Leukemia Research Vol. 16, No. 8, pp. 823-828, 1992. Printed in Great Britain.

0145--2126t92 $5.00 + .00 Pergamon Press Lid

EFFECTS OF L I T H I U M ON D I M E T H Y L S U L F O X I D E I N D U C E D D I F F E R E N T I A T I O N OF HL-60 P R O M Y E L O C Y T I C L E U K E M I A CELLS ROLF W. BECKER and ERROL M. TYOBEKA Department of Biochemistry, University of the North, Private Bag Xl106, Sovenga 0727, South Africa (Received 9 August 1991. Accepted 17 January 1992) Abstract--The human promyelocytic leukemia cell line, HL-60, was used to investigate the effects of lithium on dimethyl sulfoxide (DMSO)-induced granulocytic differentiation of these cells. Doseresponse studies showed an optimal increase of cellular proliferation when cells were incubated with 5 mM lithium for 5 days (127 --- 5% of DMSO only treated cells). This enhancement in growth was preceded by significantly increased [methyl-3H]thymidine incorporation (143 --- 4% of DMSO only treated controls) after 2 days. However, no significant changes in the ability of cells to reduce NBT could be detected irrespective of whether the cells were incubated with 1.25% (v/v) DMSO only, or with DMSO plus non-toxic concentrations (~