Kahl-Rainer P, Karner-Hanusch J, Weiss W, Marian B
Institute for Tumor Biology-Cancer Research, University of Vienna, Austria.
Carcinogenesis. 1994 Apr;15(4):779-82. doi: 10.1093/carcin/15.4.779.
Protein kinase C (PKC) isoenzyme patterns were analyzed from human colonic epithelial cells of normal, premalignant and malignant origin. PKCs alpha, beta and zeta were found predominantly in the cytosol and the subtypes delta, epsilon and neta almost exclusively in the particulate fraction. Of the isoenzymes found beta, epsilon and neta were low in abundance and could only be detected after partial purification of cellular fractions on DE52-cellulose. Only PKC beta was similar in abundance in normal mucosa, premalignant and malignant colonic epithelial cells, while all other isoenzymes were decreased in abundance in tumor cells. The loss of PKC protein in tumor cells correlated with a loss in enzyme activity, as has been described before by other groups, especially affecting the Ca(2+)-dependent isoenzymes. On the other hand, activation of PKC by phorbol ester treatment in vivo was only possible in carcinoma cells (4/4) and a subset of adenomas (3/7). Normal human colonic epithelial cells did not respond to TPA treatment with either stimulation of PKC activity or translocation of cytosolic enzymes to the particulate fraction. Instead, TPA treatment resulted in a rapid loss of protein for the isoenzymes alpha, delta and to a lesser degree also beta. We assume that this reflects qualitative differences in response between normal and tumor cells, that may be due to the differences in isoenzyme distribution.
对源自正常、癌前和恶性的人结肠上皮细胞的蛋白激酶C（PKC）同工酶模式进行了分析。PKCα、β和ζ主要存在于胞质溶胶中，而亚型δ、ε和η几乎仅存在于颗粒部分。在所发现的同工酶中，β、ε和η含量较低，只有在通过DE52纤维素对细胞组分进行部分纯化后才能检测到。只有PKCβ在正常黏膜、癌前和恶性结肠上皮细胞中的丰度相似，而所有其他同工酶在肿瘤细胞中的丰度均降低。肿瘤细胞中PKC蛋白的丢失与酶活性的丧失相关，正如其他研究小组之前所描述的那样，尤其影响依赖Ca(2+)的同工酶。另一方面，在体内通过佛波酯处理激活PKC仅在癌细胞（4/4）和一部分腺瘤（3/7）中可行。正常人结肠上皮细胞对TPA处理既没有PKC活性的刺激，也没有胞质酶向颗粒部分的转位反应。相反，TPA处理导致同工酶α、δ以及程度较轻的β的蛋白迅速丢失。我们推测这反映了正常细胞和肿瘤细胞反应的质的差异，这可能是由于同工酶分布的差异所致。
