Cytological examination of urine is the most widely used noninvasive pathologic screen for bladder urothelial carcinoma (BLCA); however, inadequate diagnostic accuracy remains a major challenge.
We performed high-throughput proteomic analysis of ten paired BLCA and benign urothelial lesion (BUL) samples to identify ancillary proteomic markers for use in liquid-based cytology (LBC). Samples were analyzed mass spectrometry to identify differentially expressed proteins (DEP) between the two groups. A total of 4,839 proteins were identified and 111 DEP were confirmed as expressed at significantly different levels between the BLCA and BUL groups. Independent proteomic data generated from tissue samples (7,916 identified proteins and 784 DEP), along with comparative mRNA expression profiles from The Cancer Genome Atlas were analyzed for biomarker discovery. Six proteins, AHNAK, EPPK1, HSP90AB1, MYH14, OLFM4, and TUBB, were thereby identified as putative candidate and analyzed by immunostaining. To determine their immunocytochemical expression levels in LBC, protein expression was screened using data from The Human Protein Atlas and five proteins were finally selected for immunoreactivity validation in two independent LBC cohorts.
These analyses confirmed AHNAK as a unique intracellular protein differing in immunohistochemical expression and subcellular localization between tumor and non-tumor cells. In conclusion, this study identified a new biomarker, AHNAK, applicable to discrimination between BLCA and BUL by LBC.
To our knowledge, the present study provides the first identification of a clinical biomarker for LBC based on in-depth proteomics.
Chnglim Hyun.
Has not received any funding.
All authors have declared no conflicts of interest.