Inhibitory Effect of Melanoma Differentiation Associated Gene-7/Interleukin-24 on Invasion In Vitro of Human Melanoma Cancer Cells

The acquisition of metastasis potential is a critical point for malignant tumors. Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a potential tumor suppress gene and frequently down-regulated in malignant tumors. It has been implicated that overexpression of MDA-7 led to proliferation inhibition in many types of human tumor. Invasion is an important process which is potential to promote tumor metastasis. However, the role and potential molecular mechanism of mda-7/IL-24 to inhibit the invasion of human melanoma cancer is not fully clear. In this report, we identified a solid role for mda-7/IL-24 in invasion inhibition of human melanoma cancer LiBr cells, including decreasing of adhesion and invasion in vitro, blocking cell cycle, down-regulating the expression of ICAM-1, MMP-2/9, CDK1, the phosphorylation of ERK and Akt, NF-kappaB and AP-1 transcription activity. Meanwhile, there was an increased expression of PTEN in mda-7/IL-24 over-expression LiBr cells. Our results demonstrated that mda-7/IL-24 is a potential invasion suppress gene, which inhibits the invasion of LiBr cells by the down-regulation of ICAM-1, MMP-2/9, PTEN, and CDK1 expression. The molecular pathways involved were the MAPK/ERK, PI3K-Akt, NF-kappaB, and AP-1. These findings suggest that mda-7/IL-24 may be used as a possible therapeutic strategy for human melanoma cancer.

Black rice anthocyanidins prevent retinal photochemical damage via involvement of the AP-1/NF-kappaB/Caspase-1 pathway in Sprague-Dawley Rats

The effects of black rice anthocyanidins (BRACs) on retinal damage induced by photochemical stress are not well known. In the present study, Sprague-Dawley rats were fed AIN-93M for 1 week, after which 80 rats were randomly divided into two groups and treated with (n = 40) or without BRACs (n = 40) for 15 days, respectively. After treatment, both groups were exposed to fluorescent light (3,000 +/- 200 lux; 25degrees C), and the protective effect of dietary BRACs were evaluated afterwards. Our results showed that dietary BRACs effectively prevented retinal photochemical damage and inhibited the retinal cells apoptosis induced by fluorescent light (p < 0.05). Moreover, dietary BRACs inhibited expression of AP-1 (c-fos/c-jun subunits), up-regulated NF-kappaB (p65) expression and phosphorylation of IkappaB-alpha, and decreased Caspase-1 expression (p < 0.05). These results suggest that BRACs improve retinal damage produced by photochemical stress in rats via AP-1/NF-kappaB/Caspase-1 apoptotic mechanisms.

Galectin-3 increases the motility of mouse melanoma cells by regulating matrix metalloproteinase-1 expression

Although mounting evidence indicates the involvement of galectin-3 in cancer progression and metastasis, the underlying molecular mechanisms remain largely unknown. In this study, we investigated the effect and possible mechanism of galectin-3 on the migration and invasion of B16F10, a metastatic melanoma cell line, in which galectin-3 and matrix metalloproteinase-1 (MMP-1) were both found to be highly expressed. Knockdown of galectin-3 with specific siRNA reduced migration and invasion, which was associated with reduced expression of MMP-1. To further investigate the underlying mechanism, we examined the effect of galectin-3 knockdown on the activity of AP-1, a transcriptional factor regulating MMP-1 expression. We found that galectin-3 directly interacted with AP-1 and facilitated the binding of this complex to the MMP-1 promoter that drives MMP-1 transcription. Moreover, silencing of galectin-3 inhibited binding of fra-1 and c-Jun to promoter sites of MMP-1 gene. Consistent with these in vitro findings, our in vivo study demonstrated that galectin-3 shRNA treatment significantly reduced the total number of mouse lung metastatic nodules. Taken together, galectin-3 facilitates cell migration and invasion in melanoma in vitro and can induce metastasis in vivo, in part through, regulating the transcription activity of AP-1 and thereby up-regulating MMP-1 expression.

Involvement of GADD153 and cardiac ankyrin repeat protein in cardiac ischemia-reperfusion injury

Oxidative stress is critical for causing cardiac injuries during ischemia-reperfusion (IR), yet the molecular mechanism for this remains unclear. In the present study, we observe that hypoxia and reoxygenation, a component of ischemia, effectively induces apoptosis in the cardiac myocytes from neonatal rats and it concomitantly leads to induction of GADD153, an apoptosis-related gene. Furthermore, IR injury of rat heart showed a GADD153 overexpression in the ischemic area where the TUNEL reaction was positive. A downregulation of cardiac ankyrin repeat protein (CARP) was also observed in this ischemic area. Promoter deletion and reporter analysis revealed that hypoxia transcriptionally activates a GADD153 promoter through the AP-1 element in neonatal cardiomyocytes. Ectopic overexpression of GADD153 resulted in the downregulation of CARP expression. Accordingly, the induction of GADD153 mRNA were followed by the CARP down-regulation in an in vivo rat coronary ischemia/reperfusion injury model. These results suggest that GADD153 over-expression and the resulting downregulation of CARP may have causative roles in apoptotic cell death during cardiac IR injury.

Multi-transmembrane protein K15 of Kaposi's sarcoma-associated herpesvirus targets Lyn kinase in the membrane raft and induces NFAT/AP1 activities

Viral proteins of gamma-2 herpesviruses, such as LMP2A of Epstein Barr virus (EBV) and Tip of herpesvirus saimiri (HVS) dysregulate lymphocyte signaling by interacting with Src family kinases. K15 open reading frame of Kaposi's sarcoma associated herpesvirus (KSHV), located at the right end of the viral genome, encodes several splicing variants differing in numbers of transmembrane domains. Previously, we demonstrated that the cytoplasmic tail of the K15 protein interfered with B cell receptor signal transduction to cellular tyrosine phosphorylation and calcium mobilization. However, the detailed mechanism underlying this phenomenon was not understood. In the C-terminal cytoplasmic region of K15, putative binding domains for Src-SH2 and -SH3 were identified. In this study, we attempted to characterize these modular elements and cellular binding protein(s) by GST pull down and co-immunoprecipitation assays. These studies revealed that K15 interacted with the major B cell tyrosine kinase Lyn. In vitro kinase and transient co-expression assays showed that the expression of K15 protein resulted in activation of Lyn kinase activity. In addition, GST pull down assay suggested that the SH2 domain of Lyn alone was necessary for interaction with the C-terminal SH2B (YEEV) of K15, but the addition of Lyn SH3 to the SH2 domain increases the binding affinity to K15 protein. The data from luciferase assays indicate that K15 expression in BJAB cells induced NFAT and AP1 activities. The tyrosine residue in the C-terminal end of K15 required for the Lyn interaction appeared to be essential for NFAT/AP1 activation, highlighting the significance of the C-terminal SH2B of K15 as a modular element in interfering with B lymphocyte signaling through interaction with Lyn kinase.

Transcriptional regulation of Zic3 by heterodimeric AP-1(c-Jun/c-Fos) during Xenopus development

The heterodimeric c-Jun/c-Fos, an activator protein-1 (AP-1) has been implicated in mesoderm induction (Dong et al., 1996; Kim et al., 1998) whereas the homodimer of c-Jun was reported to be involved in neural inhibition during the early development of Xenopus embryos. During the early vertebrate development AP-1 involvement in the neural induction is still not clearly understood. We report here that AP-1 has a role in Zic3 expression, a critical proneural gene and a primary regulator of neural and neural crest development (Nakata et al., 1997; Nakata et al., 1998). AP-1 was able to induce the Zic3 gene in a dose dependent manner but other homo- or hetero-dimeric proteins, such as c-Jun/c-Jun, JunD/FosB or JunD/Fra-1 were not. The inhibition of AP-1 activity using morpholino antisenses of c-jun mRNAs blocked the Zic3 expression induced by activin. In addition, co-injection of c-jun mRNA rescued the down-regulated Zic3 expression. The promoter region of isolated Zic3 genomic DNA was found to possess several consensus-binding site of AP-1. Thus, in the functional assays, AP-1 could increase promoter activity of Zic3 gene. These findings suggest that proneural gene, Zic3 may be regulated by heterodimeric AP-1(c-Jun/c-Fos) and it may have a role in activin signaling for the regulation of neural specific gene, Zic3.

C/EBP binding activity to site F of the rat GLUT2 glucose transporter gene promoter is attenuated by c-Jun in vitro

The expression of the GLUT2 glucose transporter gene in liver is suppressed in cultured hepatoma cell lines and primary cultured hepatocytes. Earlier report showed that CCAAT/enhancer binding protein (C/EBP) regulates the promoter activity of the rat GLUT2 glucose transporter gene in liver cells. C/EBPa and C/EBPb activated the promoter activity by binding to at least two regions of the promoter and one of the C/EBP binding sites, named as site F, also has the AP-1 binding consensus. In this study, we investigated whether the AP-1 can influence on C/EBP binding to this site. The addition of recombinant c-Jun protein with liver extract caused the attenuation of C/EBP binding to site F with the appearance of a new shifted band. The shifted band was competed out with the addition of unlabeled AP-1 consensus oligonucleotide, indicating that c-Jun also can bind to site F. Another C/EBP site on GLUT2 promoter, site H, did not bind AP-1. Analysis of the DNA-protein complex revealed that C/EBP and c-Jun bind to site F in mutually exclusive manner rather than form heterodimeric complex with each other. From these results, it is suggested that the transcriptional activation of C/EBP may be influenced by c-Jun protein in certain status of the liver cells, such as acute phase response, as well as hepatocarcinogenesis.