CAG myeloma cells transfected with the cDNA for human heparanase express high levels of the enzyme when growing either in vitro or in vivo. Neotransfected cells exhibit a low level of immunostaining for heparanase in vitro (A, cytospins) or in vivo (B, tissue section of a primary tumor). In contrast, heparanase-transfected cells stain intensely for heparanase in vitro (C, cytospin) and in vivo (D, primary tumor). (Original magnification, × 200.) The inset in panel C is a Western blot of extracts from CAG cells growing in culture. The presence of a low level of active heparanase (50 kDa) in the control-transfected cells (lane 2) and a high level of the active heparanase at 50 kDa in the heparanase-transfected cells (lane 1, bottom band) is apparent. A low level of the inactive form of the enzyme (65 kDa) is also present in the heparanase-transfected cells. Western blotting of syndecan-1 extracted from subcutaneous tumors demonstrates that the proteoglycan is dramatically reduced in size in the presence of elevated heparanase (E). Shown are the syndecans present in tumors from 3 mice bearing control-transfected cells and from 3 mice bearing heparanase-transfected cells (heparanase).