Formation of cytosine arabinoside-5'-triphosphate in different cultured lymphoblastic leukaemic cells with reference to their drug sensitivity.

The accumulation of intracellular cytosine arabinoside-5'-triphosphate (Ara-CTP) is determined in five lymphoblastic cell lines: Molt 4, H9 and three newly established cell lines from paediatric patients, KFB-1, KFB-2, KFT-1. The cell lines KFB-1 and KFB-2 are B-lymphoblastic (B-ALL), the others are T-lymphoblastic leukaemic cells (T-ALL). The Ara-CTP levels were compared with the sensitivity of the cells to Ara-C. The cells were incubated at different concentrations (100 nM-100 microM) of Ara-C for 4 h or incubated for variable times (30 min-11 h) at 0.1, 1 and 10 microM Ara-C to form Ara-CTP. The Ara-CTP-concentrations were measured by high pressure liquid chromatography (HPLC). To determine the sensitivity of the cells to Ara-C, the MTT colorimetric-assay was used. The studies indicate that different B- and T-lymphoblastic leukaemia cell lines accumulate Ara-CTP to a markedly different extent. Ara-CTP plateau levels and sensitivity of the cells to Ara-C correlated well in four of the five cells lines studied.