Combined effects of X rays, Ro 03-8799, and hyperthermia on growth, necrosis, and cell proliferation in a mouse tumor

A mouse adenocarcinoma was treated with 20 Gy X rays, hyperthermia (30 minutes at 43 degrees C), Ro-03-8799, or a combination of two or three of these agents. Combined treatments increase growth delay in the tumor and this was greatest with the combination of all three modalities. Extensive amounts of necrosis were observed after the combined treatments. This effect was most pronounced after treatment modalities including hyperthermia. On the other hand, the radiation-induced micronucleus formation was more enhanced by the sensitizer than by hyperthermia. After X irradiation and combined treatments with X rays a G2-block was observed in DNA-histograms. Tetraploid cells appeared in large amounts that started DNA synthesis followed by necrosis. From these tumors it was impossible to obtain regular DNA-histograms. Tumor regression is a combined result of reduced cell renewal, increased cytogenetic damage, and development of necrosis