Treatment of castration-resistant prostate cancer: updates on therapeutics targeting the androgen receptor signaling pathway

Assessment of Immune Cell Populations in the Peripheral Blood of Patients With Metastatic Prostate Cancer

Background Prostate cancer (PCa) encompasses a heterogeneous spectrum, ranging from indolent to highly aggressive forms, with approximately 10-20% of patients with initially localized disease later becoming metastatic. Oligometastatic PCa (OMPC) represents an intermediate state between locally advanced and high-volume metastatic disease. Understanding the immune landscape of OMPC and plurimetastatic PCa (PMPC) can provide valuable insights into disease biology, with potential implications for treatment strategies and prognosis. Aim and objective This study aimed to evaluate alterations in circulating immune cell subsets between OMPC and PMPC to identify potential immune biomarkers and therapeutic targets. Methods We conducted a retrospective cohort study of 43 mPC patients. Patients were stratified into two groups based on metastatic spread: OMPC (≤5 metastatic lesions in bone or lymph nodes) and PMPC (>5 lesions and/or visceral involvement). Peripheral blood mononuclear cells (PBMCs) were isolated and analyzed via flow cytometry for key immune subsets, including γδ T cells, αβ T cells, and regulatory T cells, with functional assessments performed using cytokine stimulation. Statistical analysis used the Mann-Whitney-Wilcoxon test, with p ≤ 0.05 considered significant. Results OMPC patients exhibited significantly increased γδ2+ T cells compared to PMPC, suggesting enhanced immune surveillance in low metastatic burden. A trend toward elevated γδ2+ T cells expressing interferon-gamma (IFN-γ) was observed in PMPC. No significant differences were observed in other immune subsets. Conclusions γδ2+ T cells represent a distinct immune subset in PCa, potentially influencing disease progression. Despite the small sample size, these findings highlight γδ2+ T cells as promising biomarkers and therapeutic targets. Prospective studies with a larger sample size are warranted to confirm the significance of these findings and explore the mechanistic roles of these cells and possible clinical applications in metastatic PCa (mPC).

Regulation of tumor cell plasticity by the androgen receptor in prostate cancer

Prostate cancer (PCa) has become the most common form of cancer in men in the developed world, and it ranks second in cancer-related deaths. Men that succumb to PCa have a disease that is resistant to hormonal therapies that suppress androgen receptor (AR) signaling, which plays a central role in tumor development and progression. Although AR continues to be a clinically relevant therapeutic target in PCa, selection pressures imposed by androgen-deprivation therapies promote the emergence of heterogeneous cell populations within tumors that dictate the severity of disease. This cellular plasticity, which is induced by androgen deprivation, is the focus of this review. More specifically, we address the emergence of cancer stem-like cells, epithelial-mesenchymal or myeloid plasticity, and neuroendocrine transdifferentiation as well as evidence that demonstrates how each is regulated by the AR. Importantly, because all of these cell phenotypes are associated with aggressive PCa, we examine novel therapeutic approaches for targeting therapy-induced cellular plasticity as a way of preventing PCa progression.

Green tea polyphenol EGCG blunts androgen receptor function in prostate cancer

Androgen deprivation therapy is the major treatment for advanced prostate cancer (PCa). However, it is a temporary remission, and the patients almost inevitably develop hormone refractory prostate cancer (HRPC). HRPC is almost incurable, although most HRPC cells still express androgen receptor (AR) and depend on the AR for growth, making AR a prime drug target. Here, we provide evidence that epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, is a direct antagonist of androgen action. In silico modeling and FRET-based competition assay showed that EGCG physically interacts with the ligand-binding domain of AR by replacing a high-affinity labeled ligand (IC(50) 0.4 μM). The functional consequence of this interaction was a decrease in AR-mediated transcriptional activation, which was due to EGCG mediated inhibition of interdomain N-C termini interaction of AR. Treatment with EGCG also repressed the transcriptional activation by a hotspot mutant AR (T877A) expressed ectopically as well as the endogenous AR mutant. As the physiological consequence of AR antagonism, EGCG repressed R1881-induced PCa cell growth. In a xenograft model, EGCG was found to inhibit AR nuclear translocation and protein expression. We also observed a significant down-regulation of androgen-regulated miRNA-21 and up-regulation of a tumor suppressor, miRNA-330, in tumors of mice treated with EGCG. Taken together, we provide evidence that EGCG functionally antagonizes androgen action at multiple levels, resulting in inhibition of PCa growth.