Objective: To investigate the role of ubiquitin-specific peptidase 22 (USP22) in colorectal cancer multidrug resistance and its correlation with multidrug resistance genes P-gp and MRP1, and to preliminarily explore the mechanism of USP22 affecting colorectal cancer resistance. Methods: USP22 over-expression plasmid was transfected into colorectal cancer cells (RKO, SW480)with low expression of USP22. Cell counting kit (CCK-8) assay was used to detect the effect of USP22 on oxaliplatin resistance in colorectal cancer cells. The cells were treated with oxaliplatin of the same concentration. Western blot method was used to detect the expression of apoptosis-related proteins cleaved-caspase3, Bcl-2, and drug resistance proteins MRP1, P-gp in the cells. The cell efflux test was used to detect the effect of up-regulated USP22 on Calcein-AM and rhodamine123. Immunohistochemical methods were used to detect the expressions of USP22 and P-gp in the oxaliplatin chemotherapy-sensitive group and the drug-resistant group and to analyze the correlation between USP22 and MRP1, P-gp. Results: CCK-8 assay showed that the IC50 values of SW480-USP22 (SW480 cells overexpressing USP22) treated with oxaliplatin for 24 h and 48 h was (4.62±0.05)μmol/L and (2.32±0.04)μmol/L respectively; which was 2.7 times and 3.0 times higher than that in control cells, respectively. After treating with 1.25 μmol/L oxaliplatin for 48 h, USP22 overexpression can inhibit SW480 cells apoptosis. The fluorescence intensity of calcein-AM and rhodamine123 in the SW480-USP22 group were significantly increased when compared with that in the control cells (both P<0.01). The protein expression levels of MRP1 and P-gp in SW480-USP22 cells were significantly increased when compared with that in the control cells(both P<0.01). Immunohistochemistry showed that the positive expression rates of USP22, MRP1, and P-gp in the oxaliplatin chemotherapy-sensitive group were significantly lower than those in the chemotherapy-resistant group, the difference was statistically significant (all P<0.05), and USP22 was positively correlated with the expressions of MRP1 and P-gp in colorectal cancer tissues (r1=0.377, r2=0.423, both P<0.05). Conclusions: The up-regulation of USP22 is related to the acquired resistance of colorectal cancer cells to oxaliplatin. USP22 may be involved in the process of platinum-based chemotherapy resistance of colorectal cancer by regulating the expressions of P-gp and MRP1.
目的： 探讨泛素特异性肽酶22（USP22）在结直肠癌多药耐药中的作用以及与多药耐药基因P-糖蛋白（P-gp）和多药耐药相关蛋白1（MRP1）的相关性。 方法： 筛选USP22低表达的结直肠癌细胞系RKO、SW480，转染USP22过表达质粒使USP22表达上调。用细胞计数试剂盒（CCK-8）检测USP22对结直肠癌细胞奥沙利铂耐药的影响。用相同的奥沙利铂浓度处理细胞，Western 印迹检测细胞中凋亡相关蛋白cleaved-caspase3、Bcl-2和耐药蛋白MRP1、P-gp的表达。细胞外排实验检测上调USP22对钙黄绿素AM（Calcein-AM）和罗丹明123（rhodamine123）的影响。免疫组化方法检测奥沙利铂化疗敏感组与耐药组中USP22、MRP1及P-gp的表达以及分析USP22与MRP1及P-gp的相关性。 结果： CCK-8实验结果表明，SW480-USP22（SW480细胞过表达USP22）对奥沙利铂处理24 h和48 h的IC50为（4.62±0.05）μmol/L和（2.32±0.04）μmol/L，与对照细胞相比分别高2.7倍和3.0倍。用1.25 μmol/L的奥沙利铂处理细胞48 h，USP22过表达可抑制SW480细胞凋亡；细胞外排实验中SW480-USP22组Calcein-AM和rhodamine123的荧光强度与对照细胞相比明显升高，差异有统计学意义（均P<0.01）；SW480-USP22细胞中MRP1和P-gp的蛋白表达水平与对照细胞相比显著增加，差异有统计学意义（均P<0.01）。免疫组化结果表明，奥沙利铂化疗敏感组USP22、MRP1、P-gp的阳性表达率和化疗耐药组相比显著降低，差异有统计学意义（P<0.05），USP22与MRP1、P-gp在结直肠癌组织中的表达均呈正相关（r1=0.377，r2=0.423，P<0.05）。 结论： USP22上调与结直肠癌细胞对奥沙利铂的获得性耐药有关，USP22可能通过调控P-gp、MRP1的表达参与结直肠癌铂类化疗耐药的过程。.