FoxO transcription factors have been reported to play pivotal roles in tumorigenesis and drug resistance. The mechanisms underlying the tumor suppression function of FoxOs in human cancers remain largely unknown. Aberrant expression and activation of Nrf2 often correlate with chemoresistance and poor prognosis. Here, we report that FoxO3 directs the basal transcription of Kelch-like ECH-associated protein 1 (Keap1), an adaptor protein that bridges Nrf2 to Cul3 for degradation. FoxO3 depletion resulted in Keap1 downregulation, thereby activating Nrf2 signaling. We further demonstrated that inhibition of the FoxO3-Keap1 axis accounts for Nrf2 induction and activation induced by constitutively active AKT signaling or tumor necrosis factor a treatment. Unlike previous findings, FoxO3 silencing led to decreased reactive oxygen species production, therefore protecting cells from oxidative stress-induced killing in an Nrf2-dependent manner. Importantly, FoxO3 deficiency strongly potentiated tumor formation in nude mice and rendered cholangiocarcinoma xenografts resistant to cisplatin-induced cell death by activating Nrf2. Additionally, we found that clinical cholangiocarcinoma samples displayed FoxO3-Keap1 down-regulation and Nrf2 hyperactivation, underscoring the essential roles of these proteins in cholangiocarcinoma development. Conclusion: Our results unravel a unique mechanism underlying the tumor suppressor function of

BackgroundHER2 gene amplification generates an enormous number of HER2 transcripts, but the global effects on endogenous miRNA targets including HER family members in breast cancer are unexplored.MethodsWe generated a HER2–3’UTR expressing vector to test the tumor-promoting properties in HER2 low expressing T47D and MCF7 cells. Through microarray analysis and real-time PCR analysis we identified genes that were regulated by HER2–3’UTR. Positive and negative manipulation of miRNA expression, response element mutational studies and transcript reporter assays were performed to explore the mechanism of competitive sequestration of miR125a/miRNA125b by HER2 3’UTR.To investigate if trastuzumab-induced upregulation of HER3 is also mediated through miRNA de-repression, we used the CRISPR/cas9 to mutate the endogenous HER2 mRNA in HER2 over-expressing Au565 cells. Finally, we looked at cohorts of breast cancer samples of our own and the TCGA to show if HER2 and HER3 mRNAs correlate with each other.ResultsThe HER2 3’UTR pronouncedly promoted cell proliferation, colony formation, and breast tumor growth. High-throughput sequencing revealed a significant increase in HER3 mRNA and protein levels by the HER2 3’untranslated region (3’UTR). The HER2 3’UTR harboring a shared miR-125a/b response element induced miR-125a/b sequestration and thus resulted in HER3 mRNA derepression. Trastuzumab treatment upregulated HER3 via elevated HER2 mRNA expression, leading to trastuzumab resistance. Depletion of miR-125a/b enhanced the antitumor activity of trastuzumab. Microarray data from HER2-overexpressing primary breast cancer showed significant elevation of mRNAs for predicted miR-125a/b targets compared to non-targets.ConclusionsThese results suggest that HER2 3’UTR-mediated HER3 upregulation is involved in breast cell transformation, increased tumor growth, and resistance to anti-HER2 therapy. The combinatorial targeting of HER3 mRNA or miR-125a/b may offer an effective tool for breast cancer therapy.Electronic supplementary materialThe online version of this article (10.1186/s12943-018-0862-5) contains supplementary material, which is available to authorized users.

Programmed death ligand 1 (PD-L1) has been recently shown to be a major obstacle to antiviral immunity by binding to its receptor programmed death 1 (PD-1) on specific IFN-γ producing T cells in chronic hepatitis B. Currently, IFN-α is widely used to treat hepatitis B virus (HBV) infection, but its antiviral effect vary greatly and the mechanism is not totally clear. We found that IFN-α/γ induced a marked increase of PD-L1 expression in hepatocytes. Signal and activators of transcription (Stat1) was then identified as a major transcription factor involved in IFN-α/γ-mediated PD-L1 elevation both in vitro and in mice. Blockage of the PD-L1/PD-1 interaction by a specific mAb greatly enhanced HBV-specific T cell activity by the gp96 adjuvanted therapeutic vaccine, and promoted HBV clearance in HBV transgenic mice. Our results demonstrate the IFN-α/γ-Stat1-PD-L1 axis plays an important role in mediating T cell hyporesponsiveness and inactivating liver-infiltrating T cells in the hepatic microenvironment. These data raise further potential interest in enhancing the anti-HBV efficacy of IFN-α and therapeutic vaccines.