MATERIALS AND METHODS: C3H/He mice bearing SCC VII
tumors subcutaneously received
TNP-470 at two doses of 100 mg/kg after
tumor cell inoculation. At the same time, the
tumor-bearing mice received
5-bromo-2'-deoxyuridine (
BrdU) continuously for 5 days via implanted mini-osmotic pumps to label all proliferating (P) cells. The mice then received TPZ administration combined with or without
MHT, gamma-ray irradiation combined with or without TPZ and/or
MHT, or
cisplatin injection with or without TPZ and/or
MHT. Another group of mice received a series of test doses of gamma-rays while alive or after being killed to obtain hypoxic fractions (HFs) in the
tumors at various time points after the above-mentioned cytotoxic treatment point. After each treatment, the
tumors were excised, minced, and trypsinized. The
tumor cell
suspensions thus obtained were incubated with
cytochalasin-B (a cytokinesis blocker), and the micronucleus (MN) frequency in cells without
BrdU labeling (or quiescent [Q] cells) was 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. For the measurement of the HFs, the MN frequency of
BrdU-unlabeled cells was then used to calculate the surviving fraction of the unlabeled cells from the regression line for the relationship between the MN frequency and the surviving fraction of total
tumor cells.
RESULTS: TPZ administration combined with
TNP-470 treatment and
MHT increased the MN frequency more markedly than treatment with TPZ alone, and this tendency was more remarkable in Q cells than total cells. In both total and Q cells, combined treatment with TPZ and
MHT produced significant increases in MN frequencies whether gamma-rays were delivered to
TNP-470 treated
tumors or
cisplatin was injected into the
TNP-470 administered mice. Although not significantly, the HFs of total and Q cell populations within solid
tumors increased after
TNP-470 treatment.
CONCLUSION: Combined treatment with TPZ and
MHT, whether other cytotoxic treatments such as gamma-ray irradiation or
chemotherapy using
cisplatin were combined or not, was useful for sensitizing
tumor cells in vivo including Q cells even after
TNP-470 treatment.