Amsacrine as a topoisomerase II poison: importance of drug-DNA interactions.
Amsacrine (m-AMSA) is an anticancer agent that displays activity against refractory acute leukemias as well as Hodgkin's and non-Hodgkin's lymphomas. The drug is comprised of an intercalative acridine moiety coupled to a 4'-amino-methanesulfon-m-anisidide headgroup. m-AMSA is historically significant in that it was the first drug demonstrated to function as a topoisomerase II poison. Although m-AMSA was designed as a DNA binding agent, the ability to intercalate does not appear to be the sole determinant of drug activity. Therefore, to more fully analyze structure-function relationships and the role of DNA binding in the action of m-AMSA, we analyzed a series of derivatives for the ability to enhance DNA cleavage mediated by human topoisomerase IIα and topoisomerase IIβ and to intercalate DNA. Results indicate that the 3'-methoxy (m-AMSA) positively affects drug function, potentially by restricting the rotation of the headgroup in a favorable orientation. Shifting the methoxy to the 2'-position (o-AMSA), which abrogates drug function, appears to increase the degree of rotational freedom of the headgroup and may impair interactions of the 1'-substituent or other portions of the headgroup within the ternary complex. Finally, the nonintercalative m-AMSA headgroup enhanced enzyme-mediated DNA cleavage when it was detached from the acridine moiety, albeit with 100-fold lower affinity. Taken together, our results suggest that much of the activity and specificity of m-AMSA as a topoisomerase II poison is embodied in the headgroup, while DNA intercalation is used primarily to increase the affinity of m-AMSA for the topoisomerase II-DNA cleavage complex.
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, United States.
Adam C
AC
Ketron
William A
WA
Denny
David E
DE
Graves
Neil
N
Osheroff
D000677:Amsacrine / Q000737:chemistry*; D000951:Antigens, Neoplasm / Q000737:chemistry; D000970:Antineoplastic Agents / Q000737:chemistry*; D001665:Binding Sites; D004247:DNA / Q000737:chemistry*; D053837:DNA Cleavage; D004250:DNA Topoisomerases, Type II / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D006801:Humans; D007364:Intercalating Agents / Q000737:chemistry; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D013329:Structure-Activity Relationship; D059005:Topoisomerase II Inhibitors / Q000737:chemistry*
D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D007364:Intercalating Agents; D059005:Topoisomerase II Inhibitors; D000677:Amsacrine; D004247:DNA; D004250:DNA Topoisomerases, Type II