Prodigiosin, a natural red pigment produced by numerous bacterial species, has exhibited promising anticancer activity; however, the molecular mechanisms of action of prodigiosin on malignant cells remain unclear. Aberrant activation of the Wnt/β-catenin signaling cascade is associated with numerous human cancers. In this study, we identified prodigiosin as a potent inhibitor of the Wnt/ β-catenin pathway. Prodigiosin blocked Wnt/β-catenin signaling by targeting multiple sites of this pathway, including the lowdensity lipoprotein-receptor-related protein (LRP) 6, Dishevelled (DVL), and glycogen synthase kinase-3β (GSK3β). In breast cancer MDA-MB-231 and MDA-MB-468 cells, nanomolar concentrations of prodigiosin decreased phosphorylation of LRP6, DVL2, and GSK3β and suppressed β-catenin-stimulated Wnt target gene expression, including expression of cyclin D1. In MDA-MB-231 breast cancer xenografts and MMTV-Wnt1 transgenic mice, administration of prodigiosin slowed tumor progression and reduced the expression of phosphorylated LRP6, phosphorylated and unphosphorylated DVL2, Ser9 phosphorylated GSK3β, active β-catenin, and cyclin D1. Through its ability to inhibit Wnt/β-catenin signaling and reduce cyclin D1 levels, prodigiosin could have therapeutic activity in advanced breast cancers.prodigiosin | Wnt/beta-catenin signaling | breast cancer | LRP6 | Dishevelled (DVL)

Prostate cancer is the third most common causes of death from cancer in men. Our previous study demonstrated that lncRNA PVT1 was overexpressed and played an oncogenic role in the progression of prostate cancer. However, the molecular mechanism of modulating the prostate cancer tumorigenesis was still unknown. In this study, we aim to investigate the interaction between PVT1 and miR‐146a in prostate cancer and reveal the potential mechanism in prostate cancer carcinogenesis. The expression level of miR‐146a was assessed by quantitative RT‐PCR. The correlation analysis and methylation status analysis was made to confirm the interaction between PVT1 and miR‐146a. Biological function analysis was performed through gain‐of‐function and loss‐of‐function strategies. Our results showed that miR‐146a was downregulated and negatively correlated with PVT1 level in prostate cancer. PVT1 mediated miR‐146a expression by inducing the methylation of CpG Island in its promoter. miR‐146a overexpression eliminated the effects of PVT1 knockdown on prostate cancer cells. PVT1 regulated prostate cancer cell viability and apoptosis depending on miR‐146a. Our study suggested a regulatory relationship between lncRNA PVT1 and miR‐146a during the process of the prostate cancer tumorigenesis. PVT1 regulated prostate cancer cell viability and apoptosis depending on miR‐146a. It would contribute to the diagnosis, treatment and prognosis of prostate cancer.

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Gut microbiota refers to the diverse community of more than 100 trillion microorganisms residing in our intestines. It is now known that any shift in the composition of gut microbiota from that present during the healthy state in an individual is associated with predisposition to multiple pathological conditions, such as diabetes, autoimmunity, and even cancer. Currently, therapies targeting programmed cell death protein 1/programmed cell death 1 ligand 1 or cytotoxic T-lymphocyte antigen-4 are the focus of cancer immunotherapy and are widely applied in clinical treatment of various tumors. Owing to relatively low overall response rate, however, it has been an ongoing research endeavor to identify the mechanisms or factors for improving the therapeutic efficacy of these immunotherapies. Other than causing mutations that affect gene expression, some gut bacteria may also activate or repress the host's response to immune checkpoint inhibitors. In this review, we have described recent advancements made in understanding the regulatory relationship between gut microbiome and cancer immunotherapy. We have also summarized the potential molecular mechanisms behind this interaction, which can serve as a basis for utilizing different kinds of gut bacteria as promising tools for reversing immunotherapy resistance in cancer.

Inhibition of DNA double-strand break (DSB) repair in cancer cells has been proposed as a new therapeutic strategy for potentiating the anticancer effects of radiotherapy. M3814 is a novel, selective pharmacologic inhibitor of the serine/ threonine kinase DNA-dependent protein kinase (DNA-PK), a key driver of nonhomologous endjoining, one of the main DSB-repair pathways, currently under clinical investigation. Here, we show that M3814 effectively blocks the repair of radiation-induced DSBs and potently enhances p53 phosphorylation and activation. In p53 wild-type cells, ataxia telangiectasia-mutated (ATM) and its targets, p53 and checkpoint kinase 2 (CHK2), were more strongly activated by combination treatment with M3814 and radiation than by radiation alone, leading to a complete p53-dependent cell-cycle block and premature cell senescence. Cancer cells with dysfunctional p53 were unable to fully arrest their cell cycle and entered S and M phases with unrepaired DNA, leading to mitotic catastrophe and apoptotic cell death. Isogenic p53-null/wild-type A549 and HT-1080 cell lines were generated and used to demonstrate that p53 plays a critical role in determining the response to ionizing radiation and M3814. Time-lapse imaging of cell death and measuring apoptosis in panels of p53 wild-type and p53-null/mutant cancer lines confirmed the clear differences in cell fate, dependent on p53 status. Implications: Our results identify p53 as a possible biomarker for response of cancer cells to combination treatment with radiation and a DNA-PK inhibitor and suggest that p53 mutation status should be considered in the design of future clinical trials.