Introduction: Labeling of bleomycin with Auger-emitter Indium-111 increases cytotoxicity in squamous cell cancer (SCC) cell lines, as we have reported earlier. In this study, we investigated whether 111In- BLMC is toxic and effective in vivo among SCC-xenografted mice. The influence of 111InBLMC on the squamous cell carcinoma cell cycle stimulated interest. Materials and methods: In an animal experiment, 10 SCC-xenografted mice were used, two for demonstrating targeting in gamma-camera images, eight for intraperitoneally receiving NaCl, BLM, or 111InBLMC as therapy. After a 2-week follow-up, the tumors were analyzed for proliferation (mitoses, Ki-67). DNA flow cytometric analysis was carried out from tumor samples and three UT-SCC cell lines. Results: Tumors were observed on gamma-camera images in xenografted mice after a 111InBLMC injection. The UT-SCC-19A-xenografted mouse had a T/non-T uptake of 7.54 at 4 hours after the injection. At the end of the therapeutic trial, the mice were alive. In spite of a small number of animals, our findings indicate that BLM and 111InBLMC seem to be more effective than NaCl in reducing tumor size. The proliferative activity was strong in BLM and in 111InBLMC groups, indicating regrowth of the tumors. In DNA analysis, the percentages of cells in the G2/M-phases increased after exposure to BLM and particularly to 111InBLMC in all three cell lines. Conclusions: The effect of BLM is preserved after the adding of Auger-emitter In-111. Tumor-seeking 111InBLMC can be administered safely at tumor-decreasing concentrations in xenograft head and neck cancers. To demonstrate the antitumor effect of 111InBLMC, the experiments should be extended to include a larger number of mice. BLM, and especially 111InBLMC, seems to induce alteration in the cell cycle by producing a G2/M block. The verification of the result requires repeated in vitro experiments.
