miR­501­3p promotes colorectal cancer progression via activation of Wnt/ß­catenin signaling.

Aberrant activation of Wnt/ß­catenin signaling is observed in >90% of colorectal cancer cases. microRNAs (miRNAs) regulate the expression of key genes in Wnt/ß­catenin signaling. As a result, abnormal expression of miRNAs regulates the activation of Wnt/ß­catenin signaling in several types of cancer. In the current study, it was demonstrated that miR­501­3p was overexpressed in colorectal tumor tissues compared to the adjacent normal tissues. Downregulation of miR­501­3p inhibited cell proliferation and sphere formation, while it induced cell cycle arrest at the G1 phase in colorectal cancer cells. Bioinformatics analysis results predicted that adenomatous polyposis coli (APC), a negative regulator of Wnt/ß­catenin signaling, was a potential target gene of miR­501­3p. Inhibition of miR­501­3p increased APC expression in colorectal cancer cells. Additionally, ß­catenin was destabilized following miR­501­3p inhibition; immunofluorescence analysis revealed that ß­catenin translocated from nucleus to cytoplasm. In addition, cyclin D1 and c­Myc, two well­characterized target genes of Wnt/ß­catenin signaling, were downregulated following miR­501­3p inhibition. Transfection of APC small interfering RNA re­activated ß­catenin and stimulated the expression of cyclin D1 and c­Myc. Furthermore, silencing of APC reversed the miR­501­3p inhibitor­induced cell cycle disruption, and the inhibition of cell proliferation and sphere formation in colorectal cancer cells. In conclusion, the present study identified miR­501­3p as a novel regulator of Wnt/ß­catenin signaling in colorectal cancer cells via targeting APC, suggesting that miR­501­3p may act as a novel oncogenic miRNA in colorectal cancer.

Exosome-mediated miR-200b promotes colorectal cancer proliferation upon TGF-ß1 exposure.

Exosome are emerging mediators of intercellular communication. Cancer-secreted exosome has an effect on the exosome donor cells and support cancer growth and metastasis. Here, we examine the TGF-ß1, a multifunctional cytokine involved in the regulation of cellular signaling pathways in human cancers, significantly contributes to upregulate miR-200b in exosome from colorectal cancer cell lines. The miR-200b enriched in exosome can be transferred into a new target cell to facilitating the colorectal cancer cells proliferation. Further studies showing that the exosomal miR-200b could directly target 3'-UTRs of p27 and RND3 resulted in knockdown of respective target proteins in recipient cells. Remarkably, the overexpression of p27/kip1 in HCT-116 cell, not RND3, resulted in effectively inhibited cell proliferation which induced by exosomal miR-200b. Moreover, animal experiment studies also confirmed a stimulating effect of exosomal miR-200b on colorectal cancer cell-derived xenografts. The expression p27/kip1 have decreased in tumors xenografts after injected with exosomal miR-200b. Our observations offer an evidence that whereby exosomal specific miRNA could amplify the proliferative element into the neighboring or distant cells to effective tumor growth.

Ginsenoside Rh2 inhibiting HCT116 colon cancer cell proliferation through blocking PDZ-binding kinase/T-LAK cell-originated protein kinase.

BACKGROUND: Ginsenoside Rh2 (GRh2) is the main bioactive component in American ginseng, a commonly used herb, and its antitumor activity had been studied in previous studies. PDZ-binding kinase/T-LAK cell-originated protein kinase (PBK/TOPK), a serine/threonine protein kinase, is highly expressed in HCT116 colorectal cancer cells. METHODS: We examined the effect of GRh2 on HCT116 cells ex vivo. Next, we performed in vitro binding assay and in vitro kinase assay to search for the target of GRh2. Furthermore, we elucidated the underlying molecular mechanisms for the antitumor effect of GRh2 ex vivo and in vivo. RESULTS: The results of our in vitro studies indicated that GRh2 can directly bind with PBK/TOPK and GRh2 also can directly inhibit PBK/TOPK activity. Ex vivo studies showed that GRh2 significantly induced cell death in HCT116 colorectal cancer cells. Further mechanistic study demonstrated that these compounds inhibited the phosphorylation levels of the extracellular regulated protein kinases 1/2 (ERK1/2) and (H3) in HCT116 colorectal cancer cells. In vivo studies showed GRh2 inhibited the growth of xenograft tumors of HCT116 cells and inhibited the phosphorylation levels of the extracellular regulated protein kinases 1/2 and histone H3. CONCLUSION: The results indicate that GRh2 exerts promising antitumor effect that is specific to human HCT116 colorectal cancer cells through inhibiting the activity of PBK/TOPK.