HMCLs that express HPSE produce higher amounts of soluble syndecan-1. (A) Syndecan-1 gene expression was determined in the 19 HMCLs using Affymetrix U133 set microarrays. (B) Mean fluorescence intensity of membrane syndecan-1 expression determined with a PE-conjugated anti-CD138 MoAb, a PE-isotype–matched control MoAb, and FACS analysis. For each cell line, the mean fluorescence intensity obtained with the control MoAb was set between 4 and 6. (C) For the 19 HMCLs, the rates of production of soluble syndecan-1 per 10⁶ cells and per 24 hours was determined during the second and third days of culture (exponential growth phase) and measured by ELISA. The dotted line indicates the detection limit of the test (< 8 ng/mL). Horizontal bars indicate the median value. (D) For XG-2 and U266 HMCLs, the cell count, the density of membrane syndecan-1, and the concentration of soluble syndecan-1 in the culture supernatant were determined each day for 3 days.