2 factors have particularly attracted the attention of scientists in recent years, the ZAG factor (Zinc alpha 2 glycoprotein), a veritable lipid mobilization factor in humans , overexpressed in the liver and adipose tissue and PIF (proteoglycan identified in mouse murine adenocarcinoma tumor cells which would be responsible for muscle wasting induced by the activation of the ubiquitin-proteasome-ATP-dependent proteolytic pathway . More recent work suggests that Myostatin and Activin A, two members of the TGFβ superfamily, may contribute to cachexia, particularly muscular atrophy, induced by certain cancers.