Imatinib targeting of KIT-mutant oncoprotein in melanoma
ABSTRACT: Metastatic melanoma is an aggressive treatment-refractory malignancy. Recently, c-Kit mutations were discovered in certain mucosal melanomas. A clinical trial was initiated with the c-Kit inhibitor imatinib mesylate. The first treated patient experienced dramatic clinical improvement within days, followed by major responses by PET/CT four weeks later at all sites of metastatic disease. Several established mucosal melanoma cell lines exhibited imatinib sensitivity in a fashion correlating with c-Kit mutational status. Although c-Kit mutations are uncommon in cutaneous melanoma, they may arise in geographically distinct subsets for whom use of c-Kit targeted kinase inhibition should be considered in a rational therapeutic approach. Keywords: Whole genome copy number analysis Overall design: Copy number analysis using high-density SNP arrays to investigate genetic gains and losses involved in the genesis of mucosal and cutaneous melanoma. GSE8164_raw_copy_number_calls.xls contains raw copy number calls generated by dChip (build 5/2007) for GIST, K008, K029, M34, MEL1, MEL40, M6, and 5 Affymetrix controls (copy number identity 2 i.e. normal), which are available on the HapMAP site.
INSTRUMENT(S): [Mapping250K_Sty] Affymetrix Mapping 250K Sty2 SNP Array
Project description:Metastatic melanoma is an aggressive treatment-refractory malignancy. Recently, c-Kit mutations were discovered in certain mucosal melanomas. A clinical trial was initiated with the c-Kit inhibitor imatinib mesylate. The first treated patient experienced dramatic clinical improvement within days, followed by major responses by PET/CT four weeks later at all sites of metastatic disease. Several established mucosal melanoma cell lines exhibited imatinib sensitivity in a fashion correlating with c-Kit mutational status. Although c-Kit mutations are uncommon in cutaneous melanoma, they may arise in geographically distinct subsets for whom use of c-Kit targeted kinase inhibition should be considered in a rational therapeutic approach. Keywords: Whole genome copy number analysis Copy number analysis using high-density SNP arrays to investigate genetic gains and losses involved in the genesis of mucosal and cutaneous melanoma. GSE8164_raw_copy_number_calls.xls contains raw copy number calls generated by dChip (build 5/2007) for GIST, K008, K029, M34, MEL1, MEL40, M6, and 5 Affymetrix controls (copy number identity 2 i.e. normal), which are available on the HapMAP site.
Project description:Amplifications and mutations in the KIT proto-oncogene in subsets of melanomas provide therapeutic opportunities.We conducted a multicenter phase II trial of imatinib in metastatic mucosal, acral, or chronically sun-damaged (CSD) melanoma with KIT amplifications and/or mutations. Patients received imatinib 400 mg once per day or 400 mg twice per day if there was no initial response. Dose reductions were permitted for treatment-related toxicities. Additional oncogene mutation screening was performed by mass spectroscopy.Twenty-five patients were enrolled (24 evaluable). Eight patients (33%) had tumors with KIT mutations, 11 (46%) with KIT amplifications, and five (21%) with both. Median follow-up was 10.6 months (range, 3.7 to 27.1 months). Best overall response rate (BORR) was 29% (21% excluding nonconfirmed responses) with a two-stage 95% CI of 13% to 51%. BORR was significantly greater than the hypothesized null of 5% and statistically significantly different by mutation status (7 of 13 or 54% KIT mutated v 0% KIT amplified only). There were no statistical differences in rates of progression or survival by mutation status or by melanoma site. The overall disease control rate was 50% but varied significantly by KIT mutation status (77% mutated v 18% amplified). Four patients harbored pretreatment NRAS mutations, and one patient acquired increased KIT amplification after treatment.Melanomas that arise on mucosal, acral, or CSD skin should be assessed for KIT mutations. Imatinib can be effective when tumors harbor KIT mutations, but not if KIT is amplified only. NRAS mutations and KIT copy number gain may be mechanisms of therapeutic resistance to imatinib.
Project description:Recent evidence suggests that the biology of noncutaneous melanoma differs significantly from cutaneous melanoma and may provide therapeutic opportunity. The most frequent sites of origin of noncutaneous melanoma are the eye and mucosal surfaces. Although noncutaneous melanomas are an uncommon group of cancers (representing less than 10% of all melanomas) a greater understanding of their genetic and molecular abnormalites is being translated into novel treatment strategies. These developments are important because there is currently no effective systemic therapy for noncutaneous melanoma. Significant attention has been focused on the role of c-kit (KIT, CD117), a transmembrane receptor with tyrosine kinase activity. In vitro and ex vivo evidence suggests that c-kit is frequently expressed/over expressed/mutated in noncutaneous melanoma. Anti-tumour effects with c-kit inhibitors are seen in pre-clinical models. A variety of multitargeted kinase inhibitors which have activity against c-kit are currently in early phase clinical trials in metastatic ocular, mucosal and acral melanoma. The few case reports of significant clinical activity with targeted therapies provides hope that greater understanding of the biology of noncutaneous melanoma can be translated into effective treatment.
Project description:Point mutations in the KIT receptor tyrosine kinase gene have recently been identified in mucosal, acral lentiginous, and chronically sun-damaged melanomas. We have identified the first human melanoma cell line with an endogenous L576P mutation, the most common KIT mutation in melanoma ( approximately 30-40%). In vitro testing showed that the cell viability of the L576P mutant cell line was not reduced by imatinib, nilotinib, or sorafenib small molecule KIT inhibitors effective in nonmelanoma cells with other KIT mutations. However, the viability of the mutant cells was reduced by dasatinib at concentrations as low as 10 nM (P = 0.004). Molecular modeling studies found that the L576P mutation induces structural changes in KIT that reduce the affinity for imatinib (DeltaDeltaGbind = -2.52 kcal/mol) but not for dasatinib (DeltaDeltaGbind = +0.32 kcal/mol). Two metastatic melanoma patients with the L576P KIT mutation were treated with dasatinib, including one patient previously treated with imatinib. Both patients had marked reduction (>50%) and elimination of tumor F18-fluorodeoxyglucose (FDG)-avidity by positron emission tomography (PET) imaging after dasatinib treatment. These data support the selective inhibitory effect of dasatinib against cells harboring the most common KIT mutation in melanoma, and thus has therapeutic implications for acrallentiginous, chronic sun-damaged, and mucosal melanomas.
Project description:BACKGROUND:Preoperative imatinib mesylate therapy for gastrointestinal stromal tumors (GISTs) is controversial. This study aimed to explore the clinical efficacy and optimal duration of preoperative imatinib mesylate (IM) therapy in patients with locally advanced and recurrent/metastatic GISTs. METHODS:We retrospectively examined patients who received preoperative imatinib mesylate therapy from January 2013 to December 2018 at Xiangya Hospital, Central South University and the Second Xiangya Hospital of Central South University, China. Clinical data, including the results of tests for mutations in KIT and PDGFR, findings from regularly conducted re-examinations, abdominal-enhanced computed tomography/magnetic resonance imaging data, responses to imatinib, progression-free survival, and overall cancer-specific survival, were recorded. RESULTS:A total of 25 patients were enrolled in our study, including 18 with a locally advanced GIST and 7 with recurrent or metastatic GISTs. Their ages ranged from 22 to 70?years (M:F = 1.6:0.9), with a mean age of 50.48 ± 12.51?years. The tumor locations included the stomach (56.0%), rectum (16.0%), enterocoelic/retroperitoneal sites (12.0%), and the small intestine (12.0%). Based on testing for mutations in KIT and PDGFR, 22 patients received 400?mg/day KIT, and 3 patients received 600?mg/day PDGFR. The median duration of preoperative IM therapy was 8.96 ± 4.81?months, ranging from 3 to 26?months. According to the Choi criteria, 24 patients achieved a partial response (PR), and 1 patient had stable disease (SD). All patients underwent surgery after preoperative IM therapy, and no postoperative complications appeared. The 2-year PFS and 5-year PFS were 92% and 60%, respectively, and the total 5-year cancer-specific survival (CSS) was 92%. CONCLUSION:Preoperative imatinib therapy is feasible for locally advanced and recurrent/metastatic GISTs and can effectively shrink the tumor size, allow organ sparing, and avoid extensive organ resection. Moreover, the optimal duration of preoperative IM therapy in patients with locally advanced and recurrent/metastatic GISTs was 8.96 ± 4.81?months, ranging from 3 to 26?months, and gastric GISTs had a better response to preoperative IM therapy than did non-gastric GISTs.
Project description:BACKGROUND:The application of precision medicine in oncology requires in-depth characterisation of a patient's tumours and the dynamics of their responses to treatment. PATIENTS AND METHODS:We used next-generation sequencing of circulating cell-free DNA (cfDNA) to monitor the response of a KIT p.L576P-mutant metastatic vaginal mucosal melanoma to sequential targeted, immuno- and chemotherapy. RESULTS:Despite a KIT mutation, the response to imatinib was mixed. Unfortunately, tumours were not accessible for molecular analysis. To study the mechanism underlying the mixed clinical response, we carried out whole-exome sequencing and targeted longitudinal analysis of cfDNA. This revealed two tumour subclones; one with a KIT mutation that responded to imatinib and a second KIT-wild-type subclone that did not respond to imatinib. Notably, the subclones also responded differently to immunotherapy. However, both subclones responded to carboplatin/paclitaxel, and although the KIT-wild-type subclone progressed after chemotherapy, it responded to subsequent re-administration of paclitaxel. CONCLUSION:We show that cfDNA can reveal tumour evolution and subclonal responses to therapy even when biopsies are not available.
Project description:c-Kit mutations are frequently detected in mucosal melanomas, but their clinical significance in metastatic oral mucosal melanomas (OMM) remains unclear. The main purpose of this study was to investigate the clinical and pathological features of metastatic OMMs with c-Kit mutations and the efficiency of the tyrosine kinase inhibitor imatinib in treating metastatic OMMs. We found thatresidual primary lesion and neck lymph nodes could act as independent prognostic factors in metastatic OMM patients. c-Kit mutations were detected in 22 out of 139 (15.8%) metastatic OMM patients. Under chemotherapy, the overall survival (OS) of c-Kit mutant patients was significantly shorter than that of wild-type patients. The Ki67 expression was significantly higher in c-Kit mutant patients than in wild-type patients. In distant metastatic OMM patients with c-Kit mutations, the treatment with c-Kit inhibitor resulted in a better OS. In conclusion, residual primary lesion, cervical lymph nodes and c-Kit mutations act as adverse prognostic factors of metastatic OMMs. The Kit inhibitor imatinib could benefit metastatic OMM patients with c-Kit mutations.
Project description:Protein kinase inhibitors can be effective in treating selected cancers, but most suppress several kinases. Imatinib mesylate has been useful in the treatment of Philadelphia chromosome-positive chronic myelogenous leukemia and B cell acute lymphoblastic leukemia through the inhibition of BCR-ABL tyrosine kinase activity. Imatinib mesylate has also been shown to inhibit KIT, ARG, and platelet-derived growth factor receptors alpha and beta, and potentially other tyrosine kinases. We have produced a mutant allele of BCR-ABL (T315A) that is uniquely inhibitable by the small molecule 4-amino-1-tert-butyl-3-(1-naphthyl)pyrazolo[3,4-d]pyrimidine and used it to demonstrate that sole suppression of BCR-ABL activity was insufficient to eliminate BCR-ABL(+) KIT(+)-expressing immature murine myeloid leukemic cells. In contrast, imatinib mesylate effectively eliminated BCR-ABL(+) KIT(+)-expressing leukemic cells. In the cellular context of mature myeloid cells and Pro/Pre B cells that do not express KIT, monospecific BCR-ABL inhibition was quantitatively as effective as imatinib mesylate in suppressing cell growth and inducing apoptosis. These results suggest that the therapeutic effectiveness of small molecule drugs such as imatinib mesylate could be due to the inhibitor's ability to suppress protein kinases in addition to the dominant target.
Project description:Mucosal melanomas are a rare subtype of melanoma, arising in mucosal tissues, which have a very poor prognosis due to the lack of effective targeted therapies. This study aimed to better understand the molecular landscape of these cancers and find potential new therapeutic targets. Whole-exome sequencing was performed on mucosal melanomas from 19 patients and 135 sun-exposed cutaneous melanomas, with matched peripheral blood samples when available. Mutational profiles were compared between mucosal subgroups and sun-exposed cutaneous melanomas. Comparisons of molecular profiles identified 161 genes enriched in mucosal melanoma (P<0.05). KIT and NF1 were frequently comutated (32%) in the mucosal subgroup, with a significantly higher incidence than that in cutaneous melanoma (4%). Recurrent SF3B1 R625H/S/C mutations were identified and validated in 7 of 19 (37%) mucosal melanoma patients. Mutations in the spliceosome pathway were found to be enriched in mucosal melanomas when compared with cutaneous melanomas. Alternative splicing in four genes were observed in SF3B1-mutant samples compared with the wild-type samples. This study identified potential new therapeutic targets for mucosal melanoma, including comutation of NF1 and KIT, and recurrent R625 mutations in SF3B1. This is the first report of SF3B1 R625 mutations in vulvovaginal mucosal melanoma, with the largest whole-exome sequencing project of mucosal melanomas to date. The results here also indicated that the mutations in SF3B1 lead to alternative splicing in multiple genes. These findings expand our knowledge of this rare disease.
Project description:Mucosal melanoma represents ~1% of all melanomas, frequently having a poor prognosis due to diagnosis at a late stage of disease. Mucosal melanoma differs from cutaneous melanoma not only in terms of poorer clinical outcome but also on the molecular level having e.g. less BRAF and more frequent KIT mutations than cutaneous melanomas. For the majority of mucosal melanomas oncogenic driver mutations remain unknown.In our study, 75 tumor tissues from patients diagnosed with mucosal melanoma were analyzed, applying a targeted next generation sequencing panel covering 29 known recurrently mutated genes in melanoma. NF1 and RAS mutations were identified as the most frequently mutated genes occurring in 18.3% and 16.9% of samples, respectively. Mutations in BRAF were identified in 8.4% and KIT in 7.0% of tumor samples.Our study identifies NF1 as the most frequently occurring driver mutation in mucosal melanoma. RAS alterations, consisting of NRAS and KRAS mutations, were the second most frequent mutation type. BRAF and KIT mutations were rare with frequencies below 10% each. Our data indicate that in mucosal melanomas RAS/NF1 alterations are frequent, implying a significant pathogenetic role for MAPK and potentially PI3K pathway activation in these tumors.