CLEAVAGE OF DNA TO LARGE KILOBASE PAIR FRAGMENTS OCCURS IN SOME FORMSOF NECROSIS AS WELL AS APOPTOSIS

In a number of cellular systems, DNA in apoptotic cells is initially d egraded into large fragments of 30-50, 200-300 and greater than or equ al to 700 kilobase pairs, which may subsequently give rise to oligonuc leosomal fragments often considered as the biochemical hallmark of apo ptosis. In this study, necrosis was induced in U937 cells by incubatio n with water. Cells yielded large DNA fragments similar in size to tho se found in apoptosis, but the DNA was then degraded to a continuous s pectrum of small fragments, confirming that death was necrotic. The re sults demonstrate that kilobase pair DNA fragments are formed in some instances of necrosis as well as in apoptosis. This indicates that apo ptosis should not simply be assessed by the formation of kilobase pair DNA fragments, but that other criteria, such as cellular morphology, must also be used to verify apoptosis. (C) 1995 Academic Press, Inc.