BRCA1-associated protein 1 (BAP1) regulates calcium flux in the endoplasmic reticulum to facilitate the execution of apoptosis, unveiling a new facet of the role of BAP1 as an environmental tumour suppressor. BAP1 is a tumour suppressor associated with germline mutations in several malignancies including uveal melanoma and mesothelioma. BAP1 tumour suppressor activity has previously been linked to its nuclear role in maintaining genome integrity. Here, the authors reveal a new role for BAP1 in the endoplasmic reticulum, where it regulates calcium flux to facilitate the execution of apoptosis. Loss of BAP1 function prevents apoptosis in transformed cells with accumulated DNA damage. The results unveil a new facet of the role of BAP1 as an environmental tumour suppressor. BRCA1-associated protein 1 (BAP1) is a potent tumour suppressor gene that modulates environmental carcinogenesis1,2,3. All carriers of inherited heterozygous germline BAP1-inactivating mutations (BAP1+/−) developed one and often several BAP1−/− malignancies in their lifetime4, mostly malignant mesothelioma, uveal melanoma2,5, and so on6,7,8,9,10. Moreover, BAP1-acquired biallelic mutations are frequent in human cancers8,11,12,13,14. BAP1 tumour suppressor activity has been attributed to its nuclear localization, where it helps to maintain genome integrity15,16,17. The possible activity of BAP1 in the cytoplasm is unknown. Cells with reduced levels of BAP1 exhibit chromosomal abnormalities and decreased DNA repair by homologous recombination18, indicating that BAP1 dosage is critical. Cells with extensive DNA damage should die and not grow into malignancies. Here we discover that BAP1 localizes at the endoplasmic reticulum. Here, it binds, deubiquitylates, and stabilizes type 3 inositol-1,4,5-trisphosphate receptor (IP3R3), modulating calcium (Ca2+) release from the endoplasmic reticulum into the cytosol and mitochondria, promoting apoptosis. Reduced levels of BAP1 in BAP1+/− carriers cause reduction both of IP3R3 levels and of Ca2+ flux, preventing BAP1+/− cells that accumulate DNA damage from executing apoptosis. A higher fraction of cells exposed to either ionizing or ultraviolet radiation, or to asbestos, survive genotoxic stress, resulting in a higher rate of cellular transformation. We propose that the high incidence of cancers in BAP1+/− carriers results from the combined reduced nuclear and cytoplasmic activities of BAP1. Our data provide a mechanistic rationale for the powerful ability of BAP1 to regulate gene–environment interaction in human carcinogenesis.

BRCA1–associated protein 1 (BAP1) is a tumor suppressor gene located on chromosome 3p21. Germline BAP1 mutations have been recently associated with an increased risk of malignant mesothelioma, atypical melanocytic tumors and other neoplasms. To answer the question if different germline BAP1 mutations may predispose to a single syndrome with a wide phenotypic range or to distinct syndromes, we investigated the presence of melanocytic tumors in two unrelated families (L and W) with germline BAP1 mutations and increased risk of malignant mesothelioma.

In a large number of cancer types, treatment selection depends on the presence of specific tumor biomarkers. Due to the dynamic nature of cancer, very often these predictive biomarkers are not uniformly present in all cancer cells. Tumor heterogeneity represents indeed one of the main causes of therapeutic failure, and its decoding remains a major ongoing challenge in the field.Liquid biopsy is the sampling and analysis of non-solid biological tissue often through rapid and non-invasive methods, which allows the assessment in real-time of the evolving landscape of cancer. Samples can be obtained from blood and most other bodily fluids. A blood-based liquid biopsy can capture circulating tumor cells and leukocytes, as well as circulating tumor-derived nucleic acids.In this review, we discuss the current and possibly future applications of blood-based liquid biopsy in oncology, its advantages and its limitations in clinical practice. We specifically focused on its role as a tool to capture tumor heterogeneity in metastatic cancer patients.

BRCA1-associated protein-1 (BAP1) mutations cause a new cancer syndrome, with a high rate of malignant mesothelioma (MM). Here, we tested the hypothesis that MM associated with germline BAP1 mutations has a better prognosis compared with sporadic MM. We compared survival among germline BAP1 mutation MM patients with that of all MM (N = 10 556) recorded in the United States Surveillance, Epidemiology, and End Results (SEER) data from 1973 to 2010. We identified 23 MM patients—11 alive—with germline BAP1 mutations and available data on survival. Ten patients had peritoneal MM, ten pleural MM and three MM in both locations. Thirteen patients had one or more malignancies in addition to MM. Actuarial median survival for the MM patients with germline BAP1 mutations was 5 years, as compared with <1 year for the median survival in the United States SEER MM group. Five-year survival was 47%, 95% confidence interval (24–67%), as compared with 6.7% (6.2–7.3%) in the control SEER group. Analysis of the pooled cohort of germline BAP1 mutation MM showed that patients with peritoneal MM (median survival of 10 years, P = 0.0571), or with a second malignancy in addition to MM (median survival of 10 years, P = 0.0716), survived for a longer time compared with patients who only had pleural MM, or MM patients without a second malignancy, respectively. In conclusion, we found that MM patients with germline BAP1 mutations have an overall 7-fold increased long-term survival, independently of sex and age. Appropriate genetic counseling and clinical management should be considered for MM patients who are also BAP1 mutation carriers.

Significance: We found that gene mutations/deletions are frequent in mesothelioma and occur through a variety of DNA alterations. We identified genes implicated in malignant mesothelioma:SETD2,SMARCC1,PBRM1. Previous next-generation studies (NGS) underestimated the frequency of genetic alterations in malignant mesothelioma because NGS mainly identifies nucleotide level mutations. Our findings are of general relevance to the field of cancer research that relies almost exclusively on NGS to identify gene alterations in cancer biopsies, and uses this information to design specific molecular therapies. An integrated approach that includes a high-density comparative genomic hybridization array and NGS or targeted-NGS, as conducted here, may reveal additional genes that are inactivated by mechanisms other than point mutations. This information may inform us on how to design more effective molecular therapies.