FST and neoplasm: In addition, mechanical stretching stimulus induces IL‐4 secretion by muscle cells.23 Recombinant follistatin counteracts C26 tumour effects on myotubes exclusively by rescuing fusion index, while recombinant IL‐4 ameliorates fusion index, as well as the myotube size, in terms of both myotube diameter and number of nuclei per myotube.