Regression of AK7 malignant mesothelioma established in immunocompetent mice following intratumoral gene transfer of interferon gamma

Abstract

Malignant mesothelioma (MM) is a lethal tumor linked with a prior exposure to asbestos in which limited progress has been made so far using conventional therapies. MM is an example of a ''nonimmunogenic'' tumor characterized by a fibrous stroma and an absence of infiltrating T lymphocytes. High levels of transforming growth factor-beta (TGF-b) produced by mesothelioma cells have been related to the immune tolerance towards the tumor. In order to evaluate the effect of local delivery of cytokines such as interferon gamma (IFN-g) by gene transfer, we characterized and used a murine model, AK7, which appeared very similar to human mesothelioma. AK7 cells expressed low levels of major histocompatibility class I and class II antigens and secreted high levels of latent TGF-b. The TGF-b pathway in AK7 cells is operative but inefficient because endogenous TGF-b is predominantly inactive. Treatment of pre-established AK7 tumors by direct intratumoral injection of an adenovirus vector expressing murine IFN-g, Ad.mIFN-g, led to significant tumor regression. Peripheral tumor infiltration by CD4+ and CD8+ T lymphocytes in the treated tumors appeared to be because of the induction of an immune response. Tumor relapse was observed, which could be due to local TGF-b secretion by remaining tumor cells.

Establishment of immortalized murine mesothelial cells and a novel mesothelioma cell line

“…The most used immortalized human mesothelial cell lines are MeT-5A immortalized with SV40 (Ke et al 1989 ) and LP9 cells immortalized with TERT1, the catalytic component of telomerase (Connell and Rheinwald 1983 ). Immortalized mesothelioma and mesothelial cells of mouse origin include cells isolated from the ascites of asbestos-exposed wild-type C57Bl/6J or BALB/c mice [40, 40L, AE17, AK7 (Cordier Kellerman et al 2003 ), and AB12 (Davis et al 1992 )], SV40 TAg transgenic mice [MexTAg, line names TGM299h, TGM304i, TGM270i, and TGM266i (Robinson et al 2006 ), conditional Nf2−/− mice (Jongsma et al 2008 )], and spontaneously immortalized cells obtained after prolonged culturing of primary mouse mesothelial cells (Sherwood et al 2008 ). Here, we established SV40-immortalized mesothelial cells of WT mice and immortalized cells derived from (Nf2+/−) mice; all lines stem from mesothelial cells isolated from mice with C57Bl/6J background.…”

Kinetics of Host Cell Recruitment During Dissemination of Diffuse Malignant Peritoneal Mesothelioma

“…This model of transplanted diffuse malignant mesothelioma shows the formation of malignant ascites, tumor masses and secondary pulmonary metastases similar to autochthonous models of diffuse malignant mesothelioma in rodents and the human disease [19, 34, 37–39] (Figs. 1 and 2).…”

“…The best documented correlation is between density of tumor-associated macrophages and poor prognosis in 80% of epithelial cancers, as well as in diffuse malignant mesothelioma [14, 15]. T-lymphocytes, macrophages, NK cells, fibroblasts, and dendritic cells have each been identified in human and murine diffuse malignant mesotheliomas [16–18] with studies showing that targeting T-lymphocytes [17, 19] or macrophages [14] delays tumor progression in murine diffuse malignant mesothelioma.…”

Oncolytic Viral Therapy for Mesothelioma

“…After passive immunotherapy with intrapleural or systemic delivery of IL-2, IFNα, and IFNγ for mesothelioma met with some success in phase I/II trials, administration of cytokines via gene therapy was proposed to improve efficacy ( 110 – 112 ). In several murine experiments, IT injection of an adenovirus with insertion of the IFNγ gene resulted in tumor regression and a CD8+ T cell-mediated response ( 113 , 114 ). By using a different mechanism to induce antitumor immunity, a replication-deficient adenovirus engineered to express the costimulatory molecule CD40L showed regression of both directly injected and distant tumors, indicative of a systemic immune response ( 115 ).…”