Thermal enhancement of tetraplatin and carboplatin in human leukaemic cells.

The thermal enhancement of tetraplatin (racemic, d-trans and l-trans isomers) and carboplatin was studied as a function of temperature in vitro in JM, a human acute lymphoblastic leukaemia cell line. Exponentially growing JM cells were exposed to tetraplatin (0-10 micrograms/ml) or carboplatin (0-45 micrograms/ml) for 1 h at 37-43 degrees C in 1 degree C increments. Graphic analysis demonstrated a breakpoint for the onset of thermal enhancement for tetraplatin at 40 degrees C. Thermal enhancement was maximal at 42 degrees C with no significant increase at 43 degrees C. The tetraplatin thermal enhancement ratio (TER) was 2.7 at 42 degrees C. The TERs for d and l isomers at 41.8 degrees C were not significantly different. The relationship of TER to temperature for carboplatin closely paralleled that of tetraplatin. The implications of these results are discussed in the context of tetraplatin's unique properties.