Changes in the sensitivity of intratumor cells during fractionated tirapazamine administration.
Mice bearing solid tumors received 10 intraperitoneal administrations of 5-bromo-2'-deoxyuridine (BrdU) to label the proliferating (P) tumor cells. Then, as a priming treatment, tirapazamine (TPZ) was intraperitoneally administered. Further, 0 through 48 h later, the tumor-bearing mice received TPZ again at various doses. The tumor cells were isolated and incubated with a cytokinesis blocker. The micronucleus (MN) frequencies in cells with and without BrdU labeling, which were regarded as P and quiescent (Q) cells at the priming treatment, respectively, were determined using immunofluorescence staining for BrdU. The MN frequency in the total (P + Q) tumor cells was determined from the tumors that were not pretreated with BrdU. In addition, P cell ratios in the tumors at the second treatment were determined using immunofluorescence staining for P cell nuclear antigen. In each cell fraction, the longer the interval between the two treatments, the higher was the sensitivity to TPZ, except 1 h after the priming treatment. More than 24 h later, total and P cells, especially P cells, showed significantly higher sensitivity to TPZ than in the case of a single TPZ treatment. The longer the period between the two TPZ treatments, the lower was the P cell ratio at the second treatment. These findings were thought to indicate that the use of TPZ in the treatment of solid tumors causes a shift from the P to the Q state in vivo.
Masunaga
S
S
Radiation Oncology Research Laboratory, Research Reactor Institute, Kyoto University, Noda, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan. smasuna@rri.kyoto-u.ac.jp
Ono
K
K
Suzuki
M
M
Kinashi
Y
Y
Takagaki
M
M
Kasai
S
S
Nagasawa
H
H
Uto
Y
Y
Hori
H
H
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D007274:Injections, Intraperitoneal; D051379:Mice; D008809:Mice, Inbred C3H; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects; D009368:Neoplasm Transplantation; D000077704:Tirapazamine; D014227:Triazines / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000970:Antineoplastic Agents; D014227:Triazines; D000077704:Tirapazamine