31P NMR SPECTROSCOPIC STUDIES OF THE EFFECTS OF CYCLOPHOSPHAMIDE ON PERFUSED RIF-1 TUMOR-CELLS

To determine whether direct cellular effects of chemotherapy are respo nsible for P-31 NMR spectral changes observed in treated tumors in viv o, RIF-I fibrosarcoma cells were examined in vitro before, during, and after treatment with 4-hydroperoxycyclophosphamide (4-HC), an activat ed form of cyclophosphamide. When RIF-1 cells were treated with 4-HC i n a metabolically stable but nonproliferating state, the P-31 NMR spec tra were identical with those of untreated cells for up to 70 h. When actively proliferating RIF-1 cells were treated with 4-HC, the intensi ties of the nucleotide triphosphate resonances, which increased linear ly during control cell growth, remained constant for 50 h or longer. T hese studies demonstrate that the bioenergetic improvement observed fo llowing treatment of RIF-1 tumors in vivo [S.-J. Li, J.P. Wehrle, S.S. Rajan, R.G. Steen, J.D. Glickson, and J. Hilton, Cancer Res. 48, 4736 (1988)] does not result from direct effects of cyclophosphamide metab olites on RIF-1 cell metabolism, but rather from indirect effects of t reatment on tumor or host physiology.