.....In this study, we aimed to elucidate the cancer-host energy production relationship, in particular, between cancer energy production and host muscle. During the development and progression of colorectal cancer, expression of the secreted autophagy-inducing stress protein HMGB1 increased in the muscle of tumor-bearing animals. This effect was associated with decreased expression of pyruvate kinase PKM1 and pyruvate kinase activity in muscle via the HMGB1 receptor for advanced glycation endproducts (RAGE). However, muscle mitochondrial energy production was maintained. In contrast, HMGB1 addition to colorectal cancer cells increased lactate fermentation. In the muscle, HMGB1 addition induced autophagy by decreasing levels of active mTOR and increasing autophagy-associated proteins, plasma glutamate, and (13)C-glutamine incorporation into acetyl-CoA. In a mouse model of colon carcinogenesis, a temporal increase in HMGB1 occurred in serum and colonic mucosa with an increase in autophagy associated with altered plasma free amino acid levels, increased glutamine, and decreased PKM1 levels. These differences were abolished by administration of an HMGB1 neutralizing antibody. Similar results were obtained in a mouse xenograft model of human colorectal cancer. Taken together, our findings suggest that HMGB1 released during tumorigenesis recruits muscle to supply glutamine to cancer cells as an energy source.