Attenuation of p53 Response to PAHs by Tumor Promoters

描述（由申请人提供）：有相当多的证据表明原型多核芳烃（PAH）苯并[a]芘（BP）诱导人类和小鼠细胞中的p53，并且12-O-十四烷酰基佛波醇-13-乙酸酯（TPA）和其他肿瘤促进剂减弱了BP诱导的p53上调。我们推测TPA抑制p53积聚是由于（i）抑制BP诱导的p53转录（其由核因子κ B（NF-κ B）激活）和（ii）降低p53蛋白稳定性（其由小鼠双微体（MDM）2蛋白水平和p53和MDM 2蛋白的翻译后修饰（通过信号转导激酶介导的磷酸化）调节）。我们选择了小鼠表皮JB 6（P+）细胞和（+）-抗BPDE（BP衍生的最终致癌物）进行拟议的研究。为了检验上述假设，我们提出（i）研究TPA对用（+）-抗-BPDE处理的细胞中p53转录物/蛋白水平、p53蛋白稳定性和NF-κ B活化的影响，（ii）检查TPA对MDM 2蛋白表达和稳定性的影响，（iii）检查TPA对PI 3-激酶和Akt的活化的影响，（iv）确定TPA对ERK 1/2和PKC激活的影响（参与p53蛋白磷酸化）与p53反应的关系。拟定研究的总体目标是了解TPA抑制（+）-抗BPDE诱导的p53上调的机制，从而阐明TPA和可能的其他肿瘤促进剂促进PAH诱导的致癌性的潜在机制。

DESCRIPTION (provided by applicant): There is considerable evidence showing that the prototype polynuclear aromatic hydrocarbon (PAH) benzo[a] pyrene (BP) induces p53 in human and mouse cells, and that 12-O-tetradecanoylphorbol-13-acetate (TPA) and other tumor promoters attenuate this BP-induced p53 up-regulation. We hypothesize that the inhibition of p53 accumulation by TPA is due to (i) inhibition of BP-induced p53 transcription which is activated by nuclear factor kappaB (NF-kappaB) and (ii) decreased p53 protein stability, which is regulated by mouse double minute (MDM) 2 protein level and post-translational modifications of p53 and MDM2 proteins by signal transducing kinase-mediated phosphorylations. We have selected mouse epidermal JB6 (P+) cells and (+)-anti-BPDE (BP-derived ultimate carcinogen) for the proposed study. In order to test the above hypotheses, we propose (i) to investigate the effect of TPA on p53 transcript/protein levels, p53 protein stability and NF-kappaB activation in cells treated with (+)-anti-BPDE, (ii) to examine the effect of TPA on MDM2 protein expression and stability, (iii) to examine the effect of TPA on the activation of PI3-kinase and Akt (involved in mdm2 protein phosphorylation) in relation to p53 response and (iv) to determine the effect of TPA on the activation of ERK1/2 and PKC (involved in p53 protein phosphorylations) in relation to p53 response. The overall objective of the proposed research is to understand the mechanism by which TPA inhibits the (+)-anti-BPDE -induced up-regulation of p53, and thereby elucidate the mechanism(s) underlying the promotion of PAH-induced carcinogenicity by TPA and possibly other tumor promoters.