Fig 2: SSA is not responsible for gross genomic instability in BRCA2-depleted cells. a Schematic representation of the EGFP-based SSA reporter assay. b BRCA2 depletion leads to an increased SSA frequency. Wild-type, RAD52-, or ERCC1-deficient U2OS SSA-EGFP cells were transfected with control siRNA or siRNA against BRCA2. Twenty-four hours post transfection, cells were electroporated with pCBASce plasmid. After 48 h, the percentage of GFP-positive cells was determined by FACS. Results represent mean ± SEM of three independent experiments. c Knockdown/knockout efficiency was confirmed by western blotting. d Loss of RAD52 or ERCC1 was unable to reverse gross genomic instability in BRCA2-depleted cells. Wild-type, RAD52-, or ERCC1-deficient HeLa cells were transfected with control siRNA or siRNA against BRCA2. Forty-eight hours post transfection, cells were exposed to 10 Gy IR and then allowed to recover for 2 or 24 h before being processed for immunofluorescence using antibodies against RPA2 and RAD51. Representative RPA2/RAD51 foci and DAPI-stained nuclei are shown. e Quantification of RPA2/RAD51 foci and nuclear fragmentation. Data represent mean ± SEM of three independent experiments. Over 100 cells were counted in each experiment. Scale bar, 10 µm

Fig 3: Overexpression of miR-485-5p reverses cisplatin resistance in SCC25-CR (cisplatin-resistant) cells. (A) MTT assay for cell viability of the SCC25-CR cells. SCC25-CR cells transfected with pre-miR-485-5p and empty vectors (mock) were untreated or treated with cisplatin. n=3. (B) Western blotting of ERCC1 and YAP in SCC25-CR cells transfected with pre-miR-485-5p and empty vectors (mock). β-actin was used as a loading control. n=3.

Fig 4: DDP in combination with curcumin promotes A549/DDP cell apoptosis. A549/DDP cells were treated with DDP (10 µM), DMC (5 µM) or both for 48 h. (A and B) TUNEL staining results showed that the apoptosis rate was significantly increased in the combined drug group (DDP group vs. DDP + DMC group; P<0.01). Scale bar, 20 µm. (C-I) Western blotting showed that the expression of the anti-apoptotic protein Bcl-2 was decreased and that of the pro-apoptotic protein Bax was increased in the combination group. DMC treatment downregulated ERCC1 expression in A549/DDP cells. Expression of cleaved caspase-3 and cleaved PARP were also increased. *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001. DDP, cisplatin; DMC, demethoxycurcumin; ERCC1, excision repair cross-complementary 1; PARP, poly ADP-ribose polymerase.

Fig 5: Knockdown of HMG20A enhanced cisplatin sensitivity, and inhibited DNA damage repair, proliferation and invasion of OSCC cells. A, cell viability of BHY and HSC3 cells transfected with si-HMG20A or si-NC at different cisplatin concentrations. B, IC50 to cisplatin of BHY and HSC3 cells transfected with si-HMG20A or si-NC. C, BHY and HSC3 cells transfected with si-HMG20A or si-NC were treated with 5 µM cisplatin for 48 h. Western blotting was used to measure the protein levels of ERCC1 and ?-H2AX. ß-actin was the internal control. D/E, BHY and HSC3 cells transfected with si-HMG20A or si-NC were treated with 5 µM cisplatin for 48 h. CCK8 and Transwell assay was used to detect cell proliferation (D) and invasion (E). **P < 0.01, si-HMG20A group vs. si-NC group