Abstract 4619: Epigenetic therapy and sensitization of lung cancer to immunotherapy.

Epigenetic alterations driving carcinogenesis and cancer progression can be specifically targeted by the demethylating agent azacitidine (Aza) and the histone deacetylase inhibitor entinostat. While this treatment combination has been effective in a limited number of patients (pts) with treatment-refractory non-small cell lung cancer (NSCLC), we observed clinical benefit in 5 of 5 patients who received immunotherapy with PD-1/PD-L1 pathway blockade immediately following epigenetic therapy. Three of 5 pts developed partial tumor regressions (RECIST criteria, duration 10+ to 20+ mo.) and 2 pts had stable disease ≥6 mo. This compares to the objective response + SD rates of NSCLC to monotherapy with anti-PD-1 (18% + 5%) or anti-PD-L1 (10% + 12%). To understand how epigenetic therapy may synergize with blockade of the immunosuppressive PD-1 pathway, we used genome wide methylation and expression profiling on 8 NSCLC cell lines treated with low dose Aza. We discovered complex immunomodulatory effects of Aza with up-regulation of diverse immune related pathways including Jun/Jnk, NFKB, viral defense, type I interferon signaling, the inflammasome, antigen processing and presentation and immune evasion including up-regulation of PD-L1 expression. Multiple cancer-testes antigens were also up-regulated, thereby conferring de novo antigenicity. Supporting the idea that Aza acts specifically through inhibition and degradation of DNA methyltransferase proteins, colon cancer cells genetically haplo-insufficient for DNMT1 and devoid of DNMT3b mirror the immunomodulatory effects of Aza. Upstream events potentially controlling these pathways were defined, and prominent among them was up-regulation of the transcription factor, interferon regulatory factor 7 (IRF7), a DNA hypermethylated gene. These data were used to query hundreds of primary NSCLC samples from the Cancer Genome Atlas project (TCGA). A low basal expression signature of interferon pathway related genes was significantly associated with low IRF7 expression and promoter methylation in squamous tumors. Another hypermethylated transcription factor, PITX1, which inhibits a subset of type I interferon signaling genes, tracked with non-squamous cancers. Together, these findings support a model in which epigenetic modulation activates innate and adaptive immune responses within the tumor microenvironment together with induction of counter-regulatory immune checkpoint ligands which can be therapeutically blocked with antibodies. Based on these findings, a clinical trial testing the efficacy of DNMT and HDAC inhibition combined with PD-1 pathway blockade is under development. This work will form the basis for an immune-classification of NSCLC, as well as biomarker discovery for a novel therapeutic paradigm combining epigenetic and immunotherapy with potentially synergistic activity against the world9s most deadly malignancy. Supported by Stand Up to Cancer. Citation Format: John Wrangle, Wei Wang, Alexander Koch, Hariharan Easwaran, Helai Mohammad, Princy Parsana, Frank Vendetti, Kristen Rodgers, Xiaoyu Pan, Kirsten Harbom, Cynthia Zahnow, Janis Taube, Julie Brahmer, Peter Jones, Suzanne Topalian, Charles Rudin, Malcolm Brock, Drew Pardoll, Stephen Baylin. Epigenetic therapy and sensitization of lung cancer to immunotherapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4619. doi:10.1158/1538-7445.AM2013-4619