title: Antitumor activity of epigenetic immunomodulation combined with CTLA-4 blockade in syngeneic mouse models.
abstract: The multifaceted immunomodulatory activity of DNA hypomethylating agents improves immunogenicity and immune recognition of neoplastic cells; thus, we predicted they could be utilized to design new immunotherapeutic combinations in cancer. Testing this hypothesis, the antitumor efficacy of the DNA hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA-CdR) combined with the anti-CTLA-4 monoclonal antibody (mAb) 9H10 in syngeneic transplantable murine models was investigated. Murine mammary carcinoma TS/A or mesothelioma AB1 cells were injected in BALB/c, athymic nude, and SCID/Beige mice that were treated with 5-AZA-CdR, mAb 9H10, or their combination. Tumor volumes were captured at different time-points; molecular and immunohistochemical assays investigated changes in neoplastic and normal tissues. A significant antitumor effect of 5-AZA-CdR combined with mAb 9H10 was found: compared to controls, a 77% (p< 0.01), 54% (p< 0.01) and 33% (p= 0.2) decrease in TS/A tumor growth was induced by 5-AZA-CdR combined with mAb 9H10, 5-AZA-CdR or mAb 9H10, respectively. These antitumor activities were confirmed utilizing the AB1 model. 5-AZA-CdR-based regimens induced a promoter-demethylation-sustained tumor expression of cancer testis antigens. MHC class I expression was up-regulated by 5-AZA-CdR. Antitumor efficacy of 5-AZA-CdR in athymic nude and SCID/Beige mice was not increased by mAb 9H10. In BALB/c mice, combined treatment induced the highest tumor infiltration by CD3+lymphocytes, which included both CD8+and CD4+T cells; no such infiltrates were observed in normal tissues. This significant immune-related antitumor activity of 5-AZA-CdR combined with CTLA-4 blockade, demonstrated in highly aggressive mouse tumor models, provides a strong scientific rationale to implement epigenetically-based immunotherapies in cancer patients.
authors.affiliation: Medical Oncology and Immunotherapy; Department of Oncology; University Hospital of Siena; Istituto Toscano Tumori ; Siena, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Covre
authors.affiliation: Medical Oncology and Immunotherapy; Department of Oncology; University Hospital of Siena; Istituto Toscano Tumori ; Siena, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Coral
authors.affiliation: Medical Oncology and Immunotherapy; Department of Oncology; University Hospital of Siena; Istituto Toscano Tumori ; Siena, Italy.
authors.forename: H
authors.initials: H
authors.lastname: Nicolay
authors.affiliation: Medical Oncology and Immunotherapy; Department of Oncology; University Hospital of Siena; Istituto Toscano Tumori ; Siena, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Parisi
authors.affiliation: Medical Oncology and Immunotherapy; Department of Oncology; University Hospital of Siena; Istituto Toscano Tumori ; Siena, Italy ; Medical Genetics; University of Siena ; Siena, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Fazio
authors.affiliation: Cancer Bioimmunotherapy Unit; Centro di Riferimento Oncologico; IRCCS ; Aviano, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Colizzi
authors.affiliation: Cancer Bioimmunotherapy Unit; Centro di Riferimento Oncologico; IRCCS ; Aviano, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Fratta
authors.affiliation: Medical Oncology and Immunotherapy; Department of Oncology; University Hospital of Siena; Istituto Toscano Tumori ; Siena, Italy.
authors.forename: A M
authors.initials: AM
authors.lastname: Di Giacomo
authors.affiliation: Cancer Bioimmunotherapy Unit; Centro di Riferimento Oncologico; IRCCS ; Aviano, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Sigalotti
authors.affiliation: Regina Elena National Cancer Institute ; Rome, Italy.
authors.forename: P G
authors.initials: PG
authors.lastname: Natali
authors.affiliation: Medical Oncology and Immunotherapy; Department of Oncology; University Hospital of Siena; Istituto Toscano Tumori ; Siena, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Maio
keywords: CTLA-4; DNA methylation; cancer; immune responses; immunomodulation; immunotherapy