DIACYLGLYCEROLS AS TUMOR PROMOTERS

SN-1，2-二酰基甘油（SN-1，2-DAGs）是细胞内的第二类脂质 信使和蛋白激酶C（PKC）的内源性配体。 各种 sn-1，2-DAG模拟了细胞的某些生物化学和形态学效应， 有效的肿瘤促进剂12-0-十四酰基佛波醇-13-乙酸酯在小鼠皮肤上的作用。 最近，sn-1，2-二癸酰甘油被证明是一种有效的 7，12-二甲基苯并[a]蒽（DMBA）引发的完全肿瘤促进剂 老鼠皮 这些结果表明，PKC和 外源性或内源性sn-1，2-DAG可能足以促进肿瘤的生长， DMBA引发的小鼠皮肤含有突变的Ha-ras癌基因（*Ha-ras）。 事实上，单独的sn-1，2-DAG治疗足以促进肿瘤的生长。 启动的小鼠皮肤可能在组织中是重要的， 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。 这种积累可以 产生异常的细胞增殖或分化， 促进刺激。 因此，这是总体目标， 确定外源性sn-1，2-DAG 促进肿瘤，如果内源性sn-1，2-DAG在 致癌作用 本提案的具体目的是确定：1）如果 通过sn-1，2-DAG下调表皮PKC允许 增生和表皮生长因子（EGF）诱导的体内有丝分裂， 2)DMBA引发的含有 *Ha-ras的肿瘤水平是否升高 游离内源性sn-1，2-DAG下调表皮PKC（由于 增加的内源性sn-1，2-DAG），TGF α的过度表达，以及如果 这些变化在自分泌循环中功能性耦合，3）为什么 需要频繁应用sn-1，2-DAG以证明其 肿瘤促进活性（可能是由于快速代谢，皮肤不良 吸收、减弱的炎症反应和/或脂肪酰基部分）。 它 假设由于突变的 *Ha-ra， 内源性sn-1，2-DAG和TGF α过表达。 的 内源性/外源性sn-1，2-DAG下调PKC，使EGF 受体保持其高亲和力形式。 这些事件是允许的 TGF α过度表达诱导的促有丝分裂反应。 的 小鼠皮肤启动-促进模型、皮肤器官外植体和小鼠 培养的角质形成细胞将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.