Anti-lamin A and anti-tubulin antibodies were used as control of efficient nuclear and cytoplasmic extraction, respectively.(B)HCT116, 2008 and A549 cells were treated with ADR or CDDP, as shown, with or without HG. Zaleplon A-sensitive phosphatase(s), able to specifically target p53Ser46 phosphorylation. The specific effect on Ser46 phosphorylation was Zaleplon addressed by analysing Ser15 phosphorylation that instead was not modified by high glucose. In agreement, a constitutively phosphorylated Ser46D p53 mutant was resistant to high glucose. As a consequence of phosphoSer46 impairment, high glucose reduced the tumor cell response to drugs, correlating with reduced p53 apoptotic transactivation. The drug-induced apoptotic cell death, reduced by high glucose, was finally restored by the phosphatase inhibitor calyculin A. == Conclusions == These data indicate that high glucose specifically inhibited Ser46 phosphorylation thus reducing p53 apoptotic activity. These results uncover a new mechanism Zaleplon of p53 inactivation providing an interesting novel molecular link between metabolic diseases such as diabetes or obesity and tumor progression and resistance to therapies. Keywords:p53, Ser46 phosphorylation, Hyperglicemia, Phosphatase, Calyculin A, Apoptosis, Chemotherapy, Gene transcription == Background == P53 is the major tumor-suppressor that functions within an extensive signalling network [1]. In response to several types of genotoxic stress p53 is activated to control genes that lead to different cellular outcome such as cell-cycle arrest and apoptosis. In this manner, p53 protects cells from tumorigenesis, reduces tumor progression, and activates tumor cell response to anticancer drugs [2]. P53 activation is achieved at multiple levels including protein stability and sub-cellular localization leading to transcriptional activation of sequence-specific target genes with specific oncosuppressor functions [3]. Apoptosis has been suggested to be a major contribution Rabbit Polyclonal to TSN to p53-mediated suppression of tumor Zaleplon formation [4] and resistance to apoptosis is one of the major hurdles in the treatment of cancer [5]. TP53 posttranslational modifications, such as phosphorylation and acetylation of specific residues, are thought to play a role for the choice among the different biological functions regulated by p53 [6]. It has been proposed that phosphorylation Zaleplon of p53 at N-terminal serine 46 (Ser46) is a necessary step for inducing apoptosis in response to severe DNA damage by shifting from cell-cycle-related to apoptosis-related gene transcription [7,8]. P53 phosphorylated at Ser46 modulates less sensitive gene regulatory elements such as those that control genes encoding proapoptotic proteins including p53AIP1, PIG3, Bax, Noxa, Puma and KILLER/DR5 [7,9-12], or the antiapoptotic factor galectin-3 [13], leading to irreversible apoptosis. To add a layer of complexity, some studies have shown that p53 Ser46 phosphorylation is dispensable for transcriptional activation [14]. However, a defect in Ser46 phosphorylation has been observed in tumor cells that are resistant to p53-mediated apoptosis, and this defect contributes to chemoresistance or the acquisition of the resistance to p53 gene transfer [15]. On the contrary, a mutant active form of p53, in which Ser46 is replaced with phenylalanine (p53-46 F), has been shown to induce apoptosis more effectively that wild-type (wt) p53 [16], while studies with knock-in mice expressing the humanTP53gene with Ser46A mutation (non phosphorylatable Ser46), reduced p53 apoptotic transactivation [17], strengthening the apoptotic role for this p53 posttranslational modification. Hyperglicaemia is a pathophysiological condition characterized by high blood glucose concentration that has been shown to predispose to cancer development and progression [18]. Hyperglicaemia is often a consequence of a Western lifestyle that is associated with metabolic syndrome and type-2 diabetes or obesity. Epidemiological evidence suggests that patients with diabetes mellitus are at significantly higher risk of developing many types of cancers [19]. Foods with high glycemic load are most closely correlated with higher recurrence of colon cancer [20]. Moreover, hyperglicaemia may inhibit tumor response to therapies conferring.