FAS and cancer: Given all the previously mentioned findings, Carracedo et al. [9] stated that “a big challenge is to unify the idea of FAO as an essential pathway in cancer cells with the fact that cancer cells also require active FAS in order to grow and divide.” Simultaneous cytosolic FAS and mitochondrial β-oxidation has been considered impossible due to the inhibition of CPTI proteins by malonyl-CoA.