Overexpression of Rho GDP-Dissociation Inhibitor Alpha Is Associated with Tumor Progression and Poor Prognosis of Colorectal Cancer Liang Zhao,†,‡ Hui Wang,§ Jianming Li,‡ Yawei Liu,| and Yanqing Ding*,†,‡ Department of Pathology, Nanfang Hospital, Southern Medical University, Guangzhou, China, Department of Pathology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China, State Key Laboratory of Oncology in Southern China and Department of Experimental Research, Sun Yat-sen University Cancer Center, Guangzhou, China, and Department of Pathophysiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China Received April 10, 2008
The GDP dissociation inhibitors (GDIs) are pivotal regulators of Rho GTPases, which are essential for tumor progression, particularly in the area of metastasis. One member of GDIs was identified as RhoGDI (Rho GDP-dissociation inhibitor alpha, or RhoGDIR), but little is known about this protein in tumors. In this study, we used comparative proteomic analysis to show that RhoGDI is markedly up-regulated in metastatic colorectal cancer (CRC). The elevated level of RhoGDI protein in metastatic CRC was confirmed by Western blot at the tissue (n ) 24) and cell (n ) 6) levels. Further, we analyzed RhoGDI protein expression in 126 clinicopathologically characterized CRC cases by immunohistochemistry. Statistical analysis showed that there were significant differences of RhoGDI overexpression in patients categorized according to tumor invasion (p ) 0.018), lymph node metastasis (p ) 0.001) and clinical stage (p ) 0.009). A trend was also identified between high expression of RhoGDI and shorter overall survival (p ) 0.013). In the present work, we also analyzed the effect of RhoGDI on CRC cell line. Gene transfection-mediated overexpression of RhoGDI in HT29 cells, containing a low detectable level of endogenous RhoGDI, resulted in a significant increase in cell proliferation and motility in vitro. These data suggest that RhoGDI may promote CRC progression and metastasis by stimulating tumor cell growth and migration. Keywords: colorectal cancer • metastasis • poor prognosis • proteomics • Rho GDP-dissociation inhibitor alpha
Introduction Colorectal cancer (CRC) is the third most common malignancy in the world, and represents the main cause for cancer deaths in Europe and the U.S.A.1,2 In China, CRC occupies the fifth position in the mortalities caused by cancer, and its incidence still continues to increase.2 Despite significant improvement in the treatment of CRC over the last decades, thanks to the introduction of new surgical techniques, improved radiotherapy techniques, and the use of chemotherapy, the overall survival rate of patients with CRC has not changed markedly.3 One of the major factors for the poor outcome is metastasis. Therefore, it is critical for us to advance in early diagnosis, before metastasis in distant organs occurs, in order to increase the survival rate of patients with CRC. Recent research revealed that the Rho family GTPases may play an important role in the process of tumor invasion and metastasis.4–6 * Correspondence to: Yanqing Ding, Department of Pathology, Southern Medical University, Guangzhou, China. E-mail:
[email protected]. † Nanfang Hospital. ‡ Department of Pathology, Southern Medical University. § Sun Yat-sen University Cancer Center. | Department of Pathophysiology, Southern Medical University.
3994 Journal of Proteome Research 2008, 7, 3994–4003 Published on Web 07/24/2008
Rho family GTPases were initially cloned on the basis of their similarity to the Ras oncogenes. So far, more than 20 members have been identified, and these can be further subdivided according to their sequence and function. Activation of growthfactor receptors and integrins can promote the exchange of GDP for GTP on Rho proteins and GTP-bound Rho proteins interact with a range of effector molecules to modulate their activity and localization.7 The regulation of these effector proteins ultimately leads to changes in cell behavior. It is clear that Rho family GTPases are involved in the control of cell morphology and motility in untransformed cells. Given the role of Rho GTPases in the regulation of cell motility in normal cells,5,7–9 and their aberrant regulation in tumor cells,6 it is likely that they are involved in the invasive phenotype of tumor cells. The importance of Rho protein in cancer progression, particularly in the area of metastasis, is becoming increasingly evident. Recently, numerous in vitro studies have indicated the Rho proteins are involved in cell motility.4 However, it is difficult to extrapolate these studies to the tumor environment. So how might Rho GTPases promote metastasis in vivo? In our previous studies, to screen metastasis-associated genes, we prepared a cDNA microarray of tumor metastasis10.1021/pr800271b CCC: $40.75
2008 American Chemical Society
research articles
RhoGDI: Association with Tumor Progression/Poor Prognosis of CRC Table 1. Clinicopathological Data of All the Subjects in Screening and Validation Analysis screening analysis characteristics
Gender Male Female Age (years)
