established a human MM model in NOD-RAG-1-null IL-2rg-null (NRG) mice and found that AKAP4 was not only highly expressed in myeloma cells, but also this protein, like CD138, could be used as a marker of myeloma cells to track the proliferation of malignant cells and to distinguish human myeloma cells from mouse cells (18). This evidence concerns the gene SDC1 and plasma cell myeloma.