SMAD2 and lung cancer: To further clarify the role of USP9X in lung cancer radioresistance and confirm whether this effect is dependent on KDM4C, we transfected exogenously expressed KDM4C into USP9X-depleted cells and found that TGF-β2, p-Smad2 and p-Smad3 protein levels were decreased when USP9X was knocked down (Fig. 8a).