TNF and reticulum cell sarcoma: We first used the human histiocytic lymphoma cell line U-937 as a differentiation model since U-937 cells are induced to monocytic/macrophage-like differentiation by phorbol esters (Fig. S2A, B, C), ATRA, 1-α-25-dihyroxycholecalciferol (vitamin D3), gamma interferon, or tumor necrosis factor [25]–[27].