DIACYLGLYCEROLS AND MULTISTAGE CARCINOGENESIS

癌症涉及内在的细胞遗传改变，然而，外在的 因素，例如来自和/或与之相互作用的可扩散信号 其他类型的细胞可引起细胞内信号的改变 可以改变基因表达并促进细菌生长的途径 基因改变的细胞。在小鼠皮肤致癌模型中， 表皮生长和鳞状乳头状瘤生长的异常 伴随着蛋白激酶C-α(PKC)和 PKC-β2.SN-1，2-二酰基甘油(DAG)是细胞内第二种 PKC的信使和配体。在DAG处理的表皮中，下调表达 PKC-α和-β2的表达与异常生长有关。外生的 应用DAG是克隆扩增细胞的效应器，该细胞含有 小鼠皮肤中突变的Ha-ras和PKC-α和-Beta2选择性地下调- 在突变型Ha-ras乳头状瘤中以非启动子依赖的方式调节。 基于这些观察结果，有人建议慢性高血压 乳头状瘤内细胞内源性DAG导致向下- 允许生长的PKC-α和PKC-β2的调节 突变的Ha-ras细胞。最近的证据表明，在 表皮PKC-β2仅在郎格汉斯细胞(LC)和 PKC-α的变化发生在角质形成细胞内。 因此，假设这些细胞在PKC中的特异性变化 异构体改变各自细胞类型的功能和/或 细胞类型之间的相互作用，并代表关键事件 增生、乳头状瘤生长和肿瘤促进。我们将进行研究 旨在了解该蛋白的功能和生物学意义。 角质形成细胞中PKC-α和LC中PKC-β2的下调 这些细胞类型之间可能改变的相互作用可能是 在促进肿瘤和乳头状瘤生长方面很重要。为了实现这一目标，我们 将：i)定位并确定PKC-α和-β2亚型的水平 在基底层和基底层以上的角质形成细胞中，树突状表皮T细胞 (DETC)未经治疗和DAG治疗的表皮和乳头状瘤； 构建反义表达载体抑制PKC-1的表达 角质形成细胞中的α，并研究其对细胞生长的影响， 分化和蛋白质磷酸化；iii)决定生物 LCS中PKC-Beta2下调对LC的影响 移行、抗原识别/处理/呈递和调节 角质形成细胞有丝分裂；以及iv)确定生理上重要的 细胞DAG池在突变型Ha-ras乳头状瘤中升高。总而言之， 我们认为突变型Ha-ras中的脂质动态平衡紊乱 乳头状瘤是PKC-α表达显著下调的原因 在LC的角质形成细胞和PKC-β2中，这些事件在不同的 细胞类型相互作用促进突变型Ha-ras的生长 乳头状瘤。

Cancer involves intrinsic cellular genetic alterations, however, extrinsic factors, such as diffusible signals from and/or physical interactions with other cell types can produce alterations in intracellular signaling pathways that can alter gene expression and contribute to the growth of a genetically altered cell. In the mouse skin model of carcinogenesis, aberrations in epidermal growth and squamous papilloma growth are accompanied by dramatic alterations in protein kinase C-alpha (PKC) and PKC-beta2. sn-1,2-Diacylglycerols (DAG) are intracellular second messengers and ligand of PKC. In DAG-treated epidermis the down-regulation of PKC-alpha and -beta2 is associated with aberrant growth. Exogenously applied DAG is an effector of the clonal expansion of cells containing mutant Ha-ras in mouse skin and PKC-alpha and -beta2 are selectively down- regulated in mutant Ha-ras papillomas in a promoter-independent manner. Based on these observations it is proposed that a chronic elevation in endogenous DAG in cells within the papilloma results in the down- regulation of PKC-alpha and PKC-beta2 which is permissive for the growth of mutant Ha-ras cells. Recent evidence indicates that within the epidermis PKC-beta2 is exclusively expressed in Langerhans cells (LC) and that the changes in PKC-alpha are occurring within the keratinocyte. Therefore it is hypothesized that these cell specific changes in PKC isoforms alter the function of the respective cell types and/or the interaction between the cell types and represent critical events in hyperplasia, papilloma growth and tumor promotion. We will conduct studies aimed at understanding the function and the biological significance of the down-regulation of PKC-alpha in keratinocytes and PKC-beta2 in LC and the possible altered interaction between these cell types which may be important in tumor promotion and papilloma growth. To accomplish this we will: i) localize and determine the level of PKC-alpha and -beta2 isoforms in basal and suprabasal keratinocytes, LCs, dendritic epidermal T-cells (DETC) in untreated and DAG-treated epidermis and papillomas; ii) construct antisense expression vectors to inhibit the expression of PKC- alpha in keratinocytes and study the ensuing effect on cell growth, differentiation and protein phosphorylation; iii) determine the biological consequences of the down-regulation of PKC-beta2 in LCs with respect to LC migration, antigen recognition/ processing/presentation and regulation of keratinocyte mitogenesis; and iv) determine if a physiologically important pool of cellular- DAG is elevated in mutant Ha-ras papillomas. In summary, we propose that perturbations in lipid homeostasis in mutant Ha-ras papillomas are responsible for the dramatic down-regulation of PKC-alpha in keratinocytes and PKC-beta2 in LC and that these events in different cell types interface to contribute to the growth of mutant Ha-ras papillomas.