title: Adriamycin sensitivity following "ultra" low dose rate irradiation of Lewis lung carcinoma in vivo.
abstract: As an extension of recent study on the response of the Lewis lung tumor to low dose rate continuous irradiation (CI) at 15 cGy/hr, we have gone on to investigate the effects of such irradiation on the sensitivity of tumor cells to treatment with Adriamycin (Adr). Cells from untreated tumors gave an exponential dose response curve to Adr in vitro, the D10 of which increased (sensitivity decreased) with the size of tumor (0.05 g to 0.6 g) from which the cells were obtained. After previous in vivo CI to a total dose of 28 Gy (irradiation time--186 hr), this size dependence was abolished and the cells showed an exponential response to Adr in vitro (D10 = 0.4 microgram/ml). The enhancement was also observed after equivalent doses of fractionated irradiation, but not after acute irradiation. It was difficult to characterize the proliferative status of the cells surviving irradiation, but repopulation studies showed that only after CI was there any delay before repopulation commenced. LL was relatively insensitive to Adr in vivo, however, we did observe an increased effect after previous CI.
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004317:Doxorubicin / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000188:drug therapy / Q000532:radiotherapy*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011879:Radiotherapy Dosage; D013997:Time Factors
chemical_list: D004317:Doxorubicin