Furthermore myeloma cells expressing CD138 maintain the tumor upon transplantation into immunodeficient mice (128); and these results have been extended in recent studies showing that the capacity to establish and sustain the tumor in immunodeficient mice resides in malignant plasma cells, some of which lack CD138 expression, but not in clonotypic B-cells (129–131). The gene discussed is SDC1; the disease is neoplasm.