OTUB1's role in promoting OSCC development by stabilizing RACK1 involves cell proliferation, migration, invasion, and tumor-associated macrophage M1 polarization.

Ovarian tumor domain, ubiquitin aldehyde binding 1 (OTUB1), a deubiquitinating enzyme known to regulate the stability of downstream proteins, has been reported to regulate various cancers tumorigenesis, yet its direct effects on oral squamous cell carcinoma (OSCC) progression are unclear. Bioinformatics analysis was performed to screen for genes of interest, and in vitro and in vivo studies were carried out to investigate the function and mechanism of OTUB1 in OSCC. We found that OTUB1 was abnormally elevated in OSCC tissues and positively associated with the pathological stage and tumor stage. Knockdown of OTUB1 impaired the malignance of OSCC cells - suppressed cell proliferation, invasion, migration, and xenografted tumor growth. OTUB1 silencing also drove tumor-associated macrophage M1 polarization but suppressed M2 polarization, and the induction of M1 polarization inhibited the survival of OSCC cells. However, OTUB1 overexpression exerted the opposite effects. Furthermore, the protein network that interacted with the OTUB1 protein was constructed based on the GeneMANIA website. Receptor for activated C kinase 1 (RACK1), a facilitator of OSCC progression, was identified as a potential target of the OTUB1 protein. We revealed that OTUB1 positively regulated RACK1 expression and inhibited RACK1 ubiquitination. Additionally, RACK1 upregulation reversed the effects of OTUB1 knockdown on OSCC progression. Overall, we demonstrated that OTUB1 might regulate OSCC progression by maintaining the stability of the RACK1 protein. These findings highlight the potential roles of the OTUB1/RACK1 axis as a potential therapeutic target in OSCC.

Prognostic implications and oncogenic roles of MYBL2 protein expression in esophageal squamous-cell carcinoma.

BACKGROUND: The MYBL2 gene, a highly conserved member of the Myb transcription-factor family, has been implicated in the genesis and progression of many types of tumors. METHODS: We analyzed the expression of MYBL2 and Ki67 in tissue samples of esophageal squamous-cell carcinoma (ESCC) patients by immunohistochemistry. We further analyzed the effect of MYBL2 on cell proliferation and DNA replication using a CCK8 assay, 5-ethynyl-2'-deoxyuridine-retention assay, flow-cytometry analysis, real-time quantitative PCR, Western blot, and a xenograft model of ESCC cells in nude mice. RESULTS: MYBL2 expression was significantly higher in ESCC tissue when compared to the adjacent normal tissue (P=0.007). MYBL2 was found to be positively correlated with Ki67 (γ=0.286, P=0.003). Furthermore, Kaplan-Meier curves indicated that MYBL2 expression in ESCC tissue was associated with poor patient outcome (P<0.001), with MYBL2-positive patients who exhibited high Ki67 expression in ESCC tissue showing the worst prognosis for overall survival (P=0.003). Our in vitro results showed that downregulation of MYBL2 in ESCC cell lines inhibited cell proliferation and DNA replication (P<0.05 for both). We also found that loss of MYBL2 caused a reduction in levels of cell cycle-related G2/M proteins CDK1 and cyclin B1 in ESCC cells. In contrast, overexpression of MYBL2 caused an increase in these proteins. In vivo, we found that in nude mice that received cells knocked down for MYBL2, tumor growth was inhibited in comparison to the group that received control cells (P<0.05). CONCLUSION: MYBL2 overexpression induces tumor proliferation in ESCC cells by regulating cell-cycle at the S and G2/M phase. Therefore, MYBL2 may serve as a novel prognostic biomarker in ESCC patients.

Role of matrix metalloproteinase-9 in transforming growth factor-ß1-induced epithelial-mesenchymal transition in esophageal squamous cell carcinoma.

Epithelial-mesenchymal transition (EMT) is thought to be a crucial event during the early metastasis of tumor cells. Transforming growth factor (TGF)-ß1 is involved in the process of EMT in a variety of human malignancies. Matrix metalloproteinase (MMP)-9 plays an important role in tumor invasion and metastasis, and its expression is regulated by various growth factors, including TGF-ß1, in different cell types. To date, the role of MMP-9 in TGF-ß1-induced EMT in esophageal squamous cell carcinoma (ESCC) remains unclear. In this study, we aimed to elucidate the mechanism underlying MMP-9-mediated TGF-ß1 induction of EMT in ESCC. We analyzed the expression of MMP-9, E-cadherin, and vimentin, in ESCC cells (EC-1), before and after the treatment with exogenous TGF-ß1 or a broad spectrum MMP inhibitor, GM6001. Additionally, we analyzed the activity of MMP-9 in these cells and performed MMP-9 knockdown experiments. The results obtained in this study demonstrated that the treatment of EC-1 cells with TGF-ß1 can induce EMT, together with the upregulation of vimentin and downregulation of E-cadherin expression in a time-dependent manner. The treatment with GM6001 was shown to attenuate TGF-ß1-induced EMT. Furthermore, the exposure of EC-1 cells to TGF-ß1 increased the expression and activity of MMP-9, while MMP-9 knockdown blocked TGF-ß1-induced EMT and inhibited cell invasiveness and migration. Additionally, treatment with the recombinant human MMP-9 was shown to induce EMT and enhance ESCC cell invasion and metastasis. The obtained data suggest that the regulation of MMP-9 by TGF-ß1 may represent a novel mechanism underlying TGF-ß1-induced EMT in ESCC.

Stat3 promotes invasion of esophageal squamous cell carcinoma through up-regulation of MMP2.

Stat3 alters the expression of its downstream genes and is associated with tumor invasion and metastasis in several human cancers. Its role in esophageal squamous cell carcinoma (ESCC) has not been well characterized. We examined the tumor sections of 100 cases of ESCC by immunohistochemistry and observed significant overexpression of Stat3 in the cytoplasm of 89% of ESCC cells and of phosphorylated Stat3 (p-Stat3) in the nuclei of 71% of ESCC when compare with normal esophageal mucosa (72%, p = 0.02; and 31%, p = 0.001). Overexpression of Stat3 and p-Stat3 positively correlated with that of matrix metalloproteinase-2 (MMP2), a known regulator for cell migration, in 65% of ESCC while only 26% shown in benign esophageal mucosa. To further investigate the association of Stat3 with tumor metastasis in vitro, invasion of EC-1 cells (a human ESCC cell line) were investigated with Boyden chambers. The results showed that transfection of Stat3 not only promoted invasion of EC-1 cells but also significantly induced MMP2 expression in a dose-dependent manner. In contrast, suppressing expression of endogenous Stat3 mRNA and protein by Stat3 siRNA significantly reduced EC-1 cell invasion and MMP2 expression. A high-affinity Stat3-binding element was localized to the positions of 648-641 bp (TTCTCGAA) in the MMP2 promoter with electrophoretic mobility shift assay. Our results suggest that Stat3, p-Stat3, and MMP2 were overexpressed in ESCC and associated with invasion of ESCC; and Stat3 up-regulated expression of MMP2 in ESCC through directly binding to the MMP2 promoter.