The Role of Ras Oncogene Product p21 in Human thyroid tissue

最近的数据表明，ras癌基因产物调节细胞膜上几种酶对细胞外信号的反应。膜组分是从六个人甲状腺癌和邻近的正常甲状腺组织中新鲜制备的。用特异性抗血清(NCC-RAS-004)进行Western blotting分析，检测膜组分中p21(ras癌基因产物)的含量。用NAD和百日咳毒素标记的方法监测Gi亚单位的水平。用放射免疫法测定在10mU/mlTSH存在下膜部分孵育30min时产生的环磷酸腺苷的腺苷环酶活性。在Western blotting分析中，单抗NCC-RAS-004在正常甲状腺组织和癌组织的细胞膜中均检测到清晰的p21条带。当用密度计检测条带的染色强度时，癌组织的p21条带的强度是…的两倍或更多6例中有5例高于邻近正常甲状腺。未发现p21异常迁移。与其他研究一致，百日咳毒素标记了正常和癌甲状腺膜中的41 KDa条带(GI)。然而，在6例患者中，有5例癌组织膜减少了50-10%的GI标记水平。Ras癌基因产物p21的表达水平与腺苷环化酶对TSH的反应增强程度呈显著正相关，与胃肠道反应水平呈负相关。因此，ras产生细胞对多种激素和生长因子高度敏感，在整个动物的生理条件下，这种高度敏感可能对这些蛋白质的致瘤性有很大的贡献。腺苷环化酶激活对TSH敏感性的改变是否由ras癌基因或其产物介导，尚需进一步研究。较少

Recent data suggest that the ras oncogene products modulate the responsiveness of several enzymes in the cell membrane that respond to the extercellular singnels.The membrane fraction were freshly prepared from six human thyroid carcinomas and adjacent normal thyroid tissues. Western blotting analysis was used to determine the amount of p21 (ras oncogene product) in membrane fraction using specific antisera (NCC-RAS-004). Levels of Gi subunit were monitored by labeling with [^<32>P] NAD and pertussis toxin. The adenyalte cylase activities were measured by RIA of the cyclic AMP generated during 30 min incubation of the membrane fraction in the presence of 10mU/ml TSH. In western blotting analysis, the monoclonal antibody NCC-RAS-004 detected clear band of p21 in membranes from both normal and carcinoma thyroid tissues. When the staining intensity of bands was examined with a densitometer, the intensity of the p21 band of carcinomas tissues was stronger by two-fold or more compared with … More that of adjacent normal thyroidas in 5 of 6 cases. No abnormally migrating p21 was detected in these cases. In agreement with other studies, pertussis toxin labeled a 41KDa band (Gi) in both normal and carcinoma thyroid membranes. However the membranes from carcinomas reduced the level of labeling of Gi by 50-10% in 5 of 6 cases. The level of enhanced expression of p21 were significantly correlated with the level of increased response of the adenylate cyclase to TSH and inversely related to the level of Gi assessed by ADP-ribosylation with petrussis toxin.Our results suggest that the ras oncogene product P21 play enhancing role in adenylate cyclase system and its modulation by the G protein. Thus a ras producing cell is hypersensitive to a variety of hormones and growth factors and this hypersensitivity might contribute significantly to the oncogenicity of these proteins under physiological conditions in the whole animal. Further studies are required to clarify whether the changes in sensitivity of adenyalte cyclase activation to TSH are mediated ras oncogene or its products. Less