Objective To investigate the expression of six-transmembrane epithelial antigen of prostate 4 (STEAP4) in prostate cancer (PCa), explore its correlation with the infiltration of regulatory T cells (Tregs) and CD8+T cells within the tumor-infiltrating T lymphocyte population, and to predict the potential role of STEAP4 in promoting PCa progression. Methods The clinicopathological data and tumor tissue specimens were collected from 90 PCa patients undergoing radical prostatectomy at our hospital during Jan.2018 and Dec.2024.The protein expressions of STEAP4, forkhead box transcription factor P3 (FoxP3), and CD8+T cells in tumor tissues were detected with immunohistochemistry.The correlation between STEAP4 expression and the infiltration of Tregs (FoxP3 T cells), CD8+T cells and clinicopathological characteristics was analyzed.The relationship between STEAP4 expression and prognosis was evaluated with Kaplan-Meier survival curves. Results STEAP4 expression was significantly higher in PCa tissues than in adjacent benign tissues (P＜0.001).STEAP4 expression was significantly associated with serum total prostate-specific antigen (tPSA) level, seminal vesicle invasion, extraprostatic extension, International Society of Urological Pathology (ISUP) grading, and pathological T stage (all P＜0.05).The mean infiltration density of Tregs (FoxP3 T cells) in PCa tissues was significantly higher than that in adjacent benign tissues[ (11.09±5.05) cells/HPF vs. (3.92±1.59) cells/HPF, P＜0.001], while the mean infiltration density of CD8+T cells was significantly lower[ (6.07±2.90) cells/HPF vs. (27.23±6.75) cells/HPF, P＜0.001].In PCa tissues, STEAP4 expression showed a significant positive correlation with Treg (FoxP3 T cells) infiltration density (r_s=0.472, P＜0.001) and a significant negative correlation with CD8+T-cell infiltration density (r_s=-0.495, P＜0.001).Kaplan-Meier survival curves indicated that high STEAP4 expression group and low STEAP4 expression group in PCa patients was not correlated with overall survival (OS) or recurrence-free survival (P=0.562, 0.346). Conclusion STEAP4 is highly expressed in PCa tissues, and its expression is closely associated with tumor-infiltrating lymphocytes, particularly Tregs and CD8+T cells, suggesting that STEAP4 may cooperate with Tregs and CD8+T cells to regulate the tumor microenvironment, thereby promoting PCa progression.

【Objective】 To explore the expression of PCDH9 loss in regulating cell cycle and promoting tumor progression. 【Methods】 The clinical records of 127 cases of prostate cancer treated during 2018 and 2023 were collected, including 87 paraffin tissue samples from the G4-5 group and 40 from the G1-3 group. The expressions of PCDH9, p53, Rb and STAT3 were detected with immunohistochemical staining, and the relationship between their expressions and clinicopathological characteristics was analyzed. 【Results】 The expression deletion rate of PCDH9 in prostate cancer tissues in G4-5 group (44.8% vs.7.5%) was significantly higher than that in G1-3 group (P<0.001). The positive expression rates of p53 and STAT3 were 34.5% and 89.7%, respectively, and the expression loss rate of Rb was 27.6% in G4-5 group. The expression loss rates of PCDH9 and Rb were associated with neuroendocrine-like histological morphology, nerve invasion and vascular invasion (P<0.05). In G4-5 group of prostate cancer, PCDH9 expression was positively correlated with the expressions of p53 (r=0.345, P<0.05), Rb (r=0.503, P<0.05) and STAT3 (r=0.224, P<0.05). 【Conclusion】 PCDH9 is prone to loss of expression in high-group prostate cancer tissues, especially in cases with neuroendocrine-like histological morphology, which may regulate the cell cycle through the STAT3 signaling pathway, thereby promoting tumor progression.