Purpose: To investigate the effects of gadolinium texaphyrin (GdTx) on the growth and radiation response of cells in vitro, in a limited set of experiments designed to examine some areas of controversy concerning the effects of this compound.
Methods and materials: Exponentially growing cultures of EMT6 mouse mammary tumor cells, grown in Dulbecco's Modified Eagle's Medium with 10% dialyzed fetal bovine serum, were treated with GdTx either prepared from powder or obtained as a solution similar to that used clinically, in either the presence or absence of equimolar ascorbic acid. Cell viability was measured using a clonogenic assay.
Results: Treatment with GdTx in the presence of ascorbic acid dramatically altered the growth, appearance, and behavior of the cells; treatment with GdTx in the absence of ascorbic acid had only minimal effects. The effects of the powdered drug and the solution were similar. GdTx used with equimolar ascorbic acid altered the radiation dose-response curves of cells irradiated under aerobic and hypoxic conditions; no significant changes were observed without ascorbic acid.
Conclusions: The details of the protocols used in experiments examining the effects of GdTx have major effects on the outcomes. Our results suggest that differences in the protocols used by different groups in past studies with GdTx probably were important in producing the disparate results reported previously.