Prognostic significance of phosphorylated RON in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the most common type of esophageal cancer. RON is a transmembrane receptor overexpressed in various cancers; however, the clinical significance of its phosphorylated form (pRON) is not fully deciphered. This report is the first to investigate the expression and clinical significance of pRON in human ESCC. Quantitative polymerase chain reaction revealed an up-regulation of RON mRNA in 70% (7/10) of ESCC tissues when compared to the adjacent nontumor tissues. An overexpression of pRON protein was found in most of the ESCC cell lines studied (4/5) when compared to two non-neoplastic esophageal epithelial cells using immunoblot. In 64 ESCC tissues, pRON was localized at the cell membrane, cytoplasm and nucleus in 15 (23.4%), 63 (98.4%) and 61 (95.3%) cases using immunohistochemistry. Patients having high expression of cytoplasmic pRON significantly associated with shorter median survival when compared to those with low expression (25.41 months vs. 14.43 months), suggesting cytoplasmic pRON as a potential marker for poor prognosis in ESCC patients.