Soluble syndecan-1 accumulates in the bone marrow interstitial matrix.

Immunohistochemistry reveals strong syndecan-1 staining around cells expressing syndecan-1 on their cell surface (Syn-1, panel B), but only very weak staining in the adjacent interstitial matrix of the bone marrow (arrow). In contrast, tumors composed of cells expressing soluble syndecan-1 (sSyn-1, panel C) show extensive accumulation of syndecan-1 within the interstitial matrix (arrow). Animals bearing tumor composed of neo-transfected cells (neo, panel A) show no immunoreactivity for syndecan-1 within the bone marrow. Original magnification × 200.