Quantitative proteomics identifies TUBB6 as a biomarker of muscle‐invasion and poor prognosis in bladder cancer

• Published in: International journal of cancer Vol. 152; no. 2; pp. 320 - 330
• Main Authors: Kim, Bohyun, Jung, Minsun, Moon, Kyung Chul, Han, Dohyun, Kim, Kwangsoo, Kim, Hyeyoon, Yang, Sunah, Lee, Dongjoo, Jun, Hyeji, Lee, Kyung‐Min, Lee, Cheng Hyun, Nikas, Ilias P., Yang, Sohyeon, Lee, Hyebin, Ryu, Han Suk
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 15.01.2023; Wiley Subscription Services, Inc
• Subjects: biomarker; Biomarkers; Biopsy; Bladder; Bladder cancer; bladder urothelial carcinoma; Cancer; Cell migration; Gene expression; Immunohistochemistry; Medical prognosis; Medical research; Patients; Phenotypes; Prognosis; Proteomics; Tubulin; tubulin beta 6 class V (TUBB6); Tumors; Urothelial cancer; Urothelial carcinoma
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.34265

Muscle‐invasive urothelial carcinoma (MIUC) of the bladder shows highly aggressive tumor behavior, which has prompted the quest for robust biomarkers predicting invasion. To discover such biomarkers, we first employed high‐throughput proteomic method and analyzed tissue biopsy cohorts from patients with bladder urothelial carcinoma (BUC), stratifying them according to their pT stage. Candidate biomarkers were selected through bioinformatic analysis, followed by validation. The latter comprised 2D and 3D invasion and migration assays, also a selection of external public datasets to evaluate mRNA expression and an in‐house patient‐derived tissue microarray (TMA) cohort to evaluate protein expression with immunohistochemistry (IHC). Our multilayered platform‐based analysis identified tubulin beta 6 class V (TUBB6) as a promising prognostic biomarker predicting MIUC of the bladder. The in vitro 2D and 3D migration and invasion assays consistently showed that inhibition of TUBB6 mRNA significantly reduced cell migration and invasion ability in two BUC cell lines with aggressive phenotype (TUBB6 migration, P = .0509 and P < .0001; invasion, P = .0002 and P = .0044; TGFBI migration, P = .0214 and P = .0026; invasion, P < .0001 and P = .0001; T24 and J82, respectively). Validation through multiple public datasets, including The Cancer Genome Atlas (TCGA) and selected GSE (Genomic Spatial Event) databases, confirmed TUBB6 as a potential biomarker predicting MIUC. Further protein‐based validation with our TMA cohort revealed concordant results, highlighting the clinical implication of TUBB6 expression in BUC patients (overall survival: P < .001). We propose TUBB6 as a novel IHC biomarker to predict invasion and poor prognosis, also select the optimal treatment in BUC patients. What's new? Improvement in the detection of muscle‐invasive urothelial carcinoma (MIUC) depends in part on the discovery of biomarkers with highly accurate predictive capability. In this study, high‐throughput proteomics and bioinformatics analyses were applied to the search for robust biomarkers linked to aggressive features in bladder urothelial carcinoma (BUC) patient‐derived tissue samples. Analyses identified tubulin beta 6 class V (TUBB6) as a promising predictive and prognostic marker in BUC. In phenotypically aggressive BUC cells, TUBB6 mRNA inhibition decreased cell migration and invasion ability. The analyses further cast light on the comprehensive proteomic landscape of BUC and its relationship with tumor stage.