Adhesion to 90K (Mac-2 BP) as a mechanism for lymphoma drug resistance in vivo.

A cell-adhesive protein of the human serum, 90K binds galactin-3, beta1-integrins, collagens, and fibronectin, and it is of importance in cell-cell and cell-extracellular matrix adhesion. Serum 90K levels in 137 patients with lymphoma were measured by enzyme-linked immunosorbent assay. Compared with healthy controls, pretreatment serum 90K levels in patients with lymphoma were elevated (P <.001). Of 97 patients who showed objective response to treatment, 20 (21%) had pretreatment 90K levels above the normal cutoff compared with 17 (53%) of 32 patients who did not respond (P =.002). When used as a plastic-immobilized substrate, 90K caused a significant reduction in chemotherapy-induced apoptosis of Jurkat T lymphoma cells. This finding could explain the lack of response in lymphoma patients with high 90K serum levels.