A morphological study of the effect of chlorambucil during the S and G2 phases of the cell cycle of synchronized HEp-2 cancer cell populations using computerized morphometry

Abstract

Chlorambucil, a bisalkylating agent, used extensively in the treatment of autoimmune and neoplastic diseases, is known to affect DNA synthesis. However recent studies have revealed that it also affects the synthesis of other nuclear protein constituents, especially histones. Since histones play a major role in both the structural and functional integrity of chromatin, we have analyzed the morphological effects of this agent, using low dose conditions and synchronized populations of HEp-2 cancer cells in the S and G2 phases of the cell cycle. Analyses at the light and electron microscopy levels were undertaken using synchronous image analysis techniques. Computerized morphometry was used so as to evaluate various nuclear and cytological morphological parameters. It was found that chlorambucil affects the organization of chromatin, as well as other cellular parameters in a manner characteristic of decreased tumor aggressiveness. A finding of significance in this study was that chlorambucil exerted its influence on all these morphological parameters only when treatment was initiated at the beginning of the S phase and not during the second half of the S phase or the G2 phase.