CCR1 expression and CCL3 secretion by MM cell lines and primary MM cells. (A) CCR1 expression on MM cell lines and patient MM cells was analyzed by flow cytometry. A representative flow cytometry shows percentage of positive cells from at least 3 different experiments. CCR1 expression on monocytes is shown as a positive control. (B) CCR5 expression on MM1.S, OPM1, INA6, and U266 was analyzed. Flow cytometry data represent several independent experiments. (C) CCL3 secretion was assessed by ELISA on 48-hour culture supernatants of MM cell lines, MM primary cells, and monocytes plated at a density of 10⁶ cells/mL. Means (± SD) are expressed as pg/mL on a logarithmic scale.