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
Authors: Verma Avanti , DeGrado Justin , Hittelman Adam B. , Wheeler Marcia A. , Kaimakliotis Hristos Z. , Weiss Robert M. 
Published: August 2010

What’s known on the subject? and What does the study add?

Mitomycin C is widely used for treatment of bladder cancer, however disease progression after mitomycin C treatment is common. We found that intravesical mitomycin C treatment increases urinary vascular endothelial growth factor (VEGF) and bladder VEGF receptor‐2 protein and mRNA in rats. Mitomycin C also increases VEGF mRNA and VEGF receptor‐2 protein and mRNA levels in bladder cancer cells. Therefore, we speculate that mitomycin C may increase the angiogenic potential of both cancer and normal cells.

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).