An Innovative Integrative Method for Bladder Cancer Diagnosis

Abstract

Bladder cancer is the most common and lethal cancer of the urinary system in the world [1]. Three-quarters of patients would present with non-muscle-invasive bladder cancer (NMIBC). Although it does not invade the muscle, patients have the risk of recurrence, with a recurrence rate of 70%. Frequent tests for surveillance and repeated treatment for recurrent bladder cancer pose a substantial economic burden [2]. Cystoscopy followed by biopsy is the gold standard for surveillance due to its high sensitivity; however, this approach is costly and invasive [3]. Noninvasive methods by urine testing are attractive alternatives since urine is easy to obtain. Urine cytology detects bladder cancer with high specificity but with low sensitivity. Although UroVysion fluorescence in situ hybridization (FISH) shows an increased sensitivity over urine cytology from 25%– 35% to 60%–80%, the sensitivity of FISH is still low and unsatisfactory for patients with low-grade or small tumors [4]. Thus, novel markers are needed to detect and monitor tumor recurrence in bladder cancer patients. DNA methylation plays a vital role in the epigenetic regulation of tumorassociated genes for decades [5]. Unlike somatic mutation, DNA methylation features tissue specificity and expression consistency. Hypermethylation of tumor suppressor genes occurs in the early stage of tumorigenesis; therefore, it can be detected early [6]. Methylation of CpG sites in urine is a promising marker to detect or monitor bladder cancer [7, 8]. A panel of 15 methylation markers termed Bladder EpiCheckTM was introduced in Europe to monitor NMIBC recurrence [9]. In the multicenter clinical trial, Bladder EpiCheckTM showed a sensitivity of 68.2% and a specificity of 88.0%, but the sensitivity increased to 91.7% as the low-grade Ta recurrences were excluded. A method based on four methylation markers (VIM, RASSF1A, GDF15, and TMEFF2) were reported to diagnose bladder cancer with a sensitivity of 82%. However, this result is not yet verified, and its specificity of 53% also limited the application [7]. Another multicenter study combined the three-gene methylation (CFTR, SALL3, and TWIST1) results and cytology results. It can identify bladder cancer with a sensitivity of 96% and a specificity of 40% [10]. Up to now, the methylation markers showed great potential to surveil bladder cancer recurrence with good sensitivities, but the specificities are relatively low. Furthermore, DNA methylation detection did not improve the efficacy of identifying low-grade recurrence, warranting new and innovative approaches. Chen et al. [11] reported a novel method, urine tumor DNA Methylation MassARRAY, termed utMeMA, to detect urine tumor DNA methylation by MassARRAY. They first identified 26 significant methylation markers of bladder cancer in the combined analyses of cohorts from Sun Yat-sen Memorial Hospital (SYSMH), The Cancer Genome Atlas (TCGA), and the Gene Expression Omnibus (GEO) [12] database. A diagnostic model that included only two CpG markers (cg21472506 and cg11437784) was built to distinguish bladder cancer patients’ subtypes. This model was trained and tested in the SYSMH cohort of 313 samples and subsequently validated in a multicenter, prospective, independent cohort of 175 samples. The overall sensitivity was 90.0%, and the specificity was 83.1%, which performed better than urine cytology (sensitivity of 58%) and FISH (sensitivity of 68.7%). For NMIBC patients, the utMeMA showed a higher sensitivity of 85.5% in modeling and validation cohorts than 67% of the aforementioned Bladder EpiCheckTM [9]. Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15213, USA