Original Articles

Effects of four antitumor agents on DNA circular dichroism

Authors: Yi-He Ling, Chun-Yi Shen, Qing-Luo Shi, Bin Xu


Actinomycin D (Act D) is an effective anticancer antibiotic. Homoharringtonine (HHT) and l0-hydroxycamptothecin (HCT) are the potent antitumor alkaloids isolated from Cephalotaxus fortunei Hook, f. and Camptotheca acuminata, respectively.
In the present work, the circular dichroism (CD) spectra of calf thymus DNA were altered by Act D 10 or 20μg/ml, i. e. the negative peak at 246 nm of DNA spectra was distinctly increased and the positive peak at 276 nm enhanced.
HHT and cephalotaxine (CT), possessing the common ring structure, showed similar CD spectra, and induced the same alteration of DNA spectra. Moreover, the change of DNA CD spectra caused by HHT was found to be reversible.
The CD spectra of DNA with or without HCT did not show any difference. The intensities of CD spectra of DNA decreased seriously only when the concentration of HCT reached 44μg/ml, indicating that there is a limit of concentration for the effect of HCT on the conformation of DNA.

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