The authors studied the localization of neocarzinostatin (NCS) in cultured cells and in tumorbearing rats by means of immunofluorescent staining. Anti-NCS antibody was obtained through immunization of rabbits with NCS. Cellular uptake of NCS was dose-dependent (1.0 to 1000 μg/ml) in 9L rat gliosarcoma cells in monolayer. In monolayer cells of 9L, KMG-4 (derived from human glioblastoma), and KMS II (human ependymoma) treated with 1 mg/ml of NCS, drug uptake occurred within a few seconds. Accumulation was much higher in the cytoplasm than in the nucleus and, although nuclear uptake increased slightly over time, there appeared to be no increase in total cellular uptake. Mitotic cells, which were spherical in culture, showed greater intracellular accumulation than other cells. There was no significant difference in uptake among non-mitotic cells. Cells surviving 20 hours of treatment retained accumulation as high as that in killed cells. In KMG-4 monolayers, cytoplasmic and nuclear NCS distribution still differed, whereas 9L monolayers exhibited more even intracellular distribution. In 9L spheroid models treated with 1 mg/ml of NCS, the drug permeated almost all layers within 10 minutes, and at 120 minutes had heavily accumulated in the central necrotic areas. In rats with transplanted brain tumors, NCS selectively accumulated in neoplastic tissues following intra-arterial administration. However, NCS uptake by arterial endothelium was also seen, which suggests the potential for vascular toxicity. The therapeutic value of NCS is discussed in terms of its pharmacokinetic characteristics.
