Effect of mitomycin C on concentrations of vascular endothelial growth factor and its receptors in bladder cancer cells and in bladders of rats intravesically instilled with mitomycin C

Abstract

Objectives: • To examine, using in vitro and in vivo models, the largely unexamined effect of mitomycin C (MMC), an effective intravesical treatment for superficial bladder cancer and carcinoma in situ, on expression of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2), which mediates many of the angiogenic properties of VEGF. • To measure, as a positive control, concentrations of the inhibitor of apoptosis, survivin, as an assessment of MMC effectiveness. • To measure MMC-induced changes in proliferation in the presence and absence of VEGF-A small interfering RNA (siRNA).

Materials and methods: • After treatment with increasing MMC concentrations (5-200 µg/mL), we measured proliferation, as well as VEGF, survivin, VEGF receptor-1 (VEGFR-1) and VEGFR-2 concentrations in RT-4 and T-24 bladder cancer cells. • The effect of pre-treatment of VEGF siRNA and survivin siRNA on MMC-induced decreases in proliferation was measured. • Urinary VEGF concentrations and bladder and kidney concentrations of VEGF-A, VEGFR-1, VEGFR-2 and interleukin-6 (IL-6) mRNA were measured in rats intravesically instilled with saline or MMC (200 µg/mL).

Results: • Although MMC treatment inhibited cell proliferation and decreased survivin mRNA expression in T-24 and RT4 cells, MMC (12-50 µg/mL) increased VEGF-A mRNA and VEGFR-2 mRNA and protein expression. • Pre-treatment with VEGF-A siRNA or survivin siRNA before MMC treatment reduced proliferation more than MMC alone. • MMC-induced reductions in proliferation were reduced additively by pre-treatment with survivin siRNA, but were potentiated by pre-treatment with VEGF-A siRNA. • VEGFR-2 mRNA and protein concentrations and urinary VEGF concentrations were increased in bladders of rats instilled with MMC.

Conclusions: • Intravesically instilled MMC increases urinary VEGF and bladder VEGFR-2 protein and mRNA in rats. • MMC increases VEGF mRNA and VEGFR-2 protein and mRNA concentrations in bladder cancer cells. Therefore, we speculate that MMC could increase the angiogenic potential of both cancer and normal cells. • In cancer cells this effect is largest at lower MMC concentrations. • Combining MMC with agents that reduce EGF concentrations could be of value in treatment of transitional cell carcinoma of the bladder (TCC).