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Loss in Cell Killing Effectiveness of Anticancer Drugs in Human Gastric Cancer Clones Due to Recovery from Potentially Lethal Damage in Vitro¹

Department of Radiation Therapy [S. C. B.] and Department of Surgery [C. M. T.], University of Texas Medical Branch, Galveston, Texas 77550

The ability of human gastric cancer clones to recover from potentially lethal damage was studied. Recovery was greatest following treatments with bleomycin or Adriamycin; the recovery ratios (i.e., survival) increased almost 8-fold during a posttreatment incubation period. Recovery was also possible following treatments with actinomycin D, 1,2:5,6-dianhydrogalactitol, and diaziquone; however, the recovery ratios never increased above 2. No recovery was observed following treatment with 5-fluorouracil.

Recovery from potentially lethal damage may be related to the heterogeneity in survival responses observed following treatment with some anticancer drugs. Bleomycin and Adriamycin treatments result in large heterogeneous survival fractions among these human stomach cancer clones, and the potentially lethal damage recovery ratios were larger (and variable). However, actinomycin D, diaziquone, and 1,2:5,6-dianhydrogalacticol produce very uniform killing effects in these cells and the recovery ratios are very much smaller and less variable.

Finally the large amount of recovery observed after bleomycin or Adriamycin treatments resulted in the loss of cell killing effectiveness of the agents. Because the survival fractions increased during the recovery period, the net effect on cell killing was reduced to an amount normally obtained with doses that were up to six times smaller.

¹ This work was supported by NIH Grants CA-15397-12 and CA-00854-03 and ACS Grant PDT-220.

² To whom requests for reprints should be addressed, at 310 Gail Borden Building, D11, Division of Research, Department of Radiation Therapy, University of Texas Medical Branch, Galveston, TX 77550.

Received 4/ 2/85. Revised 7/29/85. Accepted 10/14/85.