Are tumoral factors responsible for host tissue wasting in cancer cachexia?

Both cytokines and tumor factors have been implicated in tissue loss in cancercachexia. Loss of adipose tissue is most likely due to the tumor (and host) factorzinc-α2-glycoprotein because of its direct lipolytic effect, ability to sensitizeadipocytes to lipolytic stimuli and increased expression in cachexia. TNF-α andthe tumor factor proteolysis-inducing factor are the major contenders for skeletalmuscle at rophy; both increase protein degradat ion through theubiquitin-proteasome pathway and depres s protein synthesis throughphosphorylation of eukaryotic initiation factor 2α. However, while most studiesreport proteolysis-inducing factor levels to correlate with the appearance ofcachexia, there is some disagreement regarding a correlation between serumlevels of TNF-α and weight loss. Furthermore, only antagonists to proteolysisinducingfactor prevent muscle loss in cancer patients, suggesting that tumorfactors are the most important.