MAPK8 and cancer: TRAF2 will then be polyubiquitinated and activated, likely through a self-ubiquitination mechanism, leading to the activation of ERK1/2 and particularly JNK signaling and subsequent AP-1-dependent expression and activation of MMPs (e.g., MMP1) and finally, promotion of invasion and metastasis of cancer cells [42,96] (Figure 1A).