Growth Factors, Curcumin and Colon Carcinogenesis

描述（由申请人提供）：我们现在知道前胃泌素（PG）和胰岛素样生长因子（IGF）对结肠癌（CRC）细胞发挥强效增殖和抗凋亡作用，并可能在结肠直肠癌发生的所有阶段中作为共致癌物发挥作用。膳食剂，如姜黄素，抑制CRC细胞的生长，并在疾病的癌前和癌后阶段抑制结肠癌发生。然而，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的生长因子效应。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的存在下减弱;令人惊讶的是在IGF-II存在下的减毒程度显著高于在PG存在下的减毒程度。因此，我们的拨款提案的主要假设是姜黄素的抑制功效将由动物模型的循环生长因子谱决定，由CRC细胞中的自分泌生长因子引起。为了解决这一假设，在目标1中，我们将开发表达PG或IGF-II的等基因细胞系，并检查姜黄素对这些细胞的促凋亡和抗增殖效力。还将检查姜黄素对从过表达PG或IGF的转基因小鼠或从野生型小鼠制备的完整结肠隐窝细胞的抑制作用。在目标2中，我们将研究饮食姜黄素对过表达PG或IGF-II的转基因小鼠结肠癌发生的所有阶段的剂量依赖性作用，无论是在循环中还是在肠粘膜内。目前，我们实验室正在研究PG和IGFs对CRC和肠上皮（IEC）细胞介导抗凋亡与增殖作用的细胞内途径。姜黄素抑制IGFs和PG的生长因子效应的机制目前尚不清楚。在目标3中，我们将研究姜黄素对在等基因CRC和IEC细胞中响应PG或IGF-II而激活的几种激酶/磷酸酶的磷酸化/去磷酸化的影响。上述实验将使我们首次了解姜黄素在与疾病病因相关的生长因子存在下对结肠癌发生的相对有效性。这些研究的结果预计将有助于开发基于机制的策略，用于使用姜黄素类药物预防/治疗CRC。

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.