Progression Of Human Renal Cell Carcinoma Research Articles

Progression of Human Renal Cell Carcinoma via Inhibition of RhoA-ROCK Axis by PARG1

Renal cell carcinoma (RCC) is the most lethal urological malignancy with high risk of recurrence; thus, new prognostic biomarkers are needed. In this study, a new RCC antigen, PTPL1 associated RhoGAP1 (PARG1), was identified by using serological identification of recombinant cDNA expression cloning with sera from RCC patients. PARG1 protein was found to be differentially expressed in RCC cells among patients. High PARG1 expression is significantly correlated with various clinicopathological factors relating to cancer cell proliferation and invasion, including G3 percentage (P = .0046), Ki-67 score (p expression is also correlated with high recurrence of N0M0 patients (P = .0084) and poor prognosis in RCC patients (P = .0345). Multivariate analysis has revealed that high PARG1 expression is an independent factor for recurrence (P = .0149) of N0M0 RCC patients. In in vitro studies, depletion of PARG1by siRNA in human RCC cell lines inhibited their proliferation through inducing G1 cell cycle arrest via upregulation of p53 and subsequent p21Cip1/Waf1, which are mediated by increased RhoA-ROCK activities. Similarly, PARG1 depletion cells inhibited invasion ability via increasing RhoA-ROCK activities in the RCC cell lines. Conversely, overexpression of PARG1 on human embryonic kidney cell line HEK293T promotes its cell proliferation and invasion. These results indicate that PARG1 plays crucial roles in progression of human RCC in increasing cell proliferation and invasion ability via inhibition of the RhoA-ROCK axis, and PARG1 is a poor prognostic marker, particularly for high recurrence of N0M0 RCC patients.

Lymphangiogenesis and Angiogenesis in Conventional Renal Cell Carcinoma: Association with Vascular Endothelial Growth Factors A to D Immunohistochemistry

Lymphangiogenesis is associated with tumor progression in various cancers and is regulated by vascular endothelial growth factors (VEGFs). However, little is known about the pathologic roles of lymphangiogenesis in renal cell carcinoma (RCC). We investigated the relationships between various clinicopathologic features and lymphangiogenesis, angiogenesis, and expression of VEGFs in RCC. The TNM stage and grade of 107 conventional RCC were reviewed. Lymph vessel density (LVD) and microvessel density (MVD) were measured by quantitative immunohistochemistry using anti-D2-40 antibody and anti-CD34 antibody, respectively. Expression levels of VEGF-A, B, C, and D were examined by immunostaining. D2-40-positive lymphatic vessels were detected mainly in the peritumoral area. However, no significant difference was found between LVD in peritumoral areas of the RCC tissues and the normal kidney (P = 0.238). Intratumoral D2-40-positive lymphatic vessels were detected in only six specimens, and neither intratumoral nor peritumoral LVD correlated with the clinicopathologic features. VEGF-A expression correlated with MVD (r = 0.50, P <0.001), but not with LVD, and was also associated with pT stage, the presence of metastasis, and tumor grade. No other members of the VEGF family showed any correlation with LVD, MVD, or the clinicopathologic features. Lymphangiogenesis seems to play a minimal role in the progression of human RCC. Only VEGF-A, but not B, C, or D, was associated with the histopathologic features and MVD of RCC.

Tiam1 mutations in human renal-cell carcinomas.

Tiam1 activates the Rho-like GTPase Rac1, and studies indicate that Tiam1-Rac1 signaling affects invasion in different ways depending on the cell type studied. However, no investigations on Tiam1 in human tumors have been reported. Here, we show that for 4 of 5 human renal-cell carcinoma (RCC) cell lines the expression levels of Tiam1 tended to be inversely correlated with in vitro invasiveness, whereas no obvious correlation could be found between the expression levels of Rac1 and invasion. Subsequent mutation analysis of these cell lines revealed no mutations in Rac1 but up to 5 different point mutations in the Tiam1 gene. Of these, 1 mutation (A441G) was located in the NH2-terminal pleckstrin homology domain, which is essential for membrane localization and functional activity of Tiam1. By analysis of an additional 30 primary human RCCs, mutation A441G was found in 4 of 35 tumors and tumor cell lines (11.5%) but not in the respective normal kidney tissues. By enzymatic digestion, mutation A441G proved to be heterozygous, suggesting a dominant active function. This was supported by showing that stable over-expression of mutated A441G-Tiam1 induced transformation of NIH3T3 cells, as determined in a colony formation assay, whereas empty vector and wild-type Tiam1 failed to do so. In conclusion, a distinct Tiam1 mutation (A441G) was identified in several human RCCs. This mutation induced transformation of NIH3T3 cells and, hence, might play a major role in the progression of human RCCs. Further analyses on Tiam1 mutations in human tumors might give new clues to their role in tumor progression.

STATISTICALLY SIGNIFICANT EXPRESSION OF B-MYB IN CLINICALLY ADVANCED HUMAN RENAL-CELL CARCINOMAS

To find biologically critical factors for the tumor progression in human renal cell carcinoma (RCC), we examined expressions of c-myb and, c-myb homologous genes, A-myb and B-myb, in 34 primary human RCCs, normal kidneys and two metastatic tissues with Northern blot analysis. Seven cases (20%) exhibited positive B-myb expression. All 7 positive B-myb cases were associated with advanced stages and 5 of 7 cases had advanced metastasis. Interestingly, 2 metastatic tumors derived from the B-myb negative primary RCCs also exhibited B-myb expression. Statistical analysis proved that tumors with positive B-myb expression were significantly correlated with clinical stage III and IV (P<0.05). Four clinically advanced cases (12%) showed positive A-myb expression. These results suggest that B-myb gene expression might be involved in the progression of human RCCs. B-myb expression might be a good clinical marker for tumor aggressiveness and metastasis.