Cancer stem cells (CSCs) represent a major source of treatment resistance and tumor progression. However, regulation of CSCs stemness is not entirely understood. Here, we report that TSPAN8 expression is upregulated in breast CSCs, promotes the expression of the stemness gene NANOG, OCT4, and ALDHA1, and correlates with therapeutic resistance. Mechanistically, TSPAN8 interacts with PTCH1 and inhibits the degradation of the SHH/PTCH1 complex through recruitment of deubiquitinating enzyme ATXN3. This results in the translocation of SMO to cilia, downstream gene expression, resistance of CSCs to chemotherapeutic agents, and enhances tumor formation in mice. Accordingly, expression levels of TSPAN8, PTCH1, SHH, and ATXN3 are positively correlated in human breast cancer specimens, and high TSPAN8 and ATXN3 expression levels correlate with poor prognosis. These findings reveal a molecular basis of TSPAN8-enhanced Sonic Hedgehog signaling and highlight a role for TSPAN8 in promoting cancer stemness.

Background Hepatocellular carcinoma (HCC) is among the most common forms of cancer and is associated with poor patient outcomes. The emergence of therapeutic resistance has hampered the efficacy of targeted treatments employed to treat HCC patients to date. In this study, we conducted a series of CRISPR/Cas9 screens to identify genes associated with synthetic lethality capable of improving HCC patient clinical responses. Methods CRISPR-based loss-of-function genetic screens were used to target 18,053 protein-coding genes in HCC cells to identify chemotherapy-related synthetic lethal genes in these cells. Synergistic effects were analyzed through in vitro and in vivo analyses, while related mechanisms were explored through RNA-seq and metabolomics analyses. Potential inhibitors of identified genetic targets were selected through high-throughput virtual screening. Results The inhibition of phosphoseryl-tRNA kinase (PSTK) was found to increase HCC cell sensitivity to chemotherapeutic treatment. PSTK was associated with the suppression of chemotherapy-induced ferroptosis in HCC cells, and the depletion of PSTK resulted in the inactivation of glutathione peroxidative 4 (GPX4) and the disruption of glutathione (GSH) metabolism owing to the inhibition of selenocysteine and cysteine synthesis, thus enhancing the induction of ferroptosis upon targeted chemotherapeutic treatment. Punicalin, an agent used to treat hepatitis B virus (HBV), was identified as a possible PSTK inhibitor that exhibited synergistic efficacy when applied together with Sorafenib to treat HCC in vitro and in vivo. Conclusions These results highlight a key role for PSTK as a mediator of resistance to targeted therapeutic treatment in HCC cells that functions by suppressing ferroptotic induction. PSTK inhibitors may thus represent ideal candidates for overcoming drug resistance in HCC.

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Background Anomalous expression of glucose transporters (GLUTs) has been observed in a variety of tumor tissues. Although GLUT factors have been shown to have prognostic value for some cancer types, detailed bioinformatics investigation of the factors contributing to the prognostic prediction for patients with breast cancer (BC) has not yet been performed. Methods In this study, we examined the transcription levels of GLUT1 , GLUT3 , and GLUT4 and their associations with prognostic clinical data in patients with BC from the ONCOMINE database, using gene expression profiling interactive analysis (GEPIA), Kaplan-Meier (KM) plotter, and cBioPortal online tools. Results The transcription level of GLUT1 was significantly higher in the BC samples than in the normal tissues, whereas the levels of GLUT3 and GLUT4 were lower in the BC samples. The expression levels of GLUT1 and GLUT3 were associated with the cancer clinical stage. Consistently, survival analysis demonstrated that a high expression level of GLUT1 was associated with low relapse-free survival (RFS) in patients with BC, whereas high GLUT3 and GLUT4 levels predicted a longer RFS in these patients. Conclusions Overall, these results suggest GLUT1 as an effective target of precision therapy, while GLUT3/4 are novel biomarkers for the prognosis of patients with BC.