The High Resolution MASS spectrometry in Personalised Medicine: Retinol-Binding Protein 4 as a Candidate Biomarker Predictor of Progression in Bladder Urothelial Carcinoma

Introduction: Bladder cancer (BC) is the seventh most commonly diagnosed cancer in males. A large proportion of T1 cases and some Ta cases are under-staged and the significant risk of residual tumour after initial TURB of TaT1 lesions has been demonstrated. A second TURB is recommended in T1 tumours because it can increase recurrence-free survival (RFS) providing prognostic information. Non-invasive methods differentiating bladder cancer stages would be essential for diagnosis of under staged cases. Previously we demonstrated that a panel of urinary proteins measured by high resolution mass spectrometry could predict bladder cancer stages namely Ta, T1 and T2 cases. Our aim is to increase the accuracy of the biomarker panel for BC stage differentiation using a more patients, also intending to identify proteins that could be a signature to bladder cancer progression. Methods: Forty-eight urine samples were collected from volun- teers of these groups: 20 patients with bladder cancer stage Ta; 19 patients with BC stage T1 and 9 patients with BC stage T2+ (T2, T3 and T4). Urinary proteome was cleaned and digested using the Filter-Aided Sample Preparation methodology and analysed by liquid chromatography-mass spectrometry. For protein identification and label-free quantification we used MaxQuant, the data was further interrogated with the bioinformatics platform Perseus. Results: A biomarker panel was developed which consists of 87 proteins which were down-regulated between three different urothelial bladder carcinoma stages evaluated. Retinol-binding protein 4 (RBP4) consistently increases from Ta to T1, to T2+ (p <0.001) and in high grade tumours (p = 0.006). Conclusion: Our results showed a proteomic biomarker panel capable to differentiate bladder cancer stages. Besides, retinolbinding protein 4 can be a candidate signature of progression.