Davis, Sean

Abstract Anaplastic thyroid cancer (ATC) is one of the most lethal human malignancies, but its genetic drivers remain little understood. In this study, we report losses in expression of the miRNA miR30a, which is downregulated in ATC compared with differentiated thyroid cancer and normal tissue. miR30a downregulation was associated with advanced differentiated thyroid cancer and higher mortality. Mechanistically, we found miR30a decreased cellular invasion and migration, epithelial–mesenchymal transition marker levels, lysyl oxidase (LOX) expression, and metastatic capacity. LOX was identified as a direct target of miR30a that was overexpressed in ATC and associated with advanced differentiated thyroid cancer and higher mortality rate. Consistent with its role in other cancers, we found that LOX inhibited cell proliferation, cellular invasion, and migration and metastasis in vitro and in vivo. Together, our findings establish a critical functional role for miR30a downregulation in mediating LOX upregulation and thyroid cancer progression, with implications for LOX targeting as a rational therapeutic strategy in ATC. Cancer Res; 75(2); 367–77. ©2014 AACR.

Abstract CHEK2 codes for a serine/threonine kinase (Chk2) activated by ATM in response to DNA double-strand breaks (DSB). CHEK2 has been described as a tumor suppressor with pro-apoptotic, cell cycle checkpoint and mitotic functions. However, Chk2 is also commonly activated (phosphorylated at T68) in cancers and precancerous lesions. In the present report, we characterized CHEK2 across the panel of 60 established cancer cell lines from the NCI Anticancer Tumor Cell Line panel (the NCI-60) using genomic and proteomic analyses including exon-specific mRNA expression, DNA copy number variation (CNV) by aCGH, exome sequencing, as well as Western blotting analyses for total and activated (pT68-Chk2) Chk2. We demonstrate that the high heterogeneity of Chk2 levels in the NCI-60 is primarily due to its inactivation (owing to low gene expression, alternative splicing, point mutations, copy number alterations and premature truncation) or reduction of protein levels. Notably, we also found that a significant percentage of cancer cells (12% of the NCI-60 and the HeLa cervix cell line) display high endogenous Chk2 activation, always associated with p53 loss of function. Notably, all the 12 cancer cell lines characterized as being p53 wild-type showed almost undetectable levels of pT68-Chk2. The potential impact of endogenous Chk2 activation was analyzed by transcriptome profiling of the five highest pT68-Chk2 cell lines, comparing them with five, tissue-matched low pT68-Chk2 and p53-matched deficient cell lines. Two-sided t tests revealed 176 genes differentially expressed with statistical significance (P < 0.01, uncorrected) in the two groups (high vs. low pT68-Chk2). Among the downregulated expressed genes, a significant number codes for proteins involved in DNA recombination, replication and repair (FANCA, FANCG, FANCL, BRCA2, RAD51C, EME1, and RECQL5 being the most relevant), and centromere organization. Several of these downregulated genes were parts of the Fanconi Anemia pathway or related to homologous recombination (HR, P < 0.05 for statistically significant enrichment using Ingenuity Pathway Analysis®). In conclusion, the biology of Chk2 remains complex, multifaceted and fast evolving. Our study provides information on the relationship between different genomic and proteomic parameters related to Chk2 in cancer, and suggests a possible role for activated Chk2 in p53-deficient or HR/Fanconi Anemia-deficient cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2116. doi:1538-7445.AM2012-2116