JUN and renal cell carcinoma: In line with these results, in RCC cell lines, we also observed that CD40 ligation was able to induce an increased activation of the mitogen-activated protein kinase (MAPK) ERK, c-Jun N-terminal kinase (JNK) and p38 MAPK, together with the activation of key transcription factors, such as NFkB and AP-1, that represent key signaling pathways involved in proliferation and tumorigenesis [25].