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Background: The dysregulated mechanistic target of rapamycin complex 1 (mTORC1) signaling plays a critical role in ferroptosis resistance and tumorigenesis. However, the precise underlying mechanisms still need to be fully understood. Methods: Endoplasmic reticulum oxidoreductase 1 alpha (ERO1α) expression in mTORC1-activated mouse embryonic fibroblasts, cancer cells, and laryngeal squamous cell carcinoma (LSCC) clinical samples was examined by quantitative real-time PCR (qRT–PCR), western blotting, immunofluorescence (IF), and immunohistochemistry. Extensive in vitro and in vivo experiments were carried out to determine the role of ERO1α and its downstream target, member 11 of the solute carrier family 7 (SLC7A11), in mTORC1-mediated cell proliferation, angiogenesis, ferroptosis resistance, and tumor growth. The regulatory mechanism of ERO1α on SLC7A11 was investigated via RNA-sequencing, a cytokine array, an enzyme-linked immunosorbent assay, qRT–PCR, western blotting, IF, a luciferase reporter assay, and a chromatin immunoprecipitation assay. The combined therapeutic effect of ERO1α inhibition and the ferroptosis inducer imidazole ketone erastin (IKE) on mTORC1-activated cells was evaluated using cell line-derived xenografts, LSCC organoids, and LSCC patient-derived xenograft models. Results: ERO1α is a functional downstream target of mTORC1. Elevated ERO1α induced ferroptosis resistance and exerted pro-oncogenic roles in mTORC1-activated cells via upregulation of SLC7A11. Mechanically, ERO1α stimulated the transcription of SLC7A11 by activating the interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) pathway. Moreover, ERO1α inhibition combined with treatment using the ferroptosis inducer IKE exhibited synergistic antitumor effects on mTORC1-activated tumors. Conclusions: The ERO1α/IL-6/STAT3/SLC7A11 pathway is crucial for mTORC1-mediated ferroptosis resistance and tumor growth, and combining ERO1α inhibition with ferroptosis inducers is a novel and effective treatment for mTORC1-related tumors. [ABSTRACT FROM AUTHOR]

Background: Although hepatitis B virus (HBV) infection is a major risk factor for hepatic cancer, the majority of HBV carriers do not develop this lethal disease. Additional molecular alterations are thus implicated in the process of liver tumorigenesis. Since phosphatase and tensin homolog (PTEN) is decreased in approximately half of liver cancers, we investigated the significance of PTEN deficiency in HBV-related hepatocarcinogenesis. Methods: HBV-positive human liver cancer tissues were checked for PTEN expression. Transgenic HBV, Alb-Cre and Ptenfl/fl mice were inter-crossed to generate WT, HBV, Pten−/− and HBV; Pten−/− mice. Immunoblotting, histological analysis and qRT-PCR were used to study these livers. Gp73−/− mice were then mated with HBV; Pten−/− mice to illustrate the role of hepatic tumor biomarker golgi membrane protein 73 (GP73)/ golgi membrane protein 1 (GOLM1) in hepatic oncogenesis. Results: Pten deletion and HBV transgene synergistically aggravated liver injury, inflammation, fibrosis and development of mixed hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC). GP73 was augmented in HBV; Pten−/− livers. Knockout of GP73 blunted the synergistic effect of deficient Pten and transgenic HBV on liver injury, inflammation, fibrosis and cancer development. Conclusions: This mixed HCC-ICC mouse model mimics liver cancer patients harboring HBV infection and PTEN/AKT signaling pathway alteration. Targeting GP73 is a promising therapeutic strategy for cancer patients with HBV infection and PTEN alteration. [ABSTRACT FROM AUTHOR]

Background: Usenamine A, a novel natural compound initially isolated from the lichen Usnea longissima, has exhibited promising efficacy against hepatoma in prior investigation. Nevertheless, the underlying mechanisms responsible for its antihepatoma effects remain unclear. Furthermore, the role of the AKT/mechanistic target of the rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT3)/inhibitor of differentiation/DNA binding 1 (ID1) signaling axis in hepatocellular carcinoma (HCC), and the potential anti-HCC effects of drugs targeting this pathway are not well understood. Methods: CCK-8 assay was used to investigate the effects of usenamine A on the proliferation of human HCC cells. Moreover, the effects of usenamine A on the invasion ability of human HCC cells were evaluated by transwell assay. In addition, expression profiling analysis, quantitative real-time PCR, immunoblotting, immunohistochemistry (IHC) analysis, RNAi, immunoprecipitation, and chromatin immunoprecipitation (ChIP) assay were used to explore the effects of usenamine A on the newly identified AKT/mTOR/STAT3/ID1 signaling axis in human HCC cells. Results: Usenamine A inhibited the proliferation and invasion of human HCC cell lines (HepG2 and SK-HEP-1). Through the analysis of gene expression profiling, we identified that usenamine A suppressed the expression of ID1 in human HCC cells. Furthermore, immunoprecipitation experiments revealed that usenamine A facilitated the degradation of the ID1 protein via the ubiquitin–proteasome pathway. Moreover, usenamine A inhibited the activity of STAT3 in human HCC cells. ChIP analysis demonstrated that STAT3 positively regulated ID1 expression at the transcriptional level in human HCC cells. The STAT3/ID1 axis played a role in mediating the anti-proliferative and anti-invasive impacts of usenamine A on human HCC cells. Additionally, usenamine A suppressed the STAT3/ID1 axis through AKT/mTOR signaling in human HCC cells. Conclusion: Usenamine A displayed robust anti-HCC potential, partly attributed to its capacity to downregulate the AKT/mTOR/STAT3/ID1 signaling pathway and promote ubiquitin–proteasome-mediated ID1 degradation. Usenamine A has the potential to be developed as a therapeutic agent for HCC cases characterized by abnormal AKT/mTOR/STAT3/ID1 signaling, and targeting the AKT/mTOR/STAT3 signaling pathway may be a viable option for treating patients with HCC exhibiting elevated ID1 expression. [ABSTRACT FROM AUTHOR]

Background: Aberrantly activated mammalian target of rapamycin complex 1 (mTORC1) plays a vital role in tumor angiogenesis, but its precise mechanisms are still unclear. Methods: Micro-RNA-130b-3p (miR-130b-3p) expression in mTORC1-activated and control cells was examined by quantitative real-time PCR (qRT-PCR). MiR-130b-3p levels and their correlation with mTORC1 activity were evaluated by analyzing publicly available databases and in-house head and neck squamous cell carcinoma (HNSCC) tissues. The role of miR-130b-3p in mTORC1-mediated angiogenesis and tumor growth was examined using tube formation assay, chicken chorioallantoic membrane assay, cell line − derived xenograft models, and an HNSCC patient-derived xenograft (PDX) model. The regulatory mechanisms among signal transducer and activator of transcription 3 (STAT3), miR-130b-3p, and muscleblind-like protein 1 (MBNL1) were investigated via bioinformatics analyses, qRT-PCR, western blot, RNA immunoprecipitation, immunofluorescence, luciferase reporter assay, and chromatin immunoprecipitation assay. Results: Elevated miR-130b-3p enhanced the angiogenic and tumorigenic abilities of mTORC1-activated cells both in vitro and in vivo. STAT3, a downstream effector of mTORC1, transactivated miR-130b-3p by direct binding promoter of the miR-130b gene. MBNL1 was identified as a direct target of miR-130b-3p. MBNL1 depletion rescued the compromised angiogenesis and tumor growth caused by miR-130b-3p inhibition. MiR-130b-3p levels were significantly upregulated and positively correlated with mTORC1 signaling in multiple cancers. MiR-130b-3p inhibition attenuated tumor angiogenesis and growth in an HNSCC PDX model. MBNL1 feedback inhibited STAT3 activation in mTORC1-activated cells. Conclusions: The STAT3/miR-130b-3p/MBNL1 feedback loop plays a vital role in mTORC1-mediated angiogenesis and tumor progression. This pathway could be targeted for therapeutic intervention of mTORC1-related cancers. [ABSTRACT FROM AUTHOR]