Objective:To study the effect of thioredoxin domain containing protein 5 (TXNDC5)-peroxiredoxin 2 (Prx2) on the drug resistance of prostate cancer cells.Methods:Prostate cancer PC3 cells were cultured in vitro, treated with the chemotherapy drug cyclophosphamide (5, 10, 15 μmol/L) for 24 hours, and PC3 cells without any treatment was served as the control group. The expression levels of TXNDC5 in PC3 cells were detected by real-time fluorescent quantitative PCR (RT-qPCR) and Western blotting. PC3 cells with TXNDC5 knocking down were exposed by cyclophosphamide and CCK-8 was used to detect the cell viability of siTXNDC5 group and siNC group. The content of reactive oxygen free radicals was determined by reactive oxygen detection kit. PC3 cells and its parental cyclophosphamide-resistant ones with TXNDC5 knocking down were treated by 10 μmol/L cyclophosphamide and subjected for CCK8 assay. The expression of Prx2 in PC3 cells was detected by Western blotting after TXNDC5 was silenced. Prx2 expression was silenced in PC3 cells overexpressing TXNDC5, and cell viability and reactive oxygen free radical content were detected in Vec-Ctrl group, pcTXNDC5 group, siNC group, siPrx2 group and pcTXNDC5+ siPrx2 group. Results:Compared with the control group, cyclophosphamide treatment significantly increased the expression of TXNDC5 at mRNA and protein levels in PC3 cells. After PC3 cells were treated with cyclophosphamide (10, 15 μmol/L) for 12 h, compared with the siNC group, the cell viability in the siTXNDC5 group was significantly suppressed (0.44±0.08 vs. 0.74±0.10, t=3.647, P=0.031; 0.30±0.04 vs. 0.53±0.06, t=6.115, P=0.006). When PC3 cells were treated with 10 μmol/L cyclophosphamide for 6 and 12 h, compared with the siNC group, the production of reactive oxygen free radicals in the siTXNDC5 group was significantly increased (2.68±0.19 vs. 1.58±0.26, t=-6.027, P=0.005; 4.56±0.37 vs. 2.73±0.26, t=-6.995, P=0.003). When PC3 cells and its cyclophosphamide-resistant ones were treated with 10 μmol/L cyclophosphamide for 12 h, compared with the siNC group, the cell viability was significantly inhibited in the siTXNDC5 group. Western blotting analysis showed that the expression of Prx2 was significantly reduced when TXNDC5 was silenced. Silencing Prx2 could significantly attenuate the increase of cell viability and the decrease of reactive oxygen content resulting from TXNDC5 overexpression. PC3 cells were treated with 10 μmol/L cyclophosphamide for 12 h, and the cell viabilities of the Vec-Ctrl group, pcTXNDC5 group, siNC group, siPrx2 group and pcTXNDC5+ siPrx2 group were 0.52±0.07, 0.69±0.03, 0.56±0.05, 0.43±0.05, 0.58±0.07, respectively, and there was a statistically significant difference ( F=8.868, P=0.003). Furthermore, the cell viability in the pcTXNDC5+ siPrx2 group decreased significantly when compared to that of the pcTXNDC5 group ( P=0.045). The contents of reactive oxygen free radicals in the above 5 groups were 3.26±0.46, 2.09±0.49, 3.16±0.38, 4.62±0.26, 2.87±0.36, respectively, and there was a statistically significant difference ( F=16.037, P<0.001). The content of reactive oxygen radicals in the pcTXNDC5+ siPrx2 group was higher than that of the pcTXNDC5 group ( P=0.036). Conclusion:TXNDC5 can reduce the level of reactive oxygen free radicals in prostate cancer cells by regulating the expression of Prx2, so as to promote the drug resistance of prostate cancer cells.