RBBP8 and bladder transitional cell carcinoma: However, a significant increased RBBP8 promoter methylation was observed for high-grade bladder tumors, including pTa high-grade carcinomas, (mean methylation 20.9%; s.d. ± 4.4%) compared to low-grade BLCA (mean methylation 2.4%; s.d. ± 1.4%) (Fig. 4d).