Effects of mechlorethamine on lysosomal enzyme release from HeLa and 3T3 cells

The growth of the established malignant HeLa cells was much more inhibited by mechlorethamine (HN2) than that of the nonmalignant 3T3 cells. An initial growth inhibition was followed by complete inhibition even if HN2 was removed from the culture medium. Significant cell death did not occur during the first 24 h of HN2 treatment, but well later on. Incubation with 2.5 micrograms/ml HN2 caused increased release of lysosomal enzymes into the medium and decreased intracellular enzyme activities after a latency period of at least 6 h. The lysosomes from HeLa cells did not seem to be more fragile than those from 3T3 cells. Incubation with 0.25 micrograms/ml HN2 did not alter the intra- or extracellular enzyme levels the first 24 h, but well later on even after refeeding with medium without HN2. This study indicates that lysosomal enzymes are not involved in the genesis of the process leading to cell inactivation by HN2, but may well be correlated with the cytotoxic effects leading to cell death.