Bladder cancer genomics

Abstract

Until recently, the treatment of bladder cancer, for several years, was limited to surgery and to immunotherapy or chemotherapy. Currently, the extensive analysis of molecular alterations has led to novel treatment approaches. The advent of polymerase chain reaction and genomic hybridization techniques has allowed to investigate alterations involved in bladder cancer at DNA level. By this way, bladder cancers can be classified as papillary or non-papillary based on genetic alterations with activation or mutations in FGFR3 papillary tumors and with inactivation or mutations involving TP53 and RB1 in non-papillary tumors. Recently, the patterns of gene expression allow to differentiate basal and luminal subtypes as reported in breast cancer. In particular, basal cancers are composed of squamous and sarcomatoid pathological findings, while luminal cancers are composed of papillary finding features and genetic mutations (FGFR3). In particular, specific investigative studies demonstrated that luminal cancers are associated with secondary muscle invasive cancer while basal tumors are related to advanced disease since they are often metastatic at diagnosis. Moreover, from therapeutic point of view, different researchers showed that mutations of DNA are related to the sensitivity of bladder cancer while performing cisplatin chemotherapy. In this prospective, the bladder cancer molecular subtyping classification might allow identifying the set of patients who can safely avoid neoadjuvant chemotherapy likely because of the low response to systemic chemotherapy (chemoresistant tumors). In this context, the Cancer Genome Atlas (TCGA) project has improved the knowledge of the molecular targets of invasive urothelial cancers allowing the researchers to propose hypothesis suggesting that agents targeting the genomic alterations may be an effective strategy in managing these cancers, which occur in about 68% of muscle invasive cancers. A future goal will be to combine treatment strategies of invasive bladder cancers according to their genetic mutational load defined by molecular pathology.

Keywords: Bladder cancer; genetics; immunotherapy; molecular pathology; targeted agents.