ING4 induces G2/M cell cycle arrest and enhances the chemosensitivity to DNA‐damage agents in HepG2 cells

Abstract

The known members of inhibitor of growth (ING) gene family are considered as candidate tumor suppressor genes. ING4, a novel member of ING family, is recently reported to interact with tumor suppressor p53, p300 (a major component of histone acetyl transferase complexes), and p65(RelA) subunit of NF-jB. In this study, we investigated the cellular behaviors of HepG2 cells with exogenous ING4. Interestingly, the overexpression of ING4 negatively regulated the cell growth with significant G2/M arrest of cell cycle, and moreover, enhanced the cell apoptosis triggered by serum starvation in HepG2 cells. Furthermore, the exogenous ING4 could upregulate endogenous p21 and Bax in HepG2 cells, not in p53-deficient Saos-2 cells, suggesting that G2/M arrest induced by ING4 could be mediated by the increased p21 expression in a p53-dependent manner, although there is no significant increase of p53 expression in HepG2 cells. Moreover, HepG2 cells with exogenous ING4 could significantly increase cell death, as exposed to some DNAdamage agents, such as etoposide and doxorubicin, implying that ING4 could enhance chemosensitivity to certain DNA-damage agents in HepG2 cells.

Ing4 induces Cell Growth Inhibition in Human Lung Adenocarcinoma A549 Cells by Means of Wnt‐1/β‐Catenin Signaling Pathway

“…Thus, overexpression of ING4 might up-regulate the expression of p27 and down-regulate the expression of cyclinD1, SKP2, and Cox2 by inducing inactivation of the Wnt-1/b-catenin signaling pathway. ING4 has been reported to enhance cell death triggered by DNA-damage agents and to enhance the chemosensitivity to doxorubicin and etoposide in HepG2 cells (Zhang et al, 2004). To further confirm whether ING4 could affect the efficacy of radiotherapy or chemotherapy on lung adenocarcinoma, we evaluated the potential effects of ING4 on A549 cells irradiated with grays or treated with the chemotherapeutic drug 5-Fu.…”

“…Previous studies demonstrated that overexpression of ING4 could induce a decreased cell population in the S phase of the cell cycle and apoptosis in a p53-dependent manner with increasing p21 expression in RKO cells . ING4 could also suppress the loss of contact inhibition elicited by MYCN or MYC (Kim et al, 2004), induce significant G2/M arrest of cell cycle, and enhance chemosensitivity to doxorubicin and etoposide in HepG2 cells (Zhang et al, 2004). Finally, ING4 could inhibit NF-kB activation by physically interacting with the p65 (RelA) subunit of nuclear factor NF-kB, resulting in transcriptional repression of the downstream NF-kBresponsive genes (such as IL-8, IL-6, COX-2, and CSF-3) and many angiogenesis-related genes, causing further inhibition of tumor angiogenesis (Garkavtsev et al, 2004).…”

ING4 inhibits the translation of proto‐oncogene MYC by interacting with AUF1

“…ING4binds to AUF1 p40 by pull down (View interaction) ING4physically interacts with AUF1 by anti tag coimmunoprecipitation (View Interaction: 1, 2) ING4binds to AUF1 p37 by pull down (View Interaction: 1, 2) ING4 binds to AUF1 p42 by pull down (View interaction) ING4binds to AUF1 p45 by pull down (View interaction) ING4physically interacts with AUF1 by anti bait coimmunoprecipitation (View Interaction: 1,2,3,4,5,6) ING4binds to AUF1 by pull down (View interaction)…”

“…The expression plasmids for pGEX5x-1-ING4 and the ING4 variants were constructed as described previously [5,24]. The HA-tagged AUF1 (p37/p40/p42/p45) and Flagtagged ING4 expression vectors were constructed in pcDNA3.0 by PCR.…”

“…cancer-related cellular processes, such as DNA repair, chromatin remodeling, cell cycle control, apoptosis, proliferation, migration and tumor angiogenesis [1][2][3][4][5][6][7]. ING4 contains a novel conserved region (NCR) in the N terminus, a nuclear localization signal (NLS) in the central region, and a highly conserved plant homeodomain (PHD) in the C terminus [1].…”