mir-29 regulates Mcl-1 protein expression and apoptosis

Abstract

Cellular expression of Mcl-1, an anti-apoptotic Bcl-2 family member, is tightly regulated. Recently, Bcl-2 expression was shown to be regulated by microRNAs, small endogenous RNA molecules that regulate protein expression through sequence-specific interaction with messenger RNA. By analogy, we reasoned that Mcl-1 expression may also be regulated by microRNAs. We chose human immortalized, but non-malignant, H69 cholangiocyte and malignant KMCH cholangiocarcinoma cell lines for these studies, because Mcl-1 is dysregulated in cells with the malignant phenotype. By in silico analysis, we identified a putative target site in the Mcl-1 mRNA for the mir-29 family, and found that mir-29b was highly expressed in cholangiocytes. Interestingly, mir-29b was downregulated in malignant cells, consistent with Mcl-1 protein upregulation. Enforced mir-29b expression reduced Mcl-1 protein expression in KMCH cells. This effect was direct, as mir-29b negatively regulated the expression of an Mcl-1 3 0 untranslated region (UTR)-based reporter construct. Enforced mir-29b expression reduced Mcl-1 cellular protein levels and sensitized the cancer cells to tumor necrosis factor-related apoptosisinducing ligand (TRAIL) cytotoxicity. Transfection of non-malignant cells (that express high levels of mir-29) with a locked-nucleic acid antagonist of mir-29b increased Mcl-1 levels and reduced TRAIL-mediated apoptosis. Thus mir-29 is an endogenous regulator of Mcl-1 protein expression, and thereby, apoptosis.

MicroRNA signatures of TRAIL resistance in human non-small cell lung cancer

“…Mott et al (2007) described that miR-29b is able to regulate Mcl1-1 protein and thus TRAIL-mediated cytotoxicity in cholangiocarcinoma cell lines. Corsten et al (2007) demonstrated that the combined effect of miR-21 antagonism and soluble TRAIL delivery in glioma cells leads to increase in caspase activity and cell death in glioma cells.…”

MicroRNA-29b is involved in the Src-ID1 signaling pathway and is dysregulated in human lung adenocarcinoma

“…miR-29b was previously correlated with good prognosis in patients with acute myeloid leukemia, and has a tumor suppressor function in leukemic blasts by targeting apoptosis, cell cycle and proliferation pathways (Garzon et al, 2008). Consistently, miR-29b regulates Mcl-1 and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in cholangiocarcinoma cells, and controls Tcl-1 in chronic lymphatic leukemia cells (Pekarsky et al, 2006;Mott et al, 2007). The miR-29 family members also target DNMT3A and DNMT3B, and can thereby restore patterns of DNA methylation and expression of silenced tumor suppressor genes (Fabbri et al, 2007).…”

“…In the present study, using the Src-specific small molecule inhibitors saracatinib and dasatinib, we identified miR-29b as an important mediator of the Src-ID1 pathway, controlling lung cancer cell invasion. Members of the miRNA-29 family (miR-29a, miR-29b and miR-29c) are known to be highly expressed in normal tissues and downregulated in different types of cancer, including neuroblastoma, sarcoma, glioma, high-risk chronic lymphatic leukemia, invasive breast cancer, cholangiocarcinoma and lung cancer (Calin et microRNA-29b in lung cancer SI Rothschild et al et al, 2006;Mott et al, 2007;Wu et al, 2009;Xu et al, 2009). The three miR-29 isoforms are arranged in two clusters: miR-29b1/miR-29a located on chromosome 7q32 and miR-29b2/miR-29c located on chromosome 1q32.…”

The BCL-2 protein family, BH3-mimetics and cancer therapy

“…70,71 As for the pro-survival BCL-2 family members, BCL-2 and MCL-1 appear to be the prominent targets of miRNA-mediated regulation. Both are targeted by miR-29 and miR-153, [72][73][74] and BCL-2 expression is also regulated by miR-15, miR-16, 75 miR-195 76 and the p53-inducible miR-34. 77 BCL-XL expression appears to be controlled by miR-491.…”