Targeting polyamine metabolism in an ex vivo prostatectomy model

Ex vivo models allow for testing drug efficacy and patient response, yet it remains a challenge to develop representative 3D cultures for prostate cancer. Tissue explant models offer a more clinically relevant alternative to organoids due to their ability to provide adequate tissue quantities, maintain tumor-stromal interactions and metabolic activity, and their relatively inexpensive culturing conditions. In this chapter we outline a protocol for culturing patient prostatectomy tumors for up to 7 days on dental sponges soaked in either control or drug containing media for evaluating drug efficacy. Further, we describe the preparation of tissue samples for downstream immunohistochemistry and metabolic analysis. We have tested the efficacy of a combination therapy targeting polyamine metabolism, which is dysregulated in prostate cancer, using this patient tumor explant model. We found that activating polyamine catabolism in combination with inhibition of methionine salvage was effective at inducing target protein expression, reducing intratumoral polyamines, and inducing apoptosis in a majority of the patient samples tested. Additionally, we were able to confirm drug induced effects were specific to the malignant prostate epithelial cells. This ex vivo prostatectomy model lends itself to both targeted metabolite analyses as well as more comprehensive metabolomic analyses. This method can be applied to strategies aiming to target metabolic pathways in solid tumor diseases.