Rarely, if ever, is it practical to makesequential observations on unresectedpolyps over long periods. Thus, ourstudy data and most previous informationconcern persons who have had theirpolyps treated. Persons who have similarbut untreated polyps presumably have acancer risk that is higher than has beenpreviously observed. Further informationon the degree of risk may be derivedfrom other types of studies, such as thosein which the detection and treatment ofpolyps by screening are related to subse-quent colorectal cancer (16).

References(/) SILVERBERG E, BORING CC, SQUIRES TS: Can-

cer Statistics, 1990. CA Cancer J Clin 40:9-26, 1990

(2) LEV R: Adenomatous Polyps of the ColonNew York: Springer-Verlag, 1990

(3) PATTERSON BH, BILGRAD R: Use of theNational Death Index in cancer studies. JNC177:877-881, 1986

(4) The Death Master File. Am J Public Health77:1548, 1987

(5) YOUNG JL, PERCY CL, ASIRE AJ, ET AL: Sur-veillance, Epidemiology, and End Results:Incidence and Mortality Data, 1973-77. NatlCancer Inst Monogr 57, 1981

(6) KLEINBAUM DG, KUPPER LL, MORGENSTERNH: Epidemiologic Research, Principles andQuantitative Methods. Belmont, Calif: Life-time Learning Publications, 1982

(7) MIETTINEN O: Estimability and estimation ofcase-referent studies. Am J Epidemiol103:226-235, 1976

(8) MULDER GH: An exact method for calculatinga confidence interval for a Poisson parameter.Am J Epidemiol 117:377, 1983

(9) MANTEL N, HAENSZEL W: Statistical aspectsof the analysis of data from retrospectivestudies of disease. J Natl Cancer Inst 22:719-748. 1959

(10) PRAGER ED, SWINTON NW, YOUNG JL, ET AL:Follow-up study of patients with benignmucosal polyps discovered by proctosig-moidoscopy. Dis Colon Rectum 17:322-324,1974

(//) Lorn AM, SPENCER RJ, ILSTRUP DM, ET AL:Colorectal polyps and the risk of subsequentcarcinoma. Mayo Clin Proc 61:337-343,1986

(12) BRAHME F, EKELUND GR, NORDEN JG, ET AL:Metachronous colorectal polyps: Comparisonof development of colorectal polyps and car-cinomas in persons with and without historiesof polyps. Dis Colon Rectum 17:166-171,1974

(13) SPENCER RJ. MELTON LJ, READY RL. ET AL:Treatment of small colorectal polyps: Apopulation-based study of the risk of subse-quent carcinoma. Mayo Clin Proc 59:305-310. 1984

(14) ATKIN WS, MORSON BC. CUSICK J: Long-term risk of colorectal cancer after excision ofrectosigmoid adenomas. N Engl J Med326:658-662. 1992

(15) BROWN LJ, SMEETON NC, DIXON MF: Assess-ment of dysplasia in colorectal adenomas: Anobserver variation and morphometric study. JClin Pathol 38:174-179, 1985

(16) WlNAWER SJ, SCHOTTENFELD D, FLEHINGERBJ: Colorectal cancer screening. J Natl Can-cer Inst 83:243-253. 1991

Inhibition of MetastaticBehavior of MurineOsteosarcoma byHypophysectomy

Michael Pollak,* Alfred W. Sem,Marline Richard, Evelyn Tetenes,Robert Bell

Background: We recently reportedthat human osteogenic sarcoma cellsare mitogenically responsive in tissueculture to insulin-like growth factor I(IGF-1), a mitogen important in theregulation of cellular proliferation ofmany tissues, including bone. Purpose:The present study was designed todetermine whether these in vitro ob-servations could be extended to an invivo experimental system and whetherreduction of IGF-I levels by hypo-physectomy could inhibit the aggres-sive metastatic behavior of osteo-sarcoma. Methods: We used standardcompetitive binding and affinity-labeling techniques to characterize theIGF-I-binding sites of MGH-OGS, amodel of human osteosarcoma. Radio-immunoassay of serum, preprocessedto remove IGF-binding proteins, wasused to quantitate IGF-I levels.In vitro proliferative response ofMGH-OGS cells to IGF-I and otherpituitary-dependent factors was deter-mined by thymidine-incorporationexperiments. In vivo growth of theneoplasm in 12 hypophysectomizedC3H mice and in 14 control C3H micewas determined by serial measure-ments of implanted tumors and bygross and microscopic examination ofthe lungs for metastases. Results:MGH-OGS exhibited specific bindingsites for 1.39 pmol IGF-I per milli-gram MGH-OGS cellular membraneprotein, a concentration similar to thatwhich we previously reported forhuman osteosarcoma. In tissue cul-ture, MGH-OGS exhibited mitogenicresponse to IGF-I (P<.01) but not toother pituitary-dependent factors.Hypophysectomy reduced levels of cir-culating IGF-I to 15% of control, sig-nificantly inhibited local growth ofMGH-OGS tumors (increased time for

growth to 1 cm3 from 49 to 84 days,P<.001) , and profoundly inhibitedmetastatic behavior (decrease in meannumber of metastases per host from 16to less than one; P<.001) . Conclu-sions: This study is the first to docu-ment the profound inhibitory effect ofhypophysectomy on the metastaticbehavior of an experimental sarcoma.We conclude that the metastatic be-havior exhibited by MGH-OGS osteo-sarcoma is dependent on pituitaryfactors, and we suggest that the inhibi-tory effects of hypophysectomy arerelated, at least in part, to the reduc-tion of IGF-I levels. [J Natl CancerInst 84:966-971, 1992]

Insulin-like growth factor I (IGF-1) isa peptide mitogen known to have a keyrole in the regulation of cellular pro-liferation of many tissues, includingbone (1,2). Elaborate physiological con-trol systems exist to regulate circulatingand tissue levels of this growth factor(/). The bulk of circulating IGF-I is syn-thesized in the liver, where transcriptionof the IGF-I gene is positively regulatedby growth hormone (3). Pituitary secre-tion of growth hormone is regulated by acomplex neuroendocrine control systeminvolving the stimulatory hypothalamicpeptide growth hormone-releasing hor-mone and the inhibitory peptide somato-statin (4). IGF-I is also expressed inextrahepatic tissues, where it may act ina paracrine rather than in an endocrinefashion, but the regulation of IGF-I geneexpression in extrahepatic tissues isincompletely characterized (5). The bio-activity of IGF-I is further regulated byseveral specific high-affinity bindingproteins present in both tissues and

Received August 12, 1991; revised November 5,1991; accepted March 18, 1992.

Supported by a grant from the National CancerInstitute of Canada (M. Pollak, R. Bell).

M. Pollak, M. Richard, E. Tetenes, Departmentsof Medicine and Oncology, McGill University, andLady Davis Research Institute of the Jewish Gen-eral Hospital. Montreal, Quebec, Canada.

M. Richard, E. Tetenes, Lady Davis ResearchInstitute.

A. W. Sem, R. Bell, Division of OrthopaedicSurgery. University of Toronto, and Mount SinaiHospital, Canada.

'Correspondence to: Michael Pollak. M. D.,Departments of Medicine and Oncology, LadyDavis Research Institute of the Jewish GeneralHospital, 3755 Cote St. Catherine Rd., Montreal,PQ. H3T 1E2. Canada.

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serum (/). At target cells, the first stepin IGF-I-stimulated cellular proliferationinvolves the binding of IGF-I to specificcell-surface receptor molecules of thetyrosine kinase class known as type 1IGF receptors (6).

Because IGF-1 has been shown to be akey mitogen for normal osteoprogenitorcells (2), we recently studied its effect onosteogenic sarcoma. Our results demon-strated that human osteogenic sarcomatissue is IGF-I receptor positive and thatIGF-I is a potent mitogen for osteogenicsarcoma cells in vitro (7). These obser-vations suggested the possibility of novelendocrine therapies.

Despite recent advances in adjuvantchemotherapy and in locoregional man-agement of osteogenic sarcoma, theaggressive metastatic behavior of thisneoplasm remains an important clinicalchallenge. We therefore conducted ex-periments to determine if our in vitroobservations could be extended to an invivo experimental system and if hormo-nal manipulation could inhibit the meta-static behavior of osteosarcoma.

Materials and Methods

Hormones and Growth Factors

Recombinant human IGF-I was ob-tained from Amersham Corp. (ArlingtonHeights, 111.). Fetal calf serum was pur-chased from GIBCO BRL (Grand Island,N.Y.). Mibolerone was a gift from Dr.L. Pinsky, and human prolactin wasdonated by Dr. Paul Kelly. Other hor-mones were obtained from Sigma Chem-ical Co. (St. Louis, Mo.). Collagenasewas purchased from Worthington Bio-chemical Corp. (Freehold, N.J.).

IGF-I Binding and Affinity Labeling

Procedures for studies of IGF-1 bind-ing and affinity labeling of IGF-I re-ceptors were carried out on plasmamembrane-enriched subcellular fractionsof MGH-OGS tumors prepared by dif-ferential centrifugation, as previouslydescribed (7,8). These procedures wereused to generate specific binding data,competitive binding data, and Scatchardplots. Human MG-63 osteosarcoma cellsand human placenta were processed inthe same way and served as controltissues. Recombinant human IGF-I wasused in these experiments.

In Vitro MGH-OGS Cell Proliferation

For the in vitro work, we did notobtain a large number of independentprimary MGH-OGS tumors as sources ofcells. Our reason for not doing so wasthat the MGH-OGS system was welldescribed in our previously publishedstudies (9,10) as being clonal, and bio-logical variability was demonstrated tobe negligible between specimens carriedin different hosts.

MGH-OGS cells were obtained for invitro studies by surgically removing onetumor from each of two hosts, removingsurrounding normal tissues, mincing thepooled neoplastic tissue with scissors innutrient mixture F-12 Ham medium(Sigma Chemical Co.), and digesting thetissue in 0.09% collagenase. Cells werethen plated in 10% fetal calf serum, anddebris was removed by changing themedium after 2 days. Subsequently, cellswere replated in 35-mm plates forexperiments to measure proliferationby assaying the incorporation ofradiolabeled thymidine, as previouslydescribed (7,11,12). We assayed pro-liferative response to IGF-I, triiodo-thyronine, estradiol, the dihydrotestos-terone analogue mibolerone, cortisol,prolactin, and growth hormone. Thy-midine incorporation experiments wereconducted in quadruplicate.

Mice

Appropriate approval for animal carewas obtained from the Animal CareCommittees of the University of Torontoand McGill University. Intact and hypo-physectomized 8-week-old male C3Hmice were obtained from Charles RiverBreeding Laboratories (Wilmington,Mass.) and kept in cages under standardconditions.

Radioimmunoassay for IGF-I

Radioimmunoassay of serum pre-processed to remove IGF-binding pro-teins was used to quantitate IGF-I levels.Radioimmunoassay was conducted asdescribed and validated for rat serum byBreier et ai. (.13), using an antibody (14)provided by the National Institute of Dia-betes and Digestive and Kidney Diseases(National Institutes of Health, Bethesda,Md.).

Serum specimens (50 (xL) were di-luted 1:5 in 87.5% absolute ethanol and12.5% 2 M hydrochloric acid. They werethen processed to remove serum IGF-I-binding proteins by cryoprecipitation(13). Samples were brought to pH 7.4with tris(hydroxymethyl)aminomethaneprior to the radioimmunoassay proce-dure, which was initiated by the incuba-tion of samples with rabbit anti-IGF-Ipolyclonal antibody (14) at a 1:18000final dilution. After 24 hours, radio-labeled IGF-I (20000 counts per minute)was added to each sample, and a further24-hour incubation was carried outbefore the addition of 100 u,L of normalrabbit serum (Sigma Chemical Co.) at a1:100 dilution and 100 p-L of sheep anti-body to rabbit immunoglobulin (SigmaChemical Co.) at a 1:18 dilution. After afinal 24-hour incubation, samples werecentrifuged at 22OOg for 30 minutes, andradioactivity of the pellets was measuredwith a gamma counter. All incubationswere performed at 4 °C. IGF-I levelswere read from a standard curve, ob-tained by assaying samples containingknown amounts of human recombinantIGF-I. Samples were assayed in dupli-cate, and the interassay variation wasless than 15%.

Artifacts due to IGF-binding proteinspresent in serum were minimized byacid-ethanol cryoprecipitation and 1:200dilution of serum prior to assay. Themethodology used has been validated forrat serum (13).

Local and Metastatic Behavior of theMurine MGH-OGS OsteosarcomaModel

The murine MGH-OGS osteosarcomawas carried by serial transplantation andimplanted in the lateral gastrocnemiusmuscle of 12 hypophysectomized miceand 14 control mice, as previouslydescribed (9,10,15). Tumor volumeswere determined three times per week bymeasuring three orthogonal diameterswith calipers and multiplying the productby pi/6 (15). Mice were killed when theirprimary tumors grew to 1 cm3, and thelungs were assayed for metastasis at thistime. Metastatic involvement of thelungs was estimated by inspection at thetime of autopsy—by weighing the meta-static lesions and by microscopic exami-nation of serial sections of the lungs(9,10,15).

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Results

IGF-I-Binding Studies and AffinityLabeling of IGF-I Receptors

Figs. 1 and 2 give the results ofexperiments conducted to determine ifthe experimental MGH-OGS tumor bearsIGF-I receptors. Fig. 1 shows competi-tive binding curves for the binding ofI25I-IGF-I to membranes prepared fromMGH-OGS tumors, human MG-63 oste-osarcoma cells, and human placenta.Scatchard analysis (Fig. 1, inset) yieldedestimates of specific high-affinity (Kj =0.6 nM) binding sites for 1.39 pmolexogenous IGF-I per milligram MGH-OGS cellular membrane protein.

Under our assay conditions, specificbinding of 20% of added IGF-I wasobserved with membranes prepared fromMGH-OGS tumors, compared with 28%seen with human placenta, a tissueknown to have a particularly high con-centration of IGF-I receptors (data notshown). These results suggest thatMGH-OGS tumors have a density ofIGF-I receptors comparable to that whichwe previously described for humanosteosarcoma (7).

Affinity labeling with I25I-IGF-Ishowed the presence of labeled proteinsin the 130-kd region, consistent with thepresence of type I IGF-I receptors (Fig.2).

In Vitro Studies of MGH-OGSCell Proliferation

Results of experiments conducted invitro with disaggregated MGH-OGScells in primary culture were also con-sistent with the presence of type I IGF-Ireceptors. Thymidine incorporation stud-ies (Fig. 3) showed the rate of prolifera-tion in the presence of medium supple-mented with 5 x 10"9 M IGF-I to besignificantly higher ( P < . 0 1 , Mann-Whitney U test) than control valuesobtained when proliferation of MGH-OGS cells was assayed in the absence ofexogenous IGF-I. In contrast, there wasno statistically significant differencebetween control values and valuesobtained when proliferation of MGH-OGS cells was assayed in the presence ofother pituitary-dependent hormones atconcentrations known to be mitogenicfor cells that respond to these factors.The concentrations used were as follows:5 x 10-8 M triiodothyronine, 10"8 M

ndi

albi

o

120

100

80

60

40

20

0

-

-1

• • HP.

D MGH-OGS

" + MG-63

1 1

B/F

V \V\

\

10

IGF-1 (ng/ml)

U.D

0.4-

02-

n n -

•s

0.0

V

too

X0.1 0.2 0.3 0.4

B

1000

Fig. 1. Competitive binding of IGF-I to plasma membrane-enriched subcellular fractions prepared fromMGH-OGS tissue, human MG-63 osteosarcoma cells, and human placenta (H.P.). Inset: Scatchard plot ofcompetitive binding data for MGH-OGS tissue. B/F = bound/free; B = bound.

estradiol, 6 X 10~7 mibolerone (di-hydrotestosterone analogue), 5 x 10~7

M cortisol, 100 ng/mL human prolactin,and 100 ng/mL recombinant humangrowth hormone.

Radioimmunoassay for IGF-I

To assess the adequacy of hypo-physectomy as an IGF-I-lowering inter-vention, we obtained serum samplesfrom the hypophysectomized and thecontrol mice when they were killed.Radioimmunoassay estimates of serumIGF-I were 195 ± 8 ng/mL (SE) for thecontrol group and 29 ± 6 ng/mL for thehypophysectomized group (Table 1).

Although we have been able to dem-onstrate, by the use of ligand blots, someresidual binding proteins following theacid-ethanol-cryoprecipitation procedure(Pollak M, Polychronakos C: unpub-lished observations), the results pre-sented here are sufficient to demonstrate

1 2 3 4

200 —

116 —

Fig. 2. Affinity labeling of IGF-I receptors in sub-cellular fractions prepared from human placenta(lanes 1 and 2), human MG-63 osteosarcoma cells(lanes 3 and 4), and MGH-OGS tissue (lanes 5 and6) in the presence (lanes 2, 4, and 6) or in theabsence (lanes I, 3, and 5) of excess unlabeledIGF-I. Molecular mass in kilodaltons is shown atthe left.

the adequacy of hypophysectomiesperformed on the mice used in ourexperiments.

Table 1. Effect of hypophysectomy on host serum IGF-I levelsand metastatic behavior of MGH-OGS sarcoma

Control(n = 14)

Hypophysectomized(n = 12)

Serum IGF-I. ng/mL. mean ± SE (range)No. of mice with metastases (%)No. of metastases per host, mean ± SE

195 ± 8 (189-202)12(85.7)16 ± 6

29 ± 6 (22-36)1 (8.3)

*The single animal with metastasis had two lesions.

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200

control •

Fig. 3. Effect of mitogens on in vitro proliferationof MGH-OGS cells. Mean thymidine incorporationvalues ± SE are shown for each condition: 5 x10"9 M IGF-1 (a), 5 x 10-8 M triiodothyronine(b), 10"8 M estradiol (c), 6 x 10"7 M mibolerone(d), 5 x 10"' M cortisol (e), 100 ng/mL humanprolactin (f), and 100 ng/mL recombinant humangrowth hormone (g). Experiments were conductedin quadruplicate.

Local and Metastatic Behavior of theMurine MGH-OGS OsteosarcomaModel

Fig. 4 shows data demonstrating theeffect of prior hypophysectomy on thelocal growth of 1-mm3 MGH-OGStumors transplanted into the lateral gas-trocnemius muscle of mice. We obtaineddata on local tumor growth in 14 controlmice and in 12 hypophysectomized miceby measuring the time required for eachof the 26 tumors to reach 1 cm3. In sum-mary, the slower growth in the hypo-physectomized group was demonstrated

Fig. 4. Effect of hypophysectomy on local growth of MGH-OGS tumors in C3H mice. CTRL = controlmice; HYPOX = hypophysectomized mice.

by a longer time required for the tumorto grow to 1 cm3 (84 days versus 49 daysfor controls; P<.001, Student's / test).

Lungs were examined macroscopicallyat the time of death. The photographsshown in Fig. 5 and the data given inTable 1 illustrate the profound effect ofhypophysectomy, which virtually abol-ished the metastatic behavior of MGH-

OGS tumors. In the control group,examined when primary tumors were 1cm3, 12 (85.7%) of 14 mice were posi-tive for metastatic disease, while onlyone (8.3%) of 12 of the hypophysec-tomized mice had evidence of metastasisat the time the primary tumors were 1cm3. The difference between thesegroups, with respect to incidence of

Fig. 5. Typical gross appearance ol lungs of C3H mite lolluwmg implantatiun of l-rara' primary tumors into the lateral gastrocnemius. Lell = 50 days afterimplanuiion in a control mouse, right = 90 days after implantation in a hypophysectoinized mouse.

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metastasis, had high statistical signifi-cance (P<.001). In the control group,the mean number of metastatic lesionsper animal was 16, while in the hypo-physectomized group, the only animalwith metastasis had two lesions. Themean total weight of the metastaticlesions was 25.0 mg/animal in the con-trol group versus 0.1 mg/animal in thehypophysectomized group. Serial sec-tioning of randomly selected lungs fromboth groups revealed that, in the controlgroup, micrometastatic lesions were fre-quently detectable in the lungs that alsohad macroscopic lesions, while micro-metastases were not seen in the lungs ofhypophysectomized mice. The degree ofinhibition of metastasis that we were ableto achieve with hypophysectomy in thisstudy was considerably greater than thatwhich we achieved with adjuvant or neo-adjuvant chemotherapy in previous work(9).

Discussion

The murine MGH-OGS osteosarcomahas been previously shown to sharemany characteristics with human osteo-genic sarcoma, e.g., histological appear-ance, local invasive behavior, chemo-sensitivity, and metastatic pattern, with apredilection for the lung as a metastaticsite (9,10,15). Thus, it is an excellentmodel of the human disease.

In previous studies, we observed theresponsiveness of human osteogenic sar-coma cells to IGF-I. One of our goals inthis study was to determine whether themurine MGH-OGS osteosarcoma modelcould be used to extend these in vitroobservations to an in vivo experimentalsystem. To make this determination, weinitially characterized MGH-OGS cellswith respect to IGF-I receptors andresponse to IGF-I. Our results suggestthat the experimental MGH-OGS tumoris IGF-I receptor positive and that, likehuman osteogenic sarcoma cells, MGH-OGS cells are mitogenically responsiveto IGF-I.

Pituitary ablation, as expected, re-sulted in a profound reduction in levelsof circulating IGF-I in the C3H miceused in the experimental MGH-OGS sys-tem. Our data show that hypophysec-tomy markedly inhibited local prolifera-tion of MGH-OGS tumors. These resultsare consistent with those of a previousreport (76) demonstrating that hypo-

physectomy reduced local growth of atransplantable rat chondrosarcoma. Ourpresent study, however, is the first todocument the profound effect of hypo-physectomy on the metastatic behaviorof an experimental sarcoma.

We speculate that the IGF-I-loweringeffect of hypophysectomy is responsiblefor the inhibitory effects of this ablativesurgery on local growth and on meta-static behavior. This hypothesis is sup-ported by our observation that in vitroproliferation of MGH-OGS cells is stim-ulated by IGF-I but not by the otherpituitary-dependent hormones tested.Further experiments to determine theeffect of replacing growth hormone and/or IGF-I on the metastatic behavior ofthe MGH-OGS neoplasm in the hypo-physectomized host will be required toconclusively establish if IGF-I reductionis the particular consequence of pituitaryablation that is responsible for the inhibi-tion seen.

The degree of inhibition of the meta-static process is remarkable, especiallysince our experimental design involvedassaying for metastatic lesions whenhypophysectomized and control animalshad primary lesions of similar size.Because the primary tumors grew moreslowly in the hypophysectomy group(Fig.4), these animals were in fact at riskfor developing metastasis over a longerperiod of time than were the controls.

While it is possible that the inhibitionof metastasis we observed is a directresult of the inhibition of IGF-I-depend-ent proliferation of neoplastic cells,effects of IGF-I other than stimulation ofneoplastic cell proliferation may beinvolved. Work in other experimentalsystems (17) has shown that IGF-I canfunction as a motility factor, whichmight enhance metastatic potential inde-pendent of stimulation of proliferation.Furthermore, we cannot exclude theinteresting possibility that hypophysec-tomy inhibits the metastatic process bymechanisms that do not involve neoplas-tic cells directly, e.g., inhibition ofaspects of neovascularization that requireIGF-I or other pituitary-dependent fac-tors. To investigate this possibility fur-ther, studies of the effects of hypo-physectomy on the metastasis of otherIGF-I receptor-positive tumors as well asIGF-I receptor-negative tumors should beundertaken.

In our experimental system, gross dif-ferences in anterior pituitary function

profoundly affect metastatic behavior.Because there is considerable variabilityin anterior pituitary function among indi-viduals, our data justify studies to deter-mine if serum IGF-I level or othervariables related to pituitary function arecorrelated with prognosis and/or risk ofmetastasis in human malignancies.

Surgical hypophysectomy has, in thepast, been undertaken as a palliativemeasure in advanced metastatic breastcancer (18). Hypophysectomy has neverbeen evaluated early in the evolution ofmalignancy in a surgical adjuvant or neo-adjuvant setting. It is, however, at thisearly stage that inhibition of metastaticproliferation might be detected by anappropriately designed clinical trial ofpituitary ablation using surgical, pharma-cological, or radiotherapeutic modalitiesin the treatment of human sarcomas orother neoplasms. The morbidity associ-ated with such treatment, given withappropriate replacement of thyroid andadrenocortical hormones, would not begreater than that associated with currentadjuvant therapies.

Somatostatin analogues have beenobserved to reduce local proliferation ofexperimental sarcomas (19-21). Themechanism of action has not been wellcharacterized, and the effect of thesecompounds on the metastatic process hasnot been studied. The data presentedhere suggest that the IGF-I-loweringeffect of somatostatin analogues may, atleast in part, mediate their inhibitoryeffect on the local growth of sarcomasand provide justification for studies ofthe effects of these drugs on metastaticbehavior.

Clinical use of somatostatin ana-logues, in an attempt to achieve a selec-tive (growth hormone-specific) "medicalhypophysectomy," has resulted in only amodest decrease in IGF-I levels (22).This finding is probably due to compen-satory homeostatic mechanisms, such asincreased growth hormone-releasing hor-mone secretion, which attenuate theinhibitory effect of somatostatin ana-logues on growth hormone secretion. Wehave proposed that more complete phar-macological ablation of the pituitary-IGF-I axis may be possible by usingsomatostatin analogues in conjunctionwith growth hormone-releasing hormoneantagonists (23). Other interestingapproaches to the inhibition of IGF-I-dependent neoplastic cell proliferationinvolve the pharmacological use of

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recombinant human IGF-I-binding pro-teins (Pollak M, Maack C: manuscriptsubmitted for publication) or suramin(//). These strategies may also have rel-evance to IGF-I receptor-positive neo-plasms other than sarcomas, e.g., carci-nomas of the breast and colon (8,12).

Clinical syndromes associated withlow levels of circulating IGF-I in child-hood provide strong evidence that IGF-Iis crucial in the regulation of cellularproliferation during preadult stages ofdevelopment (24). In contrast, low levelsof circulating IGF-I appear to be welltolerated in adults (25). Our data suggestthat certain neoplasms exhibit consider-able dependency on circulating IGF-I.Such malignancies would be expected tobe IGF-I receptor positive but lacking inautocrine or paracrine sources of IGF-Istimulation. If further research demon-strates that such neoplasms exist inhumans, development of therapeuticstrategies to decrease circulating IGF-Ilevels will be warranted because suchtreatment might reduce neoplastic pro-liferation without causing serious toxiceffects.

References

(/) SARA VR, HALL K: Insulin-like growth fac-tors and their binding proteins. Physiol Rev70:591-614, 1990

(2) CANALIS E, MCCARTHY T, CENTRELLA M:Growth factors and the regulation of boneremodeling. J Clin Invest 81:277-281, 1988

(3) ROBERTS CT JR, BROWN AL, GRAHAM DE,ET AL: Growth hormone regulates the abun-

dance of insulin-like growth factor I RNA inadult rat liver. J Biol Chem 261:10025-10028, 1987

(4) TANNENBAUM GS: Interrelationship of soma-tostatin and growth hormone-releasing hor-mone in the genesis of the rhythmic secretionof growth hormone. Acta Paediatr ScandSuppl 367:76-80, 1990

(5) HAN VK, D'ERCOLE AJ. LUND PK: Cellularlocalization of somatomedin insulated-likegrowth factor messenger RNA in the humanfetus. Science 236:193-197. 1987

(6) ULLRICH A. GRAY A. TAM AW, ET AL:Insulin-like growth factor I receptor primarystructure: Comparison with insulin receptorsuggests structural determinants that definefunctional specificity. EMBO J 5:2503-2512,1986

(7) POLLAK MN. POLYCHRONAKOS C, RICHARDM: Insulinlike growth factor I: A potentmitogen for human osteogenic sarcoma. JNatl Cancer Inst 82:301-305. 1990

(8) POLLAK MN, PERDUE JF, MARGOLESE RG.ET AL Presence of somatomedin receptors onprimary human breast and colon carcinomas.Cancer Lett 38:223-230, 1987

(9) BELL RS, ROTH YF, GEBHARDT MC. ET AL:Timing of chemotherapy and surgery in amurine osteosarcoma model. Cancer Res48:5533-5538, 1988

(10) BELL RS, O'CONNOR G. BELL DF, ET AL:Effect of doxorubicin on local recurrence fol-lowing marginal resection in the MGH-OGSmurine model. J Orthop Res 8:105-118, 1990

(//) POLLAK M, RICHARD M: Suramin blockade ofinsulin like growth factor I-stimulated pro-liferation of human osteosarcoma cells. J NatlCancer Inst 82 1349-1352, 1990

(12) POLLAK MN, POLYCHRONAKOS C, YOUSEFI S,ET AL: Characterization of insulin-like growthfactor I (IGF-I) receptors of human breastcancer cells. Biochem Biophys Res Commun154:326-331, 1988

(13) BREIER BH, GALLAHER BW, GLUCKMAN PD:Radioimmunoassay for insulin-like growthfactor-I: Solution to some potential problemsand pitfalls. J Endocrinol 128:347-357, 1991

(14) FURLANETTO RW, UNDERWOOD L E , VANW Y K JJ, ET AL. Estimation of somatomedin-C

levels in normals and patients with pituitarydisease by radioimmunoassay. J Clin Invest60:648-657, 1977

(15) CHOI CH. SEDLACEK RS, Sirrr HD: Radiation-induced osteogenic sarcoma of C3H mouse:Effects of Corynebacierium panmm and WBIon its natural history and response to irradia-tion. Eur J Cancer 15:433-442. 1979

(16) MCCUMBEE WD, MCCARTY KS JR. LEBOVITZHE: Hormone responsiveness of a transplant-able rat chondrosarcoma. II. Evidence for invivo hormone dependence. Endocrinology1106:1930-1940, 1980

(17) STRACKE ML. ENGEL JD, WILSON LW, ET AL:The type I insulin-like growth factor receptoris a motility receptor in human melanomacells. J Biol Chem 264:21544-21549, 1989

(18) RAY BS, PEARSON OH: Hypophysectomy intreatment of disseminated breast cancer. SurgClin North Am 12:419-433. 1962

(19) REUBI J: A somatostatin analogue inhibitschondrosarcoma and insulinoma tumorgrowth. Acta Endocrinol 109:108-114, 1985

(20) REDDING TW, SCHALLY AV: Inhibition ofgrowth of the transplantable rat chondrosar-coma by analogs of hypothalamic hormones.Proc Natl Acad Sci USA 80:1078-1082, 1983

(21) SCHALLY AV. Oncological applications ofsomatostatin analogues. Cancer Res 48:6977-6985, 1988

(22) POLLAK MN. POLYCHRONAKOS C. GUYDA H:Somatostatin analogue SMS 201-995 reducesserum IGF-1 levels in patients with neoplasmspotentially dependent on IGF-I. AnticancerRes 9:889-891, 1989

(23) LUMPKIN MD, MULRONEY SE, HARAMATI A:Inhibition of pulsatile growth hormone (GH)secretion and somatic growth in immature ratswith a synthetic GH-releasing factor antago-nist. Endocrinology 124:1154-1159, 1989

(24) BROCK CGD. Growth hormone deficiency:Features, assessment and therapy. In Endo-crinology (Degroot LJ, ed) Philadelphia:Saunders, 1989, pp 351-362

(25) Growth hormone therapy in elderly people.Lancet 337:1131-1132, 1991

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