Abstract 6794: SETD2 loss in renal cell carcinoma generates peptides from aberrantly translated retained introns

Introduction: SETD2, a histone H3-K36 trimethyltransferase, is necessary for regulation of proper intron splicing. SETD2 is frequently inactivated in kidney cancer. We hypothesized that SETD2 deficiency would cause aberrant translation of retained introns (ATaRI) that could serve as potential immunotherapeutic targets in SETD2-mutant states. Methods and Results: We detected increased presence of retained introns in SETD2-mutant vs WT tumors in two publicly available renal cell carcinoma RNA-seq data sets. We hypothesized that if intronic sequences translated into proteins, accumulation of misfolded proteins would activate the Unfolded Protein Response (UPR). The UPR pathway was strongly transcriptionally enriched as measured by GSEA, as were several immunotherapy-relevant pathways, suggesting that tumors are inflamed, possibly related to the antigenic nature of translated introns. To investigate this further, we generated Setd2-isogenic mouse renal cancer cells using CRISPR in the RENCA cell line. RNAseq followed by GSEA confirmed upregulation of UPR pathway transcriptional signature in the Setd2-null condition, supporting our observation in human tumors. Indicators of UPR activation such as cleavage of ATF6 and increase in ATF4 and Xbp1 levels in Setd2 deficient vs. unedited RENCA cells, as well as nuclear translocation of ATF6 in SETD2-mutant human kidney cancer samples validates these findings. We then measured the presence of ATaRI-derived peptides in Setd2-mutant RENCA cells using mass spectrometry, detecting 47 such peptides. Using publicly available proteomics data from one human data set, we preliminarily identified peptides translated from 151 introns that are retained in SETD2-mutant cases. Applying netMHCpan to both the human and murine data, we found that detectable ATaRI peptides were predicted to generate multiple 10-amino acid-long peptides which strongly bind to the 8 murine MHC or to the 20 most common human HLA receptors. We propose that these presentable peptides might activate an immune response to SETD2-mutant renal cell carcinoma. Conclusions: We identified intron retention which may cause activation of the UPR as a feature of SETD2-mutant kidney cancer. ATaRI peptides are detectable and should be presented to the adaptive immune system. These features may represent a new therapeutic vulnerability for exploitation as a rationale for personalized medicine. Citation Format: Marya T. Kozinova, Alexander Metz, Robert Uzzo, Janusz Franco-Barraza, Michael Slifker, Jessica Peskin, Angel Fernández Sanromán, Samra Turajlic, Edna Cukierman, Phillip Phillip Abbosh. SETD2 loss in renal cell carcinoma generates peptides from aberrantly translated retained introns. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6794.