Extracellular Microenvironment in Patient-derived Hydrogel Organoids of Prostate Cancer Regulates Therapeutic Response

Following treatment with androgen receptor (AR) pathway inhibitors, ~20% of prostate cancer patients progress by shedding their dependence on AR. These tumors undergo epigenetic reprogramming turning castration-resistant prostate cancer adenocarcinoma (CRPC-Adeno) into neuroendocrine prostate cancer (CRPC-NEPC). Currently, no targeted therapies are available for CRPC-NEPCs. A major hurdle in the development of new therapies and treatment of CRPC-NEPC is the lack of accurate models to test candidate treatments. Such models would ideally capture components of the tumor microenvironment (TME) factors, which likely regulate the phenotypic, genetic, and epigenetic underpinnings of this aggressive subset. The TME is a complex system comprised not only of malignant prostate cells but also stromal and inflammatory cells and a scaffold of extracellular matrix (ECM). ECM proteins are implicated in the survival and progression of cancer and development of chemoresistance, while are equally integral to the development of prostate cancer organoids. Here, using a combination of patient tumor proteomics and RNA sequencing, we define putative ECM cues that may guide the growth of prostate tumors in patients. Using this molecular information, we developed synthetic hydrogels that recapitulate the tumor ECM. Organoids cultured in the synthetic hydrogel niches demonstrate that ECM subtypes regulate the morphology, transcriptome, and epigenetics hallmarks of CRPC-Adeno and CRPC-NEPC. CRPC-NEPC organoid showed a differential response to small molecule inhibitors of epigenetic repressor EZH2 and Dopamine Receptor D2 (DRD2), the latter being a novel target in CRPC-NEPC when grown in tumor-specific ECM. Finally, in those synthetic ECM niches where drug resistance was observed in CRPC-NEPCs, cellular reprogramming by a synergistic combination of EZH2 inhibitors with DRD2 antagonists inhibited tumor growth. The synthetic platform can provide a more realistic prostate-specific microenvironment and subsequently enable the development of effective targeted therapeutics for prostate cancers.