Targeted DNA- and RNA-based next-generation sequencing for identifying MET exon 14 alterations in pulmonary sarcomatoid carcinoma.

Abstract

e20591 Background:Highly diverse somatic splice site alteration at MET exon 14 ( METex14) result in exon skipping, which is supposed to be a therapeutic target in NSCLC. Here we report detection of METex14 alterations using targeted DNA- and RNA-based Next-Generation Sequencing (NGS) in pulmonary sarcomatoid carcinoma (PSC) with a high frequency of METex14 skipping. Methods: Tumor specimens were collected from 100 Chinese PSC patients. DNA and RNA were subject to targeted NGS, allowing the detection of somatic splice site alterations and intragenic METex14 skipping respectively. Then, somatic mutations that lead to METex14 skipping were recognized. Meanwhile, cross-platform performance comparison for detecting MET exon 14 skipping was achieved. Moreover, Sanger sequencing was also performed on the METex14-positive specimens. Results: So far, we have detected genetic aberrations in 34 FFPE samples. For RNA-based NGS, METex14 skipping was identified in 8 (23.5%) of 34 patient cases. The population frequency was accordant to the reported percent of 22% (PMID: 26215952). And 5 (62.5%) of 8 METex14-positive patients were detected somatic splice site mutations by DNA-based NGS, including 4 cases with known point mutations at the 3’ splice region and one case with a novel deletion (chr7: 116412027- 116412042) at MET exon14 region, which is newly discovered. No somatic mutation was found at the splice junctions of METex14 in the remaining 3 samples using DNA-based NGS. Conclusions: Mutational events of MET leading to exon 14 skipping are frequent occurred in Chinese PSC patients. Our study also suggests that RNA-based NGS could identify more METex14 skipping, and thus provide more accurate results than DNA-based NGS.