TGFβ-mediated upregulation of hepatic miR-181b promotes hepatocarcinogenesis by targeting TIMP3

Abstract

To identify microRNAs that may play a causal role in hepatocarcinogenesis, we used an animal model in which C57/BL6 mice fed choline deficient and amino acid defined (CDAA) diet develop preneoplastic lesions at 65 weeks and hepatocellular carcinomas after 84 weeks. miRNA expression profiling showed significant upregulation of miR-181b and miR-181d in the livers of mice as early as 32 weeks that persisted at preneoplastic stage. The expression of TIMP3, a tumor suppressor and a validated miR-181 target, was markedly suppressed in the livers of mice fed CDAA diet. Upregulation of hepatic TGFβ and its downstream mediators Smad 2, 3 and 4 and increase in phospho-Smad2 in the liver nuclear extract correlated with elevated miR-181b/d in mice fed CDAA diet. The levels of the precursor and mature miR-181b were augmented upon exposure of hepatic cells to TGFβ and were significantly reduced by siRNA-mediated depletion of Smad4, demonstrating the involvement of TGFβ signaling pathway in miR-181b expression. Ectopic expression and depletion of miR-181b showed that miR-181b enhanced MMP2 and MMP9 activity and promoted growth, clonogenic survival, migration and invasion of HCC cells that could be reversed by modulating TIMP3 level. Further, depletion of miR-181b inhibited tumor growth of HCC cells in nude mice. miR-181b also enhanced resistance of HCC cells to the anti-cancer drug doxorubicin. Based on these results, we conclude that upregulation of miR-181b at early stages of feeding CDAA diet promotes hepatocarcinogenesis.

TIMP3 regulates migration, invasion and in vivo tumorigenicity of thyroid tumor cells

“…Loss of TIMP3 expression, through loss of heterozigosity on chromosome 22q, is frequently observed in various cancers, such as secondary glioblastoma (Nakamura et al, 2005) and clear renal cell carcinomas (Masson et al, 2010). Evidence is emerging that downregulation of TIMP3 expression in tumors can be achieved also through deregulation of microRNAs, as TIMP3 is a target of several microRNAs upregulated in human tumors such as miR21, miR181b, miR221 and 222 (Gabriely et al, 2008;Garofalo et al, 2009;Wang et al, 2010). The tumor-suppressor role of TIMP3 is also documented by a large body of data showing its capability to inhibit growth, invasion and metastasis of several cancers (Anand-Apte et al, 1996;Qi et al, 2003).…”

Differential Regulation of Extracellular Tissue Inhibitor of Metalloproteinases-3 Levels by Cell Membrane-bound and Shed Low Density Lipoprotein Receptor-related Protein 1

“…Thus, there is considerable interest in understanding factors regulating TIMP-3 levels, and it has been shown that transcription of TIMP-3 can be increased by the histone deacetylase SirT1 (10) and growth factors such as TGF␤ (11) and oncostatin M (12) and reduced by promoter methylation (13). Translation of TIMP-3 can be reduced by miR-21 (14), miR-221 and miR-222 (15), miR-181b (16), and miR-206 (17).…”

miR-181b increases drug sensitivity in acute myeloid leukemia via targeting HMGB1 and Mcl-1

“…It is important to note that the effects of miR-181b in chemoresistance vary according to different tumor microenvironments. In hepatocellular carcinoma (HCC) cells, miR-181b enhances resistance to the anticancer drug doxorubicin (10). A markedly miR-181b increases drug sensitivity in acute myeloid leukemia via targeting HMGB1 and Mcl-1 enhanced expression of miR-181b was also shown in more aggressive breast cancers and chemotherapy-resistant breast cancer cells, and knockdown of miR-181b can be used to render breast tumors more responsive to tamoxifen (11,12).…”