Current and emerging bladder cancer biomarkers with an emphasis on urine biomarkers

Introduction: Bladder cancer detection typically requires unpleasant and costly cystoscopy, a procedure potentially harmful and often accompanied by variable adverse effects. The use of urine analysis as a noninvasive method is of great scientific interest since it is enriched in tumor-related proteins, DNA and RNA which can provide a molecular landscape with multiple alterations identified in bladder cancer. Areas covered: Current sensitivity, specificity and diagnostic accuracy of FDA approved urine-based assays are still suboptimal with none of them routinely used by clinics. The recent introduction of RNA/DNA based bladder cancer tests, some of them commercially available, establishes a promising new horizon of clinical applicability. Expert opinion: There is growing evidence toward the use of minimally invasive ‘liquid biopsies’ to identify biomarkers in urothelial malignancy. Urine has been identified as an optimal noninvasive source of proteins, DNA and RNA; therefore, it has been identified as a type of liquid biopsy likely to soon be routine clinical practice. Cell-free proteins and peptides, exosomes, cell-free DNA, methylated DNA and DNA mutations, circulating tumor cells, miRNA, lncRNA, rtRNA and mRNAs, have been assessed in urine specimens. However, lack of well-designed multicenter clinical studies remain as important limitation, and therefore, precludes their use in clinical practice.