Presentation Authors: Danielle Burner*, Theresa Mendoza, Michelle Muldong, Sanghee Lee, Catalina Arreola, Olga Miakicheva-Greenburg, William Zhu, Christina Wu, La Jolla, CA, Nicholas Cacalano, Westwood, CA, Catriona Jamieson, Christopher Kane, Anna Kulidjian, Christina Jamieson, La Jolla, CA
Introduction: Over 80% of advanced prostate cancer (PCa) patients develop bone metastases for which there is no cure. PCa lines have been used for the development of new therapies, however they do not fully represent PCa heterogeneity nor the bone metastatic disease. Thus, we established new patient-derived models for bone metastatic prostate cancer. We generated three-dimensional (3D) organoids from our patient-derived xenograft (PDX) model and characterized their response to either dihydrotestosterone (DHT) or the anti-androgen, Enzalutamide.
Methods: Intra-femoral PDX tumor cells were used to establish 3D organoids according to previously described protocols for prostate cancer. Culture medium was supplemented with 10% v/v fetal bovine serum (FBS) and +/- 1nM DHT or +/-10uM Enzalutamide in 0.1% v/v dimethyl sulfoxide (DMSO) for four weeks. Overall viability was quantified using luciferase-based viability assay. Changes to different types of multi-cellular masses were quantified as changes in cyst number, cyst lumen diameter, and spheroid area using the Keyence microscope and image analysis software. Statistical significance was determined using a student's t-test. Quantitative RT-PCR was performed for Prostate-Specific Antigen (PSA) and Prostate-Specific Membrane Antigen (PSMA). PSA immunohistochemistry (IHC) and immunofluorescence cytochemistry (IFC) for androgen receptor (AR), and cytokeratins 5 and 8 (CK5, CK8) were performed.
Results: Enzalutamide treatment did not reduce overall viability of our PDX-derived 3D organoid cultures. Intriguingly, the PDO cultures consisted of heterogeneous cell populations that formed hollow cysts or spheroids. Treatment with DHT significantly increased the average cyst lumen diameter, cyst count as well as the spheroid area in (p < 0.05). Conversely, treatment with Enzalutamide significantly decreased the average cyst lumen diameter, cyst count and spheroid area (p < 0.05). Analogous structures were observed in the PDX tumors. Quantitative RT-PCR and PSA IHC showed that Enzalutamide reduced PSA expression but did not change PSMA expression.
Conclusions: The overall resistance of the PDX-derived 3D organoids (PDO) to Enzalutamide treatment mirrored the in vivo response of our bone metastatic prostate cancer PDX model. The heterogeneous populations of hollow cysts and spheroid clusters exhibited unique responses to Enzalutamide and may require distinct therapeutic interventions.
Source of Funding: The Leo and Anne Albert Charitable Trust Foundation, Astellas, Medivation