RHD and rhabdomyosarcoma: To assess the selectivity of X-370 in the context of an isogenic cellular background, we generated a panel of Rh30 human rhabdomyosarcoma cell lines each of which stably expresses a single myristoylated (Myr)-epitope tagged p110 human class I PI3K catalytic subunit, termed as Rh30-Myr-p110α, Rh30-Myr-p110β, Rh30-Myr-p110γ or Rh30-Myr-p110δ.