miR-21 and TNF-α signaling. miR-21, microRNA-21; TNF-α, tumor necrosis factor α; TNFR1/2, tumor necrosis factor receptors 1/2; NF-κB, nuclear factor κB; JNK, c-Jun N-terminal kinase; TRAF2, TNF receptor-associated 2; SODD, silencer of death domain; TRADD, TNFRSF1A-associated via death domain; FADD, Fas-associated via death domain.