Preventive and therapeutic opportunities: targeting BAP1 and/or HMGB1 pathways to diminish the burden of mesothelioma.

Mesothelioma is a cancer typically caused by asbestos. Mechanistically, asbestos carcinogenesis has been linked to the asbestos-induced release of HMGB1 from the nucleus to the cytoplasm, where HMGB1 promotes autophagy and cell survival, and to the extracellular space where HMGB1 promotes chronic inflammation and mesothelioma growth. Targeting HMGB1 inhibited asbestos carcinogenesis and the growth of mesothelioma. It is hoped that targeting HMGB1 will be a novel therapeutic strategy that benefits mesothelioma patients. Severe restrictions and/or a complete ban on the use of asbestos were introduced in the 80 and early 90s in the Western world. These measures have proven effective as the incidence of mesothelioma/per 100,000 persons is decreasing in these countries. However, the overall number of mesotheliomas in the Western world has not significantly decreased. There are several reasons for that which are discussed here: (1) the presence of asbestos in old constructions; (2) the development of rural areas containing asbestos or other carcinogenic mineral fibers in the terrain; (3) the discovery of an increasing fraction of mesotheliomas caused by germline genetic mutations of BAP1 and other tumor suppressor genes; (4) mesotheliomas caused by radiation therapy; (5) the overall increase in the population and of the fraction of older people who are much more susceptible to develop all types of cancers, including mesothelioma. In summary, the epidemiology of mesothelioma is changing, the ban on asbestos worked, there are opportunities to help mesothelioma patients especially those who develop in a background of germline mutations and there is the opportunity to prevent a mesothelioma epidemic in the developing world, where the use of asbestos is increasing exponentially. We hope that restrictive measures similar to those introduced in the Western world will soon be introduced in developing countries to prevent a mesothelioma epidemic.

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.

Medical and Surgical Care of Patients With Mesothelioma and Their Relatives Carrying Germline BAP1 Mutations.

The most common malignancies that develop in carriers of BAP1 germline mutations include diffuse malignant mesothelioma, uveal and cutaneous melanoma, renal cell carcinoma, and less frequently, breast cancer, several types of skin carcinomas, and other tumor types. Mesotheliomas in these patients are significantly less aggressive, and patients require a multidisciplinary approach that involves genetic counseling, medical genetics, pathology, surgical, medical, and radiation oncology expertise. Some BAP1 carriers have asymptomatic mesothelioma that can be followed by close clinical observation without apparent adverse outcomes: they may survive many years without therapy. Others may grow aggressively but very often respond to therapy. Detecting BAP1 germline mutations has, therefore, substantial medical, social, and economic impact. Close monitoring of these patients and their relatives is expected to result in prolonged life expectancy, improved quality of life, and being cost-effective. The co-authors of this paper are those who have published the vast majority of cases of mesothelioma occurring in patients carrying inactivating germline BAP1 mutations and who have studied the families affected by the BAP1 cancer syndrome for many years. This paper reports our experience. It is intended to be a source of information for all physicians who care for patients carrying germline BAP1 mutations. We discuss the clinical presentation, diagnostic and treatment challenges, and our recommendations of how to best care for these patients and their family members, including the potential economic and psychosocial impact.

Heterozygous germline BLM mutations increase susceptibility to asbestos and mesothelioma.

Rare biallelic BLM gene mutations cause Bloom syndrome. Whether BLM heterozygous germline mutations (BLM+/-) cause human cancer remains unclear. We sequenced the germline DNA of 155 mesothelioma patients (33 familial and 122 sporadic). We found 2 deleterious germline BLM+/- mutations within 2 of 33 families with multiple cases of mesothelioma, one from Turkey (c.569_570del; p.R191Kfs*4) and one from the United States (c.968A>G; p.K323R). Some of the relatives who inherited these mutations developed mesothelioma, while none with nonmutated BLM were affected. Furthermore, among 122 patients with sporadic mesothelioma treated at the US National Cancer Institute, 5 carried pathogenic germline BLM+/- mutations. Therefore, 7 of 155 apparently unrelated mesothelioma patients carried BLM+/- mutations, significantly higher (P = 6.7E-10) than the expected frequency in a general, unrelated population from the gnomAD database, and 2 of 7 carried the same missense pathogenic mutation c.968A>G (P = 0.0017 given a 0.00039 allele frequency). Experiments in primary mesothelial cells from Blm+/- mice and in primary human mesothelial cells in which we silenced BLM revealed that reduced BLM levels promote genomic instability while protecting from cell death and promoted TNF-α release. Blm+/- mice injected intraperitoneally with asbestos had higher levels of proinflammatory M1 macrophages and of TNF-α, IL-1ß, IL-3, IL-10, and IL-12 in the peritoneal lavage, findings linked to asbestos carcinogenesis. Blm+/- mice exposed to asbestos had a significantly shorter survival and higher incidence of mesothelioma compared to controls. We propose that germline BLM+/- mutations increase the susceptibility to asbestos carcinogenesis, enhancing the risk of developing mesothelioma.

A Subset of Mesotheliomas With Improved Survival Occurring in Carriers of BAP1 and Other Germline Mutations.

PURPOSE: We hypothesized that four criteria could help identify malignant mesotheliomas (MMs) most likely linked to germline mutations of BAP1 or of other genes: family history of MM, BAP1-associated cancers, or multiple malignancies; or age younger than 50 years. PATIENTS AND METHODS: Over the course of 7 years, 79 patients with MM met the four criteria; 22 of the 79 (28%) reported possible asbestos exposure. They were screened for germline BAP1 mutations by Sanger sequencing and by targeted next-generation sequencing (tNGS) for germline mutations in 55 additional cancer-linked genes. Deleterious mutations detected by tNGS were validated by Sanger sequencing. RESULTS: Of the 79 patients, 43 (16 probands and 27 relatives) had deleterious germline BAP1 mutations. The median age at diagnosis was 54 years and median survival was 5 years. Among the remaining 36 patients with no BAP1 mutation, median age at diagnosis was 45 years, median survival was 9 years, and 12 had deleterious mutations of additional genes linked to cancer. When compared with patients with MMs in the SEER cohort, median age at diagnosis (72 years), median survival for all MM stages (8 months), and stage I (11 months) were significantly different from the 79 patients with MM in the current study ( P < .0001). CONCLUSION: We provide criteria that help identify a subset of patients with MM who had significantly improved survival. Most of these patients were not aware of asbestos exposure and carried either pathogenic germline mutations of BAP1 or of additional genes linked to cancer, some of which may have targeted-therapy options. These patients and their relatives are susceptible to development of additional cancers; therefore, genetic counseling and cancer screening should be considered.

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.

Randomized phase II study of cetuximab versus irinotecan and cetuximab in patients with chemo-refractory KRAS codon G13D metastatic colorectal cancer (G13D-study).

PURPOSE: This study investigated the efficacy and safety of cetuximab-based treatment in patients with chemotherapy-resistant refractory mCRC with KRAS G13D mutation. PATIENTS AND METHODS: An assessment of the efficacy and safety of cetuximab-based treatment was performed in an observation-enriched randomized controlled study comparing the cetuximab alone group (Cet group) and the combination of cetuximab and irinotecan group (CetI group) for KRAS G13D-mutated mCRC in Japan. In this study, the patients received a biweekly (500 mg/m2 on day 1) or weekly (250 mg/m2) intravenous infusion of cetuximab in Cet group, or a biweekly (500 mg/m2 on day 1) or weekly (250 mg/m2) intravenous infusion of cetuximab followed by irinotecan (150 mg/m2) in CetI group. Propensity score adjustment was used to achieve balance in the observational arm. RESULTS: Data from a total of 29 patients (10 in Cet group, 19 in CetI group) were analyzed. Crude median progression-free survival time was 2.9 months in the Cet group and 2.5 months in the CetI group. Crude disease control rates were 55.6% in the Cet group and 47.4% in the CetI group. After a median follow-up of 43 months, the crude median overall survival was 8.0 months in the Cet group and 7.6 months in the CetI group. Cetuximab-based treatment did not markedly increase any characteristic toxicity and was generally well tolerated. Propensity score analyses adjusted for performance status and number of metastases showed comparable results with the crude results. CONCLUSION: Cetuximab-based treatment seemed to benefit patients with chemotherapy-resistant, refractory KRAS G13D-mutated mCRC. Our results might support the administration of cetuximab-based treatment for KRAS-mutant mCRC and would be able to provide treatment flexibility in this setting.

Phase I study of TAS-102 and irinotecan combination therapy in Japanese patients with advanced colorectal cancer.

BACKGROUND: TAS-102 is a nucleoside antitumor agent consisting of trifluridine (FTD) and tipiracil hydrochloride (TPI). We investigated the recommended dose (RD) of TAS-102 plus irinotecan for metastatic colorectal cancer refractory to 5-fluorouracil (5-FU) and oxaliplatin. METHODS: This study was used a escalated dose of TAS-102 (40-70 mg/m(2)/day, for 5 days a week with 2 days rest for 2 weeks, followed by a 14-day rest) with a fixed dose of irinotecan (150 mg/m(2) on Days 1 and 15 of a 28-day schedule). The primary endpoints were determination of RD and assessment of safety. RESULTS: Ten patients were enrolled; 7 at the Level 1 (50 mg/m(2)/day) and 3 at the Level 2 (60 mg/m(2)/day). One patient at Level 1 was excluded from the analysis of dose-limiting toxicities (DLT) and efficacy. Five DLTs occurred in 3 patients; 1 patient at Level 1 (Grade 3 febrile neutropenia and Grade 4 neutropenia), and 2 patients at Level 2 (Grade 3 febrile neutropenia in two patients and Grade 4 neutropenia in one). Grade 3 or higher treatment-related adverse events were neutropenia (100 %), leukopenia (70 %), febrile neutropenia (30 %) and lymphopenia, anaemia (20 % each). 2 patients (22 %) achieved partial response with the duration of response were 112 and 799 days. CONCLUSION: The RD was determined to be 50 mg/m(2)/day of TAS-102 combined with 150 mg/m(2) of irinotecan although further investigation to explore optimal regimen is warranted.

[Efficacy and safety of cetuximab+irinotecan for unresectable advanced or recurrent colorectal cancer].

BACKGROUND: In July 2008, cetuximab treatment for unresectable advanced or recurrent colorectal cancer was approved in Japan, but there have been few reports on this therapy in Japan. PURPOSE: We retrospectively analyzed the efficacy and safety of cetuximab(Cmab)+irinotecan(CPT-11)for unresectable advanced or recurrent colorectal cancer from October 2008 to April 2010 at 5 centers in the Kanagawa region. PATIENTS AND METHODS: The number of patients enrolled was 38, all of whom were treated after second-line therapy. RESULTS: The RR was 24%. DCR was 68%. TTF was 105 days and OS was 242 days. CONCLUSION: At 5 centers, Cmab+CPT-11 was an effective and safe treatment after second-line therapy.

[5-FU/l-LV therapy is useful for hemodialysis patients with advanced gastric cancer].

A 71-year-old man receiving maintenance dialysis because of diabetic nephropathy presented with hematemesis at another hospital in January 2008. A gastrointestinal endoscopy demonstrated a II a-like lesion in the angle of the stomach, and he was admitted to our hospital. A diagnosis of gastric adenocarcinoma (cT2N2M0, Stage IIIA) was made. An operation could not be performed because of the high risk, so combination chemotherapy with 5-FU and l-LV was initiated. After 3 courses of treatment, the size of the primary tumor was markedly reduced. After 6 courses, the primary lesion had changed to a scar, and an endoscopic biopsy revealed no cancer cells. His performance status did not deteriorate, and no serious adverse events occurred during the course of treatment. Chemotherapy was continued because the overall response was SD. 5-FU/l-LV therapy should be considered as a safe and useful treatment for a hemodialysis patient with advanced gastric cancer.

Effect of L-NAME on the synthesis of plasma fibrinogen in mice.

The effect of nitric oxide (NO) on plasma fibrinogen was investigated by treating mice with oral N(G)-nitro-L-arginine-methyl ester (L-NAME), a non-selective NO synthase (NOS) inhibitor. Treatment with L-NAME significantly increased the concentration of plasma fibrinogen and hepatic expression of the alpha- and beta-chains of fibrinogen, whereas plasma NO(2)(-) level and hepatic expression of endothelial NOS (eNOS) mRNA were significantly decreased. These results suggest that L-NAME treatment can increase plasma fibrinogen levels via an increase in expression of fibrinogen mRNA in the liver, and NO may be involved in plasma fibrinogen increase.