Antitumor activity of 2-mercaptoethanesulfonate (mesna) in vitro.

2-Mercaptoethanesulfonate (mesna), which is used as an uroprotector during oxazaphosphorine therapy of cancer patients, was found to inhibit growth of several cultured human malignant cell lines in vitro. Dimesna, which is rapidly formed in the blood of mesna treated patients, had no effect and did not interfere with the growth inhibitory activity of mesna. For sensitive cell lines, complete growth inhibitions were usually observed at mesna concentrations of 10(-4) M. Higher concentrations were less toxic or even stimulated proliferation of some cell lines. There was no experimental evidence that the biphasic dose-response profiles were due to a more complete dimesna formation at high mesna concentrations. Since mesna, which is excreted in its monomeric form in urine, was reported to inhibit growth of superficial bladder cancer in patients, we examined the effects of repeated mesna administrations in cultures of bladder cancer cells. The results showed that this treatment caused growth inhibition of 2/4 "resistant" cell lines. The mechanisms by which mesna inhibits cell growth are unknown and it is not known if it acts selectively on malignant cells.