PTPRC and plasma cell myeloma: At end-stage myeloma development, the BM was harvested and tumor cells, identified by GFP and human leukocyte marker CD45, were analyzed for surface HLA-E and HLA-class I. This analysis revealed that both in vitro and in vivo grown U266 cells strongly expressed HLA-class I, albeit that the in vivo level was somewhat lower than the in vitro level.