Abstract 569: MicroRNA-mediated resistance to anti-PD1 therapy in lung cancer
Authors: Cortez Maria A. , Wang Xiaohong , Ivan Cristina , Schoenhals Jonathan E. , Niknam Sharareh , Li Ailin , Valdecanas David , Allison James P. , Sharma Padmanee , Overwijk Willem W. , Gomez Daniel , Chang Joey Y. , Hahn Stephen , Calin George A. , Welsh James W. 
Published: July 2016

Abstract
Immunotherapies targeting programmed cell death receptor-1 (PD-1) have shown some clinical success, validating the role of immune modulation in the treatment of cancer. However, only 18% of non-small cell lung cancer patients have responded to anti-PD1 treatment thus far, the remaining 82% have not. This raises fundamental questions about mechanisms of resistance to anti-PD1 therapy and potential strategies to overcome resistance. Previously, our group generated an anti-PD-1-resistant preclinical tumor model after sequential in vivo passage of the murine lung cancer cell line 344SQ (p53R172HΔg/+KrasLA1/+) into syngeneic mice, previously treated with anti-mouse PD-1 antibodies. In this study, we analyzed global gene expression of microRNAs and correlated with our previous mRNA microarray data to validate potential target candidates in order to identify mechanisms of resistance to anti-PD1 therapy. For the microRNA microarray studies, 344SQ_P (parental) or 344SQ_R (resistant) cells were inoculated into the right flank of 129Sv/ev mice (female mice, 12-14 weeks old, 5 mice per group). Anti-PD1 or control IgG (10mg/kg) antibodies were given on days 4 and 7 after tumor inoculation. On day 11, tumor tissues were collected and immediately frozen in liquid nitrogen. RNAs from three independent biologic replicates per group were used for GeneChip miRNA 4.0 Array (Affymetrix). Significant differences in microRNA gene expression levels between groups were defined as an adjusted P value &lt;0.05 and absolute fold change of &gt; 2. Heatmaps were created by using the heatmap.2 function in the gplots R package. Our previous studies demonstrated that major histocompatibility complex (MHC) class I and II and antigen presentation pathway, were significantly downregulated in the anti-PD-1-resistant tumors compared with parental tumors. Here, we found that microRNAs significantly upregulated in the anti-PD1 resistant model directly regulates MHC class I and II and antigen presentation machinery genes, including B2M, CIITA, PSMB8, PSMB8, TAP2 and TAPBP, promoting resistance to anti-PD1 therapy. Because activated CD8+ tumor-infiltrating lymphocytes must bind to MHC I proteins to kill target tumor cells, one way in which tumors can evade destruction by the immune system is through downregulating expression of MHC I on their surfaces. Therefore, our study identified upregulation of microRNAs that modulates the antigen presentation pathway as an underlying mechanism by which some tumors do not respond to anti-PD1 therapy. Our future goal is to validate these findings on our ongoing clinical studies.
Citation Format: Maria A. Cortez, Xiaohong Wang, Cristina Ivan, Jonathan E. Schoenhals, Sharareh Niknam, Ailin Li, David Valdecanas, James P. Allison, Padmanee Sharma, Willem W. Overwijk, Daniel Gomez, Joey Y. Chang, Stephen Hahn, George A. Calin, James W. Welsh. MicroRNA-mediated resistance to anti-PD1 therapy in lung cancer. [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 569.