one of the most aggressive human malignancies with a median survival time of less than one year. A better understanding of the molecular events involved in ATC initiation and progression that could be targeted for therapy is gravely needed. There is limited data on the role of miRNAs in ATC. Screening of miRNA expression profile in thyroid cancer samples showed significant downregulation of miR-30a in ATC compared to differentiated thyroid cancer and normal tissue. Ectopic expression of miR-30a in vitro decreased invasion and migration of ATC cells with downregulation of epithelial-mesenchymal transition (EMT) markers and Lysyl Oxidase (LOX) expression, a predicted target of miR-30a. Using an in vivo mouse model of ATC metastases, miR-30a significantly decreased lung metastasis with decreased vimentin, CD44 and LOX expression in lung metastases tumor tissue. We also found that LOX and its downstream target TWIST-1 are highly expressed in ATC, and the expression of both were significantly, inversely correlated with miR-30a expression (p= 0.0026). In addition, the analysis of 454 primary thyroid cancer samples from The Cancer Genome Atlas dataset demonstrated upregulation of LOX and downregulation of miR-30a in high-risk thyroid cancer. These findings suggest that LOX and miR-30a are prognostic markers for aggressive thyroid cancer.
To determine whether LOX is a direct effector of miR-30a, the 3′UTR region of LOX was cloned into a luciferase reporter plasmid. Transient transfection of 3′UTR-LOX along with miR-30a in ATC cell lines led to a decrease in luciferase activity when compared to the co-transfection of 3′UTR-LOX with negative control miRNA, demonstrating that LOX is a direct target of miR-30a.
In vitro treatment of 4 ATC cell lines with β-aminoproprionitrile (BAPN), an irreversible inhibitor of LOX, had no effect on cell proliferation but inhibited cell invasion and migration and significantly decreased EMT markers and CD44 expression. Moreover, BAPN-treated mice with metastatic human ATC tumors had significantly fewer tumors and smaller size of lung metastases. Our data taken together support a critical role of miR-30a in ATC progression, which is mediated by LOX, and suggests that miR-30a and LOX is possible therapeutic target in ATC.
Note: This abstract was not presented at the meeting.
Citation Format: Myriem Boufraqech, Naris Nilubol, Lisa Zhang, Samira Sadowski, Sudheer Kumar Gara, Mei He, Sean Davis, Martha Quezado, Electron Kebebew. Tumor suppressor miR-30a inhibits LOX expression and progression in anaplastic thyroid cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4367. doi:10.1158/1538-7445.AM2014-4367