Using these mAbs, we have demonstrated that: (a) tumour cells from PEL expressed a syndecan-1 isoform with a higher molecular weight than that present on malignant plasma cells; (b) syndecan-1 expressed by PEL cells had a core protein identical in size to that expressed by plasma cells, suggesting that differences in syndecan-1 size were due to different GAG chains attached to an identical protein backbone; (c) the PEL-specific isoform of syndecan-1, which probably represented the major proteoglycan expressed by these cells, was effective in mediating cell adhesion to type I collagen substrates.
The CD138/syndecan-1 isoform expressed by PEL has an average molecular weight of 420 kD, which is substantially different from that of CD138/syndecan-1 molecules generally expressed by plasma cells.