Clinical significance of Rho GDP dissociation inhibitor 2 in colorectal carcinoma

Small GTPase proteins, including RhoA, RhoB, RhoC, Rac1, and cdc42, are important molecules for linking cell shape and cell-cycle progression because of their role in both cytoskeletal arrangements and mitogenic signaling. Over-expression of wild-type or constitutively active forms of RhoA has been shown to induce invasive behavior in non-invasive rat hepatoma cells in vitro. In addition, over-expression of RhoC has been found in melanoma cells with increasing metastatic activity as well as inflammatory breast cancer. These results indicate that overexpression of Rho proteins contributes to cancer cell invasion and metastasis. Rho GDP dissociation inhibitor 2 (RhoGDI2) was recently shown to act as a metastasis suppressor gene in bladder cancer. The purpose of this study was to clarify the clinical significance of this gene expression in patients with colorectal carcinoma. Fifty pairs of normal mucosa and cancer specimens obtained at the time of surgery from patients with colorectal cancer (CRC) were subjected to reverse transcription-polymerase chain reaction for RhoGDI2. No patients with RhoGDI2-higher expression tumors had liver metastasis (0 in 8 cases); however, 33.3% (14 in 42 cases) of patients with RhoGDI2-lower expression tumors had liver metastasis. With regard to outcome in relation to RhoGDI2-positivity, RhoGDI2-higher expression tumors had a significant correlation with superior relapse-free survival (RFS) time as compared to RhoGDI2-lower expression tumors in stage III CRC (log-rank test, P < 0.05). Moreover, multivariate analysis indicated that RhoGDI2 was an independent prognostic factor for RFS. RhoGDI2 is a novel predictor of RFS in patients with colorectal carcinoma.