Synergy between preactivated photofrin-II and tamoxifen in killing retrofibroma, pseudomyxoma and breast cancer cells.
Exposure of photoactive compounds to light prior to their use in biological systems (preactivation) results in the generation of tumour cell specific metastable cytotoxic species that are no longer dependent on the light energy. Thus, preactivation renders the photoactive compounds suitable for systemic use. We have examined the in vitro effect of preactivated photofrin-II and tamoxifen in retroperitoneal fibroma, pseudomyxoma and male breast carcinoma cell lines. These cells were found to be non-responsive to tamoxifen and were negative for oestrogen receptors. Incubation of these cells with 0.5 microgram/ml preactivated photofrin-II and tamoxifen (less than 10(-6) mol/l) resulted in a significantly enhanced (P less than 0.001) inhibition of DNA synthesis compared with either agent alone. This synergistic effect between tamoxifen and preactivated photofrin-II was determined by multiple drug effect analysis. Treatment of cells with preactivated photofrin-II did not cause the increased expression of oestrogen receptors. These observations suggest that a combination of antihormonal drugs with preactivated compounds may be of clinical value.
Chang
P H
PH
Baylor Research Institute, Baylor University Medical Center, Dallas, Texas 75226.
Pervaiz
S
S
Battaglino
M
M
Matthews
J L
JL
Clark
C
C
Day
J
J
Preskitt
J
J
Vanderpool
D
D
Gulliya
K S
KS
D001943:Breast Neoplasms / Q000188:drug therapy; D002470:Cell Survival / Q000187:drug effects; D017323:Dihematoporphyrin Ether; D004357:Drug Synergism; D006415:Hematoporphyrins / Q000008:administration & dosage*; D006801:Humans; D008027:Light; D008297:Male; D009369:Neoplasms / Q000188:drug therapy*; D011960:Receptors, Estrogen / Q000032:analysis; D012185:Retroperitoneal Fibrosis / Q000188:drug therapy; D013629:Tamoxifen / Q000008:administration & dosage*; D014407:Tumor Cells, Cultured
D006415:Hematoporphyrins; D011960:Receptors, Estrogen; D013629:Tamoxifen; D017323:Dihematoporphyrin Ether