In mice inoculated with myeloma cells and analysis of patient primary myeloma cells, S100A9 promoted myeloma cell proliferation and survival through TNFSF13B production by myeloid cells, and the activation of the canonical NF-κB pathway was TNFSF13B/TNFRSF13B-dependent, as discussed later in this paper. Here, S100A9 is linked to plasma cell myeloma.