Human malignant mesothelioma is an aggressive and highly lethal cancer that is believed to be caused by chronic exposure to asbestos and erionite. Prognosis for this cancer is generally poor because ...of late-stage diagnosis and resistance to current conventional therapies. The damage-associated molecular pattern protein HMGB1 has been implicated previously in transformation of mesothelial cells. Here we show that HMGB1 establishes an autocrine circuit in malignant mesothelioma cells that influences their proliferation and survival. Malignant mesothelioma cells strongly expressed HMGB1 and secreted it at high levels in vitro. Accordingly, HMGB1 levels in malignant mesothelioma patient sera were higher than that found in healthy individuals. The motility, survival, and anchorage-independent growth of HMGB1-secreting malignant mesothelioma cells was inhibited in vitro by treatment with monoclonal antibodies directed against HMGB1 or against the receptor for advanced glycation end products, a putative HMGB1 receptor. HMGB1 inhibition in vivo reduced the growth of malignant mesothelioma xenografts in severe-combined immunodeficient mice and extended host survival. Taken together, our findings indicate that malignant mesothelioma cells rely on HMGB1, and they offer a preclinical proof-of-principle that antibody-mediated ablation of HMBG1 is sufficient to elicit therapeutic activity, suggesting a novel therapeutic approach for malignant mesothelioma treatment.
Because only a small fraction of asbestos-exposed individuals develop malignant mesothelioma, and because mesothelioma clustering is observed in some families, we searched for genetic predisposing ...factors. We discovered germline mutations in the gene encoding BRCA1 associated protein-1 (BAP1) in two families with a high incidence of mesothelioma, and we observed somatic alterations affecting BAP1 in familial mesotheliomas, indicating biallelic inactivation. In addition to mesothelioma, some BAP1 mutation carriers developed uveal melanoma. We also found germline BAP1 mutations in 2 of 26 sporadic mesotheliomas; both individuals with mutant BAP1 were previously diagnosed with uveal melanoma. We also observed somatic truncating BAP1 mutations and aberrant BAP1 expression in sporadic mesotheliomas without germline mutations. These results identify a BAP1-related cancer syndrome that is 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 to identify individuals at high risk of mesothelioma who could be targeted for early intervention.
Exposure to erionite, an asbestos-like mineral, causes unprecedented rates of malignant mesothelioma (MM) mortality in some Turkish villages. Erionite deposits are present in at least 12 US states. ...We investigated whether increased urban development has led to erionite exposure in the United States and after preliminary exploration, focused our studies on Dunn County, North Dakota (ND). In Dunn County, ND, we discovered that over the past three decades, more than 300 miles of roads were surfaced with erionite-containing gravel. To determine potential health implications, we compared erionite from the Turkish villages to that from ND. Our study evaluated airborne point exposure concentrations, examined the physical and chemical properties of erionite, and examined the hallmarks of mesothelial cell transformation in vitro and in vivo. Airborne erionite concentrations measured in ND along roadsides, indoors, and inside vehicles, including school buses, equaled or exceeded concentrations in Boyali, where 6.25% of all deaths are caused by MM. With the exception of outdoor samples along roadsides, ND concentrations were lower than those measured in Turkish villages with MM mortality ranging from 20 to 50%. The physical and chemical properties of erionite from Turkey and ND are very similar and they showed identical biological activities. Considering the known 30- to 60-y latency for MM development, there is reason for concern for increased risk in ND in the future. Our findings indicate that implementation of novel preventive and early detection programs in ND and other erionite-rich areas of the United States, similar to efforts currently being undertaken in Turkey, is warranted.
Asbestos carcinogenesis has been linked to the release of cytokines and mutagenic reactive oxygen species (ROS) from inflammatory cells. Asbestos is cytotoxic to human mesothelial cells (HM), which ...appears counterintuitive for a carcinogen. We show that asbestos-induced HM cell death is a regulated form of necrosis that links to carcinogenesis. Asbestos-exposed HM activate poly(ADP-ribose) polymerase, secrete H₂O₂, deplete ATP, and translocate high-mobility group box 1 protein (HMGB1) from the nucleus to the cytoplasm, and into the extracellular space. The release of HMGB1 induces macrophages to secrete TNF-α, which protects HM from asbestos-induced cell death and triggers a chronic inflammatory response; both favor HM transformation. In both mice and hamsters injected with asbestos, HMGB1 was specifically detected in the nuclei, cytoplasm, and extracellular space of mesothelial and inflammatory cells around asbestos deposits. TNF-α was coexpressed in the same areas. HMGB1 levels in asbestos-exposed individuals were significantly higher than in nonexposed controls (P < 0.0001). Our findings identify the release of HMGB1 as a critical initial step in the pathogenesis of asbestos-related disease, and provide mechanistic links between asbestos-induced cell death, chronic inflammation, and carcinogenesis. Chemopreventive approaches aimed at inhibiting the chronic inflammatory response, and especially blocking HMGB1, may decrease the risk of malignant mesothelioma among asbestos-exposed cohorts.
Malignant mesothelioma (MM) is an aggressive cancer, resistant to current therapies. Membrane chondroitin sulphate proteoglycan 4 (CSPG4), which has been successfully targeted in melanoma and breast ...cancer, was found highly expressed in MM, but not in normal mesothelium. Therefore, we explored CSPG4 as a suitable target for monoclonal antibody (mAb)-based immunotherapy for MM.
We assayed adhesion, motility, invasiveness, wound-healing, apoptosis, and anchorage-independent growth of MM cells on cell cultures. CSPG4 expression and signaling was studied by immunoblotting. The growth of MM severe combined immunodeficient (SCID) mice xenografts induced by PPM-Mill cells, engineered to express the luciferase reporter gene, was monitored by imaging, upon treatment with CSPG4 mAb TP41.2. Animal toxicity and survival were assayed in both tumor inhibition and therapeutic experiments.
CSPG4 was expressed on 6 out of 8 MM cell lines and in 25 out of 41 MM biopsies, with minimal expression in surrounding healthy cells. MM cell adhesion was mediated by CSPG4-dependent engagement of ECM. Cell adhesion was inhibited by mAb TP41.2 resulting in decreased phosphorylation of focal adhesion kinase (FAK) and AKT, reduced expression of cyclin D1 and apoptosis. Moreover, mAb TP41.2 significantly reduced MM cell motility, migration, and invasiveness, and inhibited MM growth in soft agar. In vivo, treatment with mAb TP41.2 prevented or inhibited the growth of MM xenografts in SCID mice, with a significant increase in animal survival.
These results establish the safety of CSPG4 mAb-based immunotherapy and suggest that CSPG4 mAb-based immunotherapy may represent a novel approach for the treatment of MM.
Dermatophytes are a uniquely pathogenic group of fungi that cause most common fungal infections globally. The major cause of athlete's foot is Trichophyton rubrum, a pathogen of human skin. A recent ...paper in this journal reported the sequencing and analysis of five additional genome sequences, including that of Trichophyton rubrum. These five join the existing two additional genome sequences to bring the total to seven dermatophyte genome sequences, a notable milestone in the study of these fungi. These additional genomes set the stage for future genome-supported studies on the biology, pathogenicity, and host specificity of this important group of pathogens. To predict how this future might play out, we review the history of Aspergillus genomics since the initial publication of the first three Aspergillus genome sequences in 2005, an event that stimulated important studies of the pathogenic Aspergillus species. From these 7 years of Aspergillus history, we offer some speculation on the future of dermatophyte studies supported by the genome sequences given the similarities, differences, and relative levels of support for studies in these two groups of fungi and the diseases they cause.
Abstract
Human malignant mesothelioma (MM) is an aggressive and highly lethal cancer that has been linked to asbestos and erionite exposure. MM causes about 3,000 deaths per year in the US and more ...than 100,000 deaths per year worldwide. We previously found that the damage-associated molecular pattern (DAMP) high-mobility group box-1 protein (HMGB1) plays a critical role in the early carcinogenic events in MM development by inducing tumor necrosis factor-alpha (TNF-α) secretion, potentiating survival of fiber-exposed primary human mesothelial cells (HM) and enabling HM malignant transformation. We recently showed that HMGB1 is upregulated in MM tumor tissues and cell lines and its levels to be significantly higher in the blood of MM patients compared to healthy individuals. Moreover, MM cells are “addicted” to HMGB1 and HMGB1 promotes proliferation, viability, motility and invasiveness of MM cells. Here we show that the use of the HMGB1 antagonists BoxA or ethyl pyruvate (EP) inhibit the motility, survival and progression of MM cells in vitro and reduce the growth of MM xenografts in SCID mice. BoxA is a fragment of HMGB1 protein that corresponds to the one of the two highly conserved DNA binding domains, and behaves as a competitive inhibitor. EP is the ethyl ester of pyruvic acid, is known to suppress oxygen radical formation, and suppresses HMGB1 secretion. Both BoxA and EP have been shown to down-regulate the activation of the proinflammatory transcription factor, NF-κB, as well as the expression of several proinflammatory proteins, such as TNF-α, IL-6, and HMGB1 itself. Taken together, our results provide a preclinical proof-of-principle that inhibition of HMGB1 activity using either BoxA or EP is sufficient to elicit therapeutic activity, offering novel therapeutic approaches for MM treatment.
Citation Format: Sandro L. Jube, Zeyana Rivera, Maura Casalgrandi, Marco Bianchi, Harvey I. Pass, Giovanni Gaudino, Michele Carbone, Haining Yang. BoxA and ethyl pyruvate offer novel therapeutic approaches for human malignant mesothelioma. abstract. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5557. doi:10.1158/1538-7445.AM2013-5557
Abstract
Malignant mesothelioma (MM) is an aggressive tumor, resistant to conventional therapies, with median survival of 1 year from diagnosis. The lack of effective therapies available prompted us ...to implement antibody-based immunotherapy against novel targets and to investigate possible synergies with chemotherapy on MM. CSPG4 is involved in the onset and progression of melanoma and other tumors, as well as in neo-angiogenesis. CSPG4-specific monoclonal antibodies (mAb) have shown anti-tumor effects in both preclinical and clinical trials of melanoma. We hypothesized that targeting CSPG4 with a CSPG4-specific mAb would have therapeutic efficacy against MM. We found that chondroitin sulphate proteoglycan 4 (CSPG4) was aberrantly expressed in 6 out of 8 MM cell lines and in 24 out of 40 MM biopsies, with minimal expression in surrounding non-malignant cells. The expression of CSPG4 in MM was higher upon engagement of extracellular matrix components (ECM) and was associated with increased MM cell viability and motility. Silencing of CSPG4 expression by siRNAs supported this functional significance of CSPG4 in MM. Consistently, the CSPG4-specific mAb TP41.2 inhibited MM cell attachment to the ECM, resulting in decreased phosphorylation of FAK and AKT, decreased expression of cyclin D1 and apoptosis. Moreover, TP41.2 significantly reduced MM cell motility, migration and invasiveness, and inhibited MM growth in soft agar. TP41.2 prevented the outgrowth of human MM tumors in SCID mice and inhibited the growth of established MM xenografts, resulting in significantly extended survival of tumor-bearing mice. These results represent a novel approach for CSPG4 mAb-based immunotherapy of MM. Combinatorial strategies with chemotherapeutic agents and with mAbs targeting c-Met related receptor are ongoing, aimed at translating CSPG4-specific mAb into clinical setting.
Citation Format: {Authors}. {Abstract title} abstract. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2514. doi:1538-7445.AM2012-2514
Abstract
The membrane bound chondroitin sulphate protidoglycan 4 (CSPG4), also known as high molecular weight-melanoma associated antigen (HMW-MAA), plays a role in tumor cell proliferation, growth ...and differentiation, as well as in angiogenesis and extracellular matrix remodeling. Contrary to the early reports which had described CSPG4 expression restricted to melanoma cells, this molecule is expressed by various types of malignant tumors. Because of its high expression on tumor cells, including cancer stem cells, and its restricted distribution in normal tissues, CSPG4 represents an attractive target for immunotherapy. The lack of effective conventional therapy and the paucity of suitable targets for immunotherapy in mesothelioma have prompted us to test whether CSPG4 is expressed by mesothelioma cells and mediates the anti-tumor activity of CSPG4-specific monoclonal antibodies (mAb). Immunohistochemical staining with mAb showed that CSPG4 was expressed on mesothelioma cells in 24 out of 40 MM biopsies with minimal expression on surrounding normal cells. Furthermore FACS analysis and western blots detected CSPG4 in all the 9 human MM cell lines tested and that the expression was induced on MM cells by their interactions with the extracellular matrix (ECM).
To test the sensitivity of MM cells to the anti-tumor activity of CSPG4-specific mAb, 3 MM cell lines were incubated with mAb TP41.2 (final concentration 10ug/ml) for up to 72hrs. Cell proliferation was determined by MTT assay. Cells incubated with normal mouse IgG antibodies were used as controls. Addition of mAb TP41.2 to cells already attached to plates had no detectable effect on their proliferation. On the other hand incubation of MM cells with mAb TP41.2 before seeding in plates markedly inhibited their growth. The effect was time-dependent. These results were observed in all 3 cell lines and each cell lines was tested 3 times. The data suggest that CSPG4 promotes MM cell growth by mediating their interactions with ECM. This conclusion is corroborated by the growth of CSPG4-positive MM cells in serum-free medium in plates coated with collagen I, collagen IV or fibronectin. Furthermore CSPG4-specific mAb decreased the expression of the angiogenic growth factors VEGF and HEY1, as determined by RT-PCR, in MM cells. These results suggest that it may be worthwhile to test the hypothesis that CSPG4-specific mAb-based immunotherapy may represent a viable approach for the treatment of MM.
Citation Format: {Authors}. {Abstract title} abstract. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2323.
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