CD19 Expression and Growth Inhibition of Tumours in Human Multiple Myeloma

Multiple myeloma (MM) is a proliferative disorder of monoclonal plasma cells which accumulate in human bone marrow (BM). CD19 is a hallmark differentiation antigen of the B cell lineage and positively regulates antigen receptor signal transduction in mature B cells. We have previously shown that malignant plasma cells (myeloma cells) isolated from the MM patients lack the CD19 expression, while non-malignant plasma cells isolated from the healthy donors do express the CD19 antigens. It is also intriguing that there exists both CD19 m and CD19 + plasma cells in some cases in pre-myeloma states including monoclonal gammopathy of undetermined significance (MGUS). It indicates that MGUS is usually composed of phenotypically non-malignant (CD19 + ) and malignant (CD19 m ) plasma cells. Furthermore, we recently demonstrate that, expression of the CD19 gene markedly inhibits the proliferation of human myeloma cell lines in vitro, and exhibits the reduced tumorigenicity in vivo and no anchorage-independent growth...