Prostate cancer is the most frequently diagnosed solid-organ malignancy in men worldwide. Metastatic castration-resistant prostate cancer represents a rapidly fatal, end-stage form of the disease for which current therapies remain palliative rather than curative. The advent of chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of refractory hematologic malignancies, and a growing number of studies are now exploring its potential in solid tumors. In this review, we first provide a concise overview of current immunotherapeutic strategies for prostate cancer, including checkpoint inhibitors, vaccine-based approaches, and bispecific antibodies. We then focus on the most recent and promising developments in CAR-T cell therapy for this malignancy. Specifically, we examine the key tumor-associated antigens targeted in prostate cancer-directed CAR-T cell therapy and summarize findings from preclinical research as well as ongoing and completed clinical trials. Finally, we discuss the main challenges that limit the efficacy of CAR-T therapy in prostate cancer, such as antigen heterogeneity, immunosuppressive tumor microenvironments, on-target/off-tumor toxicity, limited T-cell persistence, and inefficient trafficking to metastatic lesions, and outline potential strategies to overcome these barriers. Our aim is to define a translational roadmap for advancing CAR-T therapy toward clinical application in patients with metastatic castration-resistant prostate cancer.

In the eukaryotic cells, the ubiquitin–proteasome system (UPS) plays a crucial role in the intracellular protein turnover. It is involved in several cellular functions such as the control of the regular cell cycle progression, the immune surveillance, and the homeostasis. Within the 20S proteasome barrel-like structure, the catalytic subunits, β1, β2 and β5, are responsible for different proteolytic activities: caspase-like (C-L), trypsin-like (T-L) and chymotrypsin-like (ChT-L), respectively. The β5 subunit is particularly targeted for its role in antitumor activity: the synthesis of β5 subunit inhibitors could be a promising strategy for the treatment of solid and hematologic tumors. In the present work, we performed two combination studies of AM12, a recently developed synthetic proteasome inhibitor, with curcumin and quercetin, two nutraceuticals endowed of many pharmacological properties. We measured the combination index (CI), applying the Chou and Talalay method, comparing the two studies, from 50% to 90% of proteasome inhibition. In the case of the combination AM12 + curcumin, an increasing synergism was observed from 50% to 90% of proteasome inhibition, while in the case of the combination AM12 + quercetin an additive effect was observed only from 50% to 70% of β5 subunit inhibition. These results suggest that combining AM12 with curcumin is a more promising strategy than combining it with quercetin for potential therapeutic applications, especially in treating tumors.