Abstract
Epidermal growth factor (EGF) receptor expression in 31 primary human bladder tumours was quantitated using both structural and functional assays and the EGF receptor gene in the same tumours was analyzed by Southern blot analysis. Immunocytochemical studies using the EGFR1 monoclonal antibody (Mab) showed a significant correlation between EGF receptor levels and the stage and grade of the tumours. Autophosphorylation assays employed to evaluate the receptor's tyrosine kinase activity gave results which in general were consistent with the immunocytochemical data. Using internally controlled immunocytochemical studies with two Mabs and Southern blot analysis of DNA isolated from the tumours, no evidence was obtained for the production of truncated receptors similar to those encoded by the v-erb-B oncogene. Gene amplification was not found in any of the superficial tumours, but one invasive tumour with high EGF receptor expression had an 8-10 fold amplification of the EGF receptor gene. The EGF receptor isolated from this tumour showed a normal pattern of tyrosine phosphorylation at all three major autophosphorylation sites. Our detailed study is consistent with the correlation previously found between EGF receptor expression and stage and grade of bladder tumours, and suggests that at this level of analysis EGF receptors in bladder tumours are not abnormal in structure or size, autophosphorylation activity, or gene structure.
Highlights
Thirty-one tumours were evaluated by immunocytochemistry for their levels of Epidermal growth factor (EGF) receptor protein expression using the two antibodies to the EGF receptor
We graded as positive those tumours that expressed EGF receptor levels that were higher than that seen in normal urothelium; that is, weak, moderate or strong
Urine bathing the bladder mucosa contains epidermal growth factor (EGF) in ng ml-I concentrations which are substantially higher than the pg ml-1 concentrations usually found in serum (Oka & Orth, 1983; Mattila et al, 1986)
Summary
Fresh tumour samples were obtained from newly diagnosed patients with transitional carcinoma of the bladder. The tumours were staged clinically and pathologically by the urology and pathology departments of Freeman Hospital, Newcastle Upon Tyne. Bennett of the Pathology Department carried out histological grading on paraffin sections of the tumours according to standard criteria (American Joint Committee on Cancer, 1983). Superficial tumours were classified as those not invading bladder muscle (Ta, TI), and invasive tumours as those with muscle invasion identified pathologically (T2, T3) according to standard criteria (American Joint Committee on Cancer, 1983). Samples of the tumours were frozen in isopentane cooled to -180°C with liquid nitrogen and stored in liquid nitrogen. All laboratory studies were performed without knowledge of stage or grade of the tumours. Fisher's exact test was used for statistical analysis
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