Influence of the oncolytic parvovirus H-1, CTLA-4 antibody tremelimumab and cytostatic drugs on the human immune system in a human in vitro model of colorectal cancer cells

Abstract

IntroductionTumor-directed and immune-system-stimulating therapies are of special interest in cancer treatment. Here, we demonstrate the potential of parvovirus H-1 (H-1PV) to efficiently kill colorectal cancer cells and induce immunogenicity of colorectal tumors by inducing maturation of dendritic cells (DCs) alone and also in combination with cytostatic drugs in vitro. Using our cell culture model, we have additionally investigated the effects of anti-CTLA-4 (cytotoxic T-lymphocyte-associated antigen 4) receptor antibody tremelimumab on this process.Materials and methodsColon carcinoma cell lines were treated with different concentrations of cytostatic drugs or tremelimumab or were infected with H-1PV in different multiplicities of infection (MOIs), and viability was determined using MTT assays. Expression of CTLA-4 in colon carcinoma cell lines was measured by FACScan™. For the coculture model, we isolated monocytes using adherence, and differentiation into immature DCs (iDCs) was stimulated using interleukin-4 and granulocyte-macrophage colony-stimulating factor. Maturation of iDCs into mature DCs (mDCs) was induced by a cytokine cocktail. SW480 colon carcinoma cells were infected with H-1PV or treated with cytostatic drugs. Drug treated and H-1PV-infected SW480 colon carcinoma cells were cocultured with iDCs and expression of maturation markers was measured using FACScan™. Cytokine measurements were performed using enzyme-linked immunosorbent assay.ResultsColon carcinoma cells SW480 were potently infected and killed by H-1PV. CTLA-4 expression in SW480 cells increased after infection with H-1PV and also after treatment with cytostatic drugs. Tremelimumab had no influence on viability of the colon carcinoma cell line. There was no maturation of iDCs after coculture with SW480; instead, H-1PV-infected or drug pretreated SW480 induced maturation. Cytokine production was higher for H-1PV-infected cells but was not significantly enhanced by tremelimumab treatment alone or in combination. Addition of tremelimumab did not interfere with the maturation process as measured by markers of maturation as well as by determination of cytokine levels.ConclusionBy enhancing both cell death and immunogenicity of tumors, H-1PV is of special interest for tumor-directed therapy. These features make it a promising candidate for clinical application in human colorectal cancer. As tremelimumab does not significantly interfere with this process, an interesting therapeutic combination of active enhancement of tumor immunogenicity and independent masking of the CTLA-4 silencing process on tumor cells is highlighted.

Immunotherapeutic Potential of Oncolytic H-1 Parvovirus: Hints of Glioblastoma Microenvironment Conversion towards Immunogenicity

“…The ability of H-1PV-infected tumor cells to activate antitumor immune responses has been demonstrated in several preclinical cancer models, in particular hepatoma [ 34 ], melanoma [ 35 ], pancreatic [ 36 ], colorectal [ 37 , 38 ] and nasopharyngeal [ 39 ] carcinomas. In these models, H-1PV-infected tumor cell lysates induced DC maturation, proinflammatory cytokine secretion, tumor-associated antigen cross-presentation, and T/Natural Killer (NK) cell stimulation.…”

Oncolytic viruses and checkpoint inhibitors: combination therapy in clinical trials

“…Multiple vector systems are currently being tested in clinical trials in combination with anti-PD-1 or anti-CTLA-4 antibodies, and thus far the results have been encouraging. Additionally, many research groups are exploring similar treatment schemes with other vectors systems in preclinical settings, some of which include measles virus [ 96 , 97 ], vesicular stomatitis virus (VSV) [ 98 , 99 ], newcastle disease virus (NDV) [ 100 , 101 ], semlicki forest virus (SFV) [ 102 ], and parvovirus [ 103 ]. With time, it is expected that additional oncolytic vectors with be tested with checkpoint inhibitors in clinical trials.…”

Oncolytic Virotherapy as Emerging Immunotherapeutic Modality: Potential of Parvovirus H-1

“…These limitations indicate an urgent need for novel therapeutic strategies (13, 64, 66, 84). Combinations of oncolytic viruses with new targeted therapies draw much attention.…”