MAPK3 and cancer: Thus, with the MAPK (RAF–MEK–ERK) signalling cascade facilitating cell proliferation, survival and transformation in a myriad of cancers, it is of concern that Raf inhibitors such as Sorafenib can induce a paradoxical activation of the MAPK pathway resulting in increased Erk1/2 phosphorylation, which has been linked to adverse effects.46