The programmed cell death 4 (PDCD4) gene was originally identified as a tumor-related gene in humans and acts as a tumor-suppressor in mouse epidermal carcinoma cells. However, its function and regulatory mechanisms of expression in human cancer remain to be elucidated. We therefore investigated the expression of PDCD4 in human hepatocellular carcinoma (HCC) and the role of PDCD4 in human HCC cells. Downregulation of PDCD4 protein was observed in all HCC tissues tested compared with corresponding noncancerous liver, as revealed by Western blotting or immunohistochemical staining. Human HCC cell line, Huh7, transfected with PDCD4 cDNA showed nuclear fragmentation and DNA laddering characteristic of apoptotic cells associated with mitochondrial changes and caspase activation. Transforming growth factor-b1 (TGF-b1) treatment of Huh7 cells resulted in increased PDCD4 expression and occurrence of apoptosis, also concomitant with mitochondrial events and caspase activation. Transfection of Smad7, a known antagonist to TGF-b1 signaling, protected cells from TGF-b1-mediated apoptosis and suppressed TGF-b1-induced PDCD4 expression. Moreover, antisense PDCD4 transfectants were resistant to apoptosis induced by TGF-b1. In conclusion, these data suggest that PDCD4 is a proapoptotic molecule involved in TGF-b1-induced apoptosis in human HCC cells, and a possible tumor suppressor in hepatocarcinogenesis.

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SummaryWe established the role for epigenetics in regulation of NOTCH signaling in breast cancer. This may constitute a common mechanism of activation of oncogenic signals. Our study provides support for epigenetic-targeting strategies in anticancer approaches.

A new two-dimensional (2D) material, borophene (2D boron sheet), has been grown successfully recently on single crystal Ag substrates by two parallel experiments [Mannix et al., Science, 2015, 350, 1513] [Feng et al., Nature Chemistry, 2016, advance online publication]. Three main structures have been proposed (β 12 , χ 3 and striped borophene). However, the stability of three structures is still in debate. Using first principles calculations, we examine the dynamical, thermodynamical and mechanical stability of β 12 , χ 3 and striped borophene. Free-standing β 12 and χ 3 borophene is dynamically, thermodynamically, and mechanically stable, while striped borophene is dynamically and thermodynamically unstable due to high stiffness along a direction. The origin of high stiffness and high instability in striped borophene along a direction can both be attributed to strong directional bonding.This work provides a benchmark for examining the relative stability of different structures of borophene.