HSPA1A and plasma cell myeloma: Similarly, Xie et al. linked Hsp70-enriched exosomes to an increased NK cell activity, where they found exosomes isolated from J558 myeloma cells transgenically overexpressing Hsp70 stimulated dendritic cell (DC) maturation, and protection from J558 tumor cell challenge, an effect dependent on CD8 + T cell and NK cell activity [164].