporal lobar degeneration and related disorders:
an update. Hum Mutat 29: 1373–1386.
59. Gass J, Cannon A, Mackenzie IR, et al. 2006. Mutations in progranulin
are a major cause of ubiquitin-positive frontotemporal lobar degeneration.
Hum Mol Genet 15: 2988–3001.
60. van der Zee J, Le Ber I, Maurer-Stroh S, et al. 2007. Mutations other than
null mutations producing a pathogenic loss of progranulin in frontotem-
poral dementia. Hum Mutat 28: 416.
61. Shankaran SS, Capell A, Hruscha AT, et al. 2008. Missense mutations in
the progranulin gene linked to frontotemporal lobar degeneration with
ubiquitin-immunoreactive inclusions reduce progranulin production and
secretion. J Biol Chem 283: 1744–1753.
62. Gijselinck I, van der Zee J, Engelborghs S, et al. 2008. Progranulin locus
deletion in frontotemporal dementia. Hum Mutat 29: 53–58.
63. Arai T, Hasegawa M, Akiyama H, et al. 2006. TDP-43 is a component of
ubiquitin-positive tau-negative inclusions in frontotemporal lobar degen-
eration and amyotrophic lateral sclerosis. Biochem Biophys Res Commun
351: 602–611.
64. Neumann M, Sampathu DM, Kwong LK, et al. 2006. Ubiquitinated TDP-
43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis.
Science 314: 130–133.
65. Dermaut B, Kumar-Singh S, Rademakers R, et al. 2005. Tau is central in
the genetic Alzheimer-frontotemporal dementia spectrum. Trends Genet
21: 664–672.
66. Schymick JC, Yang Y, Andersen PM, et al. 2007. Progranulin mutations
and amyotrophic lateral sclerosis or amyotrophic lateral sclerosis-fronto-
temporal dementia phenotypes. J Neurol Neurosurg Psychiatry 78: 754–
756.
67. Mackenzie IR. 2007. The neuropathology and clinical phenotype of FTD
with progranulin mutations. Acta Neuropathol 114: 49–54.
68. Zhang YJ, Xu YF, Dickey CA, et al. 2007. Progranulin mediates caspase-
dependent cleavage of TAR DNA binding protein-43. J Neurosci 27:
10530–10534.
69. Igaz LM, Kwong LK, Chen-Plotkin A, et al. 2009. Expression of TDP-43
C-terminal fragments in vitro recapitulates pathological features of TDP-43
proteinopathies. J Biol Chem 284: 8516–8524.
70. Zhang YJ, Xu YF, Cook C, et al. 2009. Aberrant cleavage of TDP-43
enhances aggregation and cellular toxicity. Proc Natl Acad Sci USA 106:
7607–7612.
71. StrongMJ, Volkening K, Hammond R, et al. 2007. TDP43 is a human low
molecular weight neurofilament (hNFL) mRNA-binding protein. Mol Cell
Neurosci 35: 320–327.
72. Moisse K, Volkening K, Leystra-Lantz C, et al. 2009. Divergent patterns
of cytosolic TDP-43 and neuronal progranulin expression following axot-
omy: implications for TDP-43 in the physiological response to neuronal
injury. Brain Res 1249: 202–211.
73. Van Damme P, Van Hoecke A, Lambrechts D, et al. 2008. Progranulin
functions as a neurotrophic factor to regulate neurite outgrowth and
enhance neuronal survival. J Cell Biol 181: 37–41.
74. Guerra RR, Kriazhev L, Hernandez-Blazquez FJ, et al. 2007. Progra-
nulin is a stress-response factor in fibroblasts subjected to hypoxia and
acidosis. Growth Factors 25: 280–285.
75. Ahmed Z, Mackenzie IR, Hutton ML, et al. 2007. Progranulin in frontotem-
poral lobar degeneration and neuroinflammation. J Neuroinflammation 4: 7.
76. Sleegers K, Brouwers N, Maurer-Stroh S, et al. 2008. Progranulin
genetic variability contributes to amyotrophic lateral sclerosis. Neurology
71: 253–259.
77. Suzuki M, Yoshida S, Nishihara M, et al. 1998. Identification of a sex
steroid-inducible gene in the neonatal rat hypothalamus. Neurosci Lett
242: 127–130.
78. Suzuki M, Bannai M, Matsumuro M, et al. 2000. Suppression of copu-
latory behavior by intracerebroventricular infusion of antisense oligodeox-
ynucleotide of granulin in neonatal male rats. Physiol Behav 68: 707–713.
79. Kayasuga Y, Chiba S, Suzuki M, et al. 2007. Alteration of behavioural
phenotype in mice by targeted disruption of the progranulin gene. Behav
Brain Res 185: 110–118.
1253
My favorite molecule A. Bateman and H. P. J. Bennett
80. Deloffre L, Sautiere P-E, Sautiere P, et al. 1999. Identification of a
granulin-related peptide in a marine invertebrate, Hediste diversicolor.
J Ann Soc Zoologique (France) 124: 337–346.
81. Schlaepfer DD, Hauck CR, Sieg DJ. 1999. Signaling through focal
adhesion kinase. Prog Biophys Mol Biol 71: 435–478.
82. Sieg DJ, Hauck CR, Ilic D, et al. 2000. FAK integrates growth-factor and
integrin signals to promote cell migration. Nat Cell Biol 2: 249–256.
83. Stiles CD, Capone GT, Scher CD, et al. 1979. Dual control of cell growth
by somatomedins and platelet-derived growth factor. Proc Natl Acad Sci
USA 76: 1279–1283.
84. Swantek JL. Baserga R. 1999. Prolonged activation of ERK2 by epider-
mal growth factor and other growth factors requires a functional insulin-like
growth factor 1 receptor. Endocrinology 140: 3163–3169.
85. Hahn WC, Counter CM, Lundberg AS, et al. 1999. Creation of
human tumour cells with defined genetic elements. Nature 400: 464–
468.
86. Tangkeangsirisin W, Hayashi J, Serrero G. 2004. PC cell-derived
growth factor mediates tamoxifen resistance and promotes tumor growth
of human breast cancer cells. Cancer Res 64: 1737–1743.
87. Kim WE. Serrero G. 2006. PC cell-derived growth factor stimulates
proliferation and confers Trastuzumab resistance to Her-2-overexpres-
sing breast cancer cells. Clin Cancer Res 12: 4192–4199.
88. Pizarro GO, Zhou XC, Koch A, et al. 2007. Prosurvival function of the
granulin-epithelin precursor is important in tumor progression and che-
moresponse. Int J Cancer 120: 2339–2343.
89. Simpkins FA, Devoogdt NM, Rasool N, et al. 2008. The alarm
anti-protease, secretory leukocyte protease inhibitor, is a proliferation
and survival factor for ovarian cancer cells. Carcinogenesis 29: 466–472.
90. Devoogdt N, Rasool N, Hoskins E, et al. 2009. Overexpression of
protease inhibitor-dead secretory leukocyte protease inhibitor causes
1254
more aggressive ovarian cancer in vitro and in vivo. Cancer Sci 100:
434–440.
91. Butler GS, Dean RA, Tam EM, et al. 2008. Pharmacoproteomics of a
metalloproteinase hydroxamate inhibitor in breast cancer cells: dynamics
of membrane type 1 matrix metalloproteinase-mediated membrane pro-
tein shedding. Mol Cell Biol 28: 4896–4914.
92. Bai XH, Wang DW, Kong L, et al. 2009. ADAMTS-7, a direct target of
PTHrP, adversely regulates endochondral bone growth via associating
with and inactivating GEP growth factor. Mol Cell Biol 29: 4201–4219.
93. Liu CJ. 2009. The role of ADAMTS-7 and ADAMTS-12 in the pathogenesis
of arthritis. Nat Clin Pract Rheumatol 5: 38–45.
94. Gonzalez EM, Mongiat M, Slater SJ, et al. 2003. A novel interaction
between perlecan protein core and progranulin: potential effects on tumor
growth. J Biol Chem 278: 38113–38116.
95. Xu K, Zhang Y, Ilalov K, et al. 2007. Cartilage oligomeric matrix protein
associates with granulin-epithelin precursor (GEP) and potentiates GEP-
stimulated chondrocyte proliferation. J Biol Chem 282: 11347–11355.
96. Baladron V, Ruiz-Hidalgo MJ, Bonvini E, et al. 2002. The EGF-like
homeotic protein dlk affects cell growth and interacts with growth-mod-
ulating molecules in the yeast two-hybrid system. Biochem Biophys Res
Commun 291: 193–204.
97. Hoque M, Young TM, Lee CG, et al. 2003. The growth factor granulin
interacts with cyclin T1 and modulates P-TEFb-dependent transcription.
Mol Cell Biol 23: 1688–1702.
98. Kato M, Hasunuma N, Nakayama R, et al. 2009. Progranulin, a secreted
tumorigenesis and dementia-related factor, regulates mouse hair growth.
J Dermatol Sci 53: 234–236.
99. Leverenz JB, Yu CE, Montine TJ, et al. 2007. A novel progranulin
mutation associated with variable clinical presentation and tau, TDP43
and alpha-synuclein pathology. Brain 130: 1360–1374.
BioEssays 31:1245–1254, � 2009 Wiley Periodicals, Inc.