Heterogeneous survival responses of human gastric cancer clones to alpha difluoromethylornithine in vitro.

The effects of alpha Difluoromethylornithine (DFMO)2 on survival of human gastric cancer clones were studied in vitro. The responses were dose and time dependent. Treatments which lasted for less than 12 h were cytotoxic at only the highest doses used. The greatest effects on survival were observed only when cells were treated for 48 and 72 h. The effects on the clones produced by such prolonged treatment durations were heterogeneous, with survival values differing by as much as 460%. By contrast, the clonal survival responses to short DFMO treatments (12 h) were very uniform (dose differential of only 19%); however, this uniformity in response could be achieved only by using non-pharmacological doses of DFMO. The heterogeneity in survival responses in the clones might be slightly associated with their levels of intracellular spermidine. Clones with the smallest amounts of intracellular spermidine at the start of treatment were most sensitive to DFMO. However, this association may not hold up with further testing in other gastric cancer clones or when studied in other cancer lines in vitro.