B-cell translocation gene 2 mediates crosstalk between PI3K/Akt1 and NFκB pathways which enhances transcription of MnSOD by accelerating IκBα degradation in normal and cancer cells

Abstract

BackgroundB-cell translocation gene 2 (BTG2) belongs to antiproliferative (ARPO) gene family and the expression of BTG2, human ortholog of rat PC3 and mouse TIS21 gene, has been shown to render cancer cells more sensitive to doxorubicin treatment by upregulating MnSOD expression without regulating any other reactive oxygen species (ROS) scavenging enzymes.ResultsIn the present study, by employing exogenous and endogenous BTG2/TIS21/Pc3 expression by transfection and transduction analyses, and by knockdown of gene expression using RNA interference or using gene knockout cells, we observed that BTG2 increased the binding of activated NF-κB (p65/RelA) to the enhancer element of MnSOD gene in the 2nd intron, which was regulated by p-Akt1, and the induction of MnSOD by BTG2 was accompanied with subsequent downregulation of ROS level and cyclin B1 biosynthesis along with the increase of p21WAF1, resulting in the G2/M arrest independent of p53.ConclusionsThese results show for the first time that BTG2 mediates crosstalk between PI3K-Akt1 and NF-κB pathways, which regulates p53-independent induction of G2/M phase arrest both in normal and cancer cells.

Inhibition of breast cancer invasion by TIS21/BTG2/Pc3-Akt1-Sp1-Nox4 pathway targeting actin nucleators, mDia genes

“…As Rho family GTPases serve as a critical regulator of cell migration, cell-cell adhesion and cell-extracellular matrix adhesion by the intracellular signals that act on cytoskeleton, 34 the above observations suggest that TIS21 /BTG2/Pc3 regulates transcription of mDia genes independent of Rho and Rac activities. TIS21 /BTG2/Pc3 -mediated activation of Akt1 suppresses invasiveness of breast cancer cells In view of our recent observations of TIS21 /BTG2/Pc3 effects on tumor invasion 30 and Akt activation, 35 relationship between pAkt at serine 473 (pAkt S473 ) residue and the degree of TIS21 /BTG2/Pc3 expression was examined in the invasive breast cancer, MDA-MB-231 and MDA-MB-468, cells (Figure 2a). Transduction of Ad-TIS21 /BTG2/Pc3 significantly enhanced pAkt S473 in a dosedependent manner, the phenomenon being similar in MDA-MB-435 cells (Supplementary Figure S1).…”

“…The observation is well accordant with our previous studies shown in the TIS21 − / − MEF and bone marrow cells 32 in addition to various cancer cells regulating NFκB activation. 35 As we consider the antiproliferative activity of TIS21 /BTG2/Pc3 gene compared with LacZ control (Supplementary Figure S2), it is assumed that the TIS21 /BTG2/Pc3 -mediated reductions of cancer invasion and cell motility can simply be the outcome of inhibition of cell growth. However, siAkt1 failed to regulate the growth of TIS21 expressers, therefore, upregulation of actin cytoskeleton by siAkt1 in the TIS21 expresser support the regulation of invasion and invadopodia formation by TIS21 /BTG2/Pc3 via Akt1.…”

“…Chromatin immunoprecipitation assay was performed by our published method 35,70 using anti-Sp1 antibody. Immunoprecipitated DNA fragment was amplified by semiquantitative PCR with the forward primer 5′-AACAATCAGTCTAAAAGAGCTGTGTCTTCT-3′ and the reverse primer 5′-CTCCAAAATACTGGCAAACATGTGAACAAT-3′ to amplify promoter DNAs of Nox4 gene.…”

Transient TNF regulates the self-renewing capacity of stem-like label-retaining cells in sphere and skin equivalent models of melanoma

“…Consistently, LY294002 suppressed the TNF-induced upregulation of GFP high ABCB5 high melanoma SCs ( Figure 5D), strongly supporting AKT involvement in the TNF-mediated regulation of melanoma SC fate determination and functionality. Finally, because TNFactivated AKT targets NFκB, which is a well-known mediator of TNF responses [44][45][46] that control SC fate [47], and because NFκB can target AKT [48,49], evidencing a cross-talk between these pathways [49,50], we used the NFκB inhibitor BAY 11-7082 in combination with TNF to form melanospheres. This inhibition should distinguish which of the two pathways mediates TNF responses.…”

Stress-induced NF-κB activation differentiates promyelocytic leukemia cells to macrophages in response to all-trans-retinoic acid

“…NF-κB has been reported to upregulate the expression of several antioxidant effectors, such as MnSOD, heme oxygenase, glutathione, thioredoxin, and ferritin heavy chain [57][58][59][60]. In addition, BTG2 /TIS21 -Akt1-NF-κB mediated MnSOD induction [61] may reduce ROS increase under serum deprivation, resulting in the survival of mature cells against oxidative damage. Therefore, NF-κB has been considered as an additional target for future APL therapies.…”