RESUMO
PURPOSE: The KIT inhibitor, imatinib, has shown promising efficacy in patients with KIT-mutated melanoma; however, acquisition of resistance to imatinib occurs rapidly in the majority of patients. The mechanisms of acquired resistance to imatinib in melanoma remain unclear. METHODS: We analyzed biopsy samples from paired baseline and post-treatment tumor lesions in one patient with KIT-mutated melanoma who had had an initial objective tumor regression in response to imatinib treatment followed by disease progression 8 months later. RESULTS: Targeted deep sequencing from post-treatment biopsy samples detected an additional mutation in CTNNB1 (S33C) with original KIT L576P mutation. We examined the functional role of the additional CTNNB1 S33C mutation in resistance to imatinib indirectly using the Ba/F3 cell model. Ba/F3 cell lines transfected with both the L576P KIT mutation and the CTNNB1 S33C mutation demonstrated no growth inhibition despite imatinib treatment, whereas growth inhibition was observed in the Ba/F3 cell line transfected with the L576 KIT mutation alone. CONCLUSIONS: We report the first identification of the emergence of a CTNNB1 mutation that can confer acquired resistance to imatinib. Further investigation into the causes of acquired resistance to imatinib will be essential to improve the prognosis for patients with KIT-mutated melanoma.
Assuntos
Resistencia a Medicamentos Antineoplásicos/genética , Mesilato de Imatinib/farmacologia , Neoplasias Pulmonares/genética , Melanoma/genética , Mutação , Neoplasias Cutâneas/genética , beta Catenina/genética , Proliferação de Células/efeitos dos fármacos , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/secundário , Masculino , Melanoma/tratamento farmacológico , Melanoma/patologia , Pessoa de Meia-Idade , Prognóstico , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-kit , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/secundário , Células Tumorais CultivadasRESUMO
INTRODUCTION: Molecular targets are emerging rapidly and the development of clinical tests that simultaneously screen for multiple targets has become especially important. We assessed the gene expression levels of three known targets in advanced gastric cancer, epidermal growth factor receptor (EGFR), human epidermal growth factor 2 (HER2), and N-methyl-N-nitrosoguanidine human osteosarcoma transforming gene (MET), using the nCounter® assay (NanoString Technologies, Seattle, WA, USA) and compared these results with protein overexpression, detected by immunohistochemistry, to evaluate the performance of this new technology. METHODS: We investigated 42 formalin-fixed, paraffin-embedded tumor samples from patients with gastric cancer. A NanoString-based assay containing a 522 kinase gene panel was investigated. We analyzed the correlations between immunohistochemical findings and kinase gene expression levels of EGFR, HER2 and MET to validate this assay. RESULTS: EGFR, HER2, and MET overexpression were observed in 7 (16.6 %), 5 (11.9 %), and 3 (7.1 %) cases, respectively. For EGFR, HER2, and MET, the concordance rates between the NanoString-based assay results and the immunohistochemistry methods were 83.3, 97.6, and 100 %, respectively. Relative to immunohistochemistry findings, the NanoString-based assay sensitivities and specificities were 85.7 and 82.8 % for EGFR, 100 and 97.2 % for HER2, and 100 and 100 % for MET, respectively. CONCLUSIONS: We found a high concordance between immunohistochemistry- and nCounter-based assessments of EGFR, HER2, and MET in advanced gastric cancer. Judged against immunohistochemistry results, the NanoString assay had high sensitivities and high specificities. These results suggest that the nCounter assay provides a reliable, high-throughput assay to simultaneously screen for the overexpression of several target proteins.