A Novel CpG Oligodeoxynucleotide Enhanced the Therapeutic Effect of Epirubicin on Bladder Tumors in Rats

Abstract Background CpG oligodeoxynucleotides, which boast anti-inflammatory, anti-infectious, and chemotherapeutic activities, are promising immunomodulators. Recently, some preclinical studies have highlighted the potent immunostimulatory and anti-tumor effects of CpG oligodeoxynucleotides, which has aroused interest in their potential clinical effects on human cancers. Methods In this study, we evaluated the therapeutic effect of a new type of CpG oligodeoxynucleotide whose sequence (5’-AACGTTGTCGTCGACGTCGTCGTCAGGCCTGACGTTATCGATGGCGTTGTCGTCAACGTTGTCGTTAACGTT-3’) was designed by our laboratory in combination with epirubicin in a bladder tumor rat model induced by N-methyl-N-nitrosourea instillation. Moreover, we explored the safety of the novel CpG oligodeoxynucleotide for bladder tumor therapy by observing the degree of cystolith in the bladder and comparing the results against those of Bacillus Calmette–Guérin therapy, which is a gold-standard treatment for bladder tumor. Results All results showed that CpG oligodeoxynucleotide combined with epirubicin significantly inhibited the growth of bladder tumors and reduced the pathological grading. As compared with bladder cells or cytokines observed under the positive control or epirubicin-alone treatment conditions, all indexes including histopathological grading, Mutation P53 gene protein expression, and Interleukin-2 (IL-2) level were significantly optimized by instillation of CpG oligodeoxynucleotide. Immunohistochemical examination indicated that CpG oligodeoxynucleotide reduced the expression of Mutation P53 gene protein in the bladder tumor rat model. Specifically, the level of IL-2 in rat serum was increased by more than 30% CpG oligodeoxynucleotide treatment combined with epirubicin. Also, in comparison with the degree of cystolith observed in the Bacillus Calmette–Guérin group, no obvious side effects were caused by CpG oligodeoxynucleotide. Conclusions CpG oligodeoxynucleotide as an immunomodulator can enhance the efficacy of epirubicin and presents higher safety than Bacillus Calmette–Guérin in treating bladder cancer.