CALN1 hypomethylation as a biomarker for high-risk bladder cancer

Background DNA methylation in cancer is considered a diagnostic and predictive biomarker. We investigated the usefulness of the methylation status of CALN1 as a biomarker for bladder cancer using methylation-sensitive restriction enzyme (MSRE)-quantitative polymerase chain reaction (qPCR). Methods Eighty-two bladder cancer fresh samples were collected via transurethral resection of bladder tumors. Genomic DNA was extracted from the samples, and MSRE-qPCR was performed to determine the CALN1 methylation percentage. Reverse transcription-qPCR was performed to assess the correlation between CALN1 methylation and mRNA expression. The association between CALN1 methylation percentage and clinicopathological variables of all cases and intravesical recurrence of non-muscle-invasive bladder cancer (non-MIBC) cases were analyzed. Results Of the 82 patients, nine had MIBC and 71 had non-MIBC who had not undergone total cystectomy. The median CALN1 methylation percentage was 79.5% (interquartile range: 51.1-92.6%). The CALN1 methylation percentage had a negative relationship with CALN1 mRNA expression (Spearman's [rho] = - 0.563 and P = 0.012). Hypomethylation of CALN1 was associated with advanced tumor stage (P = 0.0007) and histologically high grade (P = 0.018). Furthermore, multivariate analysis revealed that CALN1 hypomethylation was an independent risk factor for intravesical recurrence in non-MIBC patients (hazard ratio 3.83, 95% confidence interval; 1.14-13.0, P = 0.031). Conclusion Our findings suggest that CALN1 methylation percentage could be a useful molecular biomarker for bladder cancer. Keywords: Bladder cancer, CALN1, Methylation analysis, Methylation-sensitive restriction enzyme (MSRE), Molecular diagnosis technique, Transurethral resection of bladder tumor (TURBT)