Abstract 2824: Establishing Prostate Cancer Models for Orthotopic and Bone Metastatic Growth Using the 22rv1cell Line

Abstract Prostate cancer is the second most common cancer in men with new cases diagnosed in 1.4 million men each year. Luckily the 5-year survival rates in developed countries are high reaching over 90%. However, approximately one third will develop a metastatic disease. In metastatic patients, prostate cancer almost always progresses despite the androgen deprivation therapy and is then referred to as “castration-resistant (mCRPC)”. Bone is involved in 80% of patients with metastasis, and the bone lesions are typically osteoblastic. The 22Rv1 human prostate carcinoma cell line is androgen sensitive and shown to express androgen receptor (AR). They also express low levels of prostate-specific membrane antigen (PSMA). The aim of this study was to establish orthotopic and intratibial preclinical in vivo prostate cancer models that can be used in drug development when targeting cancer cells and their local environment. Male athymic nude mice (5-6 weeks old) and NOG mice (over 20 weeks old) were used in the study. 2.5 × 105 22Rv1 cells (ATCC) were inoculated orthotopically into the prostate of NOG mice, and 5 × 105 cells were inoculated intratibially into the bone marrow cavity of athymic nude mice. Tumor growth was followed by PSA measurements every second week using Human PSA ELISA assay. In addition, in the intratibial model, tumor-induced bone changes were monitored by X-ray imaging of the hind limbs. Prostates and hind limbs were collected at sacrifice, fixed in 10% NBF, and processed to paraffin blocks for further histological analysis. Sections of prostate were stained with hematoxylin-eosin (HE) and AR. Tumor-bearing and contralateral (healthy) tibias were stained with HE - OrangeG, MGT, TRAP, and AR. The observed tumor take rate was 92% in the orthotopic and 100% in the intratibial models. Confirmed by IHC, tumors formed in both the orthotopic and intratibial models expressed AR. 22Rv1 cells formed osteoblastic - lytic mixed bone lesions in the intratibial model. Based on lesion areas, randomization of the tumor bearing mice in the intratibial model can be done after 2 weeks from cancer cell inoculation. Taken together, the 22Rv1 prostate cancer models are relatively fast growing, express AR and present good take rates. Furthermore, the intratibial model represents robust tumor-induced changes in bone with strong osteoblastic component. Thus, these models have several advantages in efficacy studies of novel drug candidates for prostate cancer. Citation Format: Justyna Zdrojewska, Katja Fagerlund, Jenni H. Mäki-Jouppila, Mari I. Suominen. Establishing prostate cancer models for orthotopic and bone metastatic growth using the 22Rv1cell line [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2824.