Hormonal

Inhibition of the MAP kinase pathway (via MEK inhibition) enhances skeletal muscle myoblast differentiation, whereas activation of the PI 3-kinase/p70S6k pathway is essential for IGF-stimulated differentiation.

This research suggests that muscle cell differentiation is not simply the absence of growth signals. Instead, it requires a specific signal (PI 3-kinase pathway) to proceed, while the growth signal (MAPK pathway) actively suppresses it. For muscle building contexts, this implies that simply stopping cell division is not enough; specific molecular pathways must be activated to trigger the structural changes of differentiation.