SIMVASTATIN IMPAIRS MITOGEN-INDUCED PROLIFERATION OF MALIGNANT B-LYMPHOCYTES FROM HUMANS - IN-VITRO AND IN-VIVO STUDIES

Chronic lymphocytic leukemia (CLL) cells express lower low density lip oprotein (LDL) receptor activity and higher 3-hydroxy-3-methylglutaryl -CoA (HMG-CoA) reductase activity than normal mononuclear blood cells indicating that CLL cells may depend on cholesterol synthesis for thei r proliferation., We studied the effects of competitive inhibitors of HMG-CoA reductase on malignant lymphocyte proliferation in vitro and i n vivo. Tumor B-cells from 13 patients with CLL, hairy cell leukemia, or immunoblastic B-cell lymphoma were cultured for 4 d in the presence of B-cell mitogens and cholesterol synthesis inhibitors. Simvastatin and lovastatin suppressed, in a concentration-dependent manner, the mi togen-induced cellular thymidin uptake in medium with 10% human AB-ser um or lipoprotein-deficient serum. Pravastatin was active only in medi um with lipoprotein-deficient serum. Ten previously untreated patients with CLL received simvastatin orally, 40 mg daily for 12 wk. Mean red uctions in total plasma and LDL cholesterol were 30% (range 9-46%) and 37% (range 16-63%), respectively. Cells from four patients showed mod erate to minor increases in the degradation rate of I-125-LDL suggesti ng that the need for exogenous cholesterol had increased, three patien ts showed an increase in HMC-CoA reductase activity, and the cells fro m one patient showed both. There was no significant change in the clin ical disease status during medication. However, four of the ten patien ts developed a therapy-demanding progressive disease during the subseq uent year. Further clinical studies with cholesterol synthesis inhibit ors in leukemia are warranted.