Mucins 1-shRNA inhibit the proliferation and HIF-1alpha protein expression on human cholangiocarcinoma cells

MUC1 induces the accumulation of Foxp3+ Treg cells in the tumor microenvironment to promote the growth and metastasis of cholangiocarcinoma through the EGFR/PI3K/Akt signaling pathway

Tumor microenvironment (TME) plays an important role in the progression of cholangiocarcinoma. This study aims to explore whether Mucin 1 (MUC1) regulates Foxp3⁺ Treg cells in the TME of cholangiocarcinoma through the epidermal growth factor receptor (EGFR)/phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway. High-throughput sequencing dataset in the GEO database combined with GeneCards and Phenolyzer databases was used to obtain key genes in cholangiocarcinoma, followed by downstream pathway prediction. The relationship among MUC1, EGFR, and PI3K/Akt signaling pathway was explored. CD4⁺ T cells extracted from peripheral blood were induced to differentiate into Treg cells, followed by co-culture with cholangiocarcinoma cells. A mouse model was constructed to detect the role of MUC1 in the accumulation of Foxp3⁺ Treg cells, malignant phenotypes of cholangiocarcinoma, and tumorigenesis in vivo. MUC1, highly expressed in cholangiocarcinoma, might be involved in cholangiocarcinoma development. MUC1 interacted with the EGFR to activate the EGFR/PI3K/Akt signaling pathway. MUC1 overexpression could activate the EGFR/PI3K/Akt signaling pathway, which promoted the accumulation of Foxp3⁺ Treg cells in the TME and the malignant phenotypes of cholangiocarcinoma cells both in vitro and in vivo and enhanced tumorigenesis in vivo. MUC1 may interact with EGFR to activate the EGFR/PI3K/Akt signaling pathway, which induces the accumulation of Foxp3⁺ Treg cells, enhancing the malignant phenotypes of cholangiocarcinoma cells and tumorigenesis in vivo and ultimately augmenting cholangiocarcinoma growth and metastasis.

E74-Like Factor 3 Promotes Endometrial Cancer Cell Proliferation, Migration and Invasion via Regulating Mucin 1/Hypoxia-Inducible Factor 1α Pathway

High expression of E74-like factor 3 (ELF3) has been reported in type 1 endometrial cancer (EC). Bioinformatics analysis predicted a positive correlation with ELF3 and mucin 1 (MUC1)/hypoxiainducible factor 1α (HIF-1α), a previously identified cancer-promoting pathway. This study focused on the MUC1/HIF-1α-involved action mechanism of ELF3 in EC. ELF3 expression in EC cell lines was measured by RT-qPCR and western blot analysis. Following the expression of ELF3 was silent, cell proliferation was examined using CCK-8 and colony formation assay, cell migration and invasion were observed using wound healing and transwell assays. The effect of ELF1 silencing on MUC1/HIF-1α expression was detected by western blot. Rescue experiments incorporating pcDNA3.1(+)/MUC1 explored the interaction between ELF3 and MUC1/HIF-1α in EC cell proliferation, migration and invasion. ELF3 was found to be expressed at a high level in EC cell lines, and the silencing of it effectively inhibited EC cell proliferation. Moreover, ELF silencing also inhibited the migration and invasion of EC cells. Consistent with the database prediction, a positive correlation between ELF3 and MUC1/HIF-1α was observed. More importantly, MUC1 overexpression abated the promotive effect of ELF3 silencing on EC cell proliferation, migration and invasion. ELF3 promotes EC cell proliferation, migration and invasion by regulating MUC1/HIF-1α pathway. Thus, ELF3 as well as MUC1/HIF-1α pathway may be particle targets in the treatment of EC.

Mucin 1 regulates the hypoxia response in head and neck cancer cells

Mucin 1 (MUC1) is a transmembrane glycoprotein that contributes to the cellular response in hypoxic conditions in different carcinomas. We investigated the gene expression pattern of MUCs (1, 2, 4, 5AC, 5B, 6, 15, 16, and 19) in isogenic primary (HN4 and HN30) and metastatic (HN12 and HN31) head and neck squamous cell carcinoma (HNSCC) cell lines. MUC1 was significantly up-regulated at the mRNA and protein levels in HN12 and HN31 cells, whereas, other MUCs exhibited diverse expression patterns between HNSCC cell lines. Immunohistochemistry demonstrated that MUC1 was exclusively expressed in cancer cells; however, there was no significant correlation between MUC1 expression and malignancy grading. Inducing hypoxia with CoCl₂ significantly increased cell viability, MUC1, hypoxia-inducible factor alpha (HIF-1α), and vascular endothelial growth factor A (VEGF-A) expression in HN12 cells, but not HN31 cells. Interestingly, in hypoxia, cell viability, HIF-1α and VEGF-A expression were significantly reduced in MUC1-knockdown HN12 cells. The current report is the first to demonstrate that MUC1 is required in the regulation of hypoxia-related genes in HNSCC cells. Thus, our results suggest that MUC1 modulates the hypoxic effects in HNSCC cells through HIF-1α regulation.

MUC13 promotes intrahepatic cholangiocarcinoma progression via EGFR/PI3K/AKT pathways

BACKGROUND & AIMS

Mucin 13 (MUC13) is reportedly overexpressed in human malignancies. However, the clinicopathological and biological significance of MUC13 in human intrahepatic cholangiocarcinoma (iCCA) remain unclear. The aim of this study was to define the role of MUC13 in the progression of iCCA.

METHODS

Expression levels of MUC13 in human iCCA samples were evaluated by immunohistochemistry, western blot, and real-time PCR. In vitro and in vivo experiments were used to assess the effect of MUC13 on iCCA cell growth and metastasis. Crosstalk between MUC13 and EGFR/PI3K/AKT signaling was analyzed by molecular methods. The upstream regulatory effects of MUC13 were evaluated by Luciferase and DNA methylation assays.

RESULTS

MUC13 was overexpressed in human iCCA specimens and iCCA cells. MUC13 overexpression positively correlated with clinicopathological characteristics of iCCA, such as vascular invasion and lymph node metastasis, and was independently associated with poor survival. Results from loss-of-function and gain-of-function experiments suggested that knockdown of MUC13 attenuated, while overexpression of MUC13 enhanced, the proliferation, motility, and invasiveness of iCCA cells in vitro and in vivo. Mechanistically, we found that the phosphatidylinositol 3-kinase-AKT signal pathway and its downstream effectors, such as tissue inhibitor of metalloproteinases 1 and matrix metallopeptidase 9, were required for MUC13-mediated tumor metastasis of iCCA. MUC13 interacted with epidermal growth factor receptor (EGFR) and subsequently activated the EGFR/PI3K/AKT signaling pathway by promoting EGFR dimerization and preventing EGFR internalization. We also found that MUC13 was directly regulated by miR-212-3p, whose downregulation was related to aberrant CpG hypermethylation in the promoter area.

CONCLUSIONS

These findings suggest that aberrant hypermethylation-induced downregulation of miR-212-3p results in overexpression of MUC13 in iCCA, leading to metastasis via activation of the EGFR/PI3K/AKT signaling pathway.

LAY SUMMARY

Mucin 13 overexpression has been implicated in the development of malignancies, although its role in intrahepatic cholangiocarcinoma has not been studied. Herein, we show that mucin 13 plays a critical role in intrahepatic cholangiocarcinoma. Mucin 13 could have therapeutic value both as a prognostic marker and as a treatment target.

MUC1: a novel metabolic master regulator

MUC1, a type I transmembrane protein, is significantly overexpressed and aberrantly glycosylated in tumors of epithelial origin. By virtue of its aberrant signaling due to loss of apical-basal polarity in cancer, MUC1 regulates the metabolite flux at multiple levels. Serving as a transcriptional co-activator, MUC1 directly regulates expression of metabolic genes. By regulating receptor tyrosine kinase signaling, MUC1 facilitates production of biosynthetic intermediates required for cell growth. Also, via direct interactions, MUC1 modulates the activity/stability of enzymes and transcription factors that directly regulate metabolic functions. Additionally, by modulation of autophagy, levels of reactive oxygen species, and metabolite flux, MUC1 facilitates cancer cell survival under hypoxic and nutrient-deprived conditions. This article provides a comprehensive review of recent literature on novel metabolic functions of MUC1.