Expression analysis of VEGF-A and VEGF-B: relationship with clinicopathological parameters in bladder cancer

The present investigation was conducted first to determine whether correlation exists between VEGF-A and -B mRNA levels and clinicopathological parameters and to assess their prognostic value in bladder cancer, then to clarify the expression level and biological significance of VEGF-A isoforms. Total RNA was isolated from 37 specimens of bladder cancer. Northern blot analysis revealed that VEGF-B mRNA was not expressed either in normal urothelium or in bladder cancer and detected three VEGF-A transcripts of 5.2, 4.5 and 1.7 kb in length, respectively. The VEGF-A transcript levels were greater in cancer tissues than in normal urothelium. They were significantly higher in pT2-T4 than in pTa and pT1 urothelial tumors and thus, were correlated to the pathologic stage. Contrary to the 4.5 kb transcript, elevated expression of the 5.2 and 1.7 kb transcripts was correlated with the histologic grade and the presence of carcinoma in situ. Patients with higher VEGF-A mRNA levels had a significantly shorter survival without progression compared to those with lower levels. Three VEGF-A splice variants were detected by southern blotting namely, VEGF121, 165 and 189. The expression intensity of each isoform was evaluated by quantitative real-time RT-PCR in 20 new fresh frozen recent tumors. VEGF121 and VEGF165 were expressed at the similar level. On the contrary, they were significantly more expressed than VEGF189 (p<0.05). The three isoforms were higher expressed in pT2 bladder cancers than in pTa tumors (p<0.05). There was only a significant correlation between the increased expression level of VEGF121 and 165 and the histological grade of the lesion (p<0.05). To conclude, VEGF-A mRNA level is a potential prognostic indicator of progression in bladder cancer as well as the expression level of the different VEGF-A splice variants.