Division of Cancer Biology and Bioinformatics, Department of Life Science, Kinki University, Higashiosaka, Osaka, Japan.
Mol Carcinog. 2011 Aug;50(8):635-42. doi: 10.1002/mc.20750. Epub 2011 Mar 3.
Aberrant expressions of lysophosphatidic acid (LPA) receptor genes have been reported in tumor cells. Here, we measured the expression levels of the Lpa5 gene and its DNA methylation status in rat tumor cells, and investigated cell growth effects of LPA in Lpa5 expressed cells. Real-time reverse transcription (RT)-polymerase chain reaction (PCR) analysis revealed that increased expressions of the Lpa5 gene were detected in rat liver-derived hepatoma RH7777 and lung-derived adenocarcinoma RLCNR cells. For the analysis of methylation status, bisulfite sequencing was performed with RH7777 and RLCNR cells and compared with other tumor cells and liver epithelial cells. The Lpa5 gene in Lpa5 unexpressed cells and liver epithelial cells were highly methylated in the 5' upstream region. In contrast, the Lpa5 gene in RH7777 and RLCNR cells was unmethylated, correlating with increased expressions of Lpa5. In the assays for cell growth effects of LPA, LPA enhanced cell proliferation and motility in RH7777 and RLCNR cells. LPA also stimulated cell invasion in RLCNR, but not in RH7777 cells. In rat liver and lung tumors induced by nitroso-compounds, 4 out of 6 hepatocellular carcinomas and 5 out of 6 lung adenocarcinomas indicated increased expressions of Lpa5 with unmethylated status. These results suggest that increased Lpa5 expressions due to aberrant DNA methylation may be involved in the acquisition of growth advantage of rat tumor cells.
溶血磷脂酸 (LPA) 受体基因的异常表达已在肿瘤细胞中报道。在这里，我们测量了大鼠肿瘤细胞中 Lpa5 基因的表达水平及其 DNA 甲基化状态，并研究了 LPA 在 Lpa5 表达细胞中的细胞生长效应。实时逆转录（RT）-聚合酶链反应（PCR）分析显示，在大鼠肝源性肝癌 RH7777 和肺源性腺癌 RLCNR 细胞中检测到 Lpa5 基因的表达增加。为了分析甲基化状态，对 RH7777 和 RLCNR 细胞进行了亚硫酸氢盐测序，并与其他肿瘤细胞和肝上皮细胞进行了比较。Lpa5 未表达细胞和肝上皮细胞中的 Lpa5 基因在 5'上游区域高度甲基化。相比之下，RH7777 和 RLCNR 细胞中的 Lpa5 基因未甲基化，与 Lpa5 的表达增加相关。在 LPA 对细胞生长效应的测定中，LPA 增强了 RH7777 和 RLCNR 细胞的增殖和迁移。LPA 还刺激 RLCNR 中的细胞侵袭，但不刺激 RH7777 细胞。在亚硝化合物诱导的大鼠肝和肺癌肿瘤中，6 个肝细胞癌中有 4 个和 6 个肺腺癌中有 5 个显示 Lpa5 表达增加，且甲基化状态未甲基化。这些结果表明，由于异常 DNA 甲基化导致的 Lpa5 表达增加可能参与了大鼠肿瘤细胞获得生长优势。
