LITHIUM ENHANCES THE PROLIFERATION OF HL-60 PROMYELOCYTIC LEUKEMIA CELLS

Abstract The effects of lithium, an agent used in the treatment of manic depression and to attenuate myelosuppression during chemotherapy, on HL-60 promyelocytic leukemia cells were investigated. By monitoring cell growth at varying concentrations (0–50 mM), as well as by following cell proliferation over 8 days, it was established that lithium stimulates HL-60 proliferation within a very narrow concentration range. Enhancement of growth was optimal at 5 mM, whereas concentrations above 10 mM were toxic. Time course studies revealed that the greatest increase in cell number occurred after 5–6 days in the presence of lithium. This was preceded by DNA synthesis reaching a maximum after 1–2 days. Viability of the cells decreased gradually after 3 days with 5 mM, but not with 2.5 mM. We suggest that HL-60 cells are a suitable model to further investigate possible mitogenic and cytotoxic effects of lithium in vitro .