MEMBRANE AFFINITY AND METABOLISM OF N-4-PALMITOYL-1-BETA-D-ARABINOFURANOSYLCYTOSINE INTO CULTURED KB-CELLS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 41  (11) , 4484-4488
Abstract
N4-Palmitoyl-1-.beta.-D-arabinofuranosylcytosine (N4-palmitoyl-ara-C), a lipophilic derivative of 1-.beta.-D-arabinofuranosylcytosine, possessed an affinity for KB [human epidermoid carcinoma] cell plasma membrane. Approximately 15-25% of the drug incorporated into KB cells was retained in plasma membrane when the cells were treated with the drug for 1-32 h at 10 .mu.M, the concentration required for 50% inhibition of cell growth. Less than 5.3% of of the drug was found in the plasma membrane when the cells were treated with 1-.beta.-D-arabinofuranosylcytosine. N4-Palmitoyl-ara-C in the membrane fraction cosedimented with plasma membrane in a sucrose density gradient at 4.degree. C, indicating a close association between the drug and the membrane. The affinity of N4-palmitoyl-ara-C for plasma membrane probably contributes to the efficient uptake rate and the strong cytotoxic effect of N4-palmitoyl-ara-C reported previously. The metabolites of N4-palmitoyl-ara-C in KB cells, treated with the drug for 32 h at the concentration required for 50% inhibition of cell growth (10 .mu.M), were analyzed by diethylaminoethyl Sepharose CL-6B column chromatography and thin-layer and paper chromatography. This analysis showed that > 98% of the drug present in the KB cell was N4-palmitoyl-ara-C. The active metabolites, 1-.beta.-D-arabinofuranosylcytosine, 1-.beta.-D-arabinofuranosylcytosine 5''-monophosphate, N4-palmitoyl-1-.beta.-D-arabinofuranosylcytosine 5''-triphosphate, were found in amounts of 0.41, 0.37, 0.17 and 0.05%, respectively, of the total drug found in the cells. Also found were the inactive metabolites of 1-.beta.-D-arabinofuranosyluracil and 1-.beta.-D-arabinofuranosylcytosine diphosphate choline in amounts of 0.61 and 0.29%, respectively. [N4-Acyl derivatives of ara-C4 with long-chain saturated fatty acids have greater chemotherapeutic activity against mouse leukemia L1210 than does ara-C.].