Abstract 2884: Cancer-associated fibroblasts potentiate subcutaneous tumor growth in a novel bladder cancer mouse model with a genotype dependency

Abstract

Abstract Introduction Interrogation of the relationship of genotype (mutation in relevant gene) and phenotype (sensitivity to therapy) in targeted therapy would be facilitated by the use of isogenic in vitro and in vivo models. The PI3K/AKT/mTOR pathway is widely activated but heretofore untargeted in bladder cancer. We sought to develop an immunocompetent CRISPR-edited bladder cancer mouse model that recapitulates common PI3K/AKT/mTOR mutations to study a genotype-phenotype relationship. Our in vitro CRISPR-edited organoids are immunogenic in vivo, as such, we explored utilizing Cancer-Associated Fibroblasts (CAFs) to mediate immunosuppression and promote a pro-tumorigenic environment. Methods and Results We isolated bladder urothelial cells from Rosa26 LSL-Cas9/GFP transgenic mice and grew them as organoids. Trp53 and Rb1 were co-edited to establish ‘base organoids’. As proof of concept, Pten was edited in base organoids in anticipation of developing a series of organoids with different mTOR pathway genotypes. We found that Pten-KO base organoids were 9x more sensitive to ipatasertib than Pten WT organoids. The edited urothelial cells were engrafted into mouse bladder to further test kinase inhibitor susceptibility as preclinical evidence to support human clinical trials. However, the cells successfully engrafted but disappeared after 3-4 weeks before tumors formed. Subcutaneous allografts were also rejected after 3-4 weeks and showed CD45+ immune infiltration during rejection. When cells were injected subcutaneously with CAFs, tumors persisted for 12 weeks, but only in organoids with both Trp53 loss and loss of murine chromosome 4qC4 (which is homologous to 9p21 loss in humans). 9p21 contains 3 genes which are co-deleted in ~40% of bladder cancers: MTAP, CDKN2A, and CDKN2B. Histopathological analysis of these masses confirmed their malignant nature and revealed an immune-excluded architecture. IHC staining of 9p21/Trp53 KO tumors for CD206 and CD11c revealed greater recruitment of M2 macrophages than M1 macrophages. Conclusions CAFs remodel the tumor-microenvironment in bladder cancer via the recruitment of pro-tumorigenic M2 macrophages. This may occur in a genotype-specific manner and 9p21 loss may be a requirement for some genotypes to be tumorigenic. Citation Format: Henkel Lee Valentine, Uttam Satyal, Alexander Metz, Laura Bukavina, Philip H. Abbosh. Cancer-associated fibroblasts potentiate subcutaneous tumor growth in a novel bladder cancer mouse model with a genotype dependency [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 2884.