CD37 and neoplasm: Other mechanisms that might contribute to the observed synergy are improved complement-dependent cytotoxicity by colocalization of CD37 and CD20 on the cell membrane (35), radiation-induced permeability of tumor vasculature (36), radiation-induced immunogenic modulation of tumor cells (37–39), rituximab-induced sensitization of tumor cells to ionizing radiation (40), and rituximab-induced increased internalization of CD37 (41) leading to increased cellular retention of 177Lu and thus to a higher cellular absorbed radiation dose (25).