Abstract LB222: An mRNA-based cancer vaccine multi-targeting KRAS mutations inhibits tumor growth by increasing immune response in KRAS mutant LL/2 mouse model

Abstract

Abstract Kirsten rat sarcoma viral oncogene (KRAS) mutations are present in 26% of non-small cell lung cancer (NSCLC) patients (The Cancer Genome Atlas data). Studies have reported the presence of spatial or intra-tumoral heterogeneity of KRAS mutations. Though resistance to mutant KRAS inhibitors targeting a specific form of major KRAS mutations (e.g, G12C or G12D) is multifaceted, intra-tumoral heterogeneity of KRAS mutation is one of the crucial factors for the intrinsic resistance to the inhibitor. Multi-targeting of different KRAS mutations can prevent resistance due to the heterogeneity of KRAS mutations within a tumor. To achieve this, we incorporated an mRNA-based cancer vaccine containing transcripts for multiple KRAS mutant antigens. Our KRAS cancer vaccine (CV) candidate showed significantly attenuated tumor growth by 37% in the syngeneic KRAS G12C-expressing LL/2 tumor-bearing mice. CV treatment group showed significantly decreased tumor size by 45.4% after biopsy. Moreover, the mice treated with KRAS CV showed spleen enlarged by 42.6% indicating increased immune responses. To confirm, the expansion of T cells in the cancer vaccine-treated group, we collected tumor tissues and analyzed proportions of CD4+ and CD8+ T lymphocytes in the tumor. We found a 14.5-fold increase in infiltration of CD8+ T cells and a 0.5-fold increase in CD8+ CD44+ memory/effector T cells in the tumors from mice treated with KRAS CV. Whereas CD4+ Foxp3+ Treg cells were decreased by 3.9-fold in the tumor. HLA-A*02 is the most common MHC class I allele. To investigate the changes in MHC expression, we conducted FACS analysis using HLA-A*02 antibodies after ex vivo treatment of KRAS CV on the human peripheral blood mononuclear cells (hPBMCs). KRAS CV treatment facilitated higher proportions of HLA-A*02+ monocytes (CD14+) and B cells (CD19+). Though LL/2 tumor model has been considered an immunosuppressive model, our results suggest that the KRAS CV can significantly enhance immune responses, thereby suppressing tumor growth. Citation Format: Seung-Hyun Shin, Youngjin Han, Chang Gyu Lim, Yong Ho Heo, Seongju Jeong, Yu-Yon Kim, In Young Choi. An mRNA-based cancer vaccine multi-targeting KRAS mutations inhibits tumor growth by increasing immune response in KRAS mutant LL/2 mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB222.