genetic markers in aml
DESCRIPTION
Genetic Markers in Acute Myeloid LeukemiaTRANSCRIPT
Genetic Markers in
Acute Myeloid Leukemia (AML) Prepared by:
Mary Suzette Angeles, RCh
Regina Marie Jastiva, RChHannah Aloyon, BSc
Ferdinand F. Fatiga, RMT
BIOMARKERS in AML
Cytogenetic Abnormalities• Chromosomes aberrations• Karyotyping
Genetic Lesions• Mutations SNPs
CYTOGENETIC ABNORMALITIES
Prognostic Subgroup Cytogenetic Abnormality
Favorable • t(15;17)/PML-RARA• t(8;21)• inv(16)/t(16;16)
Intermediate • Normal karyotype• t(9;11)• Gains of whole
chromosomes or loss of Y chromosome
Unfavorable • t(6;9)• inv(3)/t(3;3)• Complex karyotype
Normal karyotypic leukemia
(A heterogeneous group)
Helps classify AML patients
to a more Specific
Prognostic group
Genetic Markers
Significance of Genetic Markers
1. Prognostic Impact 2. Detection of Minimal Residual Disease
Classic “Two Hits” Model in Mutation
Class I Mutation Confers Myeloproliferation of abnormal
WBCs Genes coding for receptor and nonreceptor
Protein Tyrosine Kinase• FLT3, JAK2, C-KIT, ABL1
Genes coding for Proteins of GTPase activity• N-RAS and K-RAS
Class II Mutation Involves Differentiation arrest Affects genes of Transcription Factors (TFs) Chromosome Aberration Gene Fusion
– CBF, MLL, EVI1, TEL, RARA Point Mutation (CEBPA and NPM1)
ESTABLISHED Genetic Markers
FMS - like Tyrosine Kinase (FLT-3)
Nucleophosmin 1(NPM1)
CAAT/enhancer binding protein alpha (CEBPA)
Established
Likely Potential
Favorable mutations
NPM1CEBPA
Unfavorable mutations
FLT3-ITD KITFLT3-TKD
MLL-PTDWT1IDH
Unfavorable overexpression of single genes
BAALCERGMN1EVI1
HOXA9MEIS1
Genetic Markers
FLT-3 Human FLT3 gene is found on Chromosome
13q12 aka CD 135 Proto-oncogene Encodes for Class III Transmembrane
Tyrosine Kinase receptor (Cytokine receptor)
Normally expressed by hematopoietic stem cells, early Myeloid and Lymphoid precursors Supports proliferation and survival of
progenitor cells
FLT3 Mutation Categories
• Internal tandem duplications (FLT3 ITD)– Found in up to 30% of AML – mostly in normal
karyotypes– Unfavorable prognosis (high relapse risk, decrease DFS and
OS)
• Point mutation in tyrosine kinase domain (FLT3-TKD)– 7% of AML– Point mutations and small deletions mostly of
codons 835 and 836
Prognosis of CN-AML with FLT3-ITD is significantly inferior compared with FLT3-
ITD negative CN-AML
Prognostic relevance of FLT3-TKD is not as well-established, but also
appears to be unfavorable
NPM1 Located on Chromosome
5q35 Multifunctional
phosphoprotein Molecular chaperone
• Transport pre-ribosomal particles through nuclear membrane into cytoplasm
Controls duplication of centrosomes during cell cycle
Regulates tumor suppressor pathway
NPM11) NPM1 Gene Alteration
Mutated NPM1 cytoplasmic translocation dimerises with wild type NPM 1 cytoplasmic retention of NPM1
2) NPM functional Loss
mutations of NPM1 seem to simultaneouslydampen a tumor-suppressor pathway4 (p53–ARF) and enhance an oncogenic one (MYC)
Survival Rates Associated with NPM1 mutation
NPM1 Prognostic Impact
•Prognostic implications due to NPM1 mutations must be made in the context of FLT3 mutations•Only NPM1mut/FLT3-ITDneg are associated with achievement of complete remission and favorable outcome
CCAAT/enhancer binding protein(C/EBP)
A member of the leucine zipper transcription factor family-gene located on 19q13.1
In human: genes recently isolated and shown to be preferentially expressed in myelomonocytic cells (not erythroid, T or B lineages) Specifically up regulated during granulocyte
differentiation. Regulates promoters of granulocyte specific genes.
• Transcription factor whose function is crucial for the development and differentiation of granulocytes from hematopoietic precursors•Mutations lead to a loss of function, and thought to promote
leukemogenesis by blocking granulocyte differentiation• 15% of CN-AML have CEBPA mutations• Variety of mutations occur throughout the coding region, but fall
into two major types:• N-terminal frameshift → truncation of protein• C-terminal in-frame → impaired dimerization and DNA binding
• Identification of mutations requires DNA sequencing•Majority of mutations are biallelic, compound heterozygous
mutations
CCAAT/enhancer binding protein(C/EBP)
C/EBP deficient mice lacked mature granulocytes (zhang et al proc Natl Acad Sci USA, 1997)
C/EBP mutations found in 7% of AML (Gombart eg al, Blood 2002) Mutation resulted in a truncated C/EBP protein. Inhibits wild type C/EBPa DNA binding.
Frequency was highest in those with FAB subtype M2, the majority of whom had normal cytogenetics.
In pt with t(8;21)AML1-ETO fusion protein down regulates CEBPa expression to a level insufficient for granulocyte differentiationAML-M2
CCAAT/enhancer binding protein(C/EBP)
CEBPA Prognostic Impact
• Only double mutations are associated with a favorable outcome
• A series of cases with silencing of CEBPA have been identified, and associated with a distinctly poor prognosis
Response to induction
Rates of CR (standard criteria) and resistant disease were not significantly different in patients with or without CEBP mutations, p=0.17
Remission duration Median follow up 30 months
Median duration of remission: 26 months in those
without CEBP mutation.
Not reached for group with CEBP
P=0.01
Multivariate analysis
Overall survival OS longer for patients
with CEBP mutations compared to wild type.
P= 0.05
Overall survival
Multivariate analysis - OS
CEBPA – an independent prognostic marker affecting remission duration and OS
Effects of additional FLT3 mutation Among 36 pt with CEBPA mutation,
presence of FLT 3 mutation (both ITD and D835) did not significantly influence OS, p=0.71
Summary - CEBP CEBPA mutations detected in 15% of pts with
normal karyotype AML. CEBPA = an independent favourable
prognostic marker on multivariate analysis (remission duration and OS)
Presence of FLT3 mutations had no -ve impact on pt with CEBPA mutations. (not consistent with other studies)
More molecular markers under investigation
Unfavorable recurrent genetic abnormalities
• IDH1, IDH2• WT1
• MLL-PTD• NRAS• KRAS• TP53• TET2• ASXL2• RUNX1• DNMT3A
Unfavorable overexpression of single genes
• BAALC• ERG• EVI1• MN1
Thank you!