SMAD2 and lung cancer: Importantly, restoration of KDM4C partially rescued the reduced levels of TGF-β2, p-Smad2 and p-Smad3 in USP9X-depleted lung cancer cells (Fig. 8a, b), suggesting that USP9X silencing inhibits TGF-β2/Smad signaling in a KDM4C-dependent manner.