Degradation of cartilage proteoglycans by myeloid leukemia cells

Polymorphonuclear leukocytes contain proteases that are capable of degrading articular cartilage matrix in disease states such as rheumatoid arthritis and osteoarthritis. In this study, the HL-60 human promyelocytic leukemia cell line was examined for ability to degrade cartilage proteoglycans. The HL-60 cells contained proteoglycan-degrading enzymes, which may contribute to the joint inflammation sometimes seen in acute leukemia. However, the protease activity was much less than in mature neutrophils and was not enhanced by the induction of myeloid maturation with dimethyl sulfoxide or retinoic acid. The diminished enzyme activity of induced HL-60 cells compared to normal neutrophils is another functional deficiency of these cells.