PDGFRB and plasma cell myeloma: In the present study, a dual-targeting drug delivery system was designed by using a cyclic peptide with high affinity to PDGFR-β [5] as the targeting moiety, PDGFR-β overexpressed on both myeloma cells and CAFs as the therapeutic target, nanoparticles (NPs) based on FDA-approved biodegradable poly(ethylene glycol)-poly(lactic acid) as the drug carrier, and the classical chemotherapeutics paclitaxel (PTX) as the model drug (Figure 1).