The protein kinase inhibitor staurosporine induces morphological changes typical of apoptosis in MOLT-4 cells without concomitant DNA fragmentation.

The protein kinase inhibitor staurosporine induces ultrastructural changes typical of apoptotic cell death in MOLT-4 cells in a concentration range of 10-200 nM. The well known chromatin margination was indeed present, followed by characteristic nuclear protrusions. The formation of numerous homogeneously electron dense micronuclei was the final step of the process. Nevertheless we did not detect the distinctive internucleosomal DNA fragmentation which has been demonstrated to occur in a variety of cells exposed to agents causing apoptosis. Our results strengthen recent argument showing that DNA breakage cannot be considered the sole criterion for detection of apoptosis.