Role of GLI1 and NDRG1 in Increased Resistance to Apoptosis Induction

Cx43 phosphorylation-mediated effects on ERK and Akt protect against ischemia reperfusion injury and alter the stability of the stress-inducible protein NDRG1

Gap junctions contain intercellular channels that enable intercellular communication of small molecules while also serving as a signaling scaffold. Connexins, the proteins that form gap junctions in vertebrates, are highly regulated and typically have short (<2 h) half-lives. Connexin43 (Cx43), the predominate connexin in the myocardium and epithelial tissues, is phosphorylated on more than a dozen serine residues and interacts with a variety of protein kinases. These interactions regulate Cx43 and gap junction formation and stability. Casein kinase 1 (CK1)-mediated phosphorylation of Cx43 promotes gap junction assembly. Using murine knock-in technology and quantitative PCR, immunoblotting, and immunoprecipitation assays, we show here that mutation of the CK1 phosphorylation sites in Cx43 reduces the levels of total Cx43 in the myocardium and increases Cx43 phosphorylation on sites phosphorylated by extracellular signal-regulated kinase (ERK). In aged myocardium, we found that, compared with WT Cx43, mutant Cx43 expression increases ERK activation, phosphorylation of Akt substrates, and protection from ischemia-induced injury. Our findings also uncovered that Cx43 interacts with the hypoxia-inducible protein N-Myc downstream-regulated gene 1 protein (NDRG1) and that Cx43 phosphorylation status controls this interaction and dramatically affects NDRG1 stability. We propose that, in addition to altering gap junction stability, Cx43 phosphorylation directly and dynamically regulates cellular signaling through ERK and Akt in response to ischemic injury. We conclude that gap junction-dependent NDRG1 regulation might explain some cellular responses to hypoxia.

NDRG1 and FOXO1 regulate endothelial cell proliferation in infantile haemangioma

The etiopathogenesis of infantile haemangioma has not been well understood, and it is accepted that angiogenic mediator dysregulation is the main contributor to the abnormal haemangioma capillary formation. The role of NDRG1, a hypoxia-inducible protein; FOXOs, which are tumor suppressor proteins; and the mTOR complex 2 pathway in infantile haemangioma have not been studied yet. The purpose of this study was to investigate NDRG1 and FOXO1 expression in the infantile haemangioma and the correlation of these proteins with proliferation and involution. Primary endothelial cells were obtained, with parental agreement, from 12 infantile haemangioma patients during surgery; 6 patients had proliferating infantile haemangiomas and 6 had involuting IHs. We compared the infantile haemangioma tissues and primary endothelial cells with human vein endothelial cells using microarrays, real-time PCR, Western blotting and immunohistochemical staining. Our data indicated that FOXO1 expression was downregulated in proliferating infantile haemangioma tissue. We found that the expression of NDRG1, a molecule upstream of the FOXO1 pathway, increased during haemangioma proliferation. NDRG1 knockdown decreased haemangioma endothelial cell proliferation and downregulated c-MYC oncoprotein levels. Our findings suggest that NDRG1 positively regulates haemangioma proliferation. FOXO1 dysregulation plays an important role in infantile haemangiomas pathogenesis.

Role of GLI Transcription Factors in Pathogenesis and Their Potential as New Therapeutic Targets

GLI transcription factors have important roles in intracellular signaling cascade, acting as the main mediators of the HH-GLI signaling pathway. This is one of the major developmental pathways, regulated both canonically and non-canonically. Deregulation of the pathway during development leads to a number of developmental malformations, depending on the deregulated pathway component. The HH-GLI pathway is mostly inactive in the adult organism but retains its function in stem cells. Aberrant activation in adult cells leads to carcinogenesis through overactivation of several tightly regulated cellular processes such as proliferation, angiogenesis, EMT. Targeting GLI transcription factors has recently become a major focus of potential therapeutic protocols.

[The role of Sonic Hedgehog signaling pathway in the development of oral squamous cell carcinoma]

The research of the Sonic Hedgehog signaling pathway activity was carried out on biopsy specimens of 43 patients with oral hyperplasia, squamous intraepithelial neoplasia and oral squamous cell carcinoma. Tissue antigens were determined using a mouse monoclonal antibody to Ki-67 protein and rabbit monoclonal antibody to Gli-1 protein. In squamous intraepithelial neoplasia and oral squamous cell carcinoma specimens Gli-1 was detected in the cytoplasm of cells only. The correlation was found between the proliferative activity of epithelial cells and Gli-1 distribution. Protein Gli-1 can be used for early diagnosis of malignant transformation of oral stratified squamous epithelium.

NDRG1 Downregulates ATF3 and Inhibits Cisplatin-Induced Cytotoxicity in Lung Cancer A549 Cells

N-myc downstream regulated gene 1 (NDRG1) plays a variety of roles in human cancers. Our previous studies showed that NDRG1 expression is elevated in non-small cell lung cancer and contributes to cancer growth. However, its function in apoptosis and chemoresistance in malignant tumors, including lung cancer, is not yet fully understood. In this study, we investigated the roles of NDRG1 in chemoresistance to cisplatin in lung cancer cells. We found that overexpression of NDRG1 significantly reduced cisplatin-induced cytotoxicity in lung cancer A549 cells, while overexpression of activating transcription factor 3 (ATF3), a stress-inducible gene found to be associated with apoptosis in some human cancers, significantly promoted cytotoxicity (P < 0.05). Further investigation showed that overexpression of NDRG1 significantly downregulated ATF3 and P53 expression in A549 cells, while overexpression of ATF3 significantly upregulated P53 expression (P < 0.05). In addition, cisplatin significantly upregulated ATF3, phospho-P53(ser46), and cleaved caspase 3 expression in lung cancer cells, but overexpression of NDRG1 in the presence of cisplatin reduced the level of these proteins elevated by cisplatin (P < 0.05). While, overexpression of ATF3 significantly promoted the cytoxicity induced by cisplatin in 1299 cells (p<0.05) (Figure 4), but overexpression of NDRG1 didn't regulate the cytoxicity induced by cisplatin (p>0.05). These results indicate that NDRG1 may contribute to cisplatin-resistance in lung cancer, possibly due to its function in the regulation of ATF3 expression.