Person:

Oxnard, Geoffrey

PD-1 immune checkpoint blockade occasionally results in durable clinical responses in advanced metastatic cancers. However, mechanism-based predictors of response to this immunotherapy remain incompletely characterized. We performed comprehensive genomic profiling on a tumor and germline sample from a patient with refractory lung adenocarcinoma who achieved marked long-term clinical benefit from anti-PD-L1 therapy. We discovered activating somatic and germline amino acid variants in JAK3 that promoted PD-L1 induction in lung cancer cells and in the tumor immune microenvironment. These findings suggest that genomic alterations that deregulate cytokine receptor signal transduction could contribute to PD-L1 activation and engagement of the PD-1 immune checkpoint in lung cancer.

Purpose Non–small-cell lung cancers (NSCLCs) harboring mutations in MET exon 14 and its flanking introns may respond to c-Met inhibitors. We sought to describe the clinical, pathologic, and genomic characteristics of patients with cancer with MET exon 14 mutations.

Patients and Methods We interrogated next-generation sequencing results from 6,376 cancers to identify those harboring MET exon 14 mutations. Clinical characteristics of MET exon 14 mutated NSCLCs were compared with those of NSCLCs with activating mutations in KRAS and EGFR. Co-occurring genomic mutations and copy number alterations were identified. c-Met immunohistochemistry and real-time polymerase chain reaction to detect exon 14 skipping were performed where sufficient tissue was available.

Results MET exon 14 mutations were identified in 28 of 933 nonsquamous NSCLCs (3.0%) and were not seen in other cancer types in this study. Patients with MET exon 14–mutated NSCLC were significantly older (median age, 72.5 years) than patients with EGFR-mutant (median age, 61 years; P < .001) or KRAS-mutant NSCLC (median age, 65 years; P < .001). Among patients with MET exon 14 mutations, 68% were women, and 36% were never-smokers. Stage IV MET exon 14–mutated NSCLCs were significantly more likely to have concurrent MET genomic amplification (mean ratio of MET to chromosome 7, 4.3) and strong c-Met immunohistochemical expression (mean H score, 253) than stage IA to IIIB MET exon 14–mutated NSCLCs (mean ratio of MET to chromosome 7, 1.4; P = .007; mean H score, 155; P = .002) and stage IV MET exon 14–wild-type NSCLCs (mean ratio of MET to chromosome 7, 1.2; P < .001; mean H score, 142; P < .001). A patient whose lung cancer harbored a MET exon 14 mutation with concurrent genomic amplification of the mutated MET allele experienced a major partial response to the c-Met inhibitor crizotinib.

Conclusion MET exon 14 mutations represent a clinically unique molecular subtype of NSCLC. Prospective clinical trials with c-Met inhibitors will be necessary to validate MET exon 14 mutations as an important therapeutic target in NSCLC.

The increased importance of cancer genotyping in guiding cancer treatment has created a need for efficient methods for genomic analysis of patients’ cancers. This increased dependence on DNA-based tumor genotyping assays (eg, sequencing, polymerase chain reaction [PCR], fluorescence in situ hybridization [FISH]) has triggered a growing interest in the analysis of free-floating DNA present in the blood of patients with cancer—plasma cell-free DNA (cfDNA). Sensitive PCR techniques together with high-throughput next-generation sequencing (NGS) technologies have evolved to a point where genetic analysis of cfDNA is possible.