The topoisomerase II inhibitor teniposide (VM-26) induces apoptosis in unstimulated mature murine lymphocytes.
This study shows that not only concanavalin A-stimulated proliferating lymphocytes but also unstimulated mouse splenic lymphocytes are sensitive to the topoisomerase II (topo II) inhibitor teniposide (VM-26). When unstimulated lymphocytes are pretreated with VM-26 for a 2-h period and are then incubated in drug-free medium, cell viability, as determined by trypan blue exclusion, decreases to 40% of the control by 6 h. The drug-treated cultures show two to three times the level of detergent soluble DNA than the control cultures and agarose gel electrophoresis of the soluble DNA shows the presence of oligonucleosomal-sized fragments, a feature considered to be a hallmark of apoptosis. Phase contrast microscopy, Hoechst staining for DNA, and immunofluorescence microscopy of various nuclear and cytoplasmic antigens (nucleolar fibrillarin, snRNP, ubiquitin, vimentin, tubulin) in the VM-26-treated cells characterize the morphological changes during apoptosis of these cells. The role of topo II as the mediator of the VM-26 effects is supported by pulsed field gel electrophoresis, which shows the typical topo II-induced cleavage of supercoiled DNA into loop-sized 300- and 50-kbp fragments. We conclude that the cancer chemotherapeutic agent VM-26 interacts with topo II and induces apoptosis in unstimulated lymphocytes.
Roy
C
C
Department of Biology, University of Ottawa, Canada.
Brown
D L
DL
Little
J E
JE
Valentine
B K
BK
Walker
P R
PR
Sikorska
M
M
Leblanc
J
J
Chaly
N
N
D000818:Animals; D016923:Cell Death / Q000187:drug effects*; D002478:Cells, Cultured; D004249:DNA Damage; D004278:DNA, Superhelical / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008213:Lymphocyte Activation / Q000187:drug effects; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D013154:Spleen / Q000166:cytology; D013713:Teniposide / Q000494:pharmacology*; D013997:Time Factors; D059005:Topoisomerase II Inhibitors
D004278:DNA, Superhelical; D059005:Topoisomerase II Inhibitors; D013713:Teniposide