Abstract A044: Generation of a new mouse model to study the role of oncofetal Cripto in aggressive lethal prostate cancer

Abstract

Introduction: Early stages of prostate cancer (PCa) are commonly treated with surgery and androgen-deprivation therapy, but PCa can turn castration resistant due to pre-existing stem cell-like cells which might re-initiate tumor growth and lead to metastasis. Previously, it has been shown that human tumors express high levels of Cripto, an oncofetal protein, for this reason our hypothesis is that Cripto might play a role in PCa initiation and progression. We aim to study its oncogenic features in GEMMs models that are representative of early and late metastatic PCa. Methods: We performed conditional Cripto (CRIPTOflox/flox) knock out on N (Nkx3.1CreERT2, R26 LSL-YFP/LSL-YFP), NP (Nkx3.1CreERT2; Ptenflox/flox, R26 LSL-YFP/LSL-YFP) and NPK (Nkx3.1CreERT2; Ptenflox/flox; KrasLSL-G12D/+, R26 LSL-YFP/LSL-YFP) to generate respectively NC, NPC and NPKC. N animals mirror normal epithelium, whereas first stage of the disease, high-grade prostatic intraepithelial neoplasia (PIN)/carcinoma lesions with local invasive epithelium, are seen in NP. More advanced stage with invasive prostate adenocarcinoma with metastasis are developed in NPK. In vivo experiments’ workflow was the following: 8-weeks old mice were castrated and induced one month later with 5 daily injections of tamoxifen, after 2.5 weeks, animals were weekly treated with testosterone (10 weeks). Organoids were generated from YFP+/− single cell population recovered by FACS sorting. Results: Histopathological evaluation of newly generated NPC and NPKC showed presence of mPIN (100%, nNPC= 6, nNPKC=2), with a dominant cribriform morphology. NPKC additionally, features invasive PCa with an extent dominant pattern of 100%, showing portions with dense stroma forming whorl-like structures and occasional sheet-like accumulations of polygonal in stroma of regions with mPIN. In general, NPC and NPKC feature a more reactive stroma with a mild/moderate inflammation compared to the published models. OrganoidsYFP+ recapitulate molecular prostate tissue features, expressing luminal and basal markers. Organoids’ morphology varies consistently: N and NC are low in density and present a more cystic morphology, which is consistent with low-grade PIN phenotypes, whereas NP and NPK organoids are solid and denser which mimics an oncogenic transformation. In general, NC, NPC and NPKC organoids present a higher percentage of hollow organoids compared to N, NP and NPK respectively. Conclusions: NPC and NPKC phenotype specifically, showed important stromal alterations suggesting that Cripto might play a role not only on the epithelial compartment as well as in the stroma. For this reason, studies on secreted Cripto inhibition with ALK4-Fc are on-going. Our results show that organoids are an efficient in vitro model replicating different phenotypes seen in vivo. Citation Format: Elisa Rodrigues Sousa, Eugenio Zoni, Mario Scarpa, Marta De Menna, Allen Abey Alexander, Simone De Brot, George N. Thalmann, Marianna Kruithof-de Julio. Generation of a new mouse model to study the role of oncofetal Cripto in aggressive lethal prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A044.