PARTIAL CIRCUMVENTION OF MULTIDRUG-RESISTANCE BY ANNAMYCIN IS ASSOCIATED WITH COMPARABLE INHIBITION OF DNA-SYNTHESIS IN THE NUCLEAR MATRIX OF SENSITIVE AND RESISTANT CELLS

We studied the subcellular and subnuclear distributions of the partial ly cross-resistant anthracycline Annamycin (Ann) in KB-3-1 and multi-d rug resistant KB-V1 cells. Subcellular drug localization was assessed qualitatively by fluorescence microscopy and quantitatively by cell fr actionation and fluorescence measurements. Doxorubicin (Dox) localized predominantly in the nucleus in KB-3-1 cells and in the membranes in KB-V1 cells. In contrast, the subcellular distribution of Ann was iden tical in both cell lines, with preferential drug localization in the p erinuclear region, Golgi apparatus, endoplasmic reticulum and endosome s. Dox rate of efflux from the nucleus was negligible in KB-3-1 cells but markedly enhanced in KB-V1 cells, whereas Ann was lost at a simila r rate from the nucleus in both cell lines. In KB-3-1 cells Dox levels in the nuclear non-matrix were about 2-fold higher than those of Ann, while in the matrix the inverse relationship was observed. In spite o f these differences, Dox and Ann had a similar inhibitory effect on ne w DNA synthesis in the nuclear matrix and non-matrix of KB-3-1 cells. Dox levels were reduced by 10-fold in the nuclear non-matrix and 2-fol d in the matrix in KB-V1 cells compared with KB-3-1 cells, whereas Ann levels were reduced try about 2- to 3-fold in the non-matrix and were unchanged in the matrix. In correlation with these findings, Dox did not cause inhibition of new DNA synthesis in either nuclear fraction i n KB-V1 cells, whereas inhibition of new DNA synthesis in the matrix b y Ann was similar in both cell lines. Our results indicate that Ann's partial circumvention of multi-drug resistance is associated with its ability to cause comparable new DNA synthesis inhibition in the nuclea r matrix of sensitive and resistant cells. (C) 1995 Wiley-Liss, Inc.