RasGRP3, a Ras guanyl releasing protein 3 that contributes to malignant proliferation and aggressiveness in human esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide; however, clinical and pathological parameters have limited ability in discriminating between clinically significant and indolent ESCC. Since RasGRP3 transcript levels have prognostic value in discriminating ESCC with different clinical aggressiveness, we decided to investigate its putative oncogenic role in ESCC. We found that RasGRP3 was highly expressed in ESCC cells. Suppression of endogenous RasGRP3 expression in esophageal cell lines reduced Ras-GTP formation as well as AKT phosphorylation. RasGRP3 suppression also inhibited cell invasion and migration and reduced proliferation, demonstrating the importance of RasGRP3 for the transformed phenotype of melanoma cells. Suppression of RasGRP3 expression in these cells inhibited downstream RasGRP3 responses and suppressed cell growth and migration, confirming the functional role of RasGRP3 in the altered behaviour of these cells. This suggests that RasGRP3 may function as a Ras activator in the phosphoinositide signalling pathway and may potentially serve as a new therapeutic target.