Shida Dai, Kitayama Joji, Yamaguchi Hironori, Yamashita Hiroharu, Mori Ken, Watanabe Toshiaki, Nagawa Hirokazu
Department of Surgical Oncology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Japan.
World J Gastroenterol. 2005 Sep 28;11(36):5638-43. doi: 10.3748/wjg.v11.i36.5638.
To examine whether lysophosphatidic acid (LPA) induces phosphorylation of c-Met and epidermal growth factor receptor (EGFR), both of which have been proposed as prognostic markers of colorectal cancer, and whether LPA induces cyclooxygenase-2 (COX-2) expression in human colon cancer cells.
Using a human colon cancer cell line, LoVo cells, we performed immunoprecipitation analysis, followed by Western blot analysis. We also examined whether LPA induced COX-2 expression, by Western blot analysis.
Immunoprecipitation analysis revealed that 10 micromol/L LPA induced tyrosine phosphorylation of c-Met and EGFR in LoVo cells within a few minutes. We found that c-Met tyrosine phosphorylation induced by LPA was not attenuated by pertussis toxin or a matrix metalloproteinase inhibitor, in marked contrast to the results for EGFR. In addition, 0.2-40 micromol/L LPA induced COX-2 expression in a dose-dependent manner.
Our results suggest that LPA acts upstream of various receptor tyrosine kinases (RTKs) and COX-2, and thus may act as a potent stimulator of colorectal cancer.
研究溶血磷脂酸（LPA）是否诱导c-Met和表皮生长因子受体（EGFR）磷酸化（二者均被认为是结直肠癌的预后标志物），以及LPA是否诱导人结肠癌细胞中环氧化酶-2（COX-2）的表达。
利用人结肠癌细胞系LoVo细胞，我们先进行免疫沉淀分析，随后进行蛋白质印迹分析。我们还通过蛋白质印迹分析检测LPA是否诱导COX-2表达。
免疫沉淀分析显示，10微摩尔/升LPA在几分钟内即可诱导LoVo细胞中c-Met和EGFR的酪氨酸磷酸化。我们发现，与EGFR的结果形成显著对比的是，百日咳毒素或基质金属蛋白酶抑制剂不会减弱LPA诱导的c-Met酪氨酸磷酸化。此外，0.2 - 40微摩尔/升LPA以剂量依赖的方式诱导COX-2表达。
我们的结果表明，LPA作用于多种受体酪氨酸激酶（RTK）和COX-2的上游，因此可能是结直肠癌的一种强效刺激物。
