Frequent mutations in MLH1, MET, KIT, PDGFRA, and PIK3CA genes in human gastrointestinal stromal tumors.

Abstract

10544 Background: Identifying mutations in individual tumor is critical to improve the efficacy of cancer therapy by matching targeted drugs to specific mutations. Gastrointestinal stromal tumor (GIST) is a stromal or mesenchymal subepithelial neoplasm affecting the gastrointestinal tract and it frequently contains an activating mutation in either the KIT or platelet-derived growth factor A (PDGFRA) gene. Although GIST is highly responsive to several selective tyrosine kinase inhibitors, combined use of inhibitors targeting other mutations is needed to further prolong survival. Methods: In this study, we aim to screen and identify genetic mutations in GIST for targeted therapy using the new Ion Torrent next-generation sequencing platform. Results: By utilizing the Ion Ampliseq Cancer Panel, we sequenced 737 loci from 45 cancer-related genes from DNA extracted from formalin-fixed and paraffin-embedded (FFPE) samples of 125 human gastrointestinal stromal tumors, set up stringent parameters for reliable variant calling by filtering out potential raw base calling errors, and identified frequent mutations in PDGFRA, KIT, APC, MLH1, MET, RET, and PIK3CA. Moreover, frequent missense mutations were detected in MLH1 (12%), MET (16.8%), KIT (51.2%), and PIK3CA (41.6%) genes. The mutations in MLH1 gene were frequently detected in the exon 14, while MET gene was frequently mutated in the exon 2. In addition, we identified missense mutations in other genes, including FLT3, KRAS, PDGFRA, and STK11, at lower frequencies. Conclusions: This study demonstrates the utility of using Ion Torrent sequencing to efficiently identify human cancer mutations. With the finding of the frequent mutations in MLH1 and MET genes, in addition to KIT, PDGFRA and PIK3CA, in GISTs, this study provides a molecular basis for clinically developing new drugs targeting these gene mutations for GIST therapy.