CD38 and plasma cell myeloma: In the present work, we observed for the first time the extracellular release of cGAMP by human myeloma cells, strongly enhanced by the treatment with the genotoxic drug doxorubicin, and we further demonstrated a role of the NAD-glycohydrolase CD38 in the regulation of extracellular cGAMP activity, pointing at its inhibition as a potential strategy to increase extracellular cGAMP concentration for therapeutic purposes.