Identification and Characterization of Human Colorectal Cancer Cluster Predominantly Expressing EP3 Prostanoid Receptor Subtype

Colorectal cancer (CRC) is one of the common types of cancer in humans. Prostaglandin E-2 (PGE(2)) is a well-known mediator of colorectal cancer through stimulation of four E-type prostanoid (EP) receptor subtypes: EP1, EP2, EP3, and EP4 receptors. All subtypes of EP receptors are involved in CRC promotion or malignancy. However, the characteristics of CRC that highly expresses EP receptor subtypes have not been clarified. In the present study, we classified CRC from a cancer genomic database and identified CRC clusters which highly express EP receptor subtypes. Most of these clusters predominantly expressed one subtype of EP receptor and showed different gene expression patterns. Among them, we focused on the cluster highly expressing the EP3 receptor (CL-EP3). As the result of characterization of gene expression, CL-EP3 was characterized as: epithelial mesenchymal transition (EMT)-induced progressed cancer with activation of transforming growth factor-beta pathway, activation of hypoxia-inducible factor-1 alpha, and suppression of runtrelated transcription factor 3. Since we previously reported that EP3 receptor is involved in and induce colon cancer cell migration, EP3 receptor-expressing CRC may induce metastasis through these signaling pathways. Thus, the findings suggest the effectiveness of cancer clustering by gene expression of the EP receptor subtype to elucidate the mechanism of human CRC.