Crotoxin, a toxin derived from Crotalus durissus terrificus and cytotoxin 2 derived from Naja naja oxiana decreased the viability of MCF7aro cells via the inhibition of the extracellular signal-regulated kinase (ERK) pathway, inhibited cell migration by inducing the apoptosis of MCF7 cells, and showed an anticancer effect on lung cancer cells in A549 cells through the activation of the caspase-3 and p38 pathways [95,96,97]. The gene discussed is MAPK1; the disease is lung cancer.