Multitargeted kinase inhibitors imatinib, sorafenib and sunitinib perturb energy metabolism and cause cytotoxicity to cultured C2C12 skeletal muscle derived myotubes

Tyrosine kinase inhibitors (TKIs) have advanced cancer treatment and prognosis but have also resulted in adverse effects such as fatigue, diarrhea, hypothyroidism, and other toxicities. We investigated TKI effects on skeletal muscle as a possible explanation of TKI induced fatigue. Changes in mitochondrial function due to inhibition of oxidative phosphorylation complexes, generation of superoxides, and inhibition of key transporters involved in uptake of glucose and/or nucleosides may result in alteration of energy metabolism and/or mitochondrial function. We investigated effects of imatinib, sorafenib and sunitinib on these processes in cultured C2C12 murine skeletal muscle cells. Imatinib, sorafenib and sunitinib were cytotoxic to C2C12 cells with IC50 values of 20, 8 and 8 µM, respectively. Imatinib stimulated glucose uptake and inhibited complex V activity by 35% at 50 µM. Sorafenib inhibited complex II/III and V with IC50 values of 32 and 28 µM, respectively. Sorafenib caused activation of caspase 3/7 and depolarization of mitochondrial membranes occurred very rapidly with complete loss at 5-10 µM. Sunitinib inhibited Complex I with an IC50 value of 38 µM and caused ATP depletion, caspase 3/7 activation, an increase in reactive oxygen species (ROS), and decreased nucleoside and glucose uptake. In conclusion, imatinib, sunitinib and sorafenib caused changes in mitochondrial complex activities, glucose and nucleoside uptake leading to decreased energy production and mitochondrial function in a skeletal muscle cell model, suggesting that these changes may play a role in fatigue, one of the most common adverse effects of TKIs.