[A cross drug resistance of mammalian cells with a high efficiency of "DNA clearing"].

: The process of active dissociation of noncovalently bound agents from DNA or "DNA clearing" in the living cells was described elsewhere. The vital fluorescent bisbenzimidazole dye Hoechst 33342 (4342), which binds tightly but not covalently to DNA in the minor groove, was used for studying interactions of agents noncovalently binding with DNA. The "DNA clearing" is an energy-dependent process, which is suppressed by topoisomerase-II inhibitors and DNA breaks. It has been shown that the rodent fibroblast cell line AA8HoeR-7 is selected for resistance to H342, and characterized by an enhanced dissociation of the bisbenzimidazole dye-DNA complex. This cell line obtained cross-resistance to other DNA damaging drugs: mitomycin C, etoposide and ethidium bromide. That proves that AA8HoeR-7 is cell line with a new mechanism of multidrug resistance.