Eukaryotic initiation factor-4E in superficial and muscle invasive bladder cancer and its correlation with vascular endothelial growth factor expression and tumour progression

Abstract

Summary Vascular endothelial growth factor (VEGF) is an important factor mediating tumour angiogenesis. VEGF mRNA is differentially expressed in bladder cancer with high expression in superficial tumours (stage pT a and pT 1 ) contrasting with low expression in muscle invasive tumours (stage ≥ pT 2 ). To investigate mechanisms regulating VEGF expression in bladder cancer, VEGF mRNA and protein were measured in normal bladder (n = 12) and primary bladder cancers (n = 57). VEGF protein levels correlated with mRNA expression in normal bladder (r = 0.68, P = 0.02) and bladder cancer (r = 0.46, P = 0.0007). Whilst VEGF mRNA expression was threefold higher in superficial compared to muscle invasive bladder cancers (P = 0.0001) there was no difference in VEGF protein (P = 0.81). Accordingly, the median protein:mRNA ratios increased more than 15-fold with increasing tumour stage (P < 0.0001) suggesting translational regulation. Expression of the eukaryotic initiation factor-4E (eIF-4E), a factor implicated in the translational regulation of VEGF, was greater in tumours than normal bladder (P < 0.0001) and correlated with VEGF protein:mRNA ratios (n = 43, r = 0.54, P = 0.0004) pointing to its role in the regulation of VEGF. In superficial tumours (n = 37) high expression of eIF-4E was associated with a poor prognosis and reduced stage progression-free survival (P = 0.04, Cox proportional hazards model). The study demonstrates that eIF-4E may be involved in translational regulation of VEGF in bladder cancer and might have a role as a prognostic factor in bladder cancer. © 2000 Cancer Research Campaign Keywords: angiogenesis; VEGF; eIF-4E; bladder cancer 161British Journal of Cancer (2000) 82(1), 161-166 © 2000 Cancer Research Campaign Article no. bjoc.1999 Received 25 January 1999 Revised 30 June 1999 Accepted 5 July 1999Correspondence to: AL Harris, Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DU, UK at The Churchill Hospital, Oxford, UK. Twelve specimens of macroscopically normal bladder were obtained from patients undergoing surgery for bladder cancer (n = 5) or from cadaveric organ donors at the time of donor nephroureterectomy (n = 7). All specimens were snap-frozen in liquid nitrogen at the time of resection. RNA and protein preparationRNA was prepared according to the method of Chomczynski and Saachi (Chomczynski and Saachi, 1987). All RNA samples were run on a 1% agarose gel (under RNAase-free conditions) and the concentrations measured spectrophotometrically prior to ribonuclease protection analysis.Tumour protein cytosolic and membrane fractions were prepared as previously described (Sacks et al, 1993). Briefly, tumours, frozen in liquid nitrogen, were morselized (cooled with liquid nitrogen) prior to homogenization, using a Dounce homogenizer, in 4 ml of HEPES-EDTA buffer containing proteinase inhibitors. This homogenate was centrifuged at 3000 g for 10 min (+4°C) and the supernatant further centrifuged at 100 000 g for 45 min (+2°C). The pellet was resuspended in 1 ml Tris-buffered sali...

Comparison of hypoxia transcriptome in vitro with in vivo gene expression in human bladder cancer

“…We and others have previously shown the importance of angiogenic factors, such as vascular endothelial growth factor (VEGF) measured in the urine or in the tumour, in mediating bladder tumour angiogenesis (Chow et al, 1999;Crew et al, 1999;Crew et al, 2000). We showed striking luminal induction of VEGF in superficial bladder cancer (Turner et al, 2002).…”

“Translating” Tumor Hypoxia: Unfolded Protein Response (UPR)–Dependent and UPR-Independent Pathways

“…If levels of eIF4E are significantly higher than that of 4E-BP1, mTOR inhibition is less able to affect protein synthesis (66). Given that eIF4E is frequently overexpressed in cancer (67,68), mTOR inhibition under hypoxia may have substantially different consequences among different tumor cells.…”

mTOR and cancer therapy

“…Levels of eIF4E are elevated in some colon carcinomas in comparison to normal colon cells (Rosenwald et al, 1999;Berkel et al, 2001). The levels of eIF4E are also increased in some bladder and breast cancers that have a poor outcome (Crew et al, 2000;Li et al, 2002). In these cancers, a corresponding increase in vascular endothelial growth factor (VEGF) was also observed (Scott et al, 1998;Crew et al, 2000).…”