A constitutional activating MET mutation makes the genetic link between malignancies and chronic inflammatory diseases.

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 thorn 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 transgenicmice, which reproduced the autoimmune 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 ofmyeloproliferation 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.