Abstract 583: DNA demethylating agents enhance susceptibility of lung cancer cells to γδ T cell-based immunotherapy via MHC-independent mechanisms
Authors: Weng Rueyhung , Lin Chien-Ting , Huang Tai-Chung , Lu Hsuan-Hsuan , Wu Yi-Chieh , Lin Xuan-Hui , Lin Rong-Shan , Yu Chong-Jen , Tsai Hsing-Chen 
Published: August 2019

Abstract
Immune-based therapy is revolutionizing lung cancer management in the clinic. In addition to rejuvenating T cells through immune checkpoint blockade, enhancing the immunogenicity of cancer cells and their interactions with immune cells may also be key to boosting the clinical efficacy of immunotherapy. Previous transcriptomic studies have shown that DNA demethylating agents may alter antigen processing/presentation machinery, upregulate cancer-testis antigens, reactivate endogenous retroviruses to facilitate efficacy of immunotherapy. Nevertheless, how DNA demethylating agents modulate surface immune synapse proteins and affect interactions between cancer and immune cells remain unclear. We utilized stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative membrane proteomics to identify surface proteins altered in decitabine-treated human lung cancer cells. The results showed that decitabine upregulated multiple immune synapse proteins. Gene enrichment analyses discovered that these surface proteins are predominantly involved in γδT cell-mediated cytotoxicity. γδT cells are a distinct subgroup of T cells that bridge between the innate and the adaptive immune systems and do not require the major histocompatibility complexes for antigen recognition. Co-culture of decitabine-pretreated human lung cancer cells with allogenic γδT cells in vitro confirmed sensitization effects of decitabine for the killing of γδT cells. A similar effect was also observed in immunocompromised mice bearing xenograft tumors in vivo. Moreover, the comparison of decitabine-induced surface proteomes between sensitizable and unsensitizable lung cancer cells revealed that intercellular adhesion molecule 1 (ICAM1), was among the top differentially expressed proteins. Imaging analyses confirmed that ICAM1 participated in the formation of immune synapses between cancer cells and γδT cells. Increased expression of ICAM1 was also observed in xenograft tumors from mice receiving combination therapy of decitabine and γδT cells. Overall, our data characterized decitabine-induced surface proteomes and uncovered an immunomodulatory effect of decitabine for enhancing MHC-independent killing by γδT cells. These findings have great clinical implications and provide a novel molecular basis for coupling DNA demethylation agents with γδT cell-based immunotherapy in the treatment of lung cancer patients.
Citation Format: Rueyhung Weng, Chien-Ting Lin, Tai-Chung Huang, Hsuan-Hsuan Lu, Yi-Chieh Wu, Xuan-Hui Lin, Rong-Shan Lin, Chong-Jen Yu, Hsing-Chen Tsai. DNA demethylating agents enhance susceptibility of lung cancer cells to γδ T cell-based immunotherapy via MHC-independent mechanisms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 583.