Background: The gut microbiota is reportedly involved in the progression and chemoresistance of various human malignancies. However, the underlying mechanisms behind how it exerts some effect on prostate cancer, as an extra-intestinal tumor, in a contact-independent way remain elusive and deserve exploration. Antibiotic exposure, one of the various factors affecting the gut microbiota community and capable of causing gut dysbiosis, is associated with multiple disorders. This study aims to preliminarily clarify the link between gut dysbiosis and prostate cancer. Results: First, we discovered that perturbing the gut microbiota by consuming broad-spectrum antibiotics in water promoted the growth of subcutaneous and orthotopic tumors in mice. Fecal microbiota transplantation could transmit the effect of antibiotic exposure on tumor growth. Then, 16S rRNA sequencing for mouse feces indicated that the relative abundance of Proteobacteria was significantly higher after antibiotic exposure. Meanwhile, intratumoral lipopolysaccharide (LPS) profoundly increased under the elevation of gut permeability. Both in vivo and in vitro experiments revealed that the NF-κB-IL6-STAT3 axis activated by intratumoral LPS facilitated prostate cancer proliferation and docetaxel chemoresistance. Finally, 16S rRNA sequencing of patients’ fecal samples revealed that Proteobacteria was enriched in patients with metastatic prostate cancer and was positively correlated with plasma IL6 level, regional lymph node metastasis status, and distant metastasis status. The receiver operating characteristic (ROC) curves showed that the relative abundance of Proteobacteria had better performance than the prostate-specific antigen (PSA) level in predicting the probability of distant metastasis in prostate cancer (area under the ROC curve, 0.860; p < 0.001). Conclusion: Collectively, this research demonstrated that gut dysbiosis, characterized by the enrichment of Proteobacteria due to antibiotic exposure, resulted in the elevation of gut permeability and intratumoral LPS, promoting the development of prostate cancer via the NF-κB-IL6-STAT3 axis in mice. Considering findings from human patients, Proteobacteria might act as an intestinal biomarker for progressive prostate cancer.

Owing to incurable castration-resistant prostate cancer (CRPC) ultimately developing after treating with androgen deprivation therapy (ADT), it is vital to devise new therapeutic strategies to treat CRPC. Treatments that target programmed cell death protein 1 (PD-1) and programmed death ligand-1 (PD-L1) have been approved for human cancers with clinical benefit. However, many patients, especially prostate cancer, fail to respond to anti-PD-1/PD-L1 treatment, so it is an urgent need to seek a support strategy for improving the traditional PD-1/PD-L1 targeting immunotherapy. In the present study, analyzing the data from our prostate cancer tissue microarray, we found that PD-L1 expression was positively correlated with the expression of heterogeneous nuclear ribonucleoprotein L (HnRNP L). Hence, we further investigated the potential role of HnRNP L on the PD-L1 expression, the sensitivity of cancer cells to T-cell killing and the synergistic effect with anti-PD-1 therapy in CRPC. Indeed, HnRNP L knockdown effectively decreased PD-L1 expression and recovered the sensitivity of cancer cells to T-cell killing in vitro and in vivo, on the contrary, HnRNP L overexpression led to the opposite effect in CRPC cells. In addition, consistent with the previous study, we revealed that ferroptosis played a critical role in T-cell-induced cancer cell death, and HnRNP L promoted the cancer immune escape partly through targeting YY1/PD-L1 axis and inhibiting ferroptosis in CRPC cells. Furthermore, HnRNP L knockdown enhanced antitumor immunity by recruiting infiltrating CD8⁺ T cells and synergized with anti-PD-1 therapy in CRPC tumors. This study provided biological evidence that HnRNP L knockdown might be a novel therapeutic agent in PD-L1/PD-1 blockade strategy that enhanced anti-tumor immune response in CRPC.

Prostate cancer (PCa) is a high morbidity malignancy in males, and biochemical recurrence (BCR) may appear after the surgery. Our study is designed to build up a risk score model using circular RNA sequencing data for PCa. The dataset is from the GEO database, using a cohort of 144 patients in Canada. We removed the low abundance circRNAs (FPKM < 1) and obtained 546 circRNAs for the next step. BCR-related circRNAs were selected by Logistic regression using the “survival” and “survminer” R package. Least absolute shrinkage and selector operation (LASSO) regression with 10-fold cross-validation and penalty was used to construct a risk score model by “glmnet” R software package. In total, eight circRNAs (including circ_30029, circ_117300, circ_176436, circ_112897, circ_112897, circ_178252, circ_115617, circ_14736, and circ_17720) were involved in our risk score model. Further, we employed differentially expressed mRNAs between high and low risk score groups. The following Gene Ontology (GO) analysis were visualized by Omicshare Online tools. As per the GO analysis results, tumor immune microenvironment related pathways are significantly enriched. “CIBERSORT” and “ESTIMATE” R package were used to detect tumor-infiltrating immune cells and compare the level of microenvironment scores between high and low risk score groups. What’s more, we verified two of eight circRNA’s (circ_14736 and circ_17720) circular characteristics and tested their biological function with qPCR and CCK8 in vitro. circ_14736 and circ_17720 were detected in exosomes of PCa patients’ plasma. This is the first bioinformatics study to establish a prognosis model for prostate cancer using circRNA. These circRNAs were associated with CD8⁺ T cell activities and may serve as a circRNA-based liquid biopsy panel for disease prognosis.

Tumor-derived exosomes and their contents promote cancer metastasis. Phosphoglycerate mutase 1 (PGAM1) is involved in various cancer-related processes. Nevertheless, the underlying mechanism of exosomal PGAM1 in prostate cancer (PCa) metastasis remains unclear. In this study, we performed in vitro and in vivo to determine the functions of exosomal PGAM1 in the angiogenesis of patients with metastatic PCa. We performed Glutathione-S-transferase pulldown, co-immunoprecipitation, western blotting and gelatin degradation assays to determine the pathway mediating the effect of exosomal PGAM1 in PCa. Our results revealed a significant increase in exosomal PGAM1 levels in the plasma of patients with metastatic PCa compared to patients with non-metastatic PCa. Furthermore, PGAM1 was a key factor initiating PCa cell metastasis by promoting invadopodia formation and could be conveyed by exosomes from PCa cells to human umbilical vein endothelial cells (HUVECs). In addition, exosomal PGAM1 could bind to γ-actin (ACTG1), which promotes podosome formation and neovascular sprouting in HUVECs. In vivo results revealed exosomal PGAM1 enhanced lung metastasis in nude mice injected with PCa cells via the tail vein. In summary, exosomal PGAM1 promotes angiogenesis and could be used as a liquid biopsy marker for PCa metastasis.

N6-Methyladenosine (m6A) is the most prevalent RNA modification in various types of RNA, including circular RNAs (circRNAs). Mounting evidence has shown that circRNAs may play critical roles in diverse malignancies. However, the biological relevance of m6A modification of circRNAs in prostate cancer (PCa) remains unclear and needs to be elucidated. Our data showed that circRBM33 was m6A-modified and was more highly expressed in PCa cells than in normal cells/tissues. The in vitro and in vivo experiments showed that downregulation/upregulation of circRBM33 inhibited/promoted tumour growth and invasion, respectively. Decreasing m6A levels rescued the tumour-promoting effect of circRBM33. Additionally, once modified by m6A, circRBM33 interacts with FMR1 by forming a binary complex that sustains the mRNA stability of PDHA1, a downstream target gene. Suppressed/overexpressed circRBM33 lowered/enhanced the ATP production, the acetyl-CoA levels and the NADH/NAD⁺ ratio. Moreover, depletion of circRBM33 significantly increased the response sensitivity to androgen receptor signalling inhibitor (ARSI) therapy, including enzalutamide and darolutamide, in prostate tumours. Our study suggested that the m6A-mediated circRBM33-FMR1 complex can activate mitochondrial metabolism by stabilizing PDHA1 mRNA, which promotes PCa progression, and can attenuate circRBM33 increased ARSI effectiveness in PCa treatment. This newly discovered circRNA may serve as a potential therapeutic target for PCa.