Abstract 924: Modelling the metastatic castration-resistant prostate cancer in mice by orthotopic delivering multiplexed gRNAs of CRISPR/Cas9 based on AAV system

Abstract Prostate cancer (PCa) is a most common cause of cancer-related death in men. While it develops to metastatic stage, the treatment options are limited. Hence, it desires in vivo models to test novel strategies for treating PCa. Current murine models of prostate cancer need long time for the diseases to progress to an invasive and metastatic cancer. Here, we combined AAV delivery and CRISPR-Cas9 technology to mutate several genes simultaneously in the mouse prostate. Four weeks after delivering of engineered virus, benign prostatic intraepithelial neoplasia (PIN) can be achieved and within eight weeks, the tumor developed to an extremely aggressive cancer. Surprisingly, a basic virus, engineering quintuple gRNAs of Cas9 including Pten, Trp53 and Rb1 induced a primary tumor without formation of metastasis. While adding triple gRNAs targeting epigenetic factors to the basic viral vector, all mice developed lung metastasis with metastasis started to appear after 6 weeks. Castration of the tumor baring mice 5 weeks after initiation did not alter primary tumor and metastasis formation, indicating the metastatic castration-resistant prostate cancer (mCRPC) nature of the model. To reveal the molecular mechanism for cancer progression and metastasis formation, whole genome sequencing (WGS) were performed on lung metastasis samples in combination with mRNA-seq on primary and secondary tumors from the two groups and PBS-injected mice control. Up to 5,000 mutations were accumulated in the genome, although the number varied across the metastatic samples, which were mainly due to chromosome 6 and 8 and revealed heterogeneity of the tumors. Among it, novel key mutations were identified, which will be addressed in the future. Tumor cell plasticity, including epithelial-mesenchymal transition and de-differentiation, were conformed. A short 100kb genomic window at mouse chr5 was captured and found to be sensitive to mutation status of an epigenetic factor. This window is highly conserved to a region at human chr4 and in vitro work confirm evolutionary preserved mechanism. Finally, p-Src/p-Lyn-cMyc related pathways showed clear difference between the two primary tumors with and without metastasis potency. Overall, our model of mCRPC can provide very diverse angles to the initiation and progression of prostate cancer. Furthermore, this model can be used to rapidly verify ideas and hypothesis regarding the mechanism behind the disease, and to test the treatment strategies in vivo in both pre-clinic studies and pharmacy field. Citation Format: Huiqiang Cai, Bin Zhang, Johanne Ahrenfeldt, Nicolai Birkbak, Martin Thomsen. Modelling the metastatic castration-resistant prostate cancer in mice by orthotopic delivering multiplexed gRNAs of CRISPR/Cas9 based on AAV system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 924.