Growth Factors, Curcumin and Colon Carcinogenesis

描述(申请人提供)：我们现在知道孕激素(PG)和胰岛素样生长因子(IGFS)对结肠癌(CRC)细胞具有强大的增殖和抗凋亡作用，并可能在结直肠癌发生的所有阶段发挥辅助致癌物的作用。姜黄素等饮食制剂可抑制结直肠癌细胞的生长，并在疾病的癌前和癌后阶段抑制结肠癌的发生。然而，目前尚不清楚姜黄素是否能抑制结肠癌发生过程中自分泌和/或内分泌PG和IGF-II对生长因子的影响。我们的初步研究表明，姜黄素的抑制作用在生长因子如IGF-II和PG的存在下被减弱；令人惊讶的是，在IGF-II存在下的衰减程度显著高于在PG存在下的程度。因此，我们的拨款提案的主要假设是，姜黄素的抑制效果将由动物模型的循环生长因子谱或CRC细胞中的自分泌生长因子决定。为了解决这一假设，在目标1中，我们将建立表达PG或IGF-II的等基因细胞系，并检测姜黄素对这些细胞的促凋亡和抗增殖作用。姜黄素对完整的结肠隐窝细胞的抑制作用也将被检测，这些细胞是由过度表达PG或IGFS的转基因小鼠制备的，或者是从野生型小鼠制备的。在目标2中，我们将检验饮食姜黄素对转基因小鼠结肠癌发生的所有阶段的剂量依赖效应，转基因小鼠在血液循环中或在肠粘膜中局部过度表达PG或IGF-II。PG和IGFS对结直肠癌和肠上皮(IEC)细胞的抗凋亡和促增殖作用的细胞内通路目前正在我们的实验室进行研究。姜黄素抑制IGFS和PG生长因子作用的机制目前尚不清楚。在目标3中，我们将研究姜黄素对PG或IGF-II激活的几种激酶/磷酸酶在等基因CRC和IEC细胞中的磷酸化/去磷酸化的影响。上述实验将使我们首次了解在存在与疾病病因相关的生长因子的情况下，姜黄素对结肠癌发生的相对有效性。这些研究的结果有望有助于为使用姜黄素类药物的结直肠癌制定基于机制的预防/治疗方案。

DESCRIPTION (provided by applicant): We now know that progastrins (PG) and insulin-like growth factors (IGFs) exert potent proliferative and anti- apoptotic effects on colon cancer (CRC) cells and can potentially function as co-carcinogens during all phases of colorectal carcinogenesis. Dietary agents, such as curcumin, inhibit the growth of CRC cells and inhibit colon carcinogenesis at both the pre-malignant and post-malignant stages of the disease. It is, however, not known if curcumin can inhibit the growth factor effects of autocrine and/or endocrine PG and IGF-II during colon carcinogenesis. Our preliminary studies suggest that the inhibitory effects of curcumin are attenuated in the presence of growth factors, such as IGF-II and PG; surprisingly the degree of attenuation was significantly higher in the presence of IGF-II than in the presence of PG. Therefore, the major hypothesis of our grant proposal is that the inhibitory efficacy of curcumin will be dictated by either the circulating growth factor profile of animal models or by the autocrine growth factors in CRC cells. To address this hypothesis, in Aim 1, we will develop isogenic cell lines that either express PG or IGF-II, and examine the pro-apoptotic and anti-proliferative potency of curcumin on these cells. Inhibitory effects of curcumin on intact colonic crypt cells, prepared from either transgenic mice over-expressing PG or IGFs or prepared from wild type mice, will also be examined. In Aim 2, we will examine dose-dependent effects of dietary curcumin against all phases of colon carcinogenesis in transgenic mice over-expressing PG or IGF-II, either in the circulation or locally within the intestinal mucosa. The intracellular pathways that mediate anti-apoptotic vs proliferative effects of PG and IGFs, on CRC and intestinal epithelial (IEC) cells, are being currently examined in our laboratory. The mechanisms by which curcumin inhibits the growth factor effects of IGFs and PG are unknown at the present time. In Aim 3 we will examine the effect of curcumin on the phosphorylation/dephosphorylation of several kinases/phosphatases that are activated in response to PG or IGF-II in isogenic CRC and IEC cells. The above experiments will allow us to learn for the first time the relative effectiveness of curcumin on colon carcinogenesis in the presence of growth factors relevant to the etiology of the disease. The results of these studies are expected to help in developing mechanism-based strategies for preventative/treatment protocols for CRC using curcumin like agents.