. More than 80% of metastatic cancer patients experience a progressive and debilitating loss of muscle mass and function by a process known as cachexia. Cachectic patients suffer deterioration of diaphragm and cardiac muscles and often die prematurely due to respiratory and cardiac failure. The prognosis for these patients is further diminished by the fact that they are often too weak to tolerate standard doses of anti-cancer treatments. Our long-term goal is to identify and exploit the underlying mechanisms that drive the development of cachexia to improve treatment response, survival and quality of life in metastatic cancer patients. We recently identified a conserved mechanism of muscle wasting in mice and patients with metastatic cancers in which the metal ion transporter, called SLC39A14 (ZIP14), is upregulated in cachectic muscles (Wang et al., Nat Med, 2018). Muscle- specific loss of ZIP14 alleviates the development of cachexia in these mouse models. Zinc is an essential micronutrient that is often taken as a dietary supplement but in tumor bearing mice, excess supplementation accelerates muscle wasting. In addition to cancer-induced cachexia, we now find that certain chemotherapeutic drugs commonly used in patients (e.g. doxorubicin-cyclophosphamide and cisplatin) can also cause Zip14 upregulation in the muscles of healthy mice and that Zip14 is critical for chemotherapy-induced muscle atrophy in this context. Based on our preliminary studies, our central hypothesis is that a subset of chemotherapeutic drugs perturbs metal-ion homeostasis and promotes muscle wasting through the upregulation of Zip14 in muscle cells. Which chemotherapy agents induce Zip14, how Zip14 is induced and the role of ZIP14 in chemotherapy-induced muscle wasting remains to be explored. The proposed studies are expected to fill this gap and further our understanding of the functions of ZIP14 in cancer- and chemotherapy-induced cachexia. Based on our preliminary studies, in Aim 1, we will determine which chemotherapies promote muscle wasting through the ZIP14 axis and whether Osteopontin, a candidate protein from serum profiling, regulates chemotherapy-induced Zip14 expression in muscle cells.
In Aim 2, we will develop strategies to prevent chemotherapy-induced, Zip14-dependent muscle wasting in metastatic cancer models. These studies could inform the development of new dietary intervention strategies to prevent or reverse cachexia, with the aim of prolonging survival, improving treatment response and quality of life in cancer patients with cachexia, in line with the objectives of the PQ11 and NCI.
Cachexia is an important determinant of therapeutic response, outcome and survival in advanced cancer patients. We found that excess dietary zinc supplementation exacerbates cachexia in metastatic cancer models, which will be mechanistically dissected in the context of anti-cancer therapy.