Whole exome sequencing identifies a germline MET mutation in two siblings with hereditary wild-type RET medullary thyroid cancer

Whole exome sequencing (WES) was used to investigate two Italian siblings with wild-type RET genotype, who developed medullary thyroid cancers (MTCs) and, later, primary prostate and breast cancers, respectively. The proband's MTC harbored a p.Met918Thr RET mutation; his sister's MTC was RET/RAS wild-type. Both siblings had a germline mutation (p.Arg417Gln) in the extracellular Sema domain of the proto-oncogene MET. Experiments involving ectopic expression of MET p.Arg417Gln in MET-negative T47D breast cancer cells documented the mutant receptor's functionality and its ability to enhance cell migration and invasion. Our findings highlight a possible link between MET germline mutations and MTCs and suggest that MET p. Arg417Gln may promote an invasive malignant phenotype. The possibility that MTC can be driven/co-driven by a MET mutation has potential management implications, since the tyrosine-kinase inhibitor cabozantinib-approved for treating advanced MTCs-is a specific MET inhibitor.

The value of genetic screening in medullary thyroid cancer

Medullary thyroid cancer (MTC) accounts for ~10% of thyroid carcinomas and occurs in sporadic and hereditary forms. Early diagnosis significantly impacts the clinical course, management and outcome of the disease. The identification of germline-activating mutations of the rearranged during transfection oncogene in patients with hereditary MTC led to significant progress in the diagnostic and therapeutic approach, thus improving the quality of care provided, and consequently, disease prognosis. In the present review, various aspects of genetic screening (GS) in MTC will be covered, which elucidate the value of GS in guiding clinical decision making, therapy selection and appropriate genetic counseling of the affected families. GS should be offered to every MTC patient, based on the personal and family medical history, to allow optimal clinical management and follow-up.