IDENTIFICATION OF NONPROLIFERATING BUT VIABLE HYPOXIC TUMOR-CELLS IN-VIVO

We have used the combination of pimonidazole labeling of hypoxic cells , bromodeoxyuridine labeling of proliferating cells, and cell sorting based on Hoechst 33342 perfusion to directly study hypoxia and prolife ration in human tumor xenografts and transplantable murine tumors irt vivo. Hypoxia was largely confined to cells in regions with the least perfusion, although in tumors exhibiting transient blood flow, hypoxic cells were not as highly localized. Similarly, proliferation and hypo xia were mutually exclusive except in areas of a tumor subjected to tr ansient changes in perfusion. By determining the clonogenic potential, pimonidazole labeling intensity, and radiosensitivity of sorted tumor cell subpopulations, we have provided direct evidence that pimonidazo le identifies hypoxic tumor cells of therapeutic relevance Bt vivo. Gi ven that pimonidazole exhibits few diffusion or delivery problems and no apparent cytotoxicity, it appears to be a versatile and useful labe l for hypoxic cells in solid tumors.