Background Ferroptosis have been implicated in tumorigenesis, tumor progression, and chemo- and immuno-therapy in cirrhotic hepatocellular carcinoma (HCC), indicating its association with matrix stiffness and clinical benefit of targeting drugs or immune checkpoint inhibitor. Here, we postulated that increased matrix stiffness reduces ferroptosis and impairs tumor immunity by regulating the expression of ferroptosis- and immune-related genes in HCC, which might be a robust predictor of therapeutic efficacy. Methods Using publicly available tissue microarray datasets, liver cancer rat model, and clinical specimen, ferroptosis-related differential genes in HCV-infected cirrhotic HCC and its mechanical heterogeneous pattern of expression were screened and identified. Further investigation on the underlying mechanism of matrix stiffness-regulated ferroptosis and the expression of immune mediator were performed. Finally, threshold analysis of HCC cases with sorafenib treatment revealed the value of clinical applications of these potential predictors. Results STEAP3 was identified as the ferroptosis-related differential genes in HCV-infected cirrhotic HCC. Stiffer matrix decreased STEAP3 in the invasive front area of HCC and the liver cirrhotic tissue. Contrarily, softer matrix induced STEAP3 in the central area of HCC and the normal liver tissue. Immunological correlation of STEAP3 in cirrhotic HCC showed that STEAP3-mediated immune infiltration of CD4+ T and CD8+ T cells, macrophages, neutrophils, and dendritic cells and HCC prognosis, predicting to regulate immune infiltration. Overexpression of STEAP3 induced ferroptosis and inhibited the expression of immune mediator of PD-L2 on a stiff matrix. Especially, the ferroptosis- and immune-related gene predictive biomarker (FIGPB), including STEAP3 and PD-L2, predicts better clinical benefit of sorafenib in HCC patients. Conclusions This finding identifies matrix stiffness impairs ferroptosis and anti-tumor immunity by mediating STEAP3 and PD-L2. More importantly, coordinated with PD-L2, matrix stiffness-dependent STEAP3 could be applied as the independent predictors to favorable sorafenib response, and thus targeting it could be a potential diagnosis and treatment strategy for HCC.
Six-transmembrane epithelial antigen of prostate 3 (STEAP3) is associated with the progression of several human malignancies. However, its role in lung squamous cell carcinoma (LUSC) remains unclear. We measured STEAP3 expression in LUSC cell lines and tissues. LUSC cells with stable STEAP3 overexpression and knockdown were obtained through G418 selection. Multiple assays were used to evaluate the malignant phenotypes of LUSC cells and the activation of the β-catenin signaling. The potential transcriptional regulatory factors of STEAP3 were predicted using the JASPAR database, and the correlation between transcription factor AP-2 gamma (TFAP2C) and STEAP3 was analyzed through the GEPIA database. The study evaluated the regulatory relationship between a potential transcription factor and STEAP3 through ChIP and luciferase reporter assays. Additionally, rescue assays were utilized to ascertain whether TFAP2C serves as the upstream regulatory factor of STEAP3, contributing to LUSC progression. Finally, tumor growth and metastasis were evaluated in vivo. STEAP3 expression was notably higher in LUSC, and its overexpression was linked to a poor prognosis. Moreover, STEAP3 overexpression activated the β-catenin pathway, thereby accelerating cell proliferation and metastasis. Conversely, STEAP3 knockdown had an anti-tumor effect in LUSC. Additionally, TFAP2C bound directly to the STEAP3 promoter and positively regulate its expression in LUSC. The anti-tumor effects of TFAP2C knockdown were partially reversed by STEAP3 overexpression. The study indicates that the TFAP2C/STEAP3 axis may be a therapeutic target for LUSC treatment. This enhances our understanding of lung carcinogenesis.
Farnesoid X receptor (FXR) is a central regulator of hepatic metabolic homeostasis, and emerging evidence implicates FXR in iron-induced liver injury. Six-transmembrane epithelial antigen of the prostate 3 (STEAP3) is a ferrireductase involved in cellular iron processing, but its upstream regulation in the liver is poorly understood. Here, we identify mouse hepatic Steap3 as a previously unrecognized direct transcriptional target of FXR. Analysis of STEAP family expression showed that STEAP3 is highly expressed in both human and mouse liver tissues. In three mouse models, hepatic Steap3 was the only STEAP family member consistently suppressed by iron overload. Notably, Fxr deficiency in mice reduced basal hepatic Steap3 expression and attenuated iron-mediated Steap3 repression, whereas FXR activation by GW4064 induced Steap3 expression and partially restored its expression under iron-overload conditions. Further ChIP-seq analyses and luciferase reporter assays demonstrated that mouse Steap3 is a direct transcriptional target gene of FXR. Human transcriptomic, ChIP-seq, and motif analyses suggested that human STEAP3 may be regulated by FXR in human liver cells, although the FXR-binding signal near the STEAP3 promoter appeared relatively weak. Together, these findings establish Steap3 as a direct FXR target gene in mouse liver and suggest that FXR-dependent regulation of hepatic ferrireductase expression may represent a previously underappreciated component of the hepatic response to iron overload.
危险品化学品经营许可证（带存储）