Exposure to MoS2 nanosheets or bulk activated Kruppel-like factor 4 in 3D Caco-2 spheroids in vitro and mouse intestines in vivo.

MoS2 nanosheets (NSs) are novel 2D nanomaterials (NMs) being used in many important fields. Recently, we proposed the need to evaluate the influences of NMs on Kruppel-like factors (KLFs) even if these materials are relatively biocompatible. In this study, we investigated the influences of MoS2 NSs or bulk on KLF4 signaling pathway in 3D Caco-2 spheroids in vitro and mouse intestines in vivo. Through the analysis of our previous RNA-sequencing data, we found that exposure to MoS2 NSs or bulk activated KLF4 expression in 3D Caco-2 spheroids. Consistently, these materials also activated KLF4-related gene ontology (GO) terms and down-regulated a panel of KLF4-downstream genes. To verify these findings, we repeatedly exposed mice to MoS2 NSs or bulk materials via intragastrical administration (1 mg/kg bodyweight, once a day, for 4 days). It was shown that oral exposure to these materials decreased bodyweight, leading to relatively higher organ coefficients. As expected, exposure to both types of materials increased Mo elements as well as other trace elements, such as Zn, Fe, and Mn in mouse intestines. The exposure also induced morphological changes of intestines, such as shortening of intestinal villi and decreased crypt depth, which may result in decreased intestinal lipid staining. Consistent with RNA-sequencing data, we found that material exposure increased KLF4 protein staining in mouse intestines and decreased two KLF4 downstream proteins, namely extracellular signal-regulated kinase (ERK) and serine/threonine kinase (AKT). We concluded that MoS2 materials were capable to activate KLF4-signaling pathway in intestines both in vivo and in vitro.

FLI-1 mediates tumor suppressor function via Klotho signaling in regulating CRC.

Colorectal cancer (CRC) is an aggressive malignancy with a high incidence and mortality rate. Although a targeting therapy has been developed, the 5-year survival rate is still very low in CRC patients with distant metastasis. Thus, the identification of new targets is still significant for improving CRC treatment. Klotho is a tumor suppressor, and its expression is aberrant in CRC. In this study, the roles of the FLI-1 gene in regulating Klotho gene expression and Klotho-associated signaling, as well as the effects of FLI-1 on colony formation, invasion, and apoptosis were investigated in CRC cell lines. The methylation of the FLI-1 gene was analyzed using a commercial methylation kit. Results showed that FLI-1 messenger RNA and protein expression were downregulated in six CRC cell lines when compared with the normal colon mucosal epithelial cell line, which negatively correlated with the level of DNA methylation. Silencing of FLI-1 gene expression decreased Klotho protein expression and phosphorylation of ß-catenin protein at Thr41 /Ser45 , but increased Wnt3a and ß-catenin protein expression and IGF-1R phosphorylation in HT29 cells. In contrast to silencing FLI-1, overexpressing FLI-1 significantly increased Klotho protein expression and phosphorylation of ß-catenin protein at Thr41 /Ser45 , but decreased Wnt3a and ß-catenin protein expression and IGF-1R phosphorylation in Caco-2 cells. Silencing of FLI-1 gene expression significantly increased colony formation and invasion, but decreased apoptosis in HT29 cells. In contrast, overexpressing the FLI-1 gene significantly decreased colony formation and invasion, but increased apoptosis in Caco-2 cells. These findings suggest that FLI-1 functions as a tumor suppressor in CRC cells and positively regulates Klotho signaling. Hypermethylation may be one of the causes of the loss of FLI-1 gene expression in CRC cells.

Interaction between linc01615 and miR-491-5p regulates the survival and metastasis of colorectal cancer cells.

BACKGROUND: The 5-year survival of colorectal cancer (CRC) has had no obvious improvement during the past decades, although a significant progress in treatments has been established. The molecular mechanisms that drive the progression of CRC are still unclear. This study aims to determine the biological activities of linc01615 and its regulatory microRNAs in CRC cells. METHODS: The expression of linc016150 and miR-491-5p was measured in six CRC cell lines and one normal colon mucosal epithelial cell line. Their effects on cell proliferation, apoptosis, invasion, and migration were tested in Caco-2 cells. RESULTS: Linc01615 mRNA expression was upregulated in six colorectal cancer cell lines compared to the normal colon mucosal epithelial cell line, which was negatively regulated by miR-491-5p in Caco-2 cells. Silencing of linc01615 gene expression significantly decreased cell proliferation, increased apoptosis, and inhibited invasion and migration in Caco-2 cells. Overexpression of linc01615 exhibited an opposite effect on silencing of linc01615 expression. Transfection with miR-491-5p mimics downregulated linc01615 expression and inhibited the biological activities of linc01615. In contrast, the inhibitor of miR-491-5p up-regulated linc01615 expression and subsequently enhanced the biological activities of linco1615. Also, overexpression of linc01615 can block the effects of miR-491-5p mimics in Caco-2 cells. CONCLUSIONS: Linc01615 functions as an oncogene while miR-491-5p functions as a tumor suppressor in colorectal cancer cells through negatively regulating each other; both are involved in cell proliferation, apoptosis, invasion, and migration in colorectal cancer cells.