an intricate relationship between mir-155-5p expression and oxidative stress in bladder cancer patients treated with calmette-guerin immunotherapy

Treatment failure after intravesical instillation of bacillus calmette-guerin immunotherapy (bcg) for non-muscle-invasive bladder cancer (bca) occurs frequently. the exact effects of bcg on cellular redox status and gene expression remain unclear. we assessed oxidative stress biomarkers and changes in mir-155-5p expression in response to bcg. twenty-seven patients with bca were recruited for measuring tissue and serum malondialdehyde (mda) and total antioxidant capacity (tac) levels, and tissue expression of mir-155-5p at two-time points: pre and 6 weeks post bcg. recurrence of bca was observed after 20 months. r statistical software was used for paired comparisons of biomarkers, as well as the correlation between variables. significant increases in tac were observed after bcg (p= <0.001). tissue mda levels were significantly reduced (p= 0.003). mir-155-5p was slightly overexpressed after bcg (median fold change=1.3, p=0.25). at the 20-month follow-up, it was observed that improved mda and tac changes were significant only in patients without recurrence of bca. in patients with recurrence, the pre-treatment expression ratio of mir-155-p5 was positively correlated with tac (r=0.63, p= 0.032) and negatively correlated with mda (r=-0.72, p=0.037). in patients with recurrence of bca pre-treatment mir-155-5p showed negative correlation with its expression changes after bcg (r=-0.78, p=0.004). conclusions: treatment with bcg has some beneficial effects on the oxidative stress status, which is probably modulated by mir-155-5p. a well-controlled oxidative balance may enhance overall survival of bca. considering its high recurrence rate, our pilot experiment can open a window toward better management of patients with bca.