Fig. 3.

STAT3 was sufficient to induce muscle fiber atrophy both in vitro and in vivo. A: constitutively active STAT3 [Ad-cSTAT3-green fluorescent protein (GFP)] resulted in decreased C₂C₁₂ myofiber diameter 48 h after infection (n = 150–200 fibers/condition from 3 independent wells) and increased transcription of known STAT3 target genes as well as atrogin-1 (n = 3 wells/group in triplicate). B: cytomegalovirus (CMV)-cSTAT3 transfection reduced cross-sectional area (CSA) in the tibialis anterior muscle of non-tumor-bearing and C26-bearing CD2F1 mice. Mice were transfected on the same day as PBS, or tumor cells were injected and then euthanized 12 days later. Only positively transfected fibers (i.e., green fibers coexpressing pCMV-GFP) were measured (n = 650–1,900 fibers/condition; n = 8 tumor-bearing and non-tumor-bearing mice). Both experiments have been performed >3 times. **P < 0.01; ***P < 0.001.