A multicenter, randomized, phase II/III study of dendritic cells loaded with allogeneic tumor cell lysate (MesoPher) in subjects with mesothelioma as maintenance therapy after chemotherapy: DENdritic cell Immunotherapy for Mesothelioma (DENIM) trial

Integration of the PD-L1 inhibitor atezolizumab and WT1/DC vaccination into standard-of-care first-line treatment for patients with epithelioid malignant pleural mesothelioma-Protocol of the Immuno-MESODEC study

Malignant pleural mesothelioma (MPM) is an aggressive cancer with a very poor prognosis. Recently, immune checkpoint inhibition (ICI) has taken center stage in the currently ongoing revolution that is changing standard-of-care treatment for several malignancies, including MPM. As multiple arguments and accumulating lines of evidence are in support of the existence of a therapeutic synergism between chemotherapy and immunotherapy, as well as between different classes of immunotherapeutics, we designed a multicenter, single-arm, phase I/II trial in which both programmed-death-ligand 1 (PD-L1) inhibition and dendritic cell (DC) vaccination are integrated in the first-line conventional platinum/pemetrexed-based treatment scheme for epithelioid MPM patients (Immuno-MESODEC, ClinicalTrials.gov identifier NCT05765084). Fifteen treatment-naïve patients with unresectable epithelioid subtype MPM will be treated with four 3-weekly (±3 days) chemo-immunotherapy cycles. Standard-of-care chemotherapy consisting of cisplatinum (75mg/m2) and pemetrexed (500mg/m2) will be supplemented with the anti-PD-L1 antibody atezolizumab (1200 mg) and autologous Wilms' tumor 1 mRNA-electroporated dendritic cell (WT1/DC) vaccination (8-10 x 106 cells/vaccination). Additional atezolizumab (1680 mg) doses and/or WT1/DC vaccinations (8-10 x 106 cells/vaccination) can be administered optionally following completion of the chemo-immunotherapy scheme. Follow-up of patients will last for up to 90 days after final atezolizumab administration and/or WT1/DC vaccination or 24 months after diagnosis, whichever occurs later. The trial's primary endpoints are safety and feasibility, secondary endpoints are clinical efficacy and immunogenicity. This phase I/II trial will evaluate whether addition of atezolizumab and WT1/DC vaccination to frontline standard-of-care chemotherapy for the treatment of epithelioid MPM is feasible and safe. If so, this novel combination strategy should be further investigated as a promising advanced treatment option for this hard-to-treat cancer.

Immunotherapy of mesothelioma: the evolving change of a long-standing therapeutic dream

Pleural mesothelioma (PM) is an aggressive and rare disease, characterized by a very poor prognosis. For almost two decades, the world standard treatment regimen for unresectable PM has consisted of a platinum-based drug plus pemetrexed, leading to an overall survival of approximately 12 months. The dramatic therapeutic scenario of PM has recently changed with the entry into the clinic of immune checkpoint inhibition, which has proven to be an effective approach to improve the survival of PM patients. The aim of the present review is to provide a comprehensive overview of the most promising immunotherapeutic-based strategies currently under investigation for advanced PM.

The Current Treatment Landscape of Malignant Pleural Mesothelioma and Future Directions

The incidence of malignant pleural mesothelioma is expected to increase globally. New treatment options for this malignancy are eagerly awaited to improve the survival and quality of life of patients. The present article highlights the results of recent advances in this field, analyzing data from several relevant trials. The heterogeneous tumor microenvironment and biology, together with the low mutational burden, pose a challenge for treating such tumors. So far, no single biomarker has been soundly correlated with targeted therapy development; thus, combination strategies are often required to improve outcomes. Locally applied vaccines, the expansion of genetically engineered immune cell populations such as T cells, the blockage of immune checkpoints that inhibit anti-tumorigenic responses and chemoimmunotherapy are among the most promising options expected to change the mesothelioma treatment landscape.

Current State-of-the-Art Therapy for Malignant Pleural Mesothelioma and Future Options Centered on Immunotherapy

Malignant pleural mesothelioma (MPM) is a locally aggressive disease related to asbestos exposure with a median survival for untreated patients of 4-8 months. The combination of chemotherapy based on platinum and antifolate is the standard treatment, and the addition of bevacizumab adds two months to median survival. Recently, in first-line treatment, immunotherapy combining nivolumab with ipilimumab has been shown to be superior to chemotherapy in the CheckMate-743 study in terms of overall survival (18.1 months), leading to its approval by the FDA and EMA. The positive results of this study represent a new standard of treatment for patients with MPM; however, not all patients will benefit from immunotherapy treatment. In an effort to improve the selection of patient candidates for immunotherapy for different tumors, biomarkers that have been associated with a greater possibility of response to treatment have been described. MPM is a type of tumor with low mutational load and neo-antigens, making it a relatively non-immunogenic tumor for T cells and possibly less susceptible to responding to immunotherapy. Different retrospective studies have shown that PD-L1 expression occurs in 20-40% of patients and is associated with a poor prognosis; however, the predictive value of PD-L1 in response to immunotherapy has not been confirmed. The purpose of this work is to review the state of the art of MPM treatment in the year 2023, focusing on the efficacy results of first-line or subsequent immunotherapy studies on patients with MPM and possible chemo-immunotherapy combination strategies. Additionally, potential biomarkers of response to immunotherapy will be reviewed, such as histology, PD-L1, lymphocyte populations, and TMB.

Pleural Mesothelioma: Treatable Traits of a Heterogeneous Disease

Pleural mesothelioma is an aggressive disease with diffuse nature, low median survival, and prolonged latency presenting difficulty in prognosis, diagnosis, and treatment. Here, we review all these aspects to underline the progress being made in its investigation and to emphasize how much work remains to be carried out to improve prognosis and treatment.

Pembrolizumab plus lenvatinib in second-line and third-line patients with pleural mesothelioma (PEMMELA): a single-arm phase 2 study

BACKGROUND

The combination of pembrolizumab, an anti-PD-1 antibody, and lenvatinib, an antiangiogenic multikinase inhibitor, shows synergistic activity in preclinical and clinical studies in solid tumours. We assessed the clinical activity of this combination therapy in patients with pleural mesothelioma who progressed after platinum-pemetrexed chemotherapy.

METHODS

In this single-arm, single-centre, phase 2 study, done at the Netherlands Cancer Institute in Amsterdam, The Netherlands, eligible patients (aged ≥18 years) with pleural mesothelioma with an Eastern Cooperative Oncology Group performance status of 0-1, progression after chemotherapy (no previous immunotherapy), and measurable disease according to the modified Response Evaluation Criteria In Solid Tumours (mRECIST) for mesothelioma version 1.1. Patients received 200 mg intravenous pembrolizumab once every 3 weeks plus 20 mg oral lenvatinib once per day for up to 2 years or until disease progression, development of unacceptable toxicity, or withdrawal of consent. The primary endpoint was objective response rate identified by a local investigator according to mRECIST version 1.1. This trial is registered with ClinicalTrials.gov, NCT04287829, and is recruiting for the second cohort.

FINDINGS

Between March 5, 2021, and Jan 31, 2022, 42 patients were screened, of whom 38 were included in the primary endpoint and safety analyses (median age 71 years [IQR 65-75], 33 [87%] male and five [13%] female) . At data cutoff (Jan 31, 2023), with a median follow-up of 17·7 months (IQR 13·8-19·4), 22 (58%; 95% CI 41-74) of 38 patients had an objective response. The independent review showed an objective response in 17 (45%; 95% CI 29-62) of 38 patients. Serious treatment-related adverse events occurred in ten (26%) patients, including one treatment-related death due to myocardial infarction. The most common treatment-related grade 3 or worse adverse events were hypertension (eight patients [21%]) and anorexia and lymphopenia (both four patients [11%]). In 29 (76%) of 38 patients, at least one dose reduction or discontinuation of lenvatinib was required.

INTERPRETATION

Pembrolizumab plus lenvatinib showed promising anti-tumour activity in patients with pleural mesothelioma with considerable toxicity, similar to that in previous studies. Available evidence from the literature suggests a high starting dose of lenvatinib for optimal anti-tumour activity. This, however, demands a high standard of supportive care. The combination therapy of pembrolizumab and lenvatinib warrants further investigation in pleural mesothelioma.

FUNDING

Merck Sharp & Dohme.

Malignant mesothelioma tumours: molecular pathogenesis, diagnosis, and therapies accompanying clinical studies

The pathetic malignant mesothelioma (MM) is a extremely uncommon and confrontational tumor that evolves in the mesothelium layer of the pleural cavities (inner lining- visceral pleura and outer lining- parietal pleura), peritoneum, pericardium, and tunica vaginalis and is highly resistant to standard treatments. In mesothelioma, the predominant pattern of lesions is a loss of genes that limit tumour growth. Despite the worldwide ban on the manufacture and supply of asbestos, the prevalence of mesothelioma continues to increase. Mesothelioma presents and behaves in a variety of ways, making diagnosis challenging. Most treatments available today for MM are ineffective, and the median life expectancy is between 10 and 12 months. However, in recent years, considerable progress has already been made in understanding the genetics and molecular pathophysiology of mesothelioma by addressing hippo signaling pathway. The development and progression of MM are related to many important genetic alterations. This is related to NF2 and/or LATS2 mutations that activate the transcriptional coactivator YAP. The X-rays, CT scans, MRIs, and PET scans are used to diagnose the MM. The MM are treated with surgery, chemotherapy, first-line combination chemotherapy, second-line treatment, radiation therapy, adoptive T-cell treatment, targeted therapy, and cancer vaccines. Recent clinical trials investigating the function of surgery have led to the development of innovative approaches to the treatment of associated pleural effusions as well as the introduction of targeted medications. An interdisciplinary collaborative approach is needed for the effective care of persons who have mesothelioma because of the rising intricacy of mesothelioma treatment. This article highlights the key findings in the molecular pathogenesis of mesothelioma, diagnosis with special emphasis on the management of mesothelioma.

Rare thoracic cancers: a comprehensive overview of diagnosis and management of small cell lung cancer, malignant pleural mesothelioma and thymic epithelial tumours

Despite the progress in outcomes seen with immunotherapy in various malignancies, including nonsmall cell lung cancer, the benefits are less in small cell lung cancer, malignant pleural mesothelioma and thymic epithelial tumours. New effective treatment options are needed, guided via more in-depth insights into the pathophysiology of these rare malignancies. This review comprehensively presents an overview of the clinical presentation, diagnostic tools, staging systems, pathophysiology and treatment options for these rare thoracic cancers. In addition, opportunities for further improvement of therapies are discussed.

The Evolving Role of Immune-Checkpoint Inhibitors in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare cancer usually caused by asbestos exposure and associated with a very poor prognosis. After more than a decade without new therapeutic options, immune checkpoint inhibitors (ICIs) demonstrated superiority over standard chemotherapy, with improved overall survival in the first and later-line settings. However, a significant proportion of patients still do not derive benefit from ICIs, highlighting the need for new treatment strategies and predictive biomarkers of response. Combinations with chemo-immunotherapy or ICIs and anti-VEGF are currently being evaluated in clinical trials and might change the standard of care in the near future. Alternatively, some non-ICI immunotherapeutic approaches, such as mesothelin targeted CAR-T cells or denditric-cells vaccines, have shown promising results in early phases of trials and are still in development. Finally, immunotherapy with ICIs is also being evaluated in the peri-operative setting, in the minority of patients presenting with resectable disease. The goal of this review is to discuss the current role of immunotherapy in the management of malignant pleural mesothelioma, as well as promising future therapeutic directions.

The Evolving Therapeutic Landscape for Malignant Pleural Mesothelioma

PURPOSE OF REVIEW

For patients with malignant pleural mesothelioma, prognosis is poor with extremely low 5-year survival rates and limited therapeutic options. Here, we review the current treatment landscape for mesothelioma and highlight promising future therapeutic directions.

RECENT FINDINGS

Evolving frontline therapeutic options for mesothelioma include VEGF inhibition in combination with chemotherapy and dual immune checkpoint inhibition, with synergisms between the therapies and response prediction via biomarkers also being explored. Evolving experimental treatments for mesothelioma include PARP and ALK inhibitors, dendritic and CAR T-cell therapies, anti-mesothelin vaccines, and oncolytic viral therapies, representing timely advances in the field. The therapeutic landscape for malignant pleural mesothelioma is evolving and preferred treatment in the frontline and later settings will likely evolve with it. However, this does not preclude the evidence for including multi-modal therapies spanning angiogenesis and immune checkpoint inhibitors, and biomarker utilization, in current clinical trials and management.

Adoptive cell therapies in thoracic malignancies

Immunotherapy has gained great interest in thoracic malignancies in the last decade, first in non-small cell lung cancer (NSCLC), but also more recently in small-cell lung cancer (SCLC) and malignant pleural mesothelioma (MPM). However, while 15-20% of patients will greatly benefit from immune checkpoint blockers (ICBs), a vast majority will rapidly exhibit resistance. Reasons for this are multiple: non-immunogenic tumors, immunosuppressive tumor microenvironment or defects in immune cells trafficking to the tumor sites being some of the most frequent. Current progress in adoptive cell therapies could offer a way to overcome these hurdles and bring effective immune cells to the tumor site. In this review, we discuss advantages, limits and future perspectives of adoptive cell therapy (ACT) in thoracic malignancies from lymphokine-activated killer cells (LAK), cytokine-induced killer cells (CIK), natural killer cells (NK), dendritic cells (DC) vaccines and tumor-infiltrating lymphocytes (TILs) to TCR engineering and CARs. Trials are still in their early phases, and while there may still be many limitations to overcome, a combination of these different approaches with ICBs, chemotherapy and/or radiotherapy could vastly improve the way we treat thoracic cancers.

Immunotherapy approaches for malignant pleural mesothelioma

Over the past decade, immune-checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer. In mesothelioma, a rare cancer with a dismal prognosis generally caused by exposure to asbestos, treatment with single or dual ICIs results in robust improvements in overall survival over previous standard-of-care therapies, both in the first-line and relapsed disease settings. Predictive biological features that underpin response to ICIs remain poorly understood; however, insights into the immune microenvironment and genomic landscape of mesothelioma as well as into their association with response or acquired resistance to ICIs are emerging. Several studies of rational combinations involving ICIs with either another ICI or a different agent are ongoing, with emerging evidence of synergistic antitumour activity. Non-ICI-based immunotherapies, such as peptide-based vaccines and mesothelin-targeted chimeric antigen receptor T cells, have demonstrated promising efficacy. Moreover, results from pivotal trials of dendritic cell vaccines and viral cytokine delivery, among others, are eagerly awaited. In this Review, we comprehensively summarize the key steps in the development of immunotherapies for mesothelioma, focusing on strategies that have led to randomized clinical evaluation and emerging predictors of response. We then forecast the future treatment opportunities that could arise from ongoing research.

Novel Insights Into Mesothelioma Therapy: Emerging Avenues and Future Prospects

Malignant mesothelioma is a rare and aggressive cancer that develops in the thin layer surrounding the mesothelium and is mainly caused by asbestos exposure. Despite improvements in patient prognosis with conventional cancer treatments, such as surgery, chemotherapy, and radiotherapy, there are still no curative treatment modalities for advanced disease. In recent years, new therapeutic avenues have been explored. Improved understanding of the mechanisms underlying the dynamic tumor interaction with the immune system has led to the development of immunotherapeutic approaches. Numerous recent clinical trials have shown a desire to develop more effective treatments that can be used to fight against the disease. Immune checkpoint inhibitors, oncolytic adenoviruses, and their combination represent a promising strategy that can be used to synergistically overcome immunosuppression in the mesothelioma tumor microenvironment. This review provides a synthesized overview of the current state of knowledge on new therapeutic options for mesothelioma with a focus on the results of clinical trials conducted in the field.

Evolving Landscape of Initial Treatments for Patients with Malignant Pleural Mesotheliomas: Clinical Trials to Clinical Practice

Malignant pleural mesothelioma (MPM) is the most common form of mesothelioma and the type most often studied in prospective clinical trials.This review reports the trials that have shaped first-line treatment for patients with advanced/unresectable MPM and the real-world integration of first-line immune checkpoint inhibitors into clinical practice.

Advances in Drug Treatments for Mesothelioma

INTRODUCTION

The paucity of the therapeutic armamentarium currently available for patients with malignant mesothelioma clearly represents a huge unmet need. Over the last years, based on new advances in understanding the biology of mesothelioma, new therapeutic approaches have been investigated.

AREAS COVERED

In this manuscript, the literature data regarding the advances in drug treatment for patients with mesothelioma are critically reviewed, focusing particularly on immunotherapy and targeted therapy.

EXPERT OPINION

The latest findings on immunotherapy and targeted therapy are changing the therapeutic armamentarium for mesothelioma. However, mesothelioma comprises of genomically different subtypes and the phenotypic diversity combined with the rarity of this disease represents a major criticality in developing new effective therapies. Although the first clinical data are encouraging, the treatment's stratification by molecular characteristics for mesothelioma is only at the beginning. Luckily, the rapid improvement of understanding the biology of mesothelioma is producing new opportunities in discovering new therapeutic targets to test in pre-clinical settings and to transfer in the clinical setting. In this evolving scenario, the future perspectives for mesothelioma patients seem really promising.

Tsunami of immunotherapy reaches mesothelioma

Malignant pleural mesothelioma (MPM) is the most common type of malignant mesothelioma. It is a rare tumor linked to asbestos exposure and is associated with a poor prognosis. Until very recently, patients with advanced or unresectable disease had limited treatment options, primarily based on doublet chemotherapy with cisplatin and pemetrexed. In 2020 and 2021, after more than a decade with no major advances or new drugs, two phase III clinical trials published results positioning immunotherapy as a promising option for the first- and second-line treatment of MPM. Immunotherapy has revolutionized the treatment of many cancers and is also showing encouraging results in malignant mesothelioma. Both immune checkpoint inhibition and dual cytotoxic T-lymphocyte-associated antigen 4 and programmed death-ligand 1 pathway blockade resulted in significantly improved overall survival in randomized phase III trials. In the CheckMate 743 trial, first-line therapy with nivolumab plus ipilimumab outperformed standard chemotherapy, while in the CONFIRM trial, nivolumab outperformed placebo in patients previously treated with chemotherapy. These two trials represent a major milestone in the treatment of MPM and are set to position immunotherapy as a viable alternative for treatment-naïve patients and patients with progressive disease after chemotherapy.

Immunotherapy for mesothelioma: Moving beyond single immune check point inhibition

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm with low survival rates. Platinum-based chemotherapy has represented the cornerstone of treatment for over a decade, prompting the investigation of new therapeutic strategies both in the early stage of the disease and in the advanced setting. The advent of immune check-point inhibitors (ICIs) has recently revamped the enthusiasm for using immunotherapy also in MPM. However, results from first clinical trials using single immune check-point inhibition have been conflicting, and this may be mainly attributed to the lack of specific biomarkers as well as to intra- and inter- patient heterogeneity. The phase III Checkmate743 firstly demonstrated the superiority of an ICI combination (nivolumab plus ipilimumab) over chemotherapy in the first-line treatment of unresectable MPM, leading to FDA approval of this regimen and showing that moving beyond single immune check point inhibition might be a successful strategy to overcome resistance in the majority of MPM patients. In this review, we describe the emerging immunotherapy strategies for the treatment of MPM. We also discuss how refining the approach in pre-clinical studies towards a more holistic perspective (which takes into account not only genetic but also pathophysiological vulnerabilities) and strengthening multi-institutional collaboration in clinical trials is finally helping the clinical development of immunotherapy in MPM.

Image-guided interventional radiological delivery of chimeric antigen receptor (CAR) T cells for pleural malignancies in a phase I/II clinical trial

OBJECTIVES

We describe techniques and results of image-guided delivery of mesothelin-targeted chimeric antigen receptor (CAR) T cells in patients with pleural malignancies in a phase I/II trial (ClinicalTrials.gov: NCT02414269).

MATERIALS AND METHODS

Patients without a pleural catheter or who lack effusion for insertion of a catheter (31 of 41) were administered intrapleural CAR T cells by interventional radiologists under image guidance by computed tomography or ultrasound. CAR T cells were administered through a needle in an accessible pleural loculation (intracavitary) or following an induced loculated artificial pneumothorax. In patients where intracavitary infusion was not feasible, CAR T cells were injected via percutaneous approach either surrounding and/or in the pleural nodule/thickening (intratumoral). Pre- and post-procedural clinical, laboratory, and imaging findings were assessed.

RESULTS

CAR T cells were administered intrapleurally in 31 patients (33 procedures, 2 patients were administered a second dose) with successful delivery of planned dose (10-186 mL); 14/33 (42%) intracavitary and 19/33 (58%) intratumoral. All procedures were completed within 2 h of T-cell thawing. There were no procedure-related adverse events greater than grade 1 (1 in 3 patients had prior ipsilateral pleural fusion procedures). The most common imaging finding was ground glass opacities with interlobular septal thickening and/or consolidation, observed in 12/33 (36%) procedures. There was no difference in the incidence of fever, CRP, IL-6, and peak vector copy number in the peripheral blood between infusion methods.

CONCLUSION

Image-guided intrapleural delivery of CAR T cells using intracavitary or intratumoral routes is feasible, repeatable and safe across anatomically variable pleural cancers.

Current Management and Future Perspective in Pleural Mesothelioma

Pleural mesothelioma is an aggressive malignancy arising from pleural mesothelial cell lining, predominantly associated with prior exposure to asbestos. The ban on asbestos use has led to its lower incidence in many countries, but globally the disease burden is expected to rise. Therefore, well-planned research is needed to develop more effective, tolerable and affordable drugs. The development of novel treatment has been too slow, with only two regimens of systemic therapy with robust phase 3 data approved formally to date. The treatment scenario for resectable disease remains controversial. However, recent developments in the understanding of disease and clinical trials have been encouraging, and may add better treatment options in the coming years. In this review, we discuss the current treatment options for pleural mesothelioma and shed light on some recent studies and ongoing trials.

Incidence, treatment and survival of malignant pleural and peritoneal mesothelioma: a population-based study

INTRODUCTION

Malignant mesothelioma (MM) is an aggressive cancer that primarily arises from the pleura (MPM) or peritoneum (MPeM), mostly due to asbestos exposure. This study reviewed the Dutch population-based incidence, treatment and survival since the national ban on asbestos in 1993.

MATERIALS AND METHODS

Patients with MPM or MPeM diagnosed from 1993 to 2018 were selected from the Dutch cancer registry. Annual percentage change (APC) was calculated for (age-specific and sex-specific) revised European standardised incidence rates (RESR). Treatment pattern and Kaplan-Meier overall survival analyses were performed.

RESULTS

In total, 12 168 patients were included in the study. For male patients younger than 80 years, the MM incidence significantly decreased in the last decade (APC ranging between -9.4% and -1.8%, p<0.01). Among both male and female patients aged over 80 years, the incidence significantly increased during the entire study period (APC 3.3% and 4.6%, respectively, p<0.01). From 2003 onwards, the use of systemic chemotherapy increased especially for MPM (from 9.3% to 39.4%). Overall, 62.2% of patients received no antitumour treatment. The most common reasons for not undergoing antitumour treatment were patient preference (42%) and performance status (25.6%). The median overall survival improved from 7.3 (1993-2003) to 8.9 (2004-2011) and 9.3 months from 2012 to 2018 (p<0.001).

CONCLUSION

The peak of MM incidence was reached around 2010 in the Netherlands, and currently the incidence is declining in most age groups. The use of systemic chemotherapy increased from 2003, which likely resulted in improved overall survival over time. The majority of patients do not receive treatment though and prognosis is still poor.

Novel and Future Treatment Options in Mesothelioma: A Systematic Review

Mesothelioma is a rare tumor, frequently associated with asbestos exposure, arising from pleura and peritoneum. Traditionally, diagnosis and treatment have been difficult in a clinical setting. The treatment is based on a trimodal approach involving surgery, chemotherapy, and radiotherapy. The introduction of chemotherapy improved the overall survival. However, the regimen of pemetrexed/cisplatin doublet has not been changed as a standard treatment since 2004. Novel combinations of ipilimumab and nivolumab have only been approved for clinical use in late 2020. The aim of this review was to systematically summarize findings on novel treatment options in mesothelioma. We searched available medical databases online, such as PubMed and Clinicaltrials.gov, to systematically review the literature on novel approaches in immunotherapy, vaccines, and Chimeric Antigen Receptor (CAR)-T cell therapy in mesothelioma. We manually screened 1127 articles on PubMed and 450 trials on ClinicalTrials.gov, and 24 papers and 12 clinical trials published in the last ten years were included in this review. Immunotherapy that was swiftly introduced to treat other thoracic malignancies was slow to reach desirable survival endpoints in mesothelioma, possibly due to limited patient numbers. Novel treatment approaches, such as CAR-T cell therapy, are being investigated. As the incidence of mesothelioma is still rising globally, novel treatment options based on a better understanding of the tumor microenvironment and the genetic drivers that modulate it are needed to support future precision-based therapies.

Understanding and improving cellular immunotherapies against cancer: From cell-manufacturing to tumor-immune models

The tumor microenvironment (TME) is shaped by dynamic metabolic and immune interactions between precancerous and cancerous tumor cells and stromal cells like epithelial cells, fibroblasts, endothelial cells, and hematopoietically-derived immune cells. The metabolic states of the TME, including the hypoxic and acidic niches, influence the immunosuppressive phenotypes of the stromal and immune cells, which confers resistance to both host-mediated tumor killing and therapeutics. Numerous in vitro TME platforms for studying immunotherapies, including cell therapies, are being developed. However, we do not yet understand which immune and stromal components are most critical and how much model complexity is needed to answer specific questions. In addition, scalable sourcing and quality-control of appropriate TME cells for reproducibly manufacturing these platforms remain challenging. In this regard, lessons from the manufacturing of immunomodulatory cell therapies could provide helpful guidance. Although immune cell therapies have shown unprecedented results in hematological cancers and hold promise in solid tumors, their manufacture poses significant scale, cost, and quality control challenges. This review first provides an overview of the in vivo TME, discussing the most influential cell populations in the tumor-immune landscape. Next, we summarize current approaches for cell therapies against cancers and the relevant manufacturing platforms. We then evaluate current immune-tumor models of the TME and immunotherapies, highlighting the complexity, architecture, function, and cell sources. Finally, we present the technical and fundamental knowledge gaps in both cell manufacturing systems and immune-TME models that must be addressed to elucidate the interactions between endogenous tumor immunity and exogenous engineered immunity.

Biological basis for novel mesothelioma therapies

Mesothelioma is an aggressive cancer that is associated with exposure to asbestos. Although asbestos is banned in several countries, including the UK, an epidemic of mesothelioma is predicted to affect middle-income countries during this century owing to their heavy consumption of asbestos. The prognosis for patients with mesothelioma is poor, reflecting a failure of conventional chemotherapy that has ultimately resulted from an inadequate understanding of its biology. However, recent work has revolutionised the study of mesothelioma, identifying genetic and pathophysiological vulnerabilities, including the loss of tumour suppressors, epigenetic dysregulation and susceptibility to nutrient stress. We discuss how this knowledge, combined with advances in immunotherapy, is enabling the development of novel targeted therapies.

Allogeneic tumor cell line-based vaccines: A good alternative to autologous and cancer stem cell vaccines in colorectal cancer

OBJECTIVES

Besides the uncertainty about colorectal cancer stem cell (CCSC) markers, isolating, purifying, and enriching CCSCs to produce CCSC vaccines is highly challenging. However, allogeneic vaccines developed from CRC cell lines can provide universal, comprehensive, inexpensive, simple, and fast approach to cancer treatment.

MATERIALS AND METHODS

CCSCs were isolated from human CRC tissue using the in vitro sphere formation assay and then characterized through gene expression analysis, in vivo and in vitro tumor formation assay, karyotyping, and surface marker detection. Subsequently, CCSCs and two CRC cell lines (HT-29 and SW-480) were inactivated with cisplatin (CDDP) and administrated as vaccines to the three groups of athymic C57BL/6 nude mice. Afterward, tumorigenesis was challenged with HT-29 cells. The antitumor effect of vaccines was evaluated by tumor and spleen examination and immune response analysis. The cytotoxic activity of splenocytes and serum levels of TGF-β and IFN-γ were measured by Calcein-AM cytotoxicity assay and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

The results of gene expression analysis showed that CCSCs are CD44+CD133-LGR5-. All vaccinations resulted in decreased tumor growth, spleen enlargement, enhanced serum level of IFN-γ and TGF-β, and increased cytotoxic activity of natural killer (NK) cells. The antitumor efficacy of the CCSC vaccine was not more than CRC cell line-based vaccines. Interestingly, the allogeneic SW-480 vaccine could effectively inhibit tumorigenesis.

CONCLUSION

Despite the great challenge in developing CCSC vaccines, allogeneic vaccines based on CRC cell lines can efficiently induce antitumor immunity in CRC.

Novel and Promising Systemic Treatment Approaches in Mesothelioma

OPINION STATEMENT

There was limited progress in the development of novel systemic approaches in the treatment of advanced malignant mesothelioma for years following the publication of the pivotal phase III trial of Vogelzang et al. that established the cisplatin/pemetrexed regimen as a standard 1st-line systemic therapy. Since then, over the last several years, a significant step forward has been made, with incorporation of immune checkpoint inhibitors and anti-angiogenic agents. In addition, better appreciation of mesothelioma biology has allowed detection of novelmolecular therapeutic targets. All the above-mentioned strategies, along with the additional promising approaches represented by adoptive T cell therapy, dendritic cell therapy, cancer vaccines, oncoviral therapy, and agents targeting mesothelin are discussed in this review. The clinical research to identify effective biologic targets and treatment combinations in malignant mesothelioma is ongoing.

Pleural mesothelioma (PM) - The status of systemic therapy

Pleural mesothelioma (PM) remains a malignancy with poor prognosis. Despite initial disappointing response rates to single-agent chemotherapy, upfront platinum and anti-folate-based combination chemotherapy has remained the backbone of treatment for PM for the last three decades. The role of maintenance chemotherapy remains unclear; switch-maintenance gemcitabine has shown improvements in progression-free but not overall survival. The addition of antiangiogenic agents to chemotherapy yielded modest improvements in survival, both upfront in combination with platinum-pemetrexed, and in the relapsed setting. Immunotherapy, particularly PD-(L)1 inhibitors, has shown important but variable effectiveness in relapsed PM when used as monotherapy, and is an important salvage treatment after first-line chemotherapy. Furthermore, the randomized phase 3 trial of ipilimumab-nivolumab versus platinum-pemetrexed chemotherapy demonstrated improved overall survival favouring ipilimumab-nivolumab (HR 0.74, 96.6% CI 0.60-0.91; p = 0.0020), establishing this regimen as the new standard first-line treatment for PM, particularly in those with non-epithelioid histology. Increased interest in PM genomics has led to development of novel personalized therapeutics, such as those targeting DNA repair and EZH2 pathways, however with variable outcomes in trials. Targeting the membrane glycoprotein mesothelin and arginine deprivation are other important strategies under ongoing investigation. The field of PM is changing and new treatments bring hope to a largely lethal and poor prognostic malignancy. Despite these developments, current challenges include understanding the role of combination and multimodality treatments, drivers of resistance to treatment, and establishing predictive biomarkers to improve patient selection and treatment sequencing.

Malignant pleural mesothelioma: recent developments

PURPOSE OF REVIEW

Malignant pleural mesothelioma (MPM) is a rare, but aggressive tumor with still poor prognosis. In this article, we focus on recent developments in the management of MPM including diagnosis, staging, biomarkers, and treatment strategies.

RECENT FINDINGS

Molecular markers such as programmed death-ligand 1 (PDL-1), Breast Cancer gene 1-associated protein gene, and cyclin-dependent kinase inhibitor 2A (CDKN2A) have prognostic impact and should be considered for assessment in patient samples. In addition to histological subtype and tumor pattern, tumor volumetry plays an increasing important role in staging, assessment of treatment response, and prediction of survival. Several new blood-based biomarkers have been recently reported including peripheral blood DNA methylation, microRNAs, fibulin, and high-mobility group box 1, but have not been established in clinical routine use yet. Regarding treatment, targeted therapies, immunotherapy, and vaccination are considered as new promising strategies. Moreover, extended pleurectomy/decortication is favored over extrapleural pneumonectomy (EPP) and intensity-modulated radiotherapy represents a possible approach in combination with EPP and pleurectomy/decortication. Intracavitary treatment options are promising and deserve further investigations.

SUMMARY

Overall, there has not been a real breakthrough in the treatment of MPM. Further research and clinical trials are needed to evaluate outcome and to identify new potential treatment candidates.

The Immune Microenvironment of Malignant Pleural Mesothelioma: A Literature Review

Malignant pleural mesothelioma (MPM) is a rare and aggressive tumour with a poor prognosis, associated with asbestos exposure. Nowadays, treatment is based on chemotherapy with a median overall survival of less than two years. This review highlights the main characteristics of the immune microenvironment in MPM with special emphasis on recent biological advances. The MPM microenvironment is highly infiltrated by tumour-associated macrophages, mainly M2-macrophages. In line with infiltration by M2-macrophages, which contribute to immune suppression, other effectors of innate immune response are deficient in MPM, such as dendritic cells or natural killer cells. On the other hand, tumour infiltrating lymphocytes (TILs) are also found in MPM, but CD4+ and CD8+ TILs might have decreased cytotoxic effects through T-regulators and high expression of immune checkpoints. Taken together, the immune microenvironment is particularly heterogeneous and can be considered as mainly immunotolerant or immunosuppressive. Therefore, identifying molecular vulnerabilities is particularly relevant to the improvement of patient outcomes and the assessment of promising treatment approaches.

Immunotherapeutic Approaches in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and aggressive malignant disease affecting the mesothelium, commonly associated to asbestos exposure. The current therapeutic actions, based on cisplatin/pemetrexed treatment, are limited due to the late stage at which most patients are diagnosed and to the intrinsic chemo-resistance of the tumor. Another relevant point is the absence of approved therapies in the second line setting following progression of MPM after chemotherapy. Considering the poor prognosis of the disease and the fact that the incidence of this tumor is expected to increase in the next decade, novel therapeutic approaches are urgently needed. In the last few years, several studies have investigated the efficacy and safety of immune-checkpoint inhibitors (ICIs) in the treatment of unresectable advanced MPM, and a number of trials with immunotherapeutic agents are ongoing in both first line and second line settings. In this review, we describe the most promising emerging immunotherapy treatments for MPM (ICIs, engineered T cells to express chimeric antigen receptors (CARs), dendritic cells (DCs) vaccines), focusing on the biological and immunological features of this tumor as well as on the issues surrounding clinical trial design.

Long-Term Follow-Up of Mesothelioma Patients Treated with Dendritic Cell Therapy in Three Phase I/II Trials

Background: Malignant pleural mesothelioma (MPM) is a fatal neoplasm with, if untreated, poor survival of approximately nine months from diagnosis. Until recently, phase II–III immunotherapy trials did not show any significant benefit. The lack of immunotherapy efficacy can be explained by the fact that mesothelioma is a tumor with an “immune desert” phenotype, meaning a non-inflamed tumor characterized by low T-cell infiltration. By administration of DCs, which were ex-vivo cultured, exposed to (tumor-associated) antigens, and subsequently activated, this “immune desert” phenotype might be turned into an “inflamed” phenotype. Three phase I/II studies have been performed and published using activated DCs, which support this concept. We here report on the long-term survival of patients treated with DCs in three phase I/II studies. Methods: Survival data of the phase I/II trials using DC therapy in MPM patients were obtained and subsequently analyzed. In the first two trials, DCs were loaded with autologous tumor lysate. In the third trial, DCs were loaded with allogeneic mesothelioma tumor cell line lysate. Results: In the three studies combined, 29 patients with MPM were treated with DC vaccination between 2006 and 2015. At data cut-off, the median OS was 27 months (95% CI: 21–47 months). OS at 2 years was 55.2% (95% CI: 39.7–76.6%), and OS at 5 years was 20.7% (95% CI: 10.1–42.2%). Conclusions: The long-term survival of DC therapy in MPM in these three trials is promising, which is the basis for the randomized phase II/III DENIM study. This DENIM study is currently enrolling, and the results of which have to be awaited for definite conclusions.

Emerging biological therapies for the treatment of malignant pleural mesothelioma

Introduction: Malignant pleural mesothelioma (MPM) has limited treatment options with minimal new therapy approvals for unresectable disease in the past 15 years. However, considerable work has occurred to develop immunotherapies and biomarker driven therapy to improve patient outcomes over this period.Areas covered: This review examines current standard of care systemic therapy in the first- and second line setting. The last 12 months has seen 2 significant trials (Checkmate 743 and CONFIRM) which provide evidence supporting the role of immunotherapy in the management of MPM. Further trials are underway to assess the role of combination chemoimmunotherapy and personalized therapy. Additionally, a large number of clinical trials are ongoing to assess the efficacy of oncoviral, dendritic cell, anti-mesothelin and chimeric antigen receptor T cell therapy in the treatment of MPM.Expert opinion: Recent Phase III trial results have established a role for immunotherapy in the management of MPM. The optimal sequencing and combination of chemotherapy and immunotherapy remains to be determined. Novel therapies for MPM are promising however efficacy remains to be determined and issues remain regarding access to and delivery of these therapies.

Emerging avenues in immunotherapy for the management of malignant pleural mesothelioma

BACKGROUND

The role of immunotherapy in cancer is now well-established, and therapeutic options such as checkpoint inhibitors are increasingly being approved in many cancers such as non-small cell lung cancer (NSCLC). Malignant pleural mesothelioma (MPM) is a rare orphan disease associated with prior exposure to asbestos, with a dismal prognosis. Evidence from clinical trials of checkpoint inhibitors in this rare disease, suggest that such therapies may play a role as a treatment option for a proportion of patients with this cancer.

MAIN TEXT

While the majority of studies currently focus on the established checkpoint inhibitors (CTLA4 and PD1/PDL1), there are many other potential checkpoints that could also be targeted. In this review I provide a synopsis of current clinical trials of immunotherapies in MPM, explore potential candidate new avenues that may become future targets for immunotherapy and discuss aspects of immunotherapy that may affect the clinical outcomes of such therapies in this cancer.

CONCLUSIONS

The current situation regarding checkpoint inhibitors in the management of MPM whilst encouraging, despite impressive durable responses, immune checkpoint inhibitors do not provide a long-term benefit to the majority of patients with cancer. Additional studies are therefore required to further delineate and improve our understanding of both checkpoint inhibitors and the immune system in MPM. Moreover, many new potential checkpoints have yet to be studied for their therapeutic potential in MPM. All these plus the existing checkpoint inhibitors will require the development of new biomarkers for patient stratification, response and also for predicting or monitoring the emergence of resistance to these agents in MPM patients. Other potential therapeutic avenues such CAR-T therapy or treatments like oncolytic viruses or agents that target the interferon pathway designed to recruit more immune cells to the tumor also hold great promise in this hard to treat cancer.

Mouse models for mesothelioma drug discovery and development

INTRODUCTION

Mesothelioma is an aggressive mesothelial lining tumor. Available drug therapies include chemotherapeutic agents, targeted molecular therapies, and immune system modulators. Mouse models were instrumental in the discovery and evaluation of such therapies, but there is need for improved understanding of the role of inflammation, tumor heterogeneity, mechanisms of carcinogenesis, and the tumor microenvironment. Novel mouse models may provide new insights and drive drug therapy discovery that improves efficacy.

AREAS COVERED

This review concerns available mouse models for mesothelioma drug discovery and development including the advantages and disadvantages of each. Gaps in current knowledge of mesothelioma are highlighted, and future directions for mouse model research are considered.

EXPERT OPINION

Soon, CRISPR-Cas gene-editing will improve understanding of mesothelioma mechanisms foundational to the discovery and testing of efficacious therapeutic targets. There are at least two likely areas of upcoming methodology development. One is concerned with precise modeling of inflammation - is it a causal process whereby inflammatory signals contribute to tumor initiation, or is it a secondary passenger process driven by asbestos exposure effects? The other area of methods improvement regards the availability of humanized immunocompromised mice harboring patient-derived xenografts. Combining human tumors in an environment with human immune cells will enable rapid innovation in immuno-oncology therapeutics.

Cellular Immunotherapy and Locoregional Administration of CAR T-Cells in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a treatment recalcitrant tumor with a poor overall survival (OS). Current approved treatment consists of first line chemotherapy that only modestly increases OS, illustrating the desperate need for other treatment options in MPM. Unfortunately, clinical studies that investigate the effectivity of checkpoint inhibitor (CI) treatment failed to improve clinical outcome over current applied therapies. In general, MPM is characterized as an immunological cold tumor with low T-cell infiltration, which could explain the disappointing results of clinical trials investigating CI treatment in MPM. Currently, many other therapeutic approaches, such as cellular therapies and cancer vaccines are investigated that could induce a tumor-specific immune response and increase of the number of tumor-infiltrating lymphocytes. In this review we will discuss these novel treatment approaches for MPM.

Acidosis-Induced TGF-β2 Production Promotes Lipid Droplet Formation in Dendritic Cells and Alters Their Potential to Support Anti-Mesothelioma T Cell Response

For poorly immunogenic tumors such as mesothelioma there is an imperious need to understand why antigen-presenting cells such as dendritic cells (DCs) are not prone to supporting the anticancer T cell response. The tumor microenvironment (TME) is thought to be a major contributor to this DC dysfunction. We have reported that the acidic TME component promotes lipid droplet (LD) formation together with epithelial-to-mesenchymal transition in cancer cells through autocrine transforming growth factor-β2 (TGF-β2) signaling. Since TGF-β is also a master regulator of immune tolerance, we have here examined whether acidosis can impede immunostimulatory DC activity. We have found that exposure of mesothelioma cells to acidosis promotes TGF-β2 secretion, which in turn leads to LD accumulation and profound metabolic rewiring in DCs. We have further documented how DCs exposed to the mesothelioma acidic milieu make the anticancer vaccine less efficient in vivo, with a reduced extent of both DC migratory potential and T cell activation. Interestingly, inhibition of TGF-β2 signaling and diacylglycerol O-acyltransferase (DGAT), the last enzyme involved in triglyceride synthesis, led to a significant restoration of DC activity and anticancer immune response. In conclusion, our study has identified that acidic mesothelioma milieu drives DC dysfunction and altered T cell response through pharmacologically reversible TGF-β2-dependent mechanisms.

Malignant Pleural Mesothelioma: Genetic and Microenviromental Heterogeneity as an Unexpected Reading Frame and Therapeutic Challenge

Mesothelioma is a malignancy of serosal membranes including the peritoneum, pleura, pericardium and the tunica vaginalis of the testes. Malignant mesothelioma (MM) is a rare disease with a global incidence in countries like Italy of about 1.15 per 100,000 inhabitants. Malignant Pleural Mesothelioma (MPM) is the most common form of mesothelioma, accounting for approximately 80% of disease. Although rare in the global population, mesothelioma is linked to industrial pollutants and mineral fiber exposure, with approximately 80% of cases linked to asbestos. Due to the persistent asbestos exposure in many countries, a worldwide progressive increase in MPM incidence is expected for the current and coming years. The tumor grows in a loco-regional pattern, spreading from the parietal to the visceral pleura and invading the surrounding structures that induce the clinical picture of pleural effusion, pain and dyspnea. Distant spreading and metastasis are rarely observed, and most patients die from the burden of the primary tumor. Currently, there are no effective treatments for MPM, and the prognosis is invariably poor. Some studies average the prognosis to be roughly one-year after diagnosis. The uniquely poor mutational landscape which characterizes MPM appears to derive from a selective pressure operated by the environment; thus, inflammation and immune response emerge as key players in driving MPM progression and represent promising therapeutic targets. Here we recapitulate current knowledge on MPM with focus on the emerging network between genetic asset and inflammatory microenvironment which characterize the disease as amenable target for novel therapeutic approaches.

Opportunities for Conventional and in Situ Cancer Vaccine Strategies and Combination with Immunotherapy for Gastrointestinal Cancers, A Review

Survival of gastrointestinal cancer remains dismal, especially for metastasized disease. For various cancers, especially melanoma and lung cancer, immunotherapy has been proven to confer survival benefits, but results for gastrointestinal cancer have been disappointing. Hence, there is substantial interest in exploring the usefulness of adaptive immune system education with respect to anti-cancer responses though vaccination. Encouragingly, even fairly non-specific approaches to vaccination and immune system stimulation, involving for instance influenza vaccines, have shown promising results, eliciting hopes that selection of specific antigens for vaccination may prove useful for at least a subset of gastrointestinal cancers. It is widely recognized that immune recognition and initiation of responses are hampered by a lack of T cell help, or by suppressive cancer-associated factors. In this review we will discuss the hurdles that limit efficacy of conventional cancer therapeutic vaccination methods (e.g., peptide vaccines, dendritic cell vaccination). In addition, we will outline other forms of treatment (e.g., radiotherapy, chemotherapy, oncolytic viruses) that also cause the release of antigens through immunogenic tumor cell death and can thus be considered unconventional vaccination methods (i.e., in situ vaccination). Finally, we focus on the potential additive value that vaccination strategies may have for improving the effect immunotherapy. Overall, a picture will emerge that although the field has made substantial progress, successful immunotherapy through the combination with cancer antigen vaccination, including that for gastrointestinal cancers, is still in its infancy, prompting further intensification of the research effort in this respect.

The Biology of Malignant Mesothelioma and the Relevance of Preclinical Models

Malignant mesothelioma (MM), especially its more frequent form, malignant pleural mesothelioma (MPM), is a devastating thoracic cancer with limited therapeutic options. Recently, clinical trials that used immunotherapy strategies have yielded promising results, but the benefits are restricted to a limited number of patients. To develop new therapeutic strategies and define predictors of treatment response to existing therapy, better knowledge of the cellular and molecular mechanisms of MM tumors and sound preclinical models are needed. This review aims to provide an overview of our present knowledge and issues on both subjects. MM shows a complex pattern of molecular changes, including genetic, chromosomic, and epigenetic alterations. MM is also a heterogeneous cancer. The recently described molecular classifications for MPM could better consider inter-tumor heterogeneity, while histo-molecular gradients are an interesting way to consider both intra- and inter-tumor heterogeneities. Classical preclinical models are based on use of MM cell lines in culture or implanted in rodents, i.e., xenografts in immunosuppressed mice or isografts in syngeneic rodents to assess the anti-tumor immune response. Recent developments are tumoroids, patient-derived xenografts (PDX), xenografts in humanized mice, and genetically modified mice (GEM) that carry mutations identified in human MM tumor cells. Multicellular tumor spheroids are an interesting in vitro model to reduce animal experimentation; they are more accessible than tumoroids. They could be relevant, especially if they are co-cultured with stromal and immune cells to partially reproduce the human microenvironment. Even if preclinical models have allowed for major advances, they show several limitations: (i) the anatomical and biological tumor microenvironments are incompletely reproduced; (ii) the intra-tumor heterogeneity and immunological contexts are not fully reconstructed; and (iii) the inter-tumor heterogeneity is insufficiently considered. Given that these limitations vary according to the models, preclinical models must be carefully selected depending on the objectives of the experiments. New approaches, such as organ-on-a-chip technologies or in silico biological systems, should be explored in MM research. More pertinent cell models, based on our knowledge on mesothelial carcinogenesis and considering MM heterogeneity, need to be developed. These endeavors are mandatory to implement efficient precision medicine for MM.

Emerging Treatments for Malignant Pleural Mesothelioma: Where Are We Heading?

Malignant pleural mesothelioma (MPM) is an uncommon but aggressive and treatment resistant neoplasm with low survival rates. In the last years we assisted to an exponential growth in the appreciation of mesothelioma pathobiology, leading several new treatments to be investigated both in the early stage of the disease and in the advanced setting. In particular, expectations are now high that immunotherapy will have a leading role in the next years. However, caution is required as results from phase II studies in MPM were often not replicated in larger, randomized, phase III trials. In this review, we describe the most promising emerging therapies for the treatment of MPM, discussing the biological rationale underlying their development as well as the issues surrounding clinical trial design and proper selection of patients for every treatment.

Photodynamic Therapy-Based Dendritic Cell Vaccination Suited to Treat Peritoneal Mesothelioma

The potential of dendritic cell (DC)-based immunotherapy to treat cancer is, nowadays, well documented. Still, the clinical success of immune checkpoint inhibitors has dampened the interest in anticancer DC vaccination. For highly life-threatening tumors that are regarded as nonimmunogenic, such as mesothelioma, however, T helper 1 immunity-biased DC-based immunotherapy could still represent an attractive strategy. In this study, we took advantage of photodynamic therapy (PDT) to induce immunogenic cell death to generate mesothelioma cell lysates for DC priming and evaluated such a vaccine to treat peritoneal mesothelioma. We found that the white light in vitro activation of the photosensitizer OR141 led to mesothelioma cell death, together with the release of bona fide danger signals that promote DC maturation. The administration of a PDT-based DC vaccine to mice bearing peritoneal mesothelioma led to highly significant survival when compared with sham or control animals treated with anti-CTLA4 antibodies. This was further supported by a strong CD8⁺ and CD4⁺ T cell response, characterized by an increased proliferation, cytotoxic activities and the expression of activation markers, including interferon gamma (IFNγ). Moreover, the PDT-based DC vaccine led to a significant increase in IFNγ⁺ T cells infiltered within mesothelioma, as determined by flow cytometry and immunohistochemistry. Finally, in vivo tracking of intraperitoneally administered DCs led us to document rapid chemotaxis towards tumor-occupied lymphatics (vs. lipopolysaccharide (LPS)-treated DC). DCs pulsed with PDT-killed mesothelioma cells also exhibited a significant increase in CCR7 receptors, together with an intrinsic capacity to migrate towards the lymph nodes. Altogether, these results indicate that PDT-based DC vaccination is particularly suited to induce a potent immune response against peritoneal mesothelioma.

Immunotherapy for mesothelioma: a critical review of current clinical trials and future perspectives

At the clinical level the role of immunotherapy in cancer is currently at a pivotal point. Therapies such as checkpoint inhibitors are being approved at many levels in cancers such as non-small cell lung cancer (NSCLC). Mesothelioma is a rare orphan disease associated with prior exposure to asbestos, with a dismal prognosis. Various clinical trials for checkpoint inhibitors have been conducted in this rare disease, and suggest that such therapies may play a role as a treatment option for a proportion of patients with this cancer. Most recently approved as a salvage therapy in mesothelioma was granted in Japan, regulatory approval for their use in the clinic elsewhere lags. In this article we review the current pertinent clinical trials of immunotherapies in malignant mesothelioma, discuss the current issues that may affect the clinical outcomes of such therapies and further evaluate potential candidate new avenues that may become future targets for immunotherapy in this cancer.

Malignant Pleural Mesothelioma: State-of-the-Art on Current Therapies and Promises for the Future

Malignant pleural mesothelioma (MPM) is a rare, aggressive cancer of the pleural surface associated with asbestos exposure. The median survival of MPM patients is a mere 8-14 months, and there are few biomarkers and no cure available. It is hoped that, eventually, the incidence of MPM will drop and remain low and constant, given that most nations have banned the use of asbestos, but in the meantime, the incidence in Europe is still growing. The exact molecular mechanisms that explain the carcinogenicity of asbestos are not known. Standard therapeutic strategies for MPM include surgery, often coupled with chemotherapy and/or radiotherapy, in a small percentage of eligible patients and chemotherapy in tumors considered unresectable with or without adjuvant radiotherapy. In recent years, several new therapeutic avenues are being explored. These include angiogenesis inhibitors, synthetic lethal treatment, miRNA replacement, oncoviral therapies, and the fast-growing field of immunotherapy alone or in combination with chemotherapy. Of particular promise are the multiple options offered by immunotherapy: immune checkpoint inhibitors, tumor vaccines, and therapies taking advantage of tumor-specific antigens, such as specific therapeutic antibodies or advanced cell-based therapies exemplified by the CAR-T cells. This review comprehensively presents both old and new therapeutic options in MPM, focusing on the results of the numerous recent and on-going clinical trials in the field, including the latest data presented at international meetings (AACR, ASCO, and ESMO) this year, and concludes that more work has to be done in the framework of tailored therapies to identify reliable targets and novel biomarkers to impact MPM management.