A trial of intrapleural adenoviral-mediated Interferon-α2b gene transfer for malignant pleural mesothelioma

Interventional therapies for malignant pleural effusions: the present and the future

The approach to management of malignant pleural effusions (MPE) has changed over the past few decades. The key goals of MPE management are to relieve patient symptoms using the least invasive means and in the most cost-effective manner. There is now a realization that patient-reported outcome measures should be the primary goal of MPE treatment, and this now is the focus in most clinical trials. Efforts to minimize patient morbidity are complemented by development of less invasive treatments that have mostly replaced the more aggressive surgical approaches of the past. Therapeutic thoracentesis is simple, effective and generally safe, although its benefits may only be temporary. Pleurodesis is the conventional and for a long time the only definitive therapy available. However, the efficacy and safety of talc pleurodesis has been challenged. Indwelling pleural catheter (IPC) drainage is increasingly accepted worldwide and represents a new concept to improve symptoms without necessarily generating pleural symphysis. Recent studies support the effectiveness of IPC treatment and provide reassurance regarding its safety. An unprecedented number of clinical trials are now underway to improve various aspects of MPE care. However, choosing an optimal intervention for MPE in an individual patient remains a challenge due to our limited understanding of the underlying pathophysiology of breathlessness in MPE and a lack of predictors of survival and pleurodesis outcome. This review provides an overview of common pleural interventional procedures used for MPE management, controversies and limitations of current practice, and areas of research most needed to improve practice in future.

Ask the Experts: Gene therapy in malignant pleural mesothelioma

Dr Masatoshi Tagawa graduated with MD from the School of Medicine, Chiba University (Chiba, Japan) and completed the graduated course in Chiba University (awarded PhD) in 1984. He spent a few years in Stanford University (CA, USA) as a postdoctoral fellow and became an assistant professor at Chiba University. He then moved to Chiba Cancer Center Research Institute (Chiba, Japan) as the Head in Division of Pathology and Cell Therapy, and became a professor of Graduate School of Medicine at Chiba University. He is currently a council member of the Japan Society of Gene Therapy and International Society of Cell and Gene Therapy of Cancer. He also serves as an editor of Cancer Gene Therapy. His primary research field is molecular biology and oncology and he is currently working on mesothelioma at preclinical and clinical research levels.

Interferon-β produces synergistic combinatory anti-tumor effects with cisplatin or pemetrexed on mesothelioma cells

Interferons (IFNs) have been tested for the therapeutic effects in various types of malignancy, but mechanisms of the anti-tumors effects and the differential biological activities among IFN members are dependent on respective cell types. In this study, we examined growth inhibitory activities of type I and III IFNs on 5 kinds of human mesothelioma cells bearing wild-type p53 gene, and showed that type I IFNs but not type III IFNs decreased the cell viabilities. Moreover, growth inhibitory activities and up-regulated expression levels of the major histocompatibility complexes class I antigens were greater with IFN-β than with IFN-α treatments. Cell cycle analyses demonstrated that type I IFNs increased S- and G2/M-phase populations, and subsequently sub-G1-phase fractions. The cell cycle changes were also greater with IFN-β than IFN-α treatments, and these data collectively showed that IFN-β had stronger biological activities than IFN-α in mesothelioma. Type I IFNs-treated cells increased p53 expression and the phosphorylation levels, and activated apoptotic pathways. A combinatory use of IFN-β and cisplatin or pemetrexed, both of which are the current first-line chemotherapeutic agents for mesothelioma, produced synergistic anti-tumor effects, which were also evidenced by increased sub-G1-phase fractions. These data demonstrated firstly to our knowledge that IFN-β produced synergistic anti-tumor effects with cisplatin or pemetrexed on mesothelioma through up-regulated p53 expression.

Malignant pleural effusions: a review

Malignant pleural effusions are a cause of significant symptoms and distress in patients with end-stage malignancies and portend a poor prognosis. Management is aimed at symptom relief, with minimally invasive interventions and minimal requirement for hospital length of stay. The management options include watchful waiting if no symptoms are present, repeat thoracentesis, medical or surgical thoracoscopic techniques to achieve pleurodesis, pleuroperitoneal shunts, placement of tunneled pleural catheters, or a combination of modalities. To determine the best modality for management, patients must be assessed individually with concern for symptoms, functional status, prognosis, and their social and financial situations.

Defect in recruiting effector memory CD8+ T-cells in malignant pleural effusions compared to normal pleural fluid

Background

Malignant pleural effusions (MPE) are a common and fatal complication in cancers including lung or breast cancers, or malignant pleural mesothelioma (MPM). MPE animal models and immunotherapy trials in MPM patients previously suggested defects of the cellular immunity in MPE. However only few observational studies of the immune response were done in MPM patients, using questionable control groups (transudate…).

Methods

We compared T cell populations evaluated by flow cytometry from blood and pleural effusion of untreated patients with MPM (n = 58), pleural metastasis of adenocarcinoma (n = 30) or with benign pleural lesions associated with asbestos exposure (n = 23). Blood and pleural fluid were also obtained from healthy subjects, providing normal values for T cell populations.

Results

Blood CD4⁺ or CD8⁺ T cells percentages were similar in all groups of patients or healthy subjects. Whereas pleural fluid from healthy controls contained mainly CD8⁺ T cells, benign or malignant pleural effusions included mainly CD4⁺ T cells. Effector memory T cells were the main T cell subpopulation in pleural fluid from healthy subjects. In contrast, there was a striking and selective recruitment of central memory CD4+ T cells in MPE, but not of effector cells CD8⁺ T cells or NK cells in the pleural fluid as one would expect in order to obtain an efficient immune response.

Conclusions

Comparing for the first time MPE to pleural fluid from healthy subjects, we found a local defect in recruiting effector CD8⁺ T cells, which may be involved in the escape of tumor cells from immune response. Further studies are needed to characterize which subtypes of effector CD8+ T cells are involved, opening prospects for cell therapy in MPE and MPM.

T cells expressing chimeric antigen receptors can cause anaphylaxis in humans

T cells can be redirected to overcome tolerance to cancer by engineering with integrating vectors to express a chimeric antigen receptor (CAR). In preclinical models, we have previously demonstrated that transfection of T cells with messenger RNA (mRNA) coding for a CAR is an alternative strategy that has antitumor efficacy and the potential to evaluate the on-target off-tumor toxicity of new CAR targets safely due to transient mRNA CAR expression. Here, we report the safety observed in four patients treated with autologous T cells that had been electroporated with mRNA coding for a CAR derived from a murine antibody to human mesothelin. Due to the transient nature of CAR expression on the T cells, subjects in the clinical study were given repeated infusions of the CAR-T cells in order to assess their safety. One subject developed anaphylaxis and cardiac arrest within minutes of completing the 3^rd infusion. Although human anti-mouse IgG antibodies have been known to develop with CAR-transduced T cells, they have been thought to have no adverse clinical consequences. This is the first description of clinical anaphylaxis resulting from CAR-modified T cells, most likely through IgE antibodies specific to the CAR. These results indicate that the potential immunogenicity of CARs derived from murine antibodies may be a safety issue for mRNA CARs, especially when administered using an intermittent dosing schedule.

T cells expressing chimeric antigen receptors can cause anaphylaxis in humans

T cells can be redirected to overcome tolerance to cancer by engineering with integrating vectors to express a chimeric antigen receptor (CAR). In preclinical models, we have previously shown that transfection of T cells with mRNA coding for a CAR is an alternative strategy that has antitumor efficacy and the potential to evaluate the on-target off-tumor toxicity of new CAR targets safely due to transient mRNA CAR expression. Here, we report the safety observed in four patients treated with autologous T cells that had been electroporated with mRNA coding for a CAR derived from a murine antibody to human mesothelin. Because of the transient nature of CAR expression on the T cells, subjects in the clinical study were given repeated infusions of the CAR-T cells to assess their safety. One subject developed anaphylaxis and cardiac arrest within minutes of completing the third infusion. Although human anti-mouse immunoglobulin (Ig)G antibodies have been known to develop with CAR-transduced T cells, they have been thought to have no adverse clinical consequences. This is the first description of clinical anaphylaxis resulting from CAR-modified T cells, most likely through IgE antibodies specific to the CAR. These results indicate that the potential immunogenicity of CARs derived from murine antibodies may be a safety issue for mRNA CARs, especially when administered using an intermittent dosing schedule.

Intracavitary therapeutics for pleural malignancies

Pleural malignancies are ideal for novel therapeutic approaches because they are invariably fatal. Intrapleural (IP) chemotherapy has only marginal benefit in pleural malignancies, but may prove efficacious with hyperthermic chemotherapy administered in combination with maximal tumor debulking. IP immunotherapies may be most effective in those patients with early-stage pleural malignancy, and may prove superior to standard pleurodesis methods in control of effusion and prolongation of survival. Immunogene therapy may be unable to successfully treat bulky tumors on its own, but success may be achieved with combination approaches that combine debulking surgery and chemotherapy with IP genetic immunotherapy.

Gene therapy for malignant mesothelioma: current prospects and challenges

Malignant mesothelioma, developed in the thoracic cavity, is resistant to current treatments. Suppression of the local tumor growth is beneficial to the patients since mesothelioma infrequently metastasizes to extrapleural organs. A majority of the tumors have a homologous genetic deletion at the INK4A/ARF locus that includes the p14ARF and the p16INK4A genes, and the genetic defect results in an inactivation of the p53-mediated pathways and in progression of cell cycle through pRb phosphorylation. Preclinical studies targeting the genetic abnormality with adenoviruses showed that restoration of the p53 pathways induced pRb dephosphorylation and subsequently produced anti-tumor effects. A number of preclinical studies with different genes and vector systems demonstrated the therapeutic efficacy and raised the possibility of gene therapy in clinical settings. An intrapleural administration of vectors has several advantages in transducing pleural mesothelioma but activates rapid antibody production which impedes further gene expression. There have been several clinical studies conducted for mesothelioma and these trials showed the feasibility of intrapleural administrations of adenovirus vectors. In this review we summarize major preclinical and clinical gene therapy for mesothelioma, and discuss the advantages of gene therapy in the context of stimulating host immune systems. Accumulating clinical data suggest that an intrapleural administration of viral vectors has distinct aspects which are not observed in other administration routes.

Malignant pleural mesothelioma: update on treatment options with a focus on novel therapies

There is evidence that improved treatments of malignant pleural mesothelioma are increasing the quality and quantity of life for patients with mesothelioma. Multimodality treatment programs that combine maximal surgical cytoreduction with novel forms of radiation therapy and more effective chemotherapy combinations may offer significant increases in survival for certain subgroups of patients with mesothelioma. Lung-sparing surgery may allow improvements in pulmonary function after surgery-based multimodality therapy, and potential longer overall survival than that seen with extrapleural pneumonectomy. Experimental treatments provide hope for all patients with mesothelioma, and in the future may be combined with standard therapy in multimodality protocols.

A potential therapeutic strategy for malignant mesothelioma with gene medicine

Malignant mesothelioma, closely linked with occupational asbestos exposure, is relatively rare in the frequency, but the patient numbers are going to increase in the next few decades all over the world. The current treatment modalities are not effective in terms of the overall survival and the quality of life. Mesothelioma mainly develops in the thoracic cavity and infrequently metastasizes to extrapleural organs. A local treatment can thereby be beneficial to the patients, and gene therapy with an intrapleural administration of vectors is one of the potential therapeutics. Preclinical studies demonstrated the efficacy of gene medicine for mesothelioma, and clinical trials with adenovirus vectors showed the safety of an intrapleural injection and a possible involvement of antitumor immune responses. Nevertheless, low transduction efficiency remains the main hurdle that hinders further clinical applications. Moreover, rapid generation of antivector antibody also inhibits transgene expressions. In this paper, we review the current status of preclinical and clinical gene therapy for malignant mesothelioma and discuss potential clinical directions of gene medicine in terms of a combinatory use with anticancer agents and with immunotherapy.

Dendritic cell-based immunotherapy in mesothelioma

Mesothelioma is a rare thoracic malignancy with a dismal prognosis. Current treatment options are scarce and clinical outcomes are rather disappointing. Due to the immunogenic nature of mesothelioma, several studies have investigated immunotherapeutic strategies to improve the prognosis of patients with mesothelioma. In the last decade, progress in knowledge of the modulation of the immune system to attack the tumor has been remarkable, but the optimal strategy for immunotherapy has yet to be unraveled. Because of their potent antigen-presenting capacity, dendritic cells are acknowledged as a promising agent in immunotherapeutic approaches in a number of malignancies. This review gives an update and provides a future perspective in which immunotherapy may improve the outcome of mesothelioma therapy.

Cytoreduction surgery reduces systemic myeloid suppressor cell populations and restores intratumoral immunotherapy effectiveness

Background

Multiple immunotherapy approaches have improved adaptive anti-tumor immune responses in patients with early stage disease; however, results have been less dramatic when treating patients with late stage disease. These blunted responses are likely due to a host of factors, including changes in the tumor microenvironment and systemic immunosuppressive features, which accompany advanced tumor states. We hypothesized that cytoreductive surgery could control these immunosuppressive networks and restore the potency of immunotherapy in advanced disease scenarios.

Methods

To test these hypotheses, two representative intratumoral immunotherapies (an adenoviral vector encoding a suicide gene, AdV-tk, or a type-I interferon, Ad.IFNα) were tested in murine models of lung cancer. Cytoreductive surgery was performed following treatment of advanced tumors. Mechanistic underpinnings were investigated using flow cytometry, in vivo leukocyte depletion methods and in vivo tumor neutralization assays.

Results

AdV-tk and Ad.IFNα were effective in treating early lung cancers, but had little anti-tumor effects in late stage cancers. Interestingly, in late stage scenarios, surgical cytoreduction unmasked the anti-tumor potency of both immunotherapeutic approaches. Immune mechanisms that explained restoration in anti-tumor immune responses included increased CD8 T-cell trafficking and reduced myeloid derived suppressor cell populations.

Conclusion

This study demonstrates that surgical resection combined with immunotherapy may be a rational therapeutic option for patients with advanced stage cancer.

Overexpression and potential targeting of the oncofoetal antigen 5T4 in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is resistant to conventional treatments. Novel, targeted treatments are hampered by the relative lack of MPM-associated tumour antigens. The aim of this study was to evaluate the level of expression and the relevance of 5T4 as a tumour-associated antigen in MPM. 5T4 expression was assessed by Western blotting, flow cytometry, immuno-cytochemistry and -histochemistry in 11 mesothelioma cell lines, 21 tumour biopsies, and ex vivo tumour cells obtained from the pleural fluid (PF) of 10 patients. 5T4 antibody levels were also determined in the plasma of patients and healthy donors. The susceptibility of MPM cells to 5T4-specific T-cell-mediated killing was determined using an HLA-A2(+), CD8(+) T-cell line, developed against the 5T4(17-25) peptide. We report here that cell surface 5T4 expression was detected in all mesothelioma cell lines and PF cell samples. Mesothelin and CD200, a suggested mesothelioma marker, were co-expressed with 5T4 on tumour cells in PF. Immunohistochemistry confirmed overexpression of 5T4, similar to mesothelin, on tumour cells but not on reactive stroma in all tissue sections tested. Median 5T4 antibody levels were 46% higher in patient than in healthy donor plasma, indicating immune recognition. Importantly, 5T4-specific CD8(+) T-cells were able to kill four out of six HLA-A2(+) MPM cell lines but not an HLA-A2(-) cell line, demonstrating immune recognition of MPM-associated 5T4 antigen at the effector T-cell level. We conclude that 5T4 is a potential new antigen for targeted therapies such as immunotherapy in MPM, as it is overexpressed on mesothelioma cells and recognised by 5T4-specific cytotoxic T-cells. Our findings have been translated into a Phase II clinical trial applying 5T4-targeted therapies in MPM patients.

Intratumoral interleukin-2/agonist CD40 antibody drives CD4+ -independent resolution of treated-tumors and CD4+ -dependent systemic and memory responses

Targeting interleukin-2 (IL-2) and/or agonist anti-CD40 antibody (Ab) into tumors represents an effective vaccination strategy that avoids systemic toxicity and resolves treated-site tumors. Here, we examined IL-2 and/or anti-CD40 Ab-driven local versus systemic T cell function and the installation of T cell memory. Single tumor studies showed that IL-2 induced a potent CD4+ and CD8+ T cell response that was limited to the draining lymph node and treated-site tumor, and lymph node tumor-specific CD8+ T cells did not upregulate CD44. A two-tumor model showed that while IL-2-treated-site tumors resolved, distal tumors continued to grow, implying limited systemic immunity. In contrast, anti-CD40 Ab treatment with or without IL-2 expanded the systemic T cell response to non-draining lymph nodes, and distal tumors resolved. Tumor-specific T cells in lymph nodes of anti-CD40 Ab ± IL-2-treated mice upregulated CD44, demonstrating activation and transition to effector/memory migratory cells. While CD40-activated CD4+ T cells were not required for eradicating treated-site tumors, they, plus CD8+ T cells, were crucial for removing distal tumors. Rechallenge/depletion experiments showed that the effector/memory phase required the presence of previously CD40/IL-2-activated CD4+ and CD8+ T cells to prevent recurrence. These novel findings show that different T cell effector mechanisms can operate for the eradication of local treated-site tumors versus untreated distal tumors and that signaling through CD40 generates a whole of body, effector/memory CD4+ and CD8+ T cell response that is amplified and prolonged via IL-2. Thus, successful immunotherapy needs to generate collaborating CD4+ and CD8+ T cells for a complete long-term protective cure.

Treating tumors with a vaccinia virus expressing IFNβ illustrates the complex relationships between oncolytic ability and immunogenicity

Since previous work using a nonreplicating adenovirus-expressing mouse interferon-β (Ad.mIFNβ) showed promising preclinical activity, we postulated that a vector-expressing IFNβ at high levels that could also replicate would be even more beneficial. Accordingly a replication competent, recombinant vaccinia viral vector-expressing mIFNβ (VV.mIFNβ) was tested. VV.mIFNβ-induced antitumor responses in two syngeneic mouse flank models of lung cancer. Although VV.mIFNβ had equivalent in vivo efficacy in both murine tumor models, the mechanisms of tumor killing were completely different. In LKRM2 tumors, viral replication was minimal and the tumor killing mechanism was due to activation of immune responses through induction of a local inflammatory response and production of antitumor CD8 T-cells. In contrast, in TC-1 tumors, the vector replicated well, induced an innate immune response, but antitumor activity was primarily due to a direct oncolytic effect. However, the VV.mIFNβ vector was able to augment the efficacy of an antitumor vaccine in the TC-1 tumor model in association with increased numbers of infiltrating CD8 T-cells. These data show the complex relationships between oncolytic viruses and the immune system which, if understood and harnessed correctly, could potentially be used to enhance the efficacy of immunotherapy.

Gene therapy for lung neoplasms

Both advanced-stage lung cancer and malignant pleural mesothelioma are associated with a poor prognosis. Advances in treatment regimens for both diseases have had only a modest effect on their progressive course. Gene therapy for thoracic malignancies represents a novel therapeutic approach and has been evaluated in several clinical trials. Strategies have included induction of apoptosis, tumor suppressor gene replacement, suicide gene expression, cytokine-based therapy, various vaccination approaches, and adoptive transfer of modified immune cells. This review considers the clinical results, limitations, and future directions of gene therapy trials for thoracic malignancies.

Molecular pathways: targeting mechanisms of asbestos and erionite carcinogenesis in mesothelioma

Malignant mesothelioma is an aggressive malignancy related to asbestos and erionite exposure. AP-1 transcriptional activity and the NF-κB signaling pathway have been linked to mesothelial cell transformation and tumor progression. HGF and c-Met are highly expressed in mesotheliomas. Phosphoinositide 3-kinase, AKT, and the downstream mTOR are involved in cell growth and survival, and they are often found to be activated in mesothelioma. p16(INK4a) and p14(ARF) are frequently inactivated in human mesothelioma, and ∼50% of mesotheliomas contain the NF2 mutation. Molecular therapies aimed at interfering with these pathways have not improved the dismal prognosis of mesothelioma, except possibly for a small subset of patients who benefit from certain therapies. Recent studies have shown the importance of asbestos-induced inflammation in the initiation and growth of mesothelioma, and HMGB1 and Nalp3 inflammasome have been identified as key initiators of this process. Asbestos induces cell necrosis, causing the release of HMGB1, which in turn may activate Nalp3 inflammasome, a process that is enhanced by asbestos-induced production of reactive oxygen species. HMGB1 and Nalp3 induce proinflammatory responses and lead to interleukin-1β and TNF-α secretion and NF-κB activity, thereby promoting cell survival and tumor growth. Novel strategies that interfere with asbestos- and erionite-mediated inflammation might prevent or delay the onset of mesothelioma in high-risk cohorts, including genetically predisposed individuals, and/or inhibit tumor growth. The very recent discovery that germline BAP1 mutations cause a new cancer syndrome characterized by mesothelioma, uveal melanoma, and melanocytic tumors provides researchers with a novel target for prevention and early detection.