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MEVALONATE DYSREGULATION--POTENTIAL THERAPY COLON CANCER

甲羟戊酸失调——结肠癌的潜在治疗方法

基本信息

批准号：
2414247
负责人：
SELWYN A BROITMAN
金额：
$ 22.12万
依托单位：
BOSTON UNIVERSITY MEDICAL CAMPUS
依托单位国家：
美国
项目类别：
财政年份：
1994
资助国家：
美国
起止时间：
1994-07-01 至 1999-04-30
项目状态：
已结题

项目摘要

Certain colon tumor hepatic metastases exhibit a deficiency of LDL receptors (LDL-R); additionally, colon tumor cell lines, unlike normal fibroblasts or hepatocytes, are unable to reverse a mevinolin imposed inhibition of HMGCoA reductase (HMGCoA-R) in the presence of LDL. Receptor deficiency could lead to, or result from, an enhanced activity of HMGCoA- R, the key enzyme regulating synthesis of mevalonate and its derivatives. Due to the central role mevalonate metabolism plays in mammalian cells, higher endogenous concentrations of the constituents of this pathway could affect the degree to which the ras protein is incorporated into the plasma membrane, potentially permitting a higher degree of ras activity in such colonic tumors. Thus an enhancement of ras activation is potentially a selective force in the development of colon cancers that may lead to a deficiency in LDL-R expression, or an uncoupling of this pathway to cellular growth needs. The magnitude of the dysregulation of the reductase and its potential effect on the expression of the product of the ras oncogene will be determined to examine the etiologic importance of these changes in the development of certain colon cancers. The response of the cells to either mevinolin inhibition of Reductase, or growth in the presence of exogenous sterols as LDL, will be assessed in vitro and in vivo in regard to: 1) HMGCoA-R activity, and 2)transcription of the LDL-R and HMGCoA-R genes. The role of mevinolin treatment in anchorage independent growth in vitro in relation to the ras protein's: 1)isoprenylation 2) membrane association and 3) activity, will be evaluated. The ability of mevinolin treatment to affect the expression of the ras protein in vivo will be determined using tumors implanted into the hepatic site of nude mice. Intrasplenic inoculations of the tumors will be accomplished as an assessment of the impact of mevinolin treatment (ras isoprenylation) upon the metastatic propensity of the tumors in vivo. The impact of exogenously supplied human LDL upon mevinolins action will be determined. The significance of dysregulations of this pathway which can lead to or be caused by LDL-R deficiency or loss will be evaluated in human colonic tissues ranging from adenomas to carcinoma in situ and hepatic metastases by IgGC-7 staining for LDL-R, northern blot for both LDL-R and HMGCoA-R gene expression, and concurrent analysis of the membrane expression and transformed character of cellular ras genes by FITC and PCR techniques. An understanding of the control of the mevalonate pathway in colon tumors may provide a cohesive theory incorporating the proliferative response in normal and transformed colonic mucosal cells in relation to loss of LDL-R function, subsequent dysregulation of the mevalonate/cholesterol biosynthetic pathway, farnesylation of the ras protein, and the oncogenic process.

某些结肠癌肝转移瘤显示低密度脂蛋白缺乏受体(LDL-R)；此外，结肠癌细胞系不同于正常成纤维细胞或肝细胞不能逆转施加的梅维诺林低密度脂蛋白对HMGCoA还原酶(HMGCoA-R)的抑制作用。受体缺乏可能导致或导致HMGCoA活性增强- R是调节甲氧戊酸及其衍生物合成的关键酶。由于甲氧戊酸在哺乳动物细胞中的代谢起着中心作用，较高的内源浓度的这一途径的成分可以影响ras蛋白结合到血浆中的程度膜，潜在地允许更高程度的ras活性结肠肿瘤。因此，增强ras激活可能是一种结肠癌发生中的选择性力量，可能导致低密度脂蛋白受体表达不足，或这一途径的解偶联细胞生长需要。还原酶失调的程度及其对ras产物表达的潜在影响癌基因将被确定为检查这些疾病的病因学重要性某些结肠癌的发展变化。美国政府的回应细胞要不是甲氧诺林抑制还原酶，就是生长在外源性甾醇如低密度脂蛋白的存在，将在体外和在体内涉及：1)HMGCoA-R活性；2)低密度脂蛋白受体转录和HMGCoA-R基因。梅维诺林在支抗治疗中的作用体外独立生长与ras蛋白的关系： 1)异丙二烯基化2)膜缔合和3)活性，将已评估。梅维诺林治疗对血管内皮细胞生长因子表达的影响体内的ras蛋白将通过将肿瘤移植到裸鼠肝脏部位。肿瘤的脾内接种将是作为对梅维诺林治疗(RAS)影响的评估异丙二烯基化)对体内肿瘤转移倾向的影响。这个外源性供应的人低密度脂蛋白对美维诺林作用的影响下定决心。这一通路的异常调节的意义导致或由低密度脂蛋白受体缺乏或损失将在人结肠组织从腺瘤到原位癌和肝转移瘤低密度脂蛋白受体的IgGC-7染色和Northern印迹分析低密度脂蛋白受体和HMGCoA-R基因的表达，并同时分析细胞ras基因的膜表达及转化特性 FITC和聚合酶链式反应技术。对甲氧戊酸控制的几点认识结肠癌中的通路可能提供一个凝聚力理论，其中包括正常和转化的结肠粘膜细胞的增殖反应与低密度脂蛋白-受体功能丧失，随后的调节失调有关甲氧戊酸/胆固醇的生物合成途径，ras的法尼化蛋白质和致癌过程。