Apoptosis of human breast carcinoma cells in the presence of cis-platin and L-/D-PPMP: IV. Modulation of replication complexes and glycolipid: Glycosyltransferases

Apoptosis of human breast carcinoma cells (SKBR-3, MCF-7, and MDA-468) has been observed after treatment of these cells with anti-cancer drug cis-platin and glycosphingolipid biosynthesis inhibitor L- and D-PPMP, respectively. These drugs initiated apoptosis in a dose-dependent manner as measured by phenotypic morphological changes, by binding of a fluorescent phophatidyl serine-specific dye (PSS-380) onto the outer leaflet of the cell membranes, and by activation of caspases, −3, −8, and −9. It was observed that in two hours very little apoptotic process had started but predominant biochemical changes occurred after 6 h. DNA degradation started after 24 hours of drug treatment. However, very little is known about the stability of the ‘`Replication Complexes’’ during the apoptotic process. DNA helicases are motor proteins that catalyze the melting of genomic DNA during its replication, repair, and recombination processes. Previously, DNA helicase-III was characterized as a component of the replication complexes isolated from embryonic chicken brains as well as breast and colon carcinoma cells. Helicase activities were measured by a novel method (ROME assay), and DNA polymerase-α activities were determined by regular chain extension of the nicked ACT-DNA, by determining values obtained from +/− aphidicolin-treated incubation mixtures. In all three breast carcinoma cell lines, a common trend was observed: a decrease of activities of DNA polymerase-α and Helicase III. A sharp decrease of activities of the glycolipid sialyltransferases: SAT-2 (CMP-NeuAc; GD3 α2-8 sialyltransferase) and SAT-4 (CMP-NeuAc: GM1a α2-3 sialyltransferase) was observed in the apoptotic carcinoma cells treated with L-PPMP compared with cis-platin.