RTN4R and neoplasm: However, it is also worth highlighting the fact that the function of CD13 is not limited to NGR-TNF homing to tumor vessels, as upon NGR-TNF binding this membrane protein can also induce co-signaling mechanisms that impair the activation of pro-survival pathways induced by the TNF moiety (Ras, Erk, Akt, NF-kB) without affecting other pathways related to stress and cell death (p38 and JNK), a mechanism that may contribute to the overall biological activity of the fusion protein [26].