Calcium antagonist radioprotectors do not reduce radiotherapeutic efficacy in three human tumor xenografts.
OBJECTIVE
Calcium antagonists, which protect normal tissue as exemplified by bone marrow cells from radiation injury, were evaluated for radioprotection of tumor cells.


METHODS
One Ewing's sarcoma and 2 colon carcinomas were grown as xenografts in immunosuppressed mice. The mice were treated with diltiazem, nifedipine, nimodipine and nitrendipine. The effect of whole body gamma-radiation on the growth of the subcutaneously implanted tumors was assessed.


RESULTS
Growth delay or regression of the tumors in mice treated with the calcium antagonists prior to irradiation was not reduced as compared to only irradiated controls.


CONCLUSIONS
The tested calcium antagonists, which are well tolerated and protect mice from death after lethal radiation, did not prevent the radiotherapeutic effect on 3 human tumors. This points to the possibility of differential radioprotection and thus to improve the therapeutic ratio in cancer radiotherapy.
Floersheim
G L
GL
Department of Research, University Hospitals, Basel, Switzerland.
Racine
C
C
D000230:Adenocarcinoma / Q000473:pathology / Q000532:radiotherapy*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D004110:Diltiazem / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009543:Nifedipine / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D009568:Nitrendipine / Q000494:pharmacology; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D011879:Radiotherapy Dosage; D012512:Sarcoma, Ewing / Q000473:pathology / Q000532:radiotherapy*; D014183:Transplantation, Heterologous; D014916:Whole-Body Irradiation
D002121:Calcium Channel Blockers; D011837:Radiation-Protective Agents; D009553:Nimodipine; D009568:Nitrendipine; D004110:Diltiazem; D009543:Nifedipine