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Tumour radiotherapy resistance involves the cell cycle pathway. CDC25 phosphatases are key cell cycle regulators. However, how CDC25 activity is precisely controlled remains largely unknown. Here, we show that LIM domain-containing proteins, such as FHL1, increase inhibitory CDC25 phosphorylation by forming a complex with CHK2 and CDC25, and sequester CDC25 in the cytoplasm by forming another complex with 14-3-3 and CDC25, resulting in increased radioresistance in cancer cells. FHL1 expression, induced by ionizing irradiation in a SP1- and MLL1-dependent manner, positively correlates with radioresistance in cancer patients. We identify a cell-penetrating 11 amino-acid motif within LIM domains (eLIM) that is sufficient for binding CHK2 and CDC25, reducing the CHK2-CDC25 and CDC25-14-3-3 interaction and enhancing CDC25 activity and cancer radiosensitivity accompanied by mitotic catastrophe and apoptosis. Our results provide novel insight into molecular mechanisms underlying CDC25 activity regulation. LIM protein inhibition or use of eLIM may be new strategies for improving tumour radiosensitivity.

Eye absent (Eya) proteins are involved in cell fate determination in a broad spectrum of cells and tissues. Aberrant expression of Eya2 has been documented in a variety of cancers and correlates with clinical outcome. However, whether microRNAs (miRNAs) can regulate Eya2 expression remains unknown. Here, we show that miR-30a represses Eya2 expression by binding to the 3'-untranslated region of Eya2. Overexpression of Eya2 in miR-30a-transfected breast cancer cells effectively rescued the inhibition of cell proliferation and migration caused by miR-30a. Knockdown of Eya2 by small-interfering RNA (siRNA) in breast cancer cells mimicked the effect induced by miR-30a and abolished the ability of miR-30a to regulate breast cancer cell proliferation and migration. The miR-30a/Eya2 axis could regulate G1/S cell cycle progression, accompanied by the modulation of expression of cell cycle-related proteins, including cyclin A, cyclin D1, cyclin E, and c-Myc. Moreover, miR-30a expression was downregulated in breast cancer patients, and negatively correlated with Eya2, which was upregulated in breast cancer patients. These data suggest that the miR-30a/Eya2 axis may play an important role in breast cancer development and progression and that miR-30a activation or Eya2 inhibition may be a useful strategy for cancer treatment., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Vascular endothelial growth factor (VEGF) plays an important role in many disease states, including ischemia, chronic and acute inflammation, and pathologies associated with angiogenesis such as tumors and wounds. A number of factors regulate VEGF promoter activity and VEGF expression such as four and a half LIM domains 1 (FHL1) and Smad4. FHL1 belongs to a family of LIM-only proteins that regulate gene transcription, cell proliferation, differentiation and apoptosis. Smad4 is a tumor suppressor gene, initially identified as deleted in pancreatic carcinoma locus 4 (DPC4). The aim of this study was to determine whether FHL1 and Smad4 inhibited VEGF signaling. HepG2 cells were transfected with the VEGF-Luc reporter, Smad4 and FHL1 or Smad4 and FHL1 siRNA. Results showed that the overexpression of FHL1 and Smad4 synergistically inhibited the promoter activity, mRNA expression and secretion of VEGF, whereas knockdown of endogenous Smad4 and FHL1 had opposite effects. Moreover, the reduction of endogenous Smad4 eliminated FHL1-mediated inhibition of the VEGF promoter activity. In conclusion, a cooperative regulation of VEGF signaling by FHL1 and Smad4 was evidenced, which may provide a novel regulation mechanism underlying cancer development and progression.