The development of targeted inhibitors, like vemurafenib, has greatly improved the clinical outcome of BRAFV600E metastatic melanoma.,However, resistance to such compounds represents a formidable problem.,Using whole-exome sequencing and functional analyses, we have investigated the nature and pleiotropy of vemurafenib resistance in a melanoma patient carrying multiple drug-resistant metastases.,Resistance was caused by a plethora of mechanisms, all of which reactivated the MAPK pathway.,In addition to three independent amplifications and an aberrant form of BRAFV600E, we identified a new activating insertion in MEK1.,This MEK1T55delinsRT mutation could be traced back to a fraction of the pre-treatment lesion and not only provided protection against vemurafenib but also promoted local invasion of transplanted melanomas.,Analysis of patient-derived xenografts (PDX) from therapy-refractory metastases revealed that multiple resistance mechanisms were present within one metastasis.,This heterogeneity, both inter- and intra-tumorally, caused an incomplete capture in the PDX of the resistance mechanisms observed in the patient.,In conclusion, vemurafenib resistance in a single patient can be established through distinct events, which may be preexisting.,Furthermore, our results indicate that PDX may not harbor the full genetic heterogeneity seen in the patient’s melanoma.
Because only a small fraction of asbestos-exposed individuals develop malignant mesothelioma1, and because mesothelioma clustering is observed in some families1, we searched for genetic predisposing factors.,We discovered germline mutations in BAP1 (BRCA1-associated protein 1) in two families with a high incidence of mesothelioma.,Somatic alterations affecting BAP1 were observed in familial mesotheliomas, indicating biallelic inactivation.,Besides mesothelioma, some BAP1 mutation carriers developed uveal melanoma.,Germline BAP1 mutations were also found in two of 26 sporadic mesotheliomas: both patients with mutant BAP1 were previously diagnosed with uveal melanoma.,Truncating mutations and aberrant BAP1 expression were common in sporadic mesotheliomas without germline mutations.,These results reveal a BAP1-related cancer syndrome characterized by mesothelioma and uveal melanoma.,We hypothesize that other cancers may also be involved, and that mesothelioma predominates upon asbestos exposure.,These findings will help identify individuals at high risk of mesothelioma who could be targeted for early intervention.