Abstract 4013: Transcriptionally mediated effects of radiation on the expression of immune susceptibility markers in murine and human melanoma

Abstract

Radiation therapy (RT) may enhance tumor susceptibility to immune response. We and others have observed a cooperative interaction between RT and various immunotherapies, which appears dependent on the relative sequencing of each therapy. We reported a synergistic interaction between RT and the antibody-dependent cell-mediated cytotoxicity (ADCC) response to tumor-specific monoclonal antibodies (mAb) in murine melanoma. We reported enhanced cooperative effect when immunotherapy is administered 6-10 days after RT compared to administration on days 1-5 or 11-15. We hypothesized that this might reflect a delayed, transcriptionally-mediated effect of RT on the expression of tumor markers of immune susceptibility. In this study, we investigated the effect of RT on a variety of immune susceptibility markers at both transcriptional and post-translational levels to explore mechanisms behind the observed RT-induced changes. We used flow cytometry to examine the time course of phenotypic changes in immune susceptibility markers in B78 murine melanoma cells following in vitro RT. We observed a time- and RT dose-dependent increase in the expression of specific death receptors (Fas, DR5), as well as T cell co-stimulatory/co-repressor ligands (PD-L1, CD80). The timing of these changes correlated with tumor susceptibility to ADCC immune response in vivo. All protein expression changes observed by flow cytometry were found to occur over a similar time course by quantitative polymerase chain reaction (qPCR), suggesting that RT-induced protein expression changes were mediated by changes in transcriptional activity. Using high throughput qPCR, we observed a similar time course of transcriptional effects in additional markers of tumor cell immune susceptibility, including Fas, MHC I, CD40, and others. We compared the effect of RT on these markers in human and mouse melanoma cell lines and observed a comparable time course for transcript-level changes across species. This study sheds light on the mechanistic basis of time sensitivity in the interaction of RT with ADCC in vivo and suggests opportunities to enhance anti-tumor immune response by combining RT and immunotherapeutic agents. Such findings bear relevance for research investigating the potential role for RT in driving and optimizing the response to various cancer immunotherapies. Citation Format: Lauryn R. Werner, Monica Gressett, Maureen Riegert, Shyhmin Huang, Joseph G. Kern, Amy Erbe, Paul M. Harari, Paul M. Sondel, Zachary S. Morris. Transcriptionally mediated effects of radiation on the expression of immune susceptibility markers in murine and human melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4013.

Advances in Immuno-oncology for the Treatment of Colorectal and Anal Cancers

“…32,33 There are nonredundant roles for PD-1 inhibition in reinvigorating anergic CD8-positive tumor infiltrating effector T cells and for radiation in enhancing the diversity of antigens recognized by the emergent T-cell response, upregulating PD-L1 expression on radiated tumor cells and enhancing tumor infiltrating lymphocyte recruitment. [30][31][32]34 Initial studies combining radiation with immu-notherapy in CRC produced mixed results. A pilot study of the anti-PD1 antibody AMP-224 in combination with low-dose cyclophosphamide and stereotactic body radiation therapy did not show evidence of activity in 15 patients with advanced CRC.…”