DIACYLGLYCEROLS AS TUMOR PROMOTERS

SN-1，2-甘油二酯(SN-1，2-DAGs)是细胞内第二脂类 信使和蛋白激酶C(PKC)的内源性配体。五花八门 SN-1，2-DAG模拟了一些生化和形态效应 有效的肿瘤促进剂12-0-十四烷基佛波醇-13-醋酸酯对小鼠皮肤。 最近，SN-1，2-十二烷基甘油被证明是一种有效的 7，12-二甲基苯并[a]菲(DMBA)引发的完全促癌作用 老鼠的皮肤。这些结果表明，PKC和PKC之间的相互作用 外源性或内源性sn-1，2-DAG可能足以促进肿瘤的发生 DMBA启动的小鼠皮肤含有突变的Ha-ras癌基因(*Ha-ras)。 事实上，仅SN-1，2-DAG治疗就足以促进肿瘤的发生 启动的小鼠皮肤在组织中可能是重要的，其中改变 内源性sn-1，2-DAG的形成或降解可能导致 脂质第二信使的积累。这样的积累可能 产生异常的细胞增殖或分化，可能会导致 推动经济刺激。因此，这是一个总的目标， 关于确定外源sn-1，2-DAG的作用机制的建议 促进肿瘤以及内源性sn-1，2-DAGs是否在 致癌。本提案的具体目的是确定：1)如果 Sn-1，2-DAG对表皮PKC的下调作用 增殖和表皮生长因子(EGF)诱导的体内有丝分裂 2)含有a*Ha-ras的DMBA引发的肿瘤是否升高 游离内源性sn-1，2-DAGs下调表皮PKC(由于 内源性sn-1，2-DAG增加)，TGFα的过度表达，以及IF 这些变化在功能上耦合在一个自分泌循环中，以及3)为什么 频繁使用sn-1，2-DAG是必要的，以展示其 肿瘤促进活性(可能是由于新陈代谢快，皮肤不好 吸收，减弱炎症反应和/或脂肪酰基部分)。它 假设由于*Ha-ra的突变，自由基数增加 内源性sn-1，2-DAGs和TGFα的过度表达。这个 内源性/外源性sn-1，2-DAGs下调PKC，从而允许EGF 受体保持其高亲和力形式。这些活动是允许的 对TGFα过度表达所致的促分裂反应有影响。这个 小鼠皮肤启动促进模型、皮肤器官移植及小鼠 培养中的角质形成细胞将被用于解决这些重要问题。

SN-1,2-Diacylglycerols (sn-1,2-DAGs) are intracellular lipid second messengers and the endogenous ligand of protein kinase C (PKC). Various sn-1,2-DAGs mimic some of the biochemical and morphological effects of the potent tumor promoter 12-0-tetradecanoylphorbol-13-acetate on mouse skin. Recently, sn-1,2-didecanoylglycerol was demonstrated to be a potent complete tumor promoter in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin. These results suggest that an interaction between PKC and exogenous or endogenous sn-1,2-DAG may be sufficient to promote tumors in DMBA-initiated mouse skin containing a mutated Ha-ras oncogene (*Ha-ras). The fact that sn-1,2-DAG treatment alone is sufficient to promote tumors in initiated mouse skin may be of importance in tissues where an altered formation or degradation of endogenous sn-1,2-DAGs could lead to an accumulation of the lipid second messenger. Such an accumulation could produce abnormal cell proliferation or differentiation and perhaps a promoting stimulus. Therefore, it is the overall objective of this proposal to determine the mechanism through which exogenous sn-1,2-DAGs promote tumors and if there is a role for endogenous sn-1,2-DAGs in carcinogenesis. The specific aims of this proposal are to determine: 1) if the down regulation of epidermal PKC by sn-1,2-DAG is permissive for hyperplasia and epidermal growth factor (EGF)-induced mitogenesis in vivo, 2) whether DMBA-initiated tumors containing a *Ha-ras have increased levels of free endogenous sn-1,2-DAGs down regulation of epidermal PKC (due to increased endogenous sn-1,2-DAGs), over expression of TGFalpha, and if these changes are functionally coupled in an autocrine loop and 3) why more frequent application of the sn-1,2-DAGs is necessary to demonstrate their tumor promoting activity (may be due to rapid metabolism, poor cutaneous absorption, attenuated inflammatory response and/or fatty acyl moiety). It is hypothesized that due to a mutated *Ha-ra, there is an increase in free endogenous sn-1,2-DAGs and an over expression of TGFalpha. The endogenous/exogenous sn-1,2-DAGs down regulate PKC which allows the EGF receptor to remain in its high affinity form. These events are permissive for the mitogenic response induced by the over expression of TGFalpha. The mouse skin initiation-promotion model, skin organ explants and mouse keratinocytes in culture will be used to address these important issues.