Search

Ataxia-telangiectasia mutated (ATM) protein kinase is a major guardian of genomic stability, and its well-established function in cancer is tumor suppression. Here, we report an oncogenic role of ATM. Using two isogenic sets of human colon cancer cell lines that differed only in their ATM status, we demonstrated that ATM deficiency significantly inhibits cancer cell proliferation, migration, and invasion. The tumor-suppressive function of ATM depletion is not modulated by the compensatory activation of ATR, but it is associated with B56γ2-mediated Chk1/p53/CD44 signaling pathways. Under normal growth conditions, the depletion of ATM prevents B56γ2 ubiquitination and degradation, which activates PP2A-mediated Chk1/p53/p21 signaling pathways, leading to senescence and cell cycle arrest. CD44 was validated as a novel ATM target based on its ability to rescue cell migration and invasion defects in ATM-depleted cells. The activation of p53 induced by ATM depletion suppresses CD44 transcription, thus resulting in epithelial-mesenchymal transition (EMT) and cell migration suppression. Our study suggests that ATM has tumorigenic potential in post-formed colon neoplasia, and it supports ATM as an appealing target for improving cancer therapy. [ABSTRACT FROM AUTHOR]

Microvesicles (MVs) secreted from cells have been found to mediate signal transduction between cells. In the tumor microenvironment, VEGF released from cancer cells plays a key role in promoting tumor angiogenesis. In this study, we characterized the inhibitory effect of MV-delivered miR-29a/c on angiogenesis and tumor growth in gastric cancer (GC). We found that the downregulation of miR-29a/c increases VEGF expression and release in GC cells, promoting the growth of vascular cells. By simulating the tumor microenvironment, the MV-delivered miR-29a/c significantly suppresses VEGF expression in GC cells, inhibiting vascular cell growth, metastasis, and tube formation. We also used a tumor implantation mouse model to show that secreted MVs containing overexpressed miR-29a/c significantly reduced the growth rate of the vasculature and tumors in vivo. To conclude, our results contribute to a novel anti-cancer strategy using miRNA-containing MVs to control tumor cell growth by blocking angiogenesis. [ABSTRACT FROM AUTHOR]

Abstract: The over-expression of COX-2 (Cyclooxygenase 2) protein has been reported to play a key role in the incidence and development of Helicobacter pylori-associated gastric cancer. The induction of COX-2 in the gastric cancer cells with H. pylori has been demonstrated previously, but little is known about the mechanism. This study reported that the COX-2 mRNA and proteins expression level and the activity of COX-2 promoter increased remarkably with H. pylori stimulation in the MKN45 gastric cancer cells. H. pylori also stimulated phosphorylation of p38MAPK and ATF-2, which is the downstream kinase of p38MAPK. Moreover, the expression levels of COX-2 were suppressed with p38MAPK inhibitor treatment. These results suggest that H. pylori-induced activation of p38MAPK/ATF-2-mediated signal pathway is necessary for the expression of COX-2. [Copyright &y& Elsevier]