Differential expression of lysophosphatidic acid receptor-2 in intestinal and diffuse type gastric cancer

Background and Objectives: Lysophosphatidic acid (LPA), a natural phospholipid, can modulate diverse cellular responses through LPA receptor, LPA(1-4). Although LPA, is known to be widely expressed in human tissues, the distribution of other LPA receptors is not characterized in malignant tissues. Recently, it was reported that malignant transformation resulted in aberrant expression of LPA(2) in a various type of cancer, suggesting the positive role of LPA2 in tumor development. Methods: We investigated the expression of the LPA2 receptor immunohistochemically in 204 gastric cancers and analyzed the relationship between the expression of LPA2 and clinicopathological features. Results: LPA(2) was preferentially expressed (67%) in intestinal-type cancer that was significantly higher than that in diffuse-type cancer (32%, P < 0.0001). The expression of LPA2 showed correlation with a higher rate of lymphatic and venous invasion, lymphatic metastasis, and resultingly tumor stage in diffuse-type cancer, but not in intestinal-type cancer. Conclusions: Our results highlight the possibility that LPA2 expression is an important process in the carcinogenesis of gastric cancer, especially in intestinal-type cancer. Since LPA can transactivate HGF receptor (c-Met) as well as EGF-receptor, LPA may promote the progression of gastric cancer in diffuse-type with high expression of c-Met. The development of LPA(2)-specific antagonists might have future therapeutic relevance in the treatment as well as prevention of gastric cancer.