Cu-ATSM, a hypoxia imaging agent, effectively detects tumors due to the presence of hypoxia in solid tumor mass. We have reported that the intratumoral distribution of Cu-ATSM in mouse solid tumor model is quite heterogeneous and different from that of FDG. Immunohistochemical analysis of CD34 (vessel formation) and Ki-67 (cell proliferation) expression was compared with intratumoral accumulation of Cu-ATSM. The region showing high Cu-ATSM accumulation had little vessel formation and negligible proliferating cells, which suggest that the tumor cells in these regions can be resistant to conventional chemo- and radio-therapies. To further verify this inference, the proliferation capacity of the cells from various regions of mouse solid tumor mass was examined by colony formation assay, and was compared to the regional accumulation level of Cu-ATSM. The cells in the region of high Cu-ATSM accumulation showed higher clonogenicity than the region of low or moderate Cu-ATSM accumulation. Our results indicated that the tumor cells in the region of high Cu-ATSM accumulation retain high potential for proliferation though they look temporally arrested in cell cycle, and the region of high Cu-ATSM accumulation may be one of the primary targets of tumor treatment.The Fifth Annual Meeting The Society for Molecular Imagin
