PurposeN6-methyladenosine (m6A) is the most abundant internal modification on eukaryotic mRNA and gained increasing attention recently. More and more evidence suggest that m6A methylation plays crucial role in tumor genesis and development. However, its role in prostate cancer remains largely unknown.MethodsMETTL3 expression status in prostate cancer was analyzed by using TCGA database and Western blotting. m6A content was analyzed by using RNA Methylation Quantification Kit. The role of METTL3 in prostate cancer cells was determined by proliferation, survival, colony formation, and invasion assays. The m6A level of GLI1 RNA was detected by methylated RNA immunoprecipitation (MeRIP) assay. In vivo role of METTL3 was studied on xenograft models.ResultsWe found that m6A methyltransferase METTL3 was overexpressed in prostate cancer cell lines, together with increased m6A content. Functionally, silencing of METTL3 by shRNA in prostate cancer cell lines resulted in decreased m6A content, cell proliferation, survival, colony formation, and invasion. Interestingly, overexpression of wild-type METTL3 abrogated the repression effect of METTL3 depletion on m6A content, cell proliferation, survival, colony formation, and invasion, while the overexpression of m6A catalytic site mutant METTL3 was unable to rescue the inhibitory effect caused by METTL3 depletion. Further mechanism analysis demonstrated that METTL3 silence decreased the m6A modification and expression of GLI1, an important component of hedgehog pathway, which led to cell apoptosis. Moreover, depletion of METTL3 inhibited tumor growth in vivo.ConclusionOur results suggested that the m6A methyltransferase METTL3 promotes the growth and motility of prostate cancer cells by regulating hedgehog pathway.

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Photodynamic therapy (PDT) holds promise for focal therapy of prostate cancer (PCa). However, the therapeutic efficacy needs improvement, and further development of PDT for PCa has challenges, including uncertainty of photosensitizers (PSs) accumulation at the tumor site and difficulty in visualizing lesions using conventional ultrasound (US) imaging. We have developed novel porphyrin-grafted lipid (PGL) microbubbles (MBs; PGL-MBs) and propose a strategy to integrate PGL-MBs with US imaging to address these limitations and enhance PDT efficacy.Methods: PGL-MBs have two functions: imaging guidance by contrast-enhanced ultrasound (CEUS) and targeted delivery of PSs by ultrasound targeted microbubble destruction (UTMD). PGL-MBs were prepared and characterized before and after low-frequency US (LFUS) exposure. Then, in vitro studies validated the efficacy of PDT with PGL-MBs in human prostate cancer PC3 cells. PC3-xenografted nude mice were used to validate CEUS imaging, accumulation at the tumor site, and in vivo PDT efficacy.Results: PGL-MBs showed good contrast enhancement for US imaging and were converted into nanoparticles upon LFUS exposure. The resulting uniquely structured nanoparticles avoided porphyrin fluorescence quenching and efficiently accumulated at the tumor site through the sonoporation effect created with the assistance of US to achieve excellent PDT efficacy.Conclusions: This is the first preclinical investigation of MBs applied in PDT for PCa. PGL-MBs possess favorable CEUS imaging effects to enhance the localization of tumors. PGL-MBs with LFUS control PS accumulation at the tumor site to achieve highly effective PDT of PCa. This strategy carries enormous clinical potential for PCa management.

In this study, we identified CTCs using the previously reported CanPatrol CTC enrichment technique from peripheral blood samples of 126 patients with colorectal cancer (CRC) and found that CTCs could be classified into three subpopulations based on expression of epithelial cell adhesion molecule (EpCAM) (E-CTCs), the mesenchymal cell marker vimentin (M-CTCs), or both EpCAM and vimentin (biphenotypic E/M-CTCs). Circulating tumor microemboli (CTMs) were also identified in peripheral blood samples. Meanwhile, E-CTCs, M-CTCs, E/M-CTCs, and CTMs were detected in 76.98%, 42.06%, 56.35%, and 36.51% of the 126 patients, respectively. Interestingly, the presence of CTMs and each CTC subpopulation was significantly associated with blood lymphocyte counts and tumor-node-metastasis stage (P < 0.001). Lymphocyte counts and the neutrophil-to-lymphocyte ratio (NLR) in patients lacking CTCs were significantly different from those in patients testing positive for CTMs and each CTC subpopulation (P < 0.001). Our results indicate that tumor metastasis is more significantly associated with the presence of CTMs and M-CTCs than with other CTC subpopulations and suggest that EMT may be involved in CTC evasion of lymphocyte-mediated clearance.

Transient receptor potential melastatin subfamily member 7 (TRPM7) was essential in the growth and metastatic ability of prostate cancer cells. However, the effects and the relevant molecular mechanisms of TRPM7 on metastasis of prostate cancer under hypoxic atmosphere remain unclear. This study investigated the role of TRPM7 in the metastatic ability of androgen-independent prostate cancer cells under hypoxia. First, data mining was carried out to disclose the relationship between the TRPM7 gene level and the survival of prostate cancer patients. Specific siRNAs were used to knockdown target genes. Western blotting and qPCR were employed to determine protein and gene expression, respectively. The gene transcription activity was evaluated by luciferase activity assay of promoter gene. The protein interaction was determined by coimmunoprecipitation. Wound healing and transwell assays were employed to evaluated cell migration and invasion, respectively. Open access database results showed that high expression of TRPM7 was closely related to the poor survival of prostate cancer patients. Hypoxia simultaneously increased TRPM7 expression and induced HIF-1α accumulation in androgen-independent prostate cancer cells. Knockdown of TRPM7 significantly promoted HIF-1α degradation through the proteasome and inhibited EMT changes in androgen-independent prostate cancer cells under hypoxic condition. Moreover, TRPM7 knockdown increased the phosphorylation of RACK1 and strengthened the interaction between RACK1 and HIF-1α but attenuated the binding of HSP90 to HIF-1α. Whereas knockdown of RACK1 increased the binding of HSP90 to HIF-1α. Furthermore, both TRPM7 and HIF-1α knockdown significantly suppressed hypoxia-induced Annexin A1 protein expression, and suppression of HIF-1α/Annexin A1 signaling significantly inhibited hypoxia-induced cell migration and invasion of androgen-independent prostate cancer cells. Our findings demonstrate that TRPM7 knockdown promotes HIF-1α degradation via an oxygen-independent mechanism involving increased binding of RAKC1 to HIF-1α, and TRPM7-HIF-1α-Annexin A1 signaling axis plays a crucial role in the EMT, cell migration, and invasion of androgen-independent prostate cancer cells under hypoxic conditions.