Símová J

Induction of MHC class I molecule cell surface expression and epigenetic activation of antigen-processing machinery components in a murine model for human papilloma virus 16-associated tumours.

Epigenetic events play an important role in tumour progression and also contribute to escape of the tumour from immune surveillance. In this study, we investigated the up‐regulation of major histocompatibility complex (MHC) class I surface expression on tumour cells by epigenetic mechanisms using a murine tumour cell line expressing human E6 and E7 human papilloma virus 16 (HPV16) oncogenes and deficient in MHC class I expression, as a result of impaired antigen‐presenting machinery (APM). Treatment of the cells with the histone deacetylase inhibitor Trichostatin A, either alone or in combination with the DNA demethylating agent 5‐azacytidine, induced surface re‐expression of MHC class I molecules. Consequently, the treated cells became susceptible to lysis by specific cytotoxic T lymphocytes. Further analysis revealed that epigenetic induction of MHC class I surface expression was associated with the up‐regulation of APM genes [transporter associated with antigen processing 1 (TAP‐1), TAP‐2, low‐molecular‐mass protein 2 (LMP‐2) and LMP‐7]. The results demonstrate that expression of the genes involved in APM are modulated by epigenetic mechanisms and suggest that agents modifying DNA methylation and/or histone acetylation have the potential to change the effectiveness of antitumour immune responses and therapeutically may have an impact on immunological output.

Interleukin-2 gene therapy of residual EL-4 leukaemia potentiates the effect of cyclophosphamide pretreatment

Experiments were designed to investigate a possible therapeutic role of interleukin-2 (IL-2) gene transfer in the model of murine (EL-4) leukaemia pretreated with cyclophosphamide. It has been found that i. p. pretreatment of the leukaemic mice with cyclophosphamide, followed by i. v. administration of irradiated cells, genetically engineered to produce IL-2 and used as a source of the cytokine (IR-IL-2 cells), cured a substantial percentage of the leukaemic mice. Neither treatment with cyclophosphamide nor administration of the IR-IL-2 cells alone had any significant therapeutic effect. Labelling of the EL-4 and IR-IL-2 cells with different fluorescent cell linkers followed by i. v. injection and detection of the labelled cells in cryostat sections of various organs has shown that both cell populations can be detected almost exclusively in the red pulp of the spleen, close to the white pulp nodules, thus providing the possibility of short-range local interactions among the IL-2-producing cells, IL-2-responsive defence effector cells and EL-4 leukaemia targets.

Immunotherapy augments the effect of 5-azacytidine on HPV16- associated tumours with different MHC class I-expression status

Background:Epigenetic mechanisms have important roles in the tumour escape from immune responses, such as in MHC class I downregulation or altered expression of other components involved in antigen presentation. Chemotherapy with DNA methyltransferase inhibitors (DNMTi) can thus influence the tumour cell interactions with the immune system and their sensitivity to immunotherapy.Methods:We evaluated the therapeutic effects of the DNMTi 5-azacytidine (5AC) against experimental MHC class I-deficient and -positive tumours. The 5AC therapy was combined with immunotherapy, using a murine model for HPV16-associated tumours.Results:We have demonstrated 5AC additive effects against MHC class I-positive and -deficient tumours when combined with unmethylated CpG oligodeoxynucleotides or with IL-12-producing cellular vaccine. The efficacy of the combined chemoimmunotherapy against originally MHC class I-deficient tumours was partially dependent on the CD8+-mediated immune responses. Increased cell surface expression of MHC class I cell molecules, associated with upregulation of the antigen-presenting machinery-related genes, as well as of genes encoding selected components of the IFNγ-signalling pathway in tumours explanted from 5AC-treated animals, were observed.Conclusion:Our data suggest that chemotherapy of MHC class I-deficient tumours with 5AC combined with immunotherapy is an attractive setting in the treatment of MHC class I-deficient tumours.

DNA demethylating agent 5-azacytidine inhibits myeloid-derived suppressor cells induced by tumor growth and cyclophosphamide treatment

MDSCs represent one of the key players mediating immunosuppression. These cells accumulate in the TME, lymphoid organs, and blood during tumor growth. Their mobilization was also reported after CY therapy. DNMTi 5AC has been intensively studied as an antitumor agent. In this study, we examined, using two different murine tumor models, the modulatory effects of 5AC on TU‐MDSCs and CY‐MDSCs tumor growth and CY therapy. Indeed, the percentage of MDSCs in the TME and spleens of 5AC‐treated mice bearing TRAMP‐C2 or TC‐1/A9 tumors was found decreased. The changes in the MDSC percentage were accompanied by a decrease in the Arg‐1 gene expression, both in the TME and spleens. CY treatment of the tumors resulted in additional MDSC accumulation in the TME and spleens. This accumulation was subsequently inhibited by 5AC treatment. A combination of CY with 5AC led to the highest tumor growth inhibition. Furthermore, in vitro cultivation of spleen MDSCs in the presence of 5AC reduced the percentage of MDSCs. This reduction was associated with an increased percentage of CD11c+ and CD86+/MHCII+ cells. The observed modulatory effect on MDSCs correlated with a reduction of the Arg‐1 gene expression, VEGF production, and loss of suppressive capacity. Similar, albeit weaker effects were observed when MDSCs from the spleens of tumor‐bearing animals were cultivated with 5AC. Our findings indicate that beside the direct antitumor effect, 5AC can reduce the percentage of MDSCs accumulating in the TME and spleens during tumor growth and CY chemotherapy, which can be beneficial for the outcome of cancer therapy.

Interleukin-2 and dendritic cells as adjuvants for surgical therapy of tumours associated with human papillomavirus type 16.

Moderately immunogenic HPV 16-associated tumours TC-1 (MHC class I(+), HPV 16 E6/E7(+), G12V Ha-ras(+)) and MK16/1/III ABC (MHC class I(-), HPV 16 E6/E7(+), G12V Ha-ras(+)), both of the H-2(b) haplotype and transplanted in syngeneic mice, were used to examine the adjuvant effects of IL-2 and dendritic cells for surgical therapy. Mice were inoculated s.c. with the respective tumour cells, and when the tumours reached 8-12 mm in diameter, they were extirpated. Three days after surgery, the experimental mice were treated with IL-2, IL-2 gene-modified tumour vaccines, or dendritic cells, injected s.c. to the site of previous surgery. It has been found in both, MHC class I(+) and MHC class I(-) tumours that the recombinant IL-2 and IL-2 gene-modified vaccines substantially reduced the tumour recurrence rate and inhibited growth of tumour recurrences. The dendritic cells were significantly effective only in mice with surgical minimal residual TC-1 (MHC class I(+)) tumour disease and when injected before they have reached the terminal stage of their differentiation.

Metastatic MHC class I-negative mouse cells derived by transformation with human papillomavirus type 16

In the endeavour to develop a model for studying gene therapy of cancers associated with human papillomaviruses (HPVs), mouse cells were transformed with the HPV type 16 (HPV16) and activated H-ras oncogenes. This was done by contransfection of plasmid p16HHMo, carrying the HPV16 E6/E7 oncogenes, and plasmid pEJ6.6, carrying the gene coding for human H-ras oncoprotein activated by G12V mutation, into secondary C57BL/6 mouse kidney cells. An oncogenic cell line, designated MK16/1/IIIABC, was derived. The epithelial origin of the cells was confirmed by their expression of cytokeratins. No MHC class I and class II molecules were detected on the surface of MK16/1/IIIABC cells. Spontaneous metastases were observed in lymphatic nodes and lungs after prolonged growth of MK16/1/IIIABC-induced subcutaneous tumours. Lethally irradiated MK16/1/IIIABC cells induced protection against challenge with 105 homologous cells, but not against a higher cell dose (5 × 105). Plasmids p16HHMo and pEJ6.6 were also used for preventive immunization of mice. In comparison with a control group injected with pBR322, they exhibited moderate protection, in terms of prolonged survival, against MK16/1/IIIABC challenge (P < 0.03). These data suggest that MK16/1/IIIABC cells may serve as a model for studying immune reactions against HPV16-associated human tumours.

Dendritic cells pulsed with tumor cells killed by high hydrostatic pressure induce strong immune responses and display therapeutic effects both in murine TC-1 and TRAMP-C2 tumors when combined with docetaxel chemotherapy

High hydrostatic pressure (HHP) has been shown to induce immunogenic cell death of cancer cells, facilitating their uptake by dendritic cells (DC) and subsequent presentation of tumor antigens. In the present study, we demonstrated immunogenicity of the HHP-treated tumor cells in mice. HHP was able to induce immunogenic cell death of both TC-1 and TRAMP-C2 tumor cells, representing murine models for human papilloma virus-associated tumors and prostate cancer, respectively. HHP-treated cells induced stronger immune responses in mice immunized with these tumor cells, documented by higher spleen cell cytotoxicity and increased IFNγ production as compared to irradiated tumor cells, accompanied by suppression of tumor growth in vivo in the case of TC-1 tumors, but not TRAMP-C2 tumors. Furthermore, HHP-treated cells were used for DC-based vaccine antigen pulsing. DC co-cultured with HHP-treated tumor cells and matured by a TLR 9 agonist exhibited higher cell surface expression of maturation markers and production of IL-12 and other cytokines, as compared to the DC pulsed with irradiated tumor cells. Immunization with DC cell-based vaccines pulsed with HHP-treated tumor cells induced high immune responses, detected by increased spleen cell cytotoxicity and elevated IFNγ production. The DC-based vaccine pulsed with HHP-treated tumor cells combined with docetaxel chemotherapy significantly inhibited growth of both TC-1 and TRAMP-C2 tumors. Our results indicate that DC-based vaccines pulsed with HHP-inactivated tumor cells can be a suitable tool for chemoimmunotherapy, particularly with regard to the findings that poorly immunogenic TRAMP-C2 tumors were susceptible to this treatment modality.

Inhibitory effects of unmethylated CpG oligodeoxynucleotides on MHC class I-deficient and -proficient HPV16-associated tumours

Unmethylated oligodeoxynucleotides containing guanine–cytidine dimers (CpG ODN) have been described as potent inducers of selected antitumour immune responses and the immunotherapeutic efficacy of CpG ODN has been examined either alone or as a vaccine adjuvant. We hypothesized that CpG ODN therapy could be an effective tool for immunotherapy of not only conventional MHC class I+ tumours but also of those tumours that have lost MHC class I expression during their progression. To address this hypothesis, we employed the animal model resembling MHC class I‐proficient and ‐deficient human papilloma virus (HPV) 16‐associated tumours. A cell line transformed with HPV16 E6 and E7 oncogenes, TC‐1, as a prototype of MHC class I‐positive line, and its MHC class I‐deficient sublines TC‐1/A9 and TC‐1/P3C10 were injected into syngeneic C57BL/6 mice and the growing tumours were subjected to immunotherapy with CpG ODN 1826. The therapy started either 1 day after the challenge with the tumour cells or later, when the tumours had reached a palpable size. In both settings, CpG ODN 1826 significantly reduced the growth of MHC class I‐proficient and ‐deficient tumours. Furthermore, we demonstrated that CpG ODN 1585, whose mechanism of action preferably involves indirect activation of the natural killer cells, induced regression of the MHC class I‐deficient tumours TC1/A9 but not of the MHC class I‐proficient tumours TC‐1. This study infers that synthetic CpG ODN have a potential for the therapy of both MHC class I‐proficient and ‐deficient tumours and thus could be also used against tumours that tend to down‐regulate their MHC class I expression.

Genetically modified tumour vaccines producing IL-12 augment chemotherapy of HPV16-associated tumours with gemcitabine

Genetically modified tumour cells producing cytokines such as interleukin 12 (IL-12) are potent activators of the antitumour immune responses and represent a promising therapeutic modality when combined with chemotherapy. The objective of this study was to examine whether IL-12-producing cellular vaccines can augment chemotherapy of human papilloma virus (HPV) 16-associated murine tumours with the cytostatic agent gemcitabine (GEM). We found that peritumoral administration of IL-12-producing tumour vaccines enhanced the effect of cytoreductive therapy with GEM both in non-metastasizing murine carcinoma TC-1 and in metastasizing murine carcinoma MK16. The percentage of mice with MK16 metastases and the number of lung metastatic nodules was substantially decreased. In another clinically relevant setting, surgical minimal residual tumour disease, the administration of IL-12-producing tumour vaccine and GEM after the MK16 tumour surgery reduced the percentage of mice with tumour recurrences; similarly, the percentage of metastasis-bearing mice and the number of metastatic nodules was decreased. Tumour inhibitory effects exerted by GEM plus IL-12 were associated with high production of interferon-γ (IFNγ) by splenocytes. Our results suggest that the IL-12-producing vaccine can enhance the effect of GEM chemotherapy in some HPV16-associated murine tumour models.

Therapy for minimal residual tumor disease: β-galactosylceramide inhibits the growth of recurrent HPV16-associated neoplasms after surgery and chemotherapy

Natural killer T (NKT) cells are potent modulators of antitumor immunity. Their protective effects can be achieved upon their activation by glycolipid ligands presented in the context of the CD1d molecule. These CD1d‐binding glycolipid antigens have been described as potent therapeutic agents against tumors, infections, as well as autoimmune diseases. Immunoregulatory and therapeutic effects of glycolipid ligands depend on their structure and modes of administration. Therefore, more studies are needed for optimization of the particular therapeutic settings. This study was focused on the tumor‐inhibitory effects of 12 carbon acyl chain β‐galactosyl ceramide (C12 β‐D‐Galactosyl Ceramide; β‐GalCer(C12)) on the growth of human papillomavirus type 16 (HPV16)‐associated neoplasms transplanted in syngeneic mice. Treatment of tumor‐bearing mice with β‐GalCer(C12) 3–14 days after tumor cell transplantation significantly inhibited the growth of the major histocompatability complex (MHC) Class I‐positive (TC‐1), as well as MHC Class I‐deficient (TC‐1/A9) HPV16‐asssociated tumors. Moreover, administration of β‐GalCer(C12) after surgical removal of TC‐1 tumors inhibited the growth of tumor recurrences. Similar results were obtained in the treatment of tumors after chemotherapy. β‐GalCer(C12) treatment turned out to be also synergistic with immunotherapy based on administration of IL‐12‐producing cellular vaccines. These results suggest that β‐GalCer(C12), whose antitumor effects have so far not been studied in detail, can be effective for the treatment of minimal residual tumor disease as well as an adjuvant for cancer immunotherapy.