Decreased Autolysis of Dead Cells in Adriamycin-resistant Lines of the Sarcoma 180 of Mouse

Adriamycin-resistant cell lines of the sarcoma 180 of mouse reveal, besides the known resistance mechanism, a decrease in cellular autolysis compared with the original line. This decrease has been demonstrated by comparative analysis of cell-free supernatants isolated from 7-day-old sensitive and resistant ascites tumors in mice. In order to demonstrate these changes we isolated and quantified the DNA, detecting higher amounts within the supernatants of resistant lines. Furthermore, unspecific DNA-cleaving activity within raw homogenates of the cells is substantially lower in the resistant lines. Residual parts of chromatin may trap the drug and in this way lower its effective concentration. However, the results may also reflect changes in enzymatic complement playing a hitherto unknown role within living cells.