Activating MET Mutation

Abstract: Objective Germline mutations of either the endothelial cell-specific tyrosine kinase receptor TIE2 or the glomulin (GLMN) gene are responsible for rare inherited venous malformations. Both genes affect the hepatocyte growth factor receptor c-Met, inducing vascular smooth muscle cell migration. Germline mutations of hepatocyte growth factor are responsible for lymphatic malformations, leading to lymphedema. The molecular alteration leading to the abnormal mixed vascular anomaly defined as lymphovenous malformation has remained unknown. Methods A group of 4 patients with lymphovenous malformations were selected. Plasma was obtained from both peripheral and efferent vein samples at the vascular malformation site for cell-free DNA extraction. When possible, we analyzed tissue biopsy samples from the vascular lesion. Results We have demonstrated that in all four patients, an activating MET mutation was present. In three of the four patients, the same pathogenic activating mutation, T1010I, was identified. The mutation was found at the tissue level for the patient with tissue samples available, confirming its causative role in the lymphovenous malformations. Conclusions In the present study, we have demonstrated that cell-free DNA next generation sequencing liquid biopsy is able to identify the MET mutations in affected tissues. Although a wider cohort of patients is necessary to confirm its causative role in lymphovenous malformations, these data suggest that lymphovenous malformations could result from postzygotic somatic mutations in genes that are key regulators of lymphatic development. The noninvasiveness of the method avoids any risk of bleeding and can be easily performed in children. We are confident that the present pioneering results have provided a viable alternative in the future for lymphovenous malformation diagnosis, allowing for subsequent therapy tailored to the genetic defect.

Abstract: Identification of effective targeted therapies for recurrent/metastatic head and neck squamous cell carcinoma (HNSCC) remains an unmet medical need. A patient with platinum-refractory recurrent oral cavity HNSCC underwent comprehensive genomic profiling (CGP) that identified an activating MET mutation (R1004). The patient was treated with the oral MET tyrosine kinase inhibitor crizotinib with rapid response to treatment.Based on this index case, we determined the frequency of MET alterations in 1,637 HNSCC samples, which had been analyzed with hybrid capture-based CGP performed in the routine course of clinical care. The specimens were sequenced to a median depth of >500× for all coding exons from 182 (version 1, n = 24), 236 (version 2, n = 326), or 315 (version 3, n = 1,287) cancer-related genes, plus select introns from 14 (version 1), 19 (version 2), or 28 (version 3) genes frequently rearranged in cancer. We identified 13 HNSCC cases (0.79%) with MET alterations (4 point mutation events and 9 focal amplification events). MET-mutant or amplified tumors represent a small but potentially actionable molecular subset of HNSCC. KEY POINTS: This case report is believed to be the first reported pan-cancer case of a patient harboring a MET mutation at R1004 demonstrating a clinical response to crizotinib, in addition to the first documented case of head and neck squamous cell carcinoma (HNSCC) with any MET alteration responding to crizotinib.The positive response to MET inhibition in this patient highlights the significance of comprehensive genomic profiling in advanced metastatic HNSCC to identify actionable targetable molecular alterations as current treatment options are limited.

Abstract: Purpose: The genesis of all cancers results from an accumulation of mutations, constitutional and/or acquired when induced by external mutagenic factors. High-speed technologies for genome sequencing have completely changed the study of disease genetics, but with limited knowledge of the functional value of most genetic changes. Experimental Design: Here, we proposed an innovative individual approach by studying tissue samples from a young woman with an unusual association of breast cancer, polycythemia vera and rheumatoid arthritis. We performed genomic analyses for copy number variations and point mutations on laser-microdissected tumor cells from the breast cancer, and on CD34+ cells sorted from bone-marrow aspiration, to identify gene abnormalities common to these two types of cell populations. Results: Using ONCOSCAN technology, we identified a constitutional pR988C, c2962C>T mutation of MET. Using CRISPR-Cas9 technology, we established pR988C MET-mutated transgenic mice which reproduced the auto-immune diseases and myeloproliferation found in our index-case; one of the transgenic mice spontaneously developed a skin squamous cell carcinoma. We also showed that additional mutagenic factors were required to induce cancers, including skin squamous cell carcinoma and thyroid cancer. Using an anti-MET drug, cabozantinib, we demonstrated for the first time the functional role of this mutation in the maintenance of myeloproliferation and rheumatoid arthritis, and in cancer genesis. Conclusions: Our study opens a considerable field of application in the domain of constitutional genetics, to establish genetic links between cancers and other very different severe diseases.