Impaired low-density lipoprotein receptor activity in chronic B-lymphocytic leukaemia cells

Cellular degradation of 125I-labelled low-density lipoprotein (LDL) was analysed in freshly isolated blood mononuclear cells from 26 patients with chronic B-lymphocytic leukaemia (CLL) and 8 healthy subjects, and in cells following 1, 2 and 3 d of culture in medium containing 10% human lipoprotein-deficient serum (LPDS). Fresh CLL cells had lower LDL degradation rates than mononuclear cells from healthy subjects (p less than 0.01). The LDL degradation rates increased during culture (p less than 0.001), but to a lesser degree in CLL cells than in normal blood mononuclear cells (p less than 0.001). The cellular degradation rate of 125I-LDL was markedly inhibited by an excess of unlabelled LDL, indicating that most of the 125I-LDL that was degraded had been internalized following binding to the high-affinity cell surface receptor. There was a positive correlation between the LPDS-induced LDL degradation of CLL cells and the thymidine uptake in CLL cell cultures with (r = 0.70, p less than 0.001) and without (r = 0.59, p less than 0.01) the B cell mitogen, Epstein-Barr virus. The results indicate that LDL receptors might be involved in the regulation of CLL cell proliferation.