Proteomic Analysis of Urinary Bladder Cancer : Aiming for Novel Biomarkers

Sammanfattning: Urinary bladder cancer is a heterogeneous disease appearing in different forms, e.g. non-muscle invasive and muscle invasive. For all variants, the expression of proteins is interesting to analyze for diagnostic, predictive, prognostic and drug targeting purposes, since it reflects the altered gene expression causing the cancer. Since urothelial cells of the bladder are in direct contact with urine it is likely that this body fluid contains cancer-related proteins. In Paper I, unbiased analysis of proteins in urine from urinary bladder cancer patients and controls, using label-free quantification by mass spectrometry, was applied and four interesting proteins APOE, FGB, LRG and SERPINA1 were selected and further analyzed with western and dot blot. In Paper II, two more proteins, POLR1E and TOP2A, were validated as relevant proteins in bladder cancer urine. In Paper III and IV, the proteins GAL1 and STMN1 were investigated for their prognostic and therapeutic target potential in bladder cancer. In Paper II, III and IV, the expression of seven of the proteins were analyzed on tissue microarrays representing tumour tissue from 360 patients with different tumour stages. For the proteins identified by the urine screening approach, their protein expressions were confirmed in bladder cancer tissue. The expression level in tissue of five of the proteins, APOE, FGB, POLR1E (Paper II), GAL1 (Paper III) and STMN1 (Paper IV), increased with tumour stage, showing diagnostic relevance and three of the proteins, SERPINA1 (Paper II), STMN1 (Paper IV) and GAL1 (Paper III) had prognostic potential in urinary bladder cancer. In addition, GAL1 and STMN1 were demonstrated to be highly expressed in metastatic disease and inhibition of STMN1 reduced cell growth (Paper III and IV), indicating that these proteins are promising drug targets in urinary bladder cancer. In conclusion, the approach of this thesis has generated several candidate protein biomarkers in urine and tissue, validated with independent methods, which have the potential to improve the care for bladder cancer patients.