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Analysis of Contrasting Effects of Exogenous DNA on L1210 Cell Viability¹

Roswell Park Memorial Institute, New York State Department of Health, Buffalo, New York 14203

Cultured mouse leukemia L1210 cells die quickly if harvested during mid-log phase of growth and shaken gently in phosphate-buffered saline plus glucose or if harvested during other phases of growth but shaken rapidly in phosphate-buffered saline plus glucose. Addition of exogenous DNA to these fragile cells offers partial protection against the loss of viability. This effect is independent of the source of the DNA but appears to be dependent on the source of the cell line. A positive correlation was noted between the ability of exogenous DNA to protect cells against loss of viability and the ability of such cells to induce breaks in the DNA. However, extensively degraded DNA had no effect on cell viability. Partially degraded DNA offered protection against loss of viability but only on those cells which were capable of being protected by intact DNA.

If L1210 cells are incubated under conditions permitting relatively little loss of viability in phosphate-buffered saline plus glucose, addition of DBA/2 mouse thymus DNA induces cell death. This lethal effect depends on both the source of the DNA and that of the cell line. DBA/2 DNA refrigerated more than 3 weeks was not harmful to L1210 cells because of a gradual reduction in the molecular weight of the DNA. These results support the hypothesis that, whereas the lethal effect of DNA is dependent upon its genetic information, the protective effect of DNA is independent of its genetic information. The protective effect of DNA is independent of its genetic information. The protective effect appears to be due to some more general characteristic(s) of the DNA and is mediated by some unidentified substance(s) produced by the target cells.

¹ Supported in part by USPHS Grant CA-08763 and by American Cancer Society Grant P-524.

Received 1/24/69. Accepted 5/29/69.