6th ESACP Congress, Heidelberg, April 7-11, 1999

A092
A NEW GROUP OF MAMMALIAN MDR CELL LINES WITH ENHANCED CAPACITY OF µDNA CLEARING FROM NONCOVALENTLY BOUND AGENTS
Levina VV, Varfolomeeva EY, Sukhareva EB, Drobchenko EA, Filatov MV

Petersburg Nuclear Physics Institute, Gatchina, St.Petersburg, Russia

Earlier, we have described the process of active dissociation or "DNA clearing" from noncovalently bound agents in living mammalian cells. The vital fluorescent bisbenzimidazole dye Hoechst-33342, which binds tightly but not covalently to DNA in the minor groove, was used for studying interactions of noncovalently binding agents with DNA. Multiple drug resistance (MDR) in tumor cells is related to the expression of transport proteins that alter cellular drug transport and distribution. To obtain new lines characterized by enhanced process of active dissociation of noncovalently bound agent from DNA or DNA clearing, we selected human and rodent cell lines that are hyperresistant to the Hoechst 33342. The cell lines selected from Chinese hamster cell line AA8 were named AA8Hoe-R-1 - AA8Hoe-R10, and the cell lines selected from mouse L cells were called LHoe-R-1 - LHoe-R-10, cell lines selected from human cell line Mg63 were named Mg63 Hoe-R-1 - Mg63 Hoe-R-10. All mutants were analyzed with flow cytometric technique and half of them were characterized by an enchanced dissociation of the bisbenzimidazole dye - DNA complex. As we believe, the enchanced level of DNA clearing was caused by the amplification of some genes because the gradual increase of Hoechst resistance in the same cell line resulted from the increase in the ability to remove the dye from DNA. These lines were shown to be also resistant to netropsin and mitomycin C. We concluded that we obtained a new group of MDR cell lines characterized by an enhanced capacity of DNA clearing.