|
Advertisement |
|
|
||
 |
|
|||||
|
|||||
|
 |
||||||
|
||||||
|
||||||
|
© 2003 American Society for Clinical Oncology c-kit Receptor Expression in Ewing’s Sarcoma: Lack of Prognostic Value but Therapeutic Targeting Opportunities in Appropriate Conditions
From the Laboratorio di Ricerca Oncologica and Servizio di Anatomia Patologica, Istituti Ortopedici Rizzoli; Sezione di Cancerologia, Università di Bologna, Bologna, Italy. Address reprint requests to Katia Scotlandi, PhD, Laboratorio di Ricerca Oncologica, Istituti Ortopedici Rizzoli, Via Di Barbiano 1/10, 40136 Bologna, Italy; email: katia.scotlandi{at}ior.it.
Purpose: Autocrine/paracrine stimulation of c-kit has been recently observed in Ewing’s sarcoma (ES) cell lines. In this study, we tested the prognostic and therapeutic role of the receptor in this tumor. Methods: One hundred one ES tumor biopsies were evaluated for the expression of c-kit by the avidin-biotin-peroxidase procedure. Effectiveness of STI-571 (Gleevec; Novartis, Basel, Switzerland), a selective inhibitor of specific tyrosine kinases, was analyzed with respect to in vitro growth and migration inhibition, as single agent or in combination with doxorubicin. Results: Approximately 30% of patients expressed c-kit in their primary tumors. No significant association between the expression of the receptor and the clinical outcome was observed. In vitro growth of ES cell lines showing high levels of c-kit demonstrated limited inhibition by exposure to STI-571 (10 µmol/L is required to obtain 40% to 50% of growth inhibition). A decrease of stem-cell factor–mediated ES cell migration was also found. The drug acted additively with doxorubicin in inhibiting ES cell growth. Conclusion: The negative prognostic findings and the limited in vitro therapeutic activity of STI-571 indicate that the putative aberrant signaling provided by c-kit overexpression may be dispensable for ES development and unlikely to constitute a critical therapeutic target. Accordingly, the dose of STI-571 required to give a significant ES growth inhibition is much higher than for those tumors in which mutations of c-kit constitute a relevant pathogenetic event. Nevertheless, in the subset of ES patients showing a high level of c-kit expression, the activity of the drug may be exploited in combination with standard therapy.
EWING’S SARCOMA (ES) ranks second among bone tumors and is one of the most frequent solid tumor in children and adolescents. ES is characterized by the presence of specific chromosomal translocations, which produce EWS/ets gene rearrangements [in more than 95% of cases, the gene fusion is EWS/FLI-1, resulting from the t(11;22) (q24;q12), or EWS/ERG, resulting from the t(21;22) (q22;q12)],1 as well as the expression, at extremely high levels, of an antigen encoded by the MIC2 gene (also known as CD99 or p30/32MIC2).2–4 From a clinical point of view, ES shows a low survival rate despite the adoption of multimodal treatments, including local control of the disease by surgery or radiotherapy and multidrug adjuvant chemotherapy.5–9 The lack of new effective drugs in the treatment of sarcomas, together with the effect of side effects of high-dose regimens on young patients who have a long life expectancy, supports the need for innovative therapeutic strategies, including targeted therapies against molecules that seem to be critical for the pathogenesis and progression of ES. Discoveries in the last years have led to a better understanding of the mechanisms involved in the genesis of this neoplasm and allowed the identification of some biologic targets.10–14 In this article, we focused our attention on the clinical relevance of c-kit expression in ES. c-kit has been implicated in the pathophysiologic mechanisms of a variety of human tumors.15–22 Two general mechanisms of c-kit activation in malignant cells have been described: acquisition of activating mutations and autocrine or paracrine stimulation of the receptor by its ligand, the stem-cell factor (SCF). Activating mutations of c-kit have been described in cases of human mast cell disorders and gastrointestinal stromal tumors (GIST),18,23,24 neoplasms that arise in tissue types whose development depends on the activity of the SCF/c-kit system and for which aberrant activation of this axis may represent a pathogenetic mechanism. In these tumors, the presence and type of mutation have been proven to have clinical prognostic importance.25,26 Autocrine/paracrine stimulation of c-kit has been observed in some other human cancers,16,20,27 including ES.14,28 In particular, the analysis of several ES cell lines indicated that ES cells express c-kit and SCF; that SCF is capable of protecting the tumor cells against apoptosis, giving them a growth advantage; and that SCF/c-kit system may be associated with, or even partly responsible for, the peculiar pattern of ES metastasis in patients,29 which includes the appearance of bone metastases in one third of patients in the absence of lung metastases.5 Following these suggestions, we decided to analyze the expression of c-kit in a consecutive series of 101 patients with ES, homogeneously treated, to verify whether a significant association with development of metastases was present and, as a second goal of the study, to provide the rationale for the inclusion of imatinib mesylate (STI-571) in the treatment of ES patients. STI-571, now referred to as Gleevec in the United States and Glivec in Europe (Novartis, Basel, Switzerland), is a selective tyrosine kinase inhibitor of specific targets,30 including c-kit.31 STI-571 has been shown to have a promising therapeutic application in chronic myelogenous leukemia32–34 and among solid tumors, GIST,35,36 and seems to be the best current example of successful targeted therapies in human tumors.37,38
Cell Lines A panel of 14 human ES cell lines were analyzed. The ES cell lines SK-ES-1, RD-ES, and SK-N-MC were obtained from the American Type Collection (Rockville, MD). The ES cell lines TC-71 and 6647 were kindly provided by T.J. Triche (Children’s Hospital, Los Angeles, CA). All other ES cell lines (LAP35, IOR/BRZ, IOR/CAR, IOR/NGR, IOR/BER, IOR/RCH, and IOR/CLB) were established at the Laboratorio di Ricerca Oncologica, Istituti Ortopedici Rizzoli, Bologna, Italy, and previously characterized.39 The H825 and H1474 ES cell lines were obtained in the Department of Pathology, University of Valencia, Valencia, Spain, and were kindly provided by A. Llombart-Bosch, MD. Cells were routinely cultured in Iscove’s modified Dulbecco’s medium (IMDM) supplemented with 20 U/mL of penicillin, 100 µg/mL of streptomycin (Sigma, St Louis, MO), and 10% heat-inactivated fetal calf serum (Biologic Industries, Kibbutz Beth Haemek, Israel). Cells were maintained at 37°C in a humidified 5% CO2 atmosphere.
Patients and Tissue Samples
Cytofluorometric Analysis of c-kit and Platelet-Derived Growth Factor Receptor Beta c-kit and platelet-derived growth factor receptor beta (PDGF-Rß) expression was evaluated by indirect immunofluorescence and cytofluorometric analysis (FACSCalibur, Becton Dickinson, Mountain View, CA) by using the primary anti–c-kit monoclonal antibody YB5.B8 (Pharmingen, San Diego, CA; dilution, 1:50) or the anti–PDGF-Rß monoclonal antibody (Calbiochem-Novabiochem Co, San Diego, CA; dilution, 1:20) as primary antibodies.
Immunohistochemistry Analysis of c-kit in Tissue Samples
Inhibition of ES In Vitro Growth by STI-571
Soft Agar Assay
Motility Assay
Statistical Analysis
Expression of c-kit in ES Cell Lines To verify whether the expression of c-kit is a general feature of ES cells, we extended the in vitro analyses to a panel of 14 ES cell lines. A relevant expression of c-kit was found in only seven (50%) of 14 ES cell lines (Fig 1  ).
Expression of c-kit in ES Tissue Samples Immunohistochemical analysis of c-kit was performed on a consecutive series of primary tumor tissue samples from 101 patients treated at the Rizzoli Institute between 1983 and 1993 with similar therapeutic regimens, including local control of the disease by surgery or radiotherapy plus adjuvant multidrug chemotherapy.40 After 10 years, 27 patients developed lung metastases, 26 patients developed bone metastases, seven patients developed both lung and bone metastases, and one patient developed metastases in other sites. The cumulative disease-free survival rate was 47% at 3 years, 43% at 5 years, 40% at 7 years, and 39% at 10 years from diagnosis. The immunohistochemical analysis of c-kit expression was performed on tissue samples of primary tumor biopsy (ie, untreated patients). Thirty-one percent of ES samples stained positive with the anti–c-kit C-19 monoclonal antibody, showing diffuse expression of the receptor in tumor cells (weak immunostaining in 16 samples and strong immunostaining in 15 samples). Figure 2 shows the expression of c-kit in two positive samples of ES, in comparison with a sample from a patient with GIST. The level of expression of c-kit in ES patients is generally lower compared with that of GIST, a neoplasm in which the receptor appears as a ubiquitous feature.41 Immunostaining for c-kit in ES was positive more frequently in male than in female patients (37% v 20%), but this association was not statistically significant (P = .08). No significant associations were found between the incidence of c-kit positivity and age, anatomic site, or percentage of tumor necrosis after preoperative chemotherapy. All these features were analyzed with respect to clinical outcome (Table 2). Of these, only the percentage of tumor necrosis evaluated after preoperative chemotherapy was significantly associated with the course of the disease (P = .006), consistent with previously published data.42 The analysis of the prognostic relevance of c-kit in this series of patients failed to indicate a significant association with clinical outcome. c-kit–positive and c-kit–negative patients showed similar survival curves, without any statistically significant difference between the two groups (Fig 3).
In Vitro Effects of STI-571 in ES Cells Although c-kit expression did not have a prognostic role in ES, approximately 30% of patients showed an expression of this receptor in their primary tumor and may be considered for treatment with STI-571, a specific inhibitor of some tyrosine kinases (bcr/abl, abl, PDGF-R, and c-kit).30 Recent data have indicated expression of PDGF-Rß in ES cell lines,43 further supporting the possible use of this drug in ES, but we failed to observe a relevant expression of this receptor in the panel of ES cell lines here considered by cytofluorometric analysis (Fig 4 ). Only four of 14 cell lines seemed to clearly express the receptor; all others were negative or barely negative. The inhibitory growth effects observed after treatment of the ES cell lines with STI-571 confirmed the association between the effectiveness of the drug and the level of c-kit expression (r = 0.89; P < .03; Spearman’s rank correlation coefficient; Table 3). A relevant inhibition of growth was achieved, with the dose of 10 µmol/L of STI-571, only in those cell lines that showed the highest expression of c-kit receptor (Fig 5). The dose of 30 µmol/L highly inhibited the growth of all ES cell lines, but this seemed to be likely the result of aspecific toxic effects, as confirmed by the 93% of growth inhibition observed in the IOR/BRZ cell line that did not express c-kit or PDGF-Rß (data not shown). Figure 6 showed the time-dependent effects of STI-571 10 µmol/L in a representative ES cell line expressing c-kit. Similar results were also obtained when the cells were prevented to adhere. Colony formation in soft agar, which is an accepted criterion for transformation, was inhibited by STI-571 at the dose of 10 µmol/L only in those cell lines (6647, SK-M-NC, RD-ES, and SK-ES-1) that express high levels of c-kit receptor (Table 4). The specific action of STI-571 against c-kit in ES was further demonstrated by analyzing the effects of the drug against the migratory ability of 6647 cells in response to SCF. At the dose of 10 µmol/L, STI-571 induced a significant inhibition of the SCF-induced migratory ability of 6647 cells, without any activity in basal conditions (Fig 7).
Experiments were also carried out to determine the effects on the growth of ES cells of STI-571 in combination with doxorubicin. The combined treatment with 10 µmol/L of STI-571 and increasing concentrations of doxorubicin (100 pg to 10 ng/mL) resulted in additive inhibition of 6647 or SK-ES-1 cell growth with respect to the therapeutic efficacy of doxorubicin alone (Fig 8 ).
c-kit activation was found to suppress apoptosis of normal murine melanocytes, neuroblastomas, normal and malignant hematopoietic cells, and ES.14,20,28,44 In particular, we previously demonstrated that SCF gave a growth and migratory advantage to ES cells.14 Moreover, c-kit downregulation, before injection of ES cells in nude mice, significantly enhanced the survival rate of treated mice and decreased the number of lung and bone metastases, indicating that the c-kit/SCF system plays a role in sustaining ES proliferation and metastasis. Pharmacologic inhibition of c-kit may, therefore, be a potential novel approach for the treatment of ES patients. Indeed, these findings, together with the recent observation that ES cells also express PDGF-Rß,43 prompted researchers to analyze the effects of STI-571 in this neoplasm.
STI-571 was previously identified as a potent inhibitor of the c-abl protein kinase and shown to have similar activity against v-abl and both the p210 and p190 forms of bcr-abl. Additionally, STI-571 was found to inhibit the kinase activity of the In this study, we analyzed three factors: the expression of c-kit in tissue biopsy, to verify the clinical relevance of experimental results; the prognostic value of c-kit in ES, because experimental data have previously indicated the receptor as a possible homing receptor able to guide ES cells in their metastasization process to lungs and bone; and the in vitro effectiveness of STI-571 against ES cells. c-kit has been previously reported to be generally expressed on ES cell lines.14,28 Our in vitro data only partially confirmed these reports, showing an expression of the receptor in only 50% of the cell lines here considered. Interestingly, the highest levels of c-kit expression were observed among cell lines with a long in vitro history (6647, SK-N-MC, RD-ES, SK-ES-1), whereas cell lines recently obtained in our laboratory showed a generally lower level of c-kit expression. Indeed, the number of in vitro passages was significantly correlated with the level of expression of c-kit (r = 0.64; P = .01; Spearman’s rank correlation coefficient). This result indicates that c-kit expression may be somehow selected during in vitro cell maintenance and may explain the differences in what was previously observed by others. Immunohistochemical analyses of c-kit in 101 ES biopsies showed an expression of the receptor in 31% of the cases, a percentage that is quite close to that obtained among cell lines with a short in vitro history (three of eight, or 37%) and similar to that recently reported by Hornick and Fletcher45 in ES clinical samples. No significant differences were observed in the survival curves of c-kit–positive and c-kit–negative groups of patients, indicating that the expression of the receptor has no prognostic role in ES. Nevertheless, 30% of patients do express the receptor at the time of diagnosis and, therefore, could be targeted by STI-571. STI-571 exemplifies the successful development of a rationally designed, molecularly targeted therapy for the treatment of a specific cancer.36,37,38 The drug is conveniently dosed as a once-daily oral medication and is well tolerated. Therefore, given the proven clinical utility of STI-571 in chronic myeloid leukemia and GIST,32,33,35,36 it is logical to test the effectiveness of STI-571 in other diseases where these kinases are activated. With respect to ES, contradictory data have recently been reported on the possible clinical use of c-kit–targeting drugs.46–48 Our in vitro findings indicate that STI-571 induced a significant growth inhibition of only those ES cells that express high levels of c-kit. Although it is certainly difficult and frequently incorrect to relate quantitatively the c-kit expression levels in STI-571–responsive ES cell lines to the c-kit expression found by immunohistochemistry in primary tumors, highly expressing samples are usually well identified with any technique used. Because our in vitro data showed a correlation between highly c-kit–expressing samples and those that are responsive to STI-571 treatments, we believe that this information may be clinically useful. The STI-571 growth inhibitory effects were observed both in monolayer and soft-agar conditions, at a dose (10 µmol/L) that can be easily achieved in the plasma of patients treated with oral administration of the drug.49 Higher doses also gave a generally unspecific toxic effect on c-kit–negative cells. Moreover, STI-571 significantly inhibited the SCF-induced migratory ability of 6647 cells, which showed one of the highest levels of expression of c-kit among ES, supporting a possible therapeutic relevance in the prevention of metastasis from ES cells in the lungs and bones, sites that correspond to SCF-rich microenvironments. However, it should be noted that the dose of STI-571 necessary to inhibit ES cells in vitro is at least 10- to 100-fold higher than that reported to be active in GIST,50 and that the magnitude of specific growth inhibition never exceeds 50% in ES, a rather modest result in experimental conditions and definitely lower than that observed in GIST cell lines.50 This likely reflects the different level of expression of c-kit, which is quite high in GIST but rather modest in ES, and the type of activation of the receptor in the two neoplasms, activating mutations in the majority of GIST versus autocrine/paracrine stimulation in ES. In addition, whereas the presence of activating c-kit mutations is likely to be a critical pathogenetic event for GIST, the activated c-kit receptor in ES, although being relevant for the malignant potential of the cells,14 is unlikely to have a major role in the pathogenesis of this neoplasm. In fact, other molecular events are clearly more important for the genesis and progression of ES, such as fusion products of specific chromosomal translocation.10 Furthermore, the presence of other autocrine circuits11,12,51,52 could well explain why the maximum growth inhibition obtainable by STI-571 in standard culture conditions does not exceed 50%. All these aspects should be carefully considered if clinical trials with STI-571 are planned in ES. However, despite these limits and considerations, our findings demonstrate that STI-571 enhances the cytotoxic activity of doxorubicin, a leading drug in the treatment of patients with ES. An additive effect between STI-571 and doxorubicin was clearly observed in two ES cell lines, supporting the clinical attractiveness of STI-571 in combination with conventional anticancer agents for a selected group of ES patients.
We thank Antonio Llombart-Bosch, Department of Pathology, University of Valencia, Valencia, Spain, for contributing two ES cell lines, and Dr Richard Harrison, Head of Staff, Novartis Pharma AG, Basel, Switzerland, for providing STI-571.
Supported by the Italian Association for Cancer Research, Italian Ministry of Health, and Italian Ministry for Education, University, and Research. V.C. and R.S. are in receipt of Italian Foundation for Cancer Research Fellowships.
1. Delattre O, Zucman J, Melot T, et al: The Ewing family of tumors: A subgroup of small-round-cell tumors defined by specific chimeric transcripts. N Engl J Med 331:294–299, 1994 2. Ambros IM, Ambros PF, Strehl S, et al: MIC2 is a specific marker for Ewing’s sarcoma and peripheral primitive neuroectodermal tumors: Evidence for a common histogenesis of Ewing’s sarcoma and peripheral primitive neuroectodermal tumors from MIC2 expression and specific chromosome aberration. Cancer 67:1886–1893, 1991[CrossRef][Medline] 3. Kovar H, Dworzak M, Strehl S, et al: Overexpression of the pseudoautosomal gene MIC2 in Ewing’s sarcoma and peripheral primitive neuroectodermal tumor. Oncogene 5:1067–1070, 1990[Medline] 4. Noguera R, Triche TJ, Navarro S, et al: Dynamic model of differentiation in Ewing’s sarcoma cells. Lab Invest 66:143–151, 1992[Medline] 5. Bacci G, Toni A, Avella M, et al: Long-term results in 144 localized Ewing’s sarcoma patients treated with combined therapy. Cancer 63:1477–1486, 1989[CrossRef][Medline] 6. Burgert EO, Nesbit ME, Garnsey LA, et al: Multimodal therapy for the management of nonpelvic, localized Ewing’s sarcoma of bone: Intergroup study IESS-II. J Clin Oncol 8:1514–1524, 1990[Abstract]
7. Paulussen M, Ahrens S, Craft AW, et al: Ewing’s tumors with primary lung metastases: Survival analysis of 114 (European Intergroup) Cooperative Ewing’s Sarcoma Studies patients. J Clin Oncol 16:3044–3052, 1998 8. Bacci G, Picci P, Ferrari S, et al: Neoadjuvant chemotherapy for Ewing’s sarcoma of bone: No benefit observed after adding ifosfamide and etoposide to vincristine, dactinomycin, cyclophosphamide, and doxorubicin in the maintenance phase—Results of two sequential studies. Cancer 82:1174–1183, 1998[CrossRef][Medline] 9. Craft A, Cotterill S, Malcolm A, et al: Ifosfamide-containing chemotherapy in Ewing’s sarcoma: The Second United Kingdom Children’s Cancer Study Group and the Medical Research Council Ewing’s Tumor Study. J Clin Oncol 16:3628–3633, 1998[Abstract] 10. Kovar H, Aryee D, Zoubek A: The Ewing family of tumors and the search for the Achilles’ heel. Curr Opin Oncol 11:275–284, 1999[CrossRef][Medline]
11. Scotlandi K, Benini S, Nanni P, et al: Blockage of insulin-like growth factor-I receptor inhibits the growth of Ewing’s sarcoma in athymic mice. Cancer Res 58:4127–4131, 1998 12. Scotlandi K, Maini C, Manara MC, et al: Effectiveness of insulin-like growth factor receptor I antisense strategy against Ewing’s sarcoma cells. Cancer Gene Ther 9:296–307, 2002[CrossRef][Medline]
13. Scotlandi K, Baldini N, Cerisano V, et al: CD99 engagement: An effective therapeutic strategy for Ewing tumors. Cancer Res 60:5134–5142, 2000
14. Landuzzi L, De Giovanni C, Nicoletti G, et al: The metastatic ability of Ewing’s sarcoma cells is modulated by stem cell factor and by its receptor c-kit. Am J Pathol 157:1–9, 2000
15. Turner AM, Zsebo KM, Martin F, et al: Nonhematopoietic tumor cell lines express stem cell factor and display c-kit receptor. Blood 80:374–381, 1992 16. Di Paola RS, Kuczynski WI, Onodera K, et al: Evidence of a functional c-kit receptor in melanoma, breast and lung carcinoma cells. Cancer Gene Ther 4:176–182, 1997[Medline]
17. Tian Q, Frierson HFJ, Krystal GW, et al: Activating c-kit gene mutations in human germ cell tumors. Am J Pathol 154:1643–1647, 1999
18. Hirota S, Isozaki K, Moriyama Y, et al: Gain-of-function mutations of c-kit in human gastrointestinal stromal tumors. Science 279:577–580, 1998 19. Beghini A, Cairoli R, Morra E, et al: In vivo differentiation of mast cells from acute myeloid leukemia blasts carrying a novel activating ligand-independent c-kit mutation. Blood Cells Mol Dis 24:262–270, 1998[CrossRef][Medline] 20. Timeus F, Crescenzio N, Valle P, et al: Stem cell factor suppresses apoptosis in neuroblastoma cell lines. Exp Hematol 25:1253–1260, 1997[Medline]
21. Sekido Y, Takahashi T, Ueda R, et al: Recombinant human stem cell factor mediates chemotaxis of small-cell lung cancer cell lines aberrantly expressing the c-kit protooncogene. Cancer Res 53:1709–1714, 1993
22. Cohen PS, Chang JP, Lipkunskaya M, et al: Expression of stem cell factor and c-kit in human neuroblastoma. Blood 84:3465–3472, 1994
23. Lasota J, Jasinski M, Sarlomo-Rikala M, et al: Mutations in exon 11 of c-kit occur preferentially in malignant versus benign gastrointestinal stromal tumors and do not occur in leiomyomas and leiomyosarcoma. Am J Pathol 154:53–60, 1999
24. Longley BJJ, Metcalfe DD, Tharp M, et al: Activating and dominant inactivating c-kit catalytic domain mutations in distinct clinical forms of human mastocytosis. Proc Natl Acad Sci U S A 96:1609–1614, 1999 25. Worobec AS, Semere T, Nagata H, et al: Clinical correlates of the presence of Asp816Val c-kit mutation in the peripheral blood mononuclear cells of patients with mastocytosis. Cancer 83:2120–2129, 1998[CrossRef][Medline]
26. Taniguchi M, Nishida T, Hirota S, et al: Effect of c-kit mutation on prognosis of gastrointestinal stromal tumors. Cancer Res 59:4297–4300, 1999
27. Krystal GW, Hines SJ, Organ CP: Autocrine growth of small cell lung cancer mediated by coexpression of c-kit and stem cell factor. Cancer Res 56:370–376, 1996
28. Ricotti E, Fagioli F, Garelli E, et al: c-kit is expressed in soft tissue sarcoma of neuroectodermic origin and its ligand prevents apoptosis of neuroplastic cells. Blood 91:2397–2405, 1998 29. Scotlandi K, Benini S, Manara MC, et al: Murine model for skeletal metastases of Ewing’s sarcoma. J Orthop Res 18:859–866, 2000 30. Druker BJ, Lydon NB: Lessons learned from the development of an Abl tyrosine kinase inhibitor for chronic myelogenous leukemia. J Clin Invest 105:3–7, 2000[Medline]
31. Heinrich M, Griffith DJ, Druker BJ, et al: Inhibition of c-kit receptor tyrosine kinase activity by STI 571, a selective tyrosine kinase inhibitor. Blood 96:925–932, 2000
32. Kantarjian HM, Cortes J, O’Brien S et al: Imatinib mesylate (STI571) therapy for Philadelphia chromosome-positive chronic myelogenous leukemia in blast phase. Blood 99:3547–3553, 2002
33. Sawyers CL, Hochhaus A, Feldman E, et al: Imatinib induces hematologic and cytogenetic responses in patients with chronic myelogenous leukemia in myeloid blast crisis: Results of a phase II study. Blood 99:3530–3539, 2002
34. Mauro MJ, O’Dwyer M, Heinrich MC, et al: STI571: A paradigm of new agents for cancer therapeutics. J Clin Oncol 20:325–334, 2002
35. Joensuu H, Roberts PJ, Sarlomo-Rikala M, et al: Effect of the tyrosine kinase inhibitor STI571 in a patient with a metastatic gastrointestinal stromal tumor. N Engl J Med 344:1052–1056, 2001
36. Demetri GD, von Mehren M, Blanke CD, et al: Efficacy and safety of imatinib mesylate in advanced gastrointestinal stromal tumors. N Engl J Med 347:472–480, 2002
37. Heinrich MC, Blanke CD, Druker BJ, et al: Inhibition of KIT tyrosine kinase activity: A novel molecular approach to the treatment of KIT-positive malignancies. J Clin Oncol 20:1692–1703, 2002
38. Savage DG, Altman KH: Drug therapy: Imatinib Mesylate—A new oral targeted therapy. N Engl J Med 346:683–693, 2002
39. Manara MC, Perbal B, Benini S, et al: The expression of ccn3(nov) gene in musculoskeletal tumors. Am J Pathol 160:849–859, 2002
40. Bacci G, Ferrari S, Bertoni F, et al: Prognostic factors in nonmetastatic Ewing’s sarcoma of bone treated with adjuvant chemotherapy: Analysis of 359 patients at the Istituti Ortopedici Rizzoli. J Clin Oncol 18:4–11, 2000
41. Rubin BP, Singer S, Tsao C, et al: KIT activation is a ubiquitous feature of gastrointestinal stromal tumors. Cancer Res 61:8118–8121, 2001 42. Picci P, Bohling T, Bacci G, et al: Chemotherapy-induced tumor necrosis as a prognostic factor in localized Ewing’s sarcoma of the extremities. J Clin Oncol 15:1553–1559, 1997[Abstract] 43. Uren A, Chen-Chih JS, Vitolo M, et al: Expression of functional beta-PDGF receptors by Ewing’s sarcoma. Proc Am Assoc Cancer Res 43:830, 2002 (abstr 4121) 44. Ito M, Kawa Y, Ono H, et al: Removal of stem cell factor or addition of monoclonal anti c-KIT antibody induces apoptosis in murine melanocyte precursors. J Invest Dermatol 112:796–801, 1999[CrossRef][Medline]
45. Hornick JL, Fletcher CD: Immunohistochemical staining for KIT (CD117) in soft tissue sarcomas is very limited in distribution. Am J Clin Pathol 117:188–193, 2002 46. Hotfilder M, Lanvers C, Jürgens, et al: c-KIT-expressing Ewing tumor cells are insensitive to imatinib mesylate (STI571). Cancer Chemother Pharmacol 50:167–169, 2002[CrossRef][Medline]
47. Merchant MS, Woo C-W, Mackall CL, et al: Potential use of Imatinib in Ewing’s sarcoma: Evidence for in vitro and in vivo activity. J Natl Cancer Inst 94:1673–1679, 2002
48. Wisniewski D, Lambek CL, Liu C, et al: Characterization of potent inhibitors of the Bcr-Abl and the c-Kit receptor tyrosine kinases. Cancer Res 62:4244–4255, 2002
49. Mauro MJ, Druker BJ: STI571: Targeting BCR/ABL as therapy for CML. Oncologist 6:233–238, 2001 50. Tuveson DA, Willis NA, Jacks T, et al: STI571 inactivation of the gastrointestinal stromal tumor c-KIT oncoprotein: Biological and clinical implications. Oncogene 20:5054–5058, 2001[CrossRef][Medline] 51. Girnita L, Girnita A, Wang M, et al: A link between basic fibroblast growth factor (bFGF) and EWS/FLI-1 in Ewing’s sarcoma cells. Oncogene 19:4298–4301, 2000[CrossRef][Medline] 52. Westwood G, Dibling BC, Cuthbert-Heavens D, et al: Basic fibroblast growth factor (bFGF)-induced cell death is mediated through a caspase-dependent and p53-independent cell death receptor pathway. Oncogene 21:809–824, 2002[CrossRef][Medline] Submitted November 21, 2002; accepted March 5, 2003.
This article has been cited by other articles:
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|||||||||||
|
|||||||||||
|
|
Copyright © 2003 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
|
TOP
ABSTRACT
INTRODUCTION
), untreated control cells. (•), cells treated with 10 µmol/L of STI-571. Results are from one experiment performed in triplicate and representative of two.
), STI-571 10 µmol/L; (
), doxorubicin; (
), STI-571 µmol/L plus doxorubicin.
and ß chains of PDGF-R and c-kit.
