Ki-67 protein concentrations in urothelial bladder carcinomas are related to Ki-67-specific RNA concentrations in urine.

Abstract

The Ki-67 protein is a nuclear and nucleolar protein that is strictly associated with cell proliferation. Recently it has been suggested to play a role in the control of the higher order chromatin structure (1). Because the protein is produced only in dividing cells, the anti Ki-67 antibody MIB-1 has been widely used in histopathologic studies to estimate the growth fraction of human neoplastic tissue samples in situ. For a variety of human tumors, including bladder carcinomas, the Ki-67 labeling index has been shown to be of prognostic value for tumor recurrence and for patient survival (2)(3)(4). We investigated whether Ki-67 RNA in total urine of bladder tumor patients is correlated with the Ki-67 labeling index of the corresponding tumor tissue. Spontaneously voided clean-catch urines from 68 patients were collected with informed consent, stored at 4 °C, and processed within 4 h of collection. Approval was obtained from the Ethikkommission of the University of Luebeck. Three groups of patients were included: ( a ) healthy donors (n = 14); ( b ) patients with urinary tract infection as detected by analysis of urine sediment (n = 28); and ( c ) patients with bladder carcinoma (n = 26). All urine samples from patients with tumors were checked for significant bacteriuria or leukocyturia (>10/μL) as well as for the presence of erythrocytes (>10/μL). The specific weights of all urine samples were in the range 1.010–1.015 kg/L, showing that there were no major differences in urine concentration. After routine diagnostics were completed, 1 mL of urine was mixed 1:1 with lysis buffer [5.64 mol/L guanidinium thiocyanate, 5 g/L sarcosyl, 50 mmol/L sodium acetate (pH 6.5), 1 mmol/L β-mercaptoethanol], the pH was adjusted to 7 by addition of 1.5 mol/L HEPES (pH 8.0), and samples were frozen at −80 °C until RNA extraction was performed. …