Jill M. Miller

Asbestos and erionite prime and activate the NLRP3 inflammasome that stimulates autocrine cytokine release in human mesothelial cells

BackgroundPleural fibrosis and malignant mesotheliomas (MM) occur after exposures to pathogenic fibers, yet the mechanisms initiating these diseases are unclear.ResultsWe document priming and activation of the NLRP3 inflammasome in human mesothelial cells by asbestos and erionite that is causally related to release of IL-1β, IL-6, IL-8, and Vascular Endothelial Growth Factor (VEGF). Transcription and release of these proteins are inhibited in vitro using Anakinra, an IL-1 receptor antagonist that reduces these cytokines in a human peritoneal MM mouse xenograft model.ConclusionsThese novel data show that asbestos-induced priming and activation of the NLRP3 inflammasome triggers an autocrine feedback loop modulated via the IL-1 receptor in mesothelial cell type targeted in pleural infection, fibrosis, and carcinogenesis.

Extracellular signal regulated kinase 5: A potential therapeutic target for malignant mesotheliomas

Purpose: Malignant mesothelioma is a devastating disease with a need for new treatment strategies. In the present study, we showed the importance of extracellular signal–regulated kinase 5 (ERK5) in malignant mesothelioma tumor growth and treatment. Experimental Design: ERK5 as a target for malignant mesothelioma therapy was verified using mesothelial and mesothelioma cell lines as well as by xenograft severe combined immunodeficient (SCID) mouse models. Results: We first showed that crocidolite asbestos activated ERK5 in LP9 cells and mesothelioma cell lines exhibit constitutive activation of ERK5. Addition of doxorubicin resulted in further activation of ERK5 in malignant mesothelioma cells. ERK5 silencing increased doxorubicin-induced cell death and doxorubicin retention in malignant mesothelioma cells. In addition, shERK5 malignant mesothelioma lines exhibited both attenuated colony formation on soft agar and invasion of malignant mesothelioma cells in vitro that could be related to modulation of gene expression linked to cell proliferation, apoptosis, migration/invasion, and drug resistance as shown by microarray analysis. Most importantly, injection of shERK5 malignant mesothelioma cell lines into SCID mice showed significant reduction in tumor growth using both subcutaneous and intraperitoneal models. Assessment of selected human cytokine profiles in peritoneal lavage fluid from intraperitoneal shERK5 and control tumor-bearing mice showed that ERK5 was critical in regulation of various proinflammatory (RANTES/CCL5, MCP-1) and angiogenesis-related (interleukin-8, VEGF) cytokines. Finally, use of doxorubicin and cisplatin in combination with ERK5 inhibition showed further reduction in tumor weight and volume in the intraperitoneal model of tumor growth. Conclusion: ERK5 inhibition in combination with chemotherapeutic drugs is a beneficial strategy for combination therapy in patients with malignant mesothelioma. Clin Cancer Res; 19(8); 2071–83. ©2013 AACR.

Curcumin: A Double Hit on Malignant Mesothelioma

Inflammation is a key mediator in the development of malignant mesothelioma, which has a dismal prognosis and poor therapeutic strategies. Curcumin, a naturally occurring polyphenol in turmeric, has been shown to possess anticarcinogenic properties through its anti-inflammatory effects. Inflammasomes, a component of inflammation, control the activation of caspase-1 leading to pyroptosis and processing of proinflammatory cytokines, interleukin (IL)-1β and IL-18. In the present study, we investigate the role of curcumin in pyroptotic cell death of malignant mesothelioma cells. Using in vitro models with mouse and human malignant mesothelioma cells, curcumin is shown to induce pyroptosis through activation of caspase-1 and increased release of high-mobility group box 1 (HMGB1) without processing of IL-1β and IL-18. Absence of IL-1β processing in response to curcumin-mediated caspase-1 activation is attributed to blockade of pro-IL-1β priming through inhibition of the NF-κB pathway. Furthermore, curcumins cytotoxicity in malignant mesothelioma cells is demonstrated to be dependent on pyroptosis as inhibition of caspase-1 resulted in protection against curcumin-induced cell death. We also demonstrate that curcumin-mediated caspase-1 activation is oxidant dependent by using N-acetyl-L-cysteine (NAC) to inhibit pyroptosis. PCR array analysis using the human inflammasome template revealed that curcumin significantly downregulated levels of inflammasome-related gene expression involved in inflammation, e.g., NF-κB, toll-like receptors (TLR), and IL-1β. Our data indicate that curcumin has a double effect on malignant mesothelioma cells through induction of pyroptosis while subsequently protecting against inflammation. Cancer Prev Res; 7(3); 330–40. ©2014 AACR.

Extracellular Signal-Regulated Kinase 5 and Cyclic AMP Response Element Binding Protein Are Novel Pathways Inhibited by Vandetanib (ZD6474) and Doxorubicin in Mesotheliomas

Malignant mesothelioma (MM), lung cancers, and asbestosis are hyperproliferative diseases associated with exposures to asbestos. All have a poor prognosis; thus, the need to develop novel and effective therapies is urgent. Vandetanib (Van) (ZD6474, ZACTIMA) is a tyrosine kinase inhibitor that has shown equivocal results in clinical trials for advanced non-small cell lung cancer. However, tyrosine kinase inhibitors alone have shown no significant clinical activity in phase II trials of patients with unresectable MM. Using epithelioid (HMESO) and sarcomatoid (H2373) human MM lines, the efficacy of tumor cell killing and signaling pathways modulated by Van with and without doxorubicin (Dox) was examined. Van alone reduced total cell numbers in HMESO MM and synergistically increased the toxicity of Dox in HMESO and H2373 cells. Most importantly, we identified two novel cell survival/resistance pathways, ERK5 and cyclic AMP response element binding protein (CREB), that were inhibited by Van and Dox. After silencing of either ERK5 or CREB, significant decreases in cell numbers in the Dox-resistant sarcomatoid H2373 line were observed. Results suggest that a plethora of cell signaling pathways associated with cell survival are induced by Dox but inhibited by the addition of Van in MM. Data from our study support the combined efficacy of Van and Dox as a novel approach in the treatment of MM that is further enhanced by blocking ERK5 or CREB signaling cascades.

Abstract 5461: Role of the NLRP3 inflammasome in the development and drug resistance of malignant mesothelioma

Inflammation plays an important role in development of various cancers including malignant mesothelioma (MM). We have shown that asbestos activates NOD-like receptor protein 3 (NLRP3), a component of the inflammasome in human macrophages. As chronic asbestos exposure is a key risk factor for the development of MM, we hypothesized that inflammasome-mediated inflammation might underlie the pathogenesis of this cancer. To show the involvement of NLRP3 in asbestos-induced mesothelioma, we demonstrated that exposure of asbestos to immortalized human mesothelial cells (LP9/hTERT), a cell type responsible for origin of MM, caused mRNA increase and activation of NLRP3 as measured by caspase-1 activation and IL-1β release. Inhibition of NLRP3 by siRNA caused significant decreases in NLRP3 mRNA levels as well as asbestos-induced IL-1β release in medium. On the other hand, human MM lines and tumor tissues showed significantly decreased levels of NLRP3 and caspase-1 as compared to LP9 or matching normal tissues respectively. Our findings suggest that initial exposure to asbestos causes increased mRNA levels and activity of NLRP3, which may help in MM development by promoting mesothelial cell transformation. However, tumor development culminates in MM with decreased NLRP3 protein and increased drug resistance which may be due to caspase-1 inactivation. Thus NLRP3 may be an appropriate target for therapy of MM, especially in combination with cytotoxic chemotherapeutic drugs and IL-1 receptor antagonists. This study is supported by a Meothelioma Applied Research Foundation (MARF) grant (AS) and by NIEHS grants T32 ES07122 (BM). 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 5461. doi:1538-7445.AM2012-5461

Extracellular signal regulated kinase 5 and inflammasome in progression of mesothelioma

Malignant mesothelioma is an aggressive cancer in desperate need of treatment. We have previously shown that extracellular signaling regulated kinase 5 (ERK5) plays an important role in mesothelioma pathogenesis using ERK5 silenced human mesothelioma cells exhibiting significantly reduced tumor growth in immunocompromised mice. Here, we used a specific ERK 5 inhibitor, XMD8-92 in various in vitro and in vivo models to demonstrate that inhibition of ERK5 can slow down mesothelioma tumorigenesis. First, we show a dose dependent toxicity of XMD8-92 to 2 human mesothelioma cell lines growing as a monolayer. We also demonstrate the inhibition of ERK5 phosphorylation in various human mesothelioma cell lines by XMD8-92. We further confirmed the toxicity of XMD8-92 towards mesothelioma cell lines grown as spheroids in a 3-D model as well as in intraperitoneal (immune-competent) and intrapleural (immune-deficient) mouse models with and without chemotherapeutic drugs. To ascertain the mechanism, we explored the role of the nod-like receptor family member containing a pyrin domain 3 (NLRP3) inflammasome in the process. We found XMD8-92 attenuated naïve and chemotherapeutic-induced inflammasome priming and activation in mesothelioma cells. It can thus be concluded that ERK5 inhibition attenuates mesothelioma tumor growth and this phenomenon in part is regulated by the inflammasome.

Abstract 4046: The role of TFPI2 and FGF2 in asbestos-induced mesothelial to fibroblastic transition

Mechanisms involved in the tumorigenesis of the devastating cancer, malignant mesothelioma (MM) are poorly understood. We have recently shown that interleukin-1β (IL-1β), an inflammatory cytokine is upregulated by asbestos via the activation of the inflammasome (a molecular platform that assembles for the activation of caspase-1) in mesothelial cells. Furthermore we have demonstrated that IL-1β secretion may lead to the activation of downstream signaling cascades involved in malignant transformation of mesothelial cells. Preliminary data from our lab indicate that in addition to IL-1β, asbestos exposure upregulated the secretion of basic fibroblast growth factor (bFGF/FGF2) and tissue factor pathway inhibitor 2 ((TFPI2) a kunitz type protease inhibitor). These factors were also regulated by the inflammasome and have never before been implicated in asbestos-induced mesothelial to fibroblastic transition (MFT). Based on our preliminary data, we hypothesized that upregulation of IL-1β by asbestos-induced inflammasome activation increases FGF2 secretion and signaling. Furthermore, we hypothesize that FGF2 together with increased TFPI2 secretion induces transition of mesothelial cells to a fibroblastic phenotype that facilitates MM carcinogenesis. In the proposed study we will delineate the role of TFPI2 (siRNA) and FGF2 (pan FGFR inhibitor, BGJ398) in the process of asbestos-induced MFT. Data from this study will provide added insight into the mechanisms involved in the initiation of MM and indicate whether TFPI2 and FGF2 can serve as drugable targets for combination therapy against MM. This work is supported by NIH grant, RO1 ES021110. Citation Format: Joyce K. Thompson, Jill Miller, Maximilian B. MacPherson, Arti Shukla. The role of TFPI2 and FGF2 in asbestos-induced mesothelial to fibroblastic transition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4046.

Abstract 4315: Extracellular signal regulated kinase 5 inpathogenesis of malignant mesothelioma.

Malignant mesothelioma (MM) is a neoplastic disease of the pleural, peritoneal or pericardial cavity. Currently, there is no therapy for MM as it is resistant to most of the common chemotherapies and therefore, there is a need for new treatment strategies. In the present study we demonstrated that ERK5 is important in MM tumor growth and can potentially be targeted in combination with the chemotherapeutic drugs for more effective treatment. Human MM cell lines exhibit constitutive activation of ERK5. Addition of doxorubicin to these MM cell lines resulted in further activation of ERK5. ERK5 silencing by small hairpin RNA (shERK5) increased DOX-induced cell death and DOX retention in human MM cells. In addition, shERK5 MM lines exhibited both attenuated colony formation on soft agar and invasion of MM cells in vitro. Most importantly, injection of shERK5 MM cell lines into SCID mice showed significant reduction in tumor growth using both subcutaneous and intraperitoneal models. Finally, use of doxorubicin and cisplatin in combination with ERK5 inhibition showed further reduction in tumor weight and volume in the IP model of tumor growth, proving our hypothesis that ERK5 inhibition in combination with chemotherapeutic drugs is a beneficial strategy for combination therapy in MM patients. This work is supported by Mesothelioma Applied Research Foundation (AS), NIEHS-RO1ES021110 (AS) and T32 ES07122 (BM) grants. Citation Format: Arti Shukla, Jill Miller, Christopher Cason, Mutlay Sayan, Maximilian MacPherson, Stacie Beuschel, Brooke Mossman. Extracellular signal regulated kinase 5 inpathogenesis of 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 4315. doi:10.1158/1538-7445.AM2013-4315