Novel induction therapies for pleural mesothelioma

A Redox-Silent Analogue of Tocotrienol May Break the Homeostasis of Proteasomes in Human Malignant Mesothelioma Cells by Inhibiting STAT3 and NRF1

6-O-Carboxypropyl-alpha-tocotrienol (α-T3E) is a multi-target redox-silent analogue of tocotrienol that exhibits cytotoxicity against many cancer cells, including malignant mesothelioma (MM) cells. α-T3E has several molecular targets to effectively induce cytotoxicity against MM cells; however, the mechanisms underlying this cytotoxicity remain unclear. In the present study, we demonstrated that the α-T3E-dependent disruption of the homeostasis of proteasomes strongly induced endoplasmic reticulum (ER) stress, which resulted in effective cytotoxicity against MM cells. The α-T3E-dependent disruption of the homeostasis of proteasomes depended on decreases in proteasome subunits via the inactivation of signal transducer and activator of transcription 3 (STAT3) and nuclear factor erythroid 2 related factor-1 (NRF1), which inhibited protease activity, such as chymotrypsin-like activity, in proteasomes. The α-T3E-dependent inhibition of this activity also induced severe ER stress and ultimately resulted in effective cytotoxicity against MM cells with chemoresistance. The present results indicate that α-T3E acts as an effective anti-mesothelioma agent by disrupting the homeostasis of proteasomes through the simultaneous inactivation of STAT3 and NRF1.

The Role of Neoadjuvant Chemotherapy in Patients With Resectable Malignant Pleural Mesothelioma-An Institutional and National Analysis

BACKGROUND

There is no standard of care with respect to the use of neoadjuvant chemotherapy (NAC) in resectable malignant pleural mesothelioma (MPM). We performed an intention-to-treat analysis with data from a single institution and the National Cancer Database (NCDB) to identify whether the use of NAC impacts survival in resectable MPM.

METHODS

Patients with MPM who had surgery with curative intent at Duke University from 1995 to 2017 were selected, and the 2004-2015 NCDB was used to identify MPM patients with clinical stage I-IIIB who underwent definitive surgery. For both cohorts, patients were stratified by receipt of NAC. Primary outcomes were overall survival and postresection survival (RS), which were estimated using Kaplan-Meier and multivariable Cox proportional hazards models.

RESULTS

A total of 257 patients met inclusion criteria in the Duke cohort. Compared with immediate resection (IR), NAC was associated with similar overall survival but an increased risk for postresection mortality in both unmatched (adjusted hazard ratio [HR] = 1.85, 95% confidence interval [CI] = 1.21 to 2.83) and propensity-matched (HR = 1.62, 95% CI = 1.03 to 2.55) cohorts. A total of 1949 NCDB patients were included: 1597 (81.9%) IR and 352 (18.1%) NAC. RS was worse for patients undergoing NAC in both unmatched (HR = 1.85, 95% CI = 1.21 to 2.83) and propensity-matched (HR = 1.29, 95% CI = 1.06 to 1.57) analyses compared with patients receiving IR.

CONCLUSIONS

In this intention-to-treat study, NAC was associated with worse RS compared with IR in patients with MPM. The risks and benefits of induction therapy should be weighed before offering it to patients with resectable MPM.

Scientific Advances and New Frontiers in Mesothelioma Therapeutics

Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer that arises from the mesothelial surface of the pleural and peritoneal cavities, the pericardium, and rarely, the tunica vaginalis. The incidence of MPM is expected to increase worldwide in the next two decades. However, even with the use of multimodality treatment, MPM remains challenging to treat, with a 5-year survival rate of less than 5%. The International Association for the Study of Lung Cancer has gathered experts in different areas of mesothelioma research and management to summarize the most significant scientific advances and new frontiers related to mesothelioma therapeutics.

A Succinate Ether Derivative of Tocotrienol Enhances Dickkopf-1 Gene Expression through Epigenetic Alterations in Malignant Mesothelioma Cells

BACKGROUND

Wnt signaling plays an essential role in tumor cell growth, including the development of malignant mesothelioma (MM). Epigenetic silencing of negative Wnt regulators leading to constitutive Wnt signaling has been observed in various cancers and warrants further attention. We have reported that a succinate ether derivative of α-tocotrienol (T3E) has potent cytotoxic effects in MM cells. Thus, in this study, we investigated whether the anti-MM effect of T3E could be mediated via the epigenetic alteration of the Wnt antagonist gene, Dickkopf-1 (DKK1).

METHODS

WST-1 and cell analyzers were employed to analyze the effects of T3E on cell viability and apoptosis of human MM cell lines (H2452, H28). Real-time PCR and Western blot were performed to evaluate the expression at mRNA and protein levels. Methylation status and epigenetic modifications of DKK1's promoter regions after T3E treatment in MM cells were studied using methylation-specific PCR and Chromatin immunoprecipitation. Small interfering RNA-mediated knockdown -(siRNA), and specific inhibitors, were used to validate DKK1 as a target of T3E.

RESULTS

T3E markedly impaired MM cell viability, increased the expression of phosphorylated-JNK and DKK1 and suppressed cyclin D, a downstream target gene of Wnt signaling. Knockdown of DKK1 expression by siRNA or a specific JNK inhibitor confirmed the contribution of DKK1 and JNK to T3E-induced cytotoxicity in MM cells. On the other hand, cytoskeleton-associated protein 4 (CKAP4) expression, which promotes cell proliferation as a Wnt-independent DKK1 receptor was inhibited by T3E. Silencing CKAP4 by -siRNA did not appear to directly affect MM cell viability, thereby indicating that expression of both DKK1 and CKAP4 is required. Furthermore, T3E-mediated inhibition of both DNA methyltransferases (DNMT1, 3A, and 3B) and histone deacetylases (HDAC1, 2, 3, and 8) in MM cells leads to increased DKK1 expression, thereby promoting tumor growth inhibition. MM cells treated with Zebularine (a DNMT inhibitor) and sodium butyrate (an HDAC inhibitor) exhibited cytotoxic effects, which may explain the inhibitory action of T3E on MM cells. In addition, an enhanced expression of DKK1 in MM cells following T3E treatment is positively correlated with the methylation status of its promoter; T3E decreased DNA methylation and increased histone acetylation. Moreover, T3E specifically increased histone H3 lysine 4 (H3K4) methylation activity, whereas no effects were observed on histone H3K9 and H3K27.

CONCLUSIONS

Targeting the epigenetic induction of DKK1 may lead to effective treatment of MM, and T3E has great potential to induce anti-MM activity.

P2X7 targeting inhibits growth of human mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive tumor refractory to anti-blastic therapy. MPM cells show several genetic and biochemical defects, e.g. overexpression of oncogenes, downregulation of onco-suppressor genes, dysregulation of microRNA, or alteration of intracellular Ca²⁺ homeostasis and of apoptosis. No information is as yet available on purinergic signalling in this tumor. Signalling via the P2×7 (P2RX7 or P2×7R) purinergic receptor is attracting increasing attention as a pathway involved in cancer cell death or proliferation. In this report we show that the P2×7R is expressed by three MPM cell lines established from MPM patients but not by mesothelial cells from healthy subjects (healthy mesothelial cells, HMCs). MPM cell proliferation was inhibited by in vitro incubation in the presence of selective P2×7R antagonists, as well as by stimulation with the P2×7R agonist BzATP. Systemic administration of the selective P2×7R blocker AZ10606120 inhibited in vivo growth of MPM tumors whether implanted subcutaneously (s.c.) or intraperitoneally (i.p.). Our findings suggest that the P2×7R might be a novel target for the therapy of mesothelioma.

Treatment of Malignant Pleural Mesothelioma: American Society of Clinical Oncology Clinical Practice Guideline

Purpose To provide evidence-based recommendations to practicing physicians and others on the management of malignant pleural mesothelioma. Methods ASCO convened an Expert Panel of medical oncology, thoracic surgery, radiation oncology, pulmonary, pathology, imaging, and advocacy experts to conduct a literature search, which included systematic reviews, meta-analyses, randomized controlled trials, and prospective and retrospective comparative observational studies published from 1990 through 2017. Outcomes of interest included survival, disease-free or recurrence-free survival, and quality of life. Expert Panel members used available evidence and informal consensus to develop evidence-based guideline recommendations. Results The literature search identified 222 relevant studies to inform the evidence base for this guideline. Recommendations Evidence-based recommendations were developed for diagnosis, staging, chemotherapy, surgical cytoreduction, radiation therapy, and multimodality therapy in patients with malignant pleural mesothelioma. Additional information is available at www.asco.org/thoracic-cancer-guidelines and www.asco.org/guidelineswiki .

How does the timing of chemotherapy affect outcome following radical surgery for malignant pleural mesothelioma?

OBJECTIVES

There is little evidence regarding the use of chemotherapy as part of multimodality treatment of malignant pleural mesothelioma (MPM). We aimed to determine whether, in those patients fit for chemotherapy, a delay in this treatment affected survival.

MATERIALS AND METHODS

We analysed postoperative variables of 229 patients undergoing either extrapleural pneumonectomy (EPP) (81 patients) or extended pleurectomy-decortication (EPD) (197 patients) for MPM at a single centre. There was no standard protocol for additional chemotherapy and varied with referral centre. Outcome was compared between 4 chemotherapy strategies: true adjuvant therapy, neo-adjuvant therapy, therapy reserved until evidence of disease progression in those otherwise fit in the post-operative setting, and those unfit for chemotherapy.

RESULTS

There was no effect of the timing of chemotherapy on overall or progression free survival in patients fit enough for treatment (p=0.39 and p=0.33 respectively). However delaying chemotherapy until evidence of disease progression in patients with non-epithelioid disease had a detrimental effect on overall survival (OS), and on progression free survival (PFS) in lymph node positive patients (15.6 vs. 8.2 months p=0.001, and 14.9 vs. 6.0 months p=0.016). Further analysis of 169 patients receiving platinum/pemetrexed as first line treatment, showed similar results; there was no effect of the timing of chemotherapy on OS or PFS (p=0.80 and p=0.53 respectively) and an improved OS in patients with non-epithelioid disease, and improved PFS in those with lymph node metastases, if chemotherapy was given in the immediate adjuvant setting (p=0.001 and 0.038) when therapy was not delayed until disease progression.

CONCLUSION

Our results suggest that the timing of additional chemotherapy may be important in those with a poorer prognosis on the basis of cell type and nodal stage. In these patients additional postoperative chemotherapy should not be delayed.

Is the patient with mesothelioma without hope?

Hope is a very important mindset for malignant pleural mesothelioma patients as their cancer has a grim prognosis and limited therapeutic options. In this paper, we briefly discuss what hope means for a patient and how hope can help to cope with this disease. In addition, we discuss false hope. We also briefly touch on a few of the new therapies currently under development.