FUNCTION OF THE PCPH ONCOGENE IN MAMM;CARCINOGENESIS

描述(由申请人提供)：PCPH最初在PI的实验室被鉴定为原癌基因，因为在化学启动的、致癌的叙利亚仓鼠胚胎细胞中经常检测到PCPH是激活的癌基因(mt-PCPH)。后来发现PCPH在脊椎动物中高度保守，在小鼠NIH3T3成纤维细胞的转化过程中，mt-PCPH癌基因与人H-ras癌基因具有协同作用。这一继续应用的中心目标是研究PCPH的正常功能，并建立PCPH改变促进肿瘤发展的机制(S)。本资助期内获得的结果表明：i)PCPH和mt-PCPH都具有主要的细胞内定位；ii)mt-PCPH癌蛋白中疏水的C末端尾部是其转化活性的关键决定因素；iii)mt-PCPH的表达而不是PCPH的表达激活ERK1激酶；iv)PCPH和mt-PCPH都具有内在的ATP二磷酸水解酶(Apyrase)活性，v)mt-PCPH的表达通过部分耗尽内源性ATP库来提供细胞生存功能，并且vi)在肿瘤动物和人类细胞中，PCPH多肽的表达经常被解除调控。我们假设PCPH是细胞ATP感知机制的一个组成部分，通过与负责平衡内源性ATP池和外部供应的信号电路相互作用，这些相互作用的改变通过PCPH突变激活为癌蛋白(mt-PCPH)或通过放松PCPH表达调控而促进肿瘤的发展。这一假说将通过几种方法来验证：1)分析mt-PCPH的转化机制或PCPH的非调控表达；2)PCPH参与调节细胞ATP池的研究；3)酵母细胞中PCPH/mTOR功能相互作用的分析；以及4)PCPH参与人类癌症的研究。这些研究将为了解野生型和致癌型PCPH在正常和恶性细胞中的功能和调控提供基础，并可能对人类肿瘤的诊断和治疗具有重要意义。

DESCRIPTION (provided by applicant): PCPH was initially identified as a proto-oncogene in the PI's laboratory on the basis of its frequent detection as an activated oncogene (mt-PCPH) in chemically initiated, tumorigenic Syrian hamster embryo cells. It was later shown that PCPH is highly conserved in vertebrates, and that the mt-PCPH oncogene synergized with the human H-ras oncogene in the transformation of murine NIH3T3 fibroblasts. The central objective of this continuation application is to investigate the normal PCPH function and to establish the mechanism(s) by which PCPH alterations contribute to tumor development. Results obtained during the current funding period have shown that: i) Both PCPH and mt-PCPH have a predominant intracellular location; ii) the hydrophobic C-terminal tail present in the mt-PCPH oncoprotein is a key determinant of its transforming activity; iii) expression of mt-PCPH, but not of PCPH, activates the ERK1 kinase; iv) both PCPH and mt-PCPH have intrinsic ATP diphosphohydrolase (apyrase) activity, v) mt- PCPH expression provides cell survival functions by partially depleting endogenous ATP pools to levels below those optimal for stress-induced signaling and apoptosis, and vi) expression of PCPH polypeptides is frequently deregulated in neoplastic animal and human cells. We hypothesize that PCPH is a component of the cellular ATP-sensing machinery and functions by interacting with signaling circuits in charge of balancing endogenous ATP pools and external supplies, Alterations of these interactions by either mutational activation of PCPH into an oncoprotein (mt-PCPH) or by deregulation of PCPH expression contribute to tumor development. This hypothesis will be tested by several approaches: 1) Analysis of mechanisms of transformation by mt-PCPH or deregulated expression of PCPH; 2) Study of the involvement of PCPH in regulating cellular ATP pools; 3) Analysis of PCPH/mTOR functional interactions in yeast cells; and 4) Study of the participation of PCPH in human cancer. These studies will provide a fundamental understanding of the function and regulation of wild type and oncogenic PCPH in normal and malignant cells, and may have important implications for the diagnosis and management of human tumors.