TNFSF13B and plasma cell myeloma: The interaction with the APRIL or BAFF (B-cell activating factor) ligand activates the NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), PI3K/AKT (phosphatidylinositol-3-kinase/protein kinase B), and MAPK/ERK (mitogen-activated protein kinase/extracellular signal-regulated kinase) signaling cascades, which promote the growth, survival, and resistance of myeloma cells to apoptosis [101,102].