Experimental approach:
The expression of HSP90 and the activation of STAT3 were detected in muscle from the patients with cancer cachexia or the tumour-bearing cachectic mice. HSP90 inhibitors, including 17DMAG and PU-H71, were administered to cachexic mice, and cachexia parameters, such as weight loss, food intake, survival rate, body mass composition, serum metabolites, muscle wasting pathology and catabolic activation, were measured and analysed. The in vitro coculture of C2C12 myotube cells with C26 conditioned media (CM) was performed to address the pathological mechanism of catabolic muscle wasting. The roles of HSP90, STAT3 and FOXO1 in myotube atrophy were explored via overexpression or knockdown.