BAP1 is a novel regulator of HIF-1α.

BAP1 is a powerful tumor suppressor gene characterized by haplo insufficiency. Individuals carrying germline BAP1 mutations often develop mesothelioma, an aggressive malignancy of the serosal layers covering the lungs, pericardium, and abdominal cavity. Intriguingly, mesotheliomas developing in carriers of germline BAP1 mutations are less aggressive, and these patients have significantly improved survival. We investigated the apparent paradox of a tumor suppressor gene that, when mutated, causes less aggressive mesotheliomas. We discovered that mesothelioma biopsies with biallelic BAP1 mutations showed loss of nuclear HIF-1α staining. We demonstrated that during hypoxia, BAP1 binds, deubiquitylates, and stabilizes HIF-1α, the master regulator of the hypoxia response and tumor cell invasion. Moreover, primary cells from individuals carrying germline BAP1 mutations and primary cells in which BAP1 was silenced using siRNA had reduced HIF-1α protein levels in hypoxia. Computational modeling and co-immunoprecipitation experiments revealed that mutations of BAP1 residues I675, F678, I679, and L691 -encompassing the C-terminal domain-nuclear localization signal- to A, abolished the interaction with HIF-1α. We found that BAP1 binds to the N-terminal region of HIF-1α, where HIF-1α binds DNA and dimerizes with HIF-1ß forming the heterodimeric transactivating complex HIF. Our data identify BAP1 as a key positive regulator of HIF-1α in hypoxia. We propose that the significant reduction of HIF-1α activity in mesothelioma cells carrying biallelic BAP1 mutations, accompanied by the significant reduction of HIF-1α activity in hypoxic tissues containing germline BAP1 mutations, contributes to the reduced aggressiveness and improved survival of mesotheliomas developing in carriers of germline BAP1 mutations.

Trabectedin use in soft-tissue sarcoma patients in a real-world setting: Data from an Italian national drug-access registry.

Trabectedin is a marine-derived anticancer drug approved for the treatment of patients with advanced soft-tissue sarcomas (STS). Here, we aimed to analyze its use in a large cohort of STS patients treated in Italy in a real-world setting. Data on STS patients treated with trabectedin in Italy were prospectively collected from January 2013 to December 2019 by the national drug regulator, the Italian Medicines Agency (AIFA). Time-to-off-treatment (TToT) was defined as the time between the initial prescription of trabectedin and the date of treatment discontinuation for any cause. The impact of the different baseline covariates, including the initial prescribed dose of trabectedin, on TToT was evaluated using an accelerated failure time (AFT) models with log-logistic distribution. In total, we analyzed data from 2633 sarcoma patients and 14 950 individual cycles of trabectedin. The median number of cycles of trabectedin received per patient was 3 (interquartile range 2-7). The labeled 1.5 mg/sqm dose was used in 27.3% of all first prescriptions. Overall, the median TToT was 93 days. In the final AFT model, the variables significantly associated to longer TToT were female gender (+13% increase in TToT); ECOG performance status 0 (+50%); histological diagnosis of leiomyosarcoma (+22%), well-differentiated/dedifferentiated liposarcoma (+72%) or myxoid liposarcoma (+61%); receiving treatment in a high-volume center (+23%). In this large real-world cohort of STS patients treated with trabectedin, our findings support the use of trabectedin in STS patients, in particular in leiomyosarcoma and liposarcoma patients, and highlight the role of treatment center volume in their management.

BAP1 regulates IP3R3-mediated Ca2+ flux to mitochondria suppressing cell transformation.

BRCA1-associated protein 1 (BAP1) is a potent tumour suppressor gene that modulates environmental carcinogenesis. All carriers of inherited heterozygous germline BAP1-inactivating mutations (BAP1+/-) developed one and often several BAP1-/- malignancies in their lifetime, mostly malignant mesothelioma, uveal melanoma, and so on. Moreover, BAP1-acquired biallelic mutations are frequent in human cancers. BAP1 tumour suppressor activity has been attributed to its nuclear localization, where it helps to maintain genome integrity. 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 recombination, 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.

Validation of a novel risk score to predict early and late recurrence in solitary fibrous tumour.

BACKGROUND: Current risk models in solitary fibrous tumour (SFT) were developed using cohorts with short follow-up and cannot reliably identify low-risk patients. We recently developed a novel risk model (G-score) to account for both early and late recurrences. Here, we aimed to validate the G-score in a large international cohort with long-term follow-up. METHODS: Data were collected from nine sarcoma referral centres worldwide. Recurrence-free interval (RFi) was the primary endpoint. RESULTS: The cohort comprised 318 patients with localised extrameningeal SFTs. Disease recurrence occurred in 96 patients (33%). The estimated 5-year RFi rate was 72%, and the 10-year RFi rate was 52%. G-score precisely predicted recurrence risk with estimated 10-year RFi rate of 84% in low risk, 54% in intermediate risk and 36% in high risk (p < 0.001; C-index 0.691). The mDemicco (p < 0.001; C-index 0.749) and SalasOS (p < 0.001; C-index 0.674) models also predicted RFi but identified low-risk patients less accurate with 10-year RFi rates of 72% and 70%, respectively. CONCLUSIONS: G-score is a highly significant predictor of early and late recurrence in SFT and is superior to other models to predict patients at low risk of relapse. A less intensive follow-up schedule could be considered for patients at low recurrence risk according to G-score.

Ripretinib in advanced gastrointestinal stromal tumors: an overview of current evidence and drug approval.

Over the past 20 years, the management of gastrointestinal stromal tumors has acted as an important model in the advancement of molecularly targeted therapies for solid tumors. The success of imatinib has established it as a lasting therapy in the management of early-stage and advanced disease in the first-line setting. Imatinib resistance inevitably develops, resulting in the need for further lines of therapy. Ripretinib is an orally administered switch-control tyrosine kinase inhibitor, specifically developed to target both primary and secondary KIT and PDGFRα resistance mutations. Herein, the authors discuss the molecular rationale, the preclinical evidence and the clinical use of ripretinib in the treatment of gastrointestinal stromal tumors in the advanced stages of disease.

KIT Exon 9-Mutated Gastrointestinal Stromal Tumours: Biology and Treatment.

BACKGROUND: The majority of gastroinstestinal stromal tumours (GISTs) harbour oncogenic mutations in the gene encoding for the tyrosine kinase (TK) KIT. The most common mutations are found in exon 11, followed by mutations in exon 9. The latter mutations are associated more frequently with GISTs in extra-gastric locations and with a more aggressive clinical behaviour. SUMMARY: Here, we review the unique and often poorly recognized molecular, biological, and clinical characteristics that differentiate KIT exon 9-mutant GISTs from other GIST subtypes. In particular, KIT exon 9 mutations are associated to KIT mutants with retained sensitivity to stimulation by stem cell factor and localization to the cell membrane. Moreover, KIT exon 9-mutant GISTs display significant activation of KIT-independent oncogenic pathways. These characteristics may explain the limited activity of the TK inhibitor imatinib in the adjuvant setting in KIT exon 9-mutant GISTs, as well as their lower sensitivity to standard dose imatinib in the advanced setting. In contrast, the multi-TK inhibitor sunitinib displays better activity in KIT exon 9-mutant GISTs compared to others. KEY MESSAGES: KIT exon 9-mutant GISTs represent a subtype of GIST distinct from other GISTs, including the more common KIT exon 11-mutant GISTs. A better understanding of the molecular biology and clinical behaviour of KIT exon 9-mutant GISTs may help identify more improved treatment options.

Biological Effects of Cyclin-Dependent Kinase Inhibitors Ribociclib, Palbociclib and Abemaciclib on Breast Cancer Bone Microenvironment.

The CDK4/6 inhibitors (CDKi) palbociclib, ribociclib, and abemaciclib are currently approved in combination with anti-estrogen therapy for the treatment of advanced and/or metastatic hormone receptor-positive/HER2-neu-negative breast cancer patients. Given the high incidence of bone metastases in this population, we investigated and compared the potential effects of palbociclib, ribociclib, and abemaciclib on the breast cancer bone microenvironment. Primary osteoclasts (OCs) and osteoblasts (OBs) were obtained from human monocyte and mesenchymal stem cells, respectively. OC function was evaluated by tartrate-resistant acid phosphatase assay and real-time PCR; OB activity was assessed by an alizarin red assay. OB/breast cancer co-culture models were generated via the seeding of MCF-7 cells on a layer of OBs, and tumor cell proliferation was analyzed using flow cytometry. Here, we showed that ribociclib, palbociclib, and abemaciclib exerted similar inhibitory effects on the OC differentiation and expression of bone resorption markers without affecting OC viability. On the other hand, the three CDKi did not affect the ability of OB to produce bone matrix, even if the higher doses of palbociclib and abemaciclib reduced the OB viability. In OB/MCF-7 co-culture models, palbociclib demonstrated a lower anti-tumor effect than ribociclib and abemaciclib. Overall, our results revealed the direct effects of CDKi on the tumor bone microenvironment, highlighting differences potentially relevant for clinical practice.

S-Adenosylmethionine Supplementation May Reduce Cancer-Related Fatigue: A Prospective Evaluation Using the FACIT-F Questionnaire in Colon Cancer Patients Undergoing Oxaliplatin-Based Chemotherapy Regimens.

BACKGROUND: Fatigue is a common distressing symptom for patients living with chronic or acute diseases, including liver disorders and cancer (Cancer-Related Fatigue, CRF). Its etiology is multifactorial, and some hypotheses regarding the pathogenesis are summarized, with possible shared mechanisms both in cancer and in chronic liver diseases. A deal of work has investigated the role of a multifunctional molecule in improving symptoms and outcomes in different liver dysfunctions and associated symptoms, including chronic fatigue: S-adenosylmethionine (SAM; AdoMet). The aim of this work is actually to consider its role also in oncologic settings. PATIENTS AND METHODS: Between January 2006 and December 2009, at the University Campus Bio-Medico of Rome, 145 patients affected by colorectal cancer in adjuvant (n = 91) or metastatic (n = 54; n = 40 with liver metastases) setting and treated with oxaliplatin-based regimen (FOLFOX for adjuvant and bevacizumab + XELOX for metastatic ones), 76 of which with the supplementation of S-adenosylmethionine (AdoMet; 400 mg b.i.d.) (57% of adjuvant patients and 44% of metastatic ones) and 69 without AdoMet supplementation, were evaluated for fatigue prevalence using the Functional Assessment of Chronic Illnesses Therapy-Fatigue (FACIT-F) questionnaire, at 3 and 6 months after the beginning of oncologic treatment. Notably, the number of patients with liver metastases was well balanced between the group of patients treated with AdoMet and those who were not. RESULTS: Among patients receiving oxaliplatin-based chemotherapy, both in adjuvant and in metastatic settings, after just 3 months from the beginning of chemotherapy, mean scores from questionnaire domains like FACIT-F subscale (7.9 vs. 3.1, p = 0.006), FACIT physical (6.25 vs. 3.32, p = 0.020), FACIT emotional (4.65 vs. 2.19, p = 0.045), and FACIT-F total score (16.5 vs. 8.27, p = 0.021) were higher in those receiving supplementation of AdoMet, resulting in reduced fatigue; a significant difference was maintained even after 6 months of treatment. DISCUSSION AND CONCLUSIONS: Mechanisms and strategies for managing CRF are not fully understood. This work aimed at investigating the possible role of S-adenosylmethionine supplementation in improving fatigue scores in a specific setting of cancer patients, using a FACIT-F questionnaire, a well-validated quality of life instrument widely used for the assessment of CRF in clinical trials.

Identification of Aneuploid Circulating Tumor Cells in Soft-Tissue Sarcoma Patients: A Pilot Study.

BACKGROUND: Circulating tumor cells (CTCs) have been identified and shown to have prognostic and predictive roles in several types of carcinoma. More recently, aneuploid CTCs have become subject of a growing interest, as aneuploidy is considered a hallmark of cancer often associated with poor prognosis. Here, we aimed to identify for the first time aneuploid CTCs in soft-tissue sarcoma (STS) patients and show supportive in silico evidence on the prognostic role of aneuploidy in mesenchymal cancers. METHODS: In our pilot study, we collected blood from 4 metastatic STS patients and 4 age- and sex-matched healthy controls. After sample processing, cells were cyto-centrifuged onto glass slides and FISH was performed using 5 probes. The in silico analysis was performed using data from The Cancer Genome Atlas cohort of STS patients, using the validated Aneuploidy Score. We divided the patients in two populations (aneuploidy-high, Ane-Hi, and aneuploidy-low, Ane-Lo) using the median value of the Aneuploidy Score as a cutoff. Kaplan-Meier curves associated with log-rank test were used to compare progression-free and overall survival between groups. GraphPad Prism 8.0 (La Jolla, CA, USA) was used for statistical analyses. RESULTS: Aneuploid CTCs were identified in all 4 STS patients and in none of the controls, with a median value of 4 (range 3-6) per 7 mL of blood. Ane-Hi patients showed a significantly worse progression-free and overall survival compared to Ane-Lo patients. The same trend was maintained when analyzing the data based on the different histologies. CONCLUSIONS: We identified for the first time aneuploid CTCs in STS patients using fluorescence in situ hybridization in a surface marker-independent way. We also showed that the Aneuploidy Score has a prognostic value both in terms of progression-free survival and overall survival in STS patients using The Cancer Genome Atlas data, regardless of the histology.

Secondary KIT mutations: the GIST of drug resistance and sensitivity.

Pharmacological targeting of KIT in gastrointestinal stromal tumours has dramatically changed the clinical outcome of this disease. Tyrosine kinase inhibitors are the cornerstone of this improvement, but resistance occurs through secondary KIT mutations. Studies aimed at improving our understanding of the molecular basis of sensitivity and resistance will soon allow us to further tailor our therapeutic strategies.

Use of Cardioprotective Dexrazoxane Is Associated with Increased Myelotoxicity in Anthracycline-Treated Soft-Tissue Sarcoma Patients.

BACKGROUND: Dexrazoxane (DEX) is indicated as a cardioprotective agent for breast cancer patients receiving the anthracycline doxorubicin. Two meta-analyses in metastatic breast cancer reported an apparent increase in the severity of myelosuppression when DEX was used. So far, no data in soft-tissue sarcoma (STS) patients are available. METHODS: We retrospectively analyzed hematological toxicity data from 133 consecutive STS patients who received a chemotherapy regimen containing an anthracycline and ifosfamide (AI) in the perioperative or metastatic settings between January 2006 and December 2017. Of these, 46 received off-label DEX concurrently with the AI treatment. The differences between incidence of any of the explored outcomes were assessed according to the Fisher exact test. RESULTS: Compared with the non-DEX group, DEX treatment was associated with significantly higher rates of grade 3/4 hematological toxicities: leukopenia (56.5 vs. 28.7%; p = 0.0014), neutropenia (69.6 vs. 24.1%; p = 0.0001), febrile neutropenia (52.2 vs. 20.7%; p = 0.0004), anemia (41.3 vs. 28.7%; p = 0.1758), and thrombocytopenia (54.3 vs. 32.1%; p = 0.0159). Similarly, in the DEX group dose reductions were more frequent compared to the non-DEX group (39.1 vs. 19.5%; p = 0.0221). CONCLUSION: Adding DEX to AI in STS patients leads to higher rates of bone marrow suppression in all blood components, as well as to more frequent events of febrile neutropenia and dose reductions.

High-density array-CGH with targeted NGS unmask multiple noncontiguous minute deletions on chromosome 3p21 in mesothelioma.

We used a custom-made comparative genomic hybridization array (aCGH; average probe interval 254 bp) to screen 33 malignant mesothelioma (MM) biopsies for somatic copy number loss throughout the 3p21 region (10.7 Mb) that harbors 251 genes, including BRCA1 (breast cancer 1)-associated protein 1 (BAP1), the most commonly mutated gene in MM. We identified frequent minute biallelic deletions (<3 kb) in 46 of 251 genes: four were cancer-associated genes: SETD2 (SET domain-containing protein 2) (7 of 33), BAP1 (8 of 33), PBRM1 (polybromo 1) (3 of 33), and SMARCC1 (switch/sucrose nonfermentable- SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily c, member 1) (2 of 33). These four genes were further investigated by targeted next-generation sequencing (tNGS), which revealed sequence-level mutations causing biallelic inactivation. Combined high-density aCGH and tNGS revealed biallelic gene inactivation in SETD2 (9 of 33, 27%), BAP1 (16 of 33, 48%), PBRM1 (5 of 33, 15%), and SMARCC1 (2 of 33, 6%). The incidence of genetic alterations detected is much higher than reported in the literature because minute deletions are not detected by NGS or commercial aCGH. Many of these minute deletions were not contiguous, but rather alternated with segments showing oscillating copy number changes along the 3p21 region. In summary, we found that in MM: (i) multiple minute simultaneous biallelic deletions are frequent in chromosome 3p21, where they occur as distinct events involving multiple genes; (ii) in addition to BAP1, mutations of SETD2, PBRM1, and SMARCC1 are frequent in MM; and (iii) our results suggest that high-density aCGH combined with tNGS provides a more precise estimate of the frequency and types of genes inactivated in human cancer than approaches based exclusively on NGS strategy.

Body Mass Index as a Risk Factor for Toxicities in Patients with Advanced Soft-Tissue Sarcoma Treated with Trabectedin.

OBJECTIVES: Low body mass index (BMI) and/or low lean body mass have been shown to be risk factors for chemotherapy-related toxicities in a number of different cancers. However, no data are available regarding the role of BMI as a risk factor for developing toxicities related to the novel anticancer agent, trabectedin, in patients with soft-tissue sarcoma (STS). We evaluated the role of BMI as a risk factor for trabectedin-related toxicity in patients with STS. METHODS: Data from 51 patients with metastatic/advanced STS treated with trabectedin after progression on ≥1 anthracycline ± ifosfamide regimen were retrospectively reviewed. RESULTS: Eighteen patients (35.3%) were underweight, and the remainder were of normal bodyweight (45.1%) or overweight (19.6%). Neutropenia of any grade (77.8 vs. 33.3%) and grade 3-4 neutropenia (50.0 vs. 18.2%) occurred more frequently in the underweight versus normal/overweight patients (p = 0.025). Febrile neutropenia also occurred more frequently in underweight patients. Differences remained statistically significant after adjusting for other predictors of toxicity. There were no significant differences in other hematological and nonhematological toxicities between the groups. CONCLUSIONS: The data suggest for the first time that BMI should be considered a risk factor for neutropenia in patients with STS treated with trabectedin.

Combined Genetic and Genealogic Studies Uncover a Large BAP1 Cancer Syndrome Kindred Tracing Back Nine Generations to a Common Ancestor from the 1700s.

We recently discovered an inherited cancer syndrome caused by BRCA1-Associated Protein 1 (BAP1) germline mutations, with high incidence of mesothelioma, uveal melanoma and other cancers and very high penetrance by age 55. To identify families with the BAP1 cancer syndrome, we screened patients with family histories of multiple mesotheliomas and melanomas and/or multiple cancers. We identified four families that shared an identical BAP1 mutation: they lived across the US and did not appear to be related. By combining family histories, molecular genetics, and genealogical approaches, we uncovered a BAP1 cancer syndrome kindred of ~80,000 descendants with a core of 106 individuals, whose members descend from a couple born in Germany in the early 1700s who immigrated to North America. Their descendants spread throughout the country with mutation carriers affected by multiple malignancies. Our data show that, once a proband is identified, extended analyses of these kindreds, using genomic and genealogical studies to identify the most recent common ancestor, allow investigators to uncover additional branches of the family that may carry BAP1 mutations. Using this knowledge, we have identified new branches of this family carrying BAP1 mutations. We have also implemented early-detection strategies that help identify cancers at early-stage, when they can be cured (melanomas) or are more susceptible to therapy (MM and other malignancies).

FTY720 inhibits mesothelioma growth in vitro and in a syngeneic mouse model.

BACKGROUND: Malignant mesothelioma (MM) is a very aggressive type of cancer, with a dismal prognosis and inherent resistance to chemotherapeutics. Development and evaluation of new therapeutic approaches is highly needed. Immunosuppressant FTY720, approved for multiple sclerosis treatment, has recently raised attention for its anti-tumor activity in a variety of cancers. However, its therapeutic potential in MM has not been evaluated yet. METHODS: Cell viability and anchorage-independent growth were evaluated in a panel of MM cell lines and human mesothelial cells (HM) upon FTY720 treatment to assess in vitro anti-tumor efficacy. The mechanism of action of FTY720 in MM was assessed by measuring the activity of phosphatase protein 2A (PP2A)-a major target of FTY720. The binding of the endogenous inhibitor SET to PP2A in presence of FTY720 was evaluated by immunoblotting and immunoprecipitation. Signaling and activation of programmed cell death were evaluated by immunoblotting and flow cytometry. A syngeneic mouse model was used to evaluate anti-tumor efficacy and toxicity profile of FTY720 in vivo. RESULTS: We show that FTY720 significantly suppressed MM cell viability and anchorage-independent growth without affecting normal HM cells. FTY720 inhibited the phosphatase activity of PP2A by displacement of SET protein, which appeared overexpressed in MM, as compared to HM cells. FTY720 promoted AKT dephosphorylation and Bcl-2 degradation, leading to induction of programmed cell death, as demonstrated by caspase-3 and PARP activation, as well as by cytochrome c and AIF intracellular translocation. Moreover, FTY720 administration in vivo effectively reduced tumor burden in mice without apparent toxicity. CONCLUSIONS: Our preclinical data indicate that FTY720 is a potentially promising therapeutic agent for MM treatment.

Investigating palygorskite's role in the development of mesothelioma in southern Nevada: Insights into fiber-induced carcinogenicity.

Similar to asbestos fibers, nonregulated mineral fibers can cause malignant mesothelioma (MM). Recently, increased proportions of women and young individuals with MM were identified in southern Nevada, suggesting that environmental exposure to carcinogenic fibers was causing the development of MM. Palygorskite, a fibrous silicate mineral with a history of possible carcinogenicity, is abundant in southern Nevada. In this study, our aim was to determine whether palygorskite was contributing to the development of MM in southern Nevada. While palygorskite, in vitro, displayed some cytotoxicity toward primary human mesothelial (HM) cells and reduced their viability, the effects were roughly half of those observed when using similar amounts of crocidolite asbestos. No Balb/c (0/19) or MexTAg (0/18) mice injected with palygorskite developed MM, while 3/16 Balb/c and 13/14 MexTAg mice injected with crocidolite did. Lack of MM development was associated with a decreased acute inflammatory response, as injection of palygorskite resulted in lower percentages of macrophages (p = .006) and neutrophils (p = .02) in the peritoneal cavity 3 d after exposure compared to injection of crocidolite. Additionally, compared to mice injected with crocidolite, palygorskite-injected mice had lower percentages of M2 (tumor-promoting) macrophages (p = .008) in their peritoneal cavities when exposed to fiber for several weeks. Our study indicates that palygorskite found in the environment in southern Nevada does not cause MM in mice, seemingly because palygorskite, in vivo, fails to elicit inflammation that is associated with MM development. Therefore, palygorskite is not a likely contributor to the MM cases observed in southern Nevada.

Mesothelioma patients with germline BAP1 mutations have 7-fold improved long-term survival.

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.

Evaluation of clonal origin of malignant mesothelioma.

BACKGROUND: The hypothesis that most cancers are of monoclonal origin is often accepted as a fact in the scientific community. This dogma arose decades ago, primarily from the study of hematopoietic malignancies and sarcomas, which originate as monoclonal tumors. The possible clonal origin of malignant mesothelioma (MM) has not been investigated. Asbestos inhalation induces a chronic inflammatory response at sites of fiber deposition that may lead to malignant transformation after 30-50 years latency. As many mesothelial cells are simultaneously exposed to asbestos fibers and to asbestos-induced inflammation, it may be possible that more than one cell undergoes malignant transformation during the process that gives rise to MM, and result in a polyclonal malignancy. METHODS AND RESULTS: To investigate the clonality patterns of MM, we used the HUMARA (Human Androgen Receptor) assay to examine 16 biopsies from 14 women MM patients. Out of 16 samples, one was non-informative due to skewed Lyonization in its normal adjacent tissue. Fourteen out of the 15 informative samples revealed two electrophoretically distinct methylated HUMARA alleles, the Corrected Allele Ratio (CR) calculated on the allele peak areas indicating polyclonal origin MM. CONCLUSIONS: Our results show that MM originate as polyclonal tumors and suggest that the carcinogenic "field effect" of mineral fibers leads to several premalignant clones that give rise to these polyclonal malignancies.

Continuous exposure to chrysotile asbestos can cause transformation of human mesothelial cells via HMGB1 and TNF-α signaling.

Malignant mesothelioma is strongly associated with asbestos exposure. Among asbestos fibers, crocidolite is considered the most and chrysotile the least oncogenic. Chrysotile accounts for more than 90% of the asbestos used worldwide, but its capacity to induce malignant mesothelioma is still debated. We found that chrysotile and crocidolite exposures have similar effects on human mesothelial cells. Morphological and molecular alterations suggestive of epithelial-mesenchymal transition, such as E-cadherin down-regulation and ß-catenin phosphorylation followed by nuclear translocation, were induced by both chrysotile and crocidolite. Gene expression profiling revealed high-mobility group box-1 protein (HMGB1) as a key regulator of the transcriptional alterations induced by both types of asbestos. Crocidolite and chrysotile induced differential expression of 438 out of 28,869 genes interrogated by oligonucleotide microarrays. Out of these 438 genes, 57 were associated with inflammatory and immune response and cancer, and 14 were HMGB1 targeted genes. Crocidolite-induced gene alterations were sustained, whereas chrysotile-induced gene alterations returned to background levels within 5 weeks. Similarly, HMGB1 release in vivo progressively increased for 10 or more weeks after crocidolite exposure, but returned to background levels within 8 weeks after chrysotile exposure. Continuous administration of chrysotile was required for sustained high serum levels of HMGB1. These data support the hypothesis that differences in biopersistence influence the biological activities of these two asbestos fibers.