A regulatory loop involving miR-29c and Sp1 elevates the TGF-β1 mediated epithelial-to-mesenchymal transition in lung cancer

// Hai-wei Zhang 1, 2 , En-wen Wang 3 , Li-xian Li 1, 2 , Shou-hui Yi 1, 2 , Lu-chun Li 3 , Fa-liang Xu 4 , Dong-lin Wang 3 , Yong-zhong Wu 5 , Wei-qi Nian 1, 2 1 Key Laboratory of Oncology, Chongqing Cancer Institute, Chongqing Cancer Hospital, Chongqing Cancer Center, Chongqing, China 2 Chongqing Key Laboratory of Translational Research for Cancer Metastasis and Individualized Treatment, Chongqing Cancer Institute, Chongqing, China 3 Department of Oncology, Chongqing Cancer Institute, Chongqing, China 4 Center of Breast Cancer, Chongqing Cancer Institute, Chongqing, China 5 Department of Radiotherapy, Chongqing Cancer Institute, Chongqing, China Correspondence to: Wei-qi Nian, email: nwqone@126.com Keywords: miR-29c, metastasis, TGF-β1, sp1, EMT Received: March 27, 2016      Accepted: October 31, 2016      Published: November 05, 2016 ABSTRACT Specificity protein1 (Sp1) is required for TGF-β-induced epithelial-to-mesenchymal transition (EMT) which has been demonstrated to aggravate the progression of cancer including lung cancer. microRNA-29c (miR-29c) is identified to inhibit EMT, but the correlation between miR-29c and Sp1 in human lung cancer remain incompletely clarified. Here, we confirmed decreased expression of miR-29c and enhanced expression of Sp1 in lung cancer tissues ( n = 20) and found that Sp1 could be targeted and inhibited by miR-29c. Besides, the expression of miR-29c was down-regulated in high-metastatic lung cancer cell lines and TGF-β1-treated cells. The inhibition of miR-29c or overexpression of Sp1 in 95C and A549 cells dramatically enhanced the cell migration and invasion, and also induced the decrease in the expression of epithelial markers, e.g. thyroid transcription factor 1 (TTF-1) and E-cadherin, together with an increase in mesenchymal markers including vimentin, α-smooth muscle actin (α-SMA), which could be restored by overexpression of miR-29c mimics during the TGF-β-induced EMT. Moreover, dual-luciferase reporter assay was performed and the results indicated that miR-29c/Sp1 could form an auto-regulatory loop with TGF-β1, which impaired TGFB1 transcription. Furthermore, miR-29c overexpression could abrogate the tumor progression and inhibit the Sp1/TGF-β expressions in vivo , indicating that miR-29c could be a tumor suppressor and repress the Sp1/TGF-β axis-induced EMT in lung cancer.