Normal and malignant human urothelium: in vitro response to blockade of polyamine synthesis and interconversion

To assess the effect of polyamine blockade on urinary epithelium, growth of normal human urothelial cell cultures and human transitional cell carcinoma (TCC) cell lines in the presence of various inhibitors of polyamine synthesis was evaluated. All four human TCC cell lines tested were quite sensitive to the specific inhibitor of ornithine decarboxylase, alpha-difluoromethylornithine (DFMO), requiring less than or equal to 1.0 mM DFMO to double generation time. Alternatively, all three human urothelial cultures tested required 5-20-fold higher DFMO concentrations to achieve similar growth inhibition. The inhibitory effect of DFMO on TCC was found to act synergistically with that of the inhibitor of S-adenosylmethionine decarboxylase, methylglyoxal bis(guanylhydrazone), and additively with that of recombinant beta-serine interferon. Addition of individual polyamines entirely prevented the inhibitory effects of DFMO and/or methylglyoxal bis(guanylhydrazone) but not that of beta-serine interferon. It appears that inhibition of polyamine synthesis and/or interconversion holds promise in the management of TCC and that the in vitro model described will be of value in investigating such clinical applications.