Fig 2: UBE2B expression levels are a prognostic marker for patients with NPC receiving cisplatin-based chemoradiotherapy. Immunohistochemical analysis of UBE2B indicated nuclear and cytoplasmic staining in representative NPC cases with (A) low (H-score=125) and (B) high (H-score=375) expression (scale bars, 100 µm). (C) Survival analysis revealed that high expression of UBE2B was a prognostic marker for poor disease-specific survival, distal metastasis-free survival and local recurrence-free survival. NPC, nasopharyngeal carcinoma; UBE2B, ubiquitin-conjugating enzyme E2 B; Cum, cumulative.

Fig 3: UBE2B has an important role in the carcinogenesis of NPC cells. (A) Western blot analysis demonstrated that UBE2B expression levels were higher in TW01 cells than those in DOK cells. (B) Bar graphs indicated a higher UBE2B/actin ratio in TW01 cells compared with that in DOK cells. (C) Expression levels of UBE2B in NPC cells treated with control or UBE2B-targeting siRNA were determined using western blot analysis. (D) By using methylene blue staining, the numbers of colonies formed, which consist of at least 50 tumor cells, were manually recorded and compared. (E) Bar graphs indicated decreased numbers of formed colonies in UBE2B-deficient NPC cells as compared with UBE2B-proficient cells. At least three independent experiments were performed and values were expressed as the mean ± standard deviation. ****P<0.01 for NPC cells vs. DOK cells and siUBE2B vs. control. Fold changes in protein levels listed under each blot were normalized to the levels of the control counterparts and analyzed by using ImageJ densitometry analysis. NPC, nasopharyngeal carcinoma; UBE2B, ubiquitin-conjugating enzyme E2 B; siRNA, small interfering RNA.

Fig 4: UBE2B modulates cisplatin cytotoxicity in nasopharyngeal carcinoma cells by targeting MGMT expression. (A) Western blot analysis demonstrated UBE2B and MGMT expression in TW01 cells with distinctive siRNA or plasmid transfection. (B) Cell viability assays were performed with TW01 cells to analyze the role of UBE2B and MGMT in cisplatin-induced cell death by using methylene blue staining. At least three independent experiments were performed. Cell survival results were presented as the mean ± standard deviation and compared using analysis of variance with Tukey's post-hoc test. *P<0.01, ***P<0.0001, 2BKD group vs. control group; #P<0.01, ###P<0.0001, 2BKD + MGMT group vs. 2BKD group. Ctrl, cells transfected with scrambled siRNA; 2BKD, cells transfected with siUBE2B; 2BKD + MGMT, cells transfected with siUBE2B plus pEGFPc1-MGMT. UBE2B, ubiquitin-conjugating enzyme E2 B; siRNA, small interfering RNA; MGMT, O6-methylguanine-DNA methyltransferase; pEGFP, plasmid expressing enhanced green fluorescence protein.