Fig. 8: USP9X promotes tumor progression and radioresistance by stabilizing KDM4C in lung cancer.

a SPC-A1 cells transfected with indicated siRNAs or SFB-KDM4C plasmid were collected and analyzed by Western blotting using indicated antibodies (n = 3). b SPC-A1 cells were transfected with indicated siRNAs or SFB-KDM4C plasmid, followed by real-time PCR to determine the mRNA levels of TGF-β2, KDM4C and USP9X. ***P < 0.001 (n = 3). c SPC-A1 cells transfected with the indicated siRNAs and plasmids were seeded and calculated every other day. Data are shown as the mean ± SD. ***P < 0.001 (n = 3). d SPC-A1 cells transfected with the indicated siRNAs and plasmids were seeded and cultured for 2 weeks. The colonies were stained using crystal violet solution and then counted under a microscope. ***P < 0.001 (n = 3). e Representative pictures of Comet assays performed 4 h after IR. ***P < 0.001 (n = 3). Scale bar, 20 μm. f SPC-A1 cells transfected with the indicated siRNAs and plasmids were irradiated with indicated doses. The percentages of surviving colonies were evaluated 2 weeks later. ***P < 0.001 (n = 3). g Representative immunohistochemical staining for USP9X and KDM4C in lung cancer tissues. Scale bar, 10 μm. h Positive correlation between USP9X and KDM4C protein levels in lung cancer tissues (P < 0.001, chi-square test). i Schematic diagram summarizes aberrant epigenetic networks and therapeutic potentials of targeting KDM4C in lung cancer. Upper panel: Deubiquitinase USP9X-mediated aberrant recruitment of KDM4C activates TGF-β2/Smad signaling to promote lung cancer progression and radioresistance. Lower panel: Pharmacological targeting of KDM4C using SD70 inhibits the activation of TGF-β2/Smad signaling, which in turn leads to enhanced radiosensitization.