In vitro cytotoxicity of human urine and its potential toxic parameters towards bladder cancer cells

Abstract

Background Bladder cancer (CaB) has a high recurrence rate despite surgery. As bladder is constantly filled with urine, it is worthwhile to investigate whether it could have any detrimental effects on bladder cancer cells. Methods We investigated the cytotoxicity of urine samples from CaB patients and normal controls on four CaB cell lines and tested the percentage of cell death, proliferation, adhesion, invasion and colonies formation ability. In order to identify the potential components involving in urine cytotoxicity, we evaluated some basic physiochemical parameters of urines, such as pH, osmolarity, creatinine (Cr), sodium (Na), potassium (K), chloride (Cl), calcium (Ca) and phosphate (PO4). We further compared the pH values of urine samples between CaB who developed recurrence versus those who did not. A more in-depth analysis on inflammatory markers was performed for two representative urine samples which demonstrated opposite cytoxic effects. Results 23 CaB patients and 20 normal controls were recruited into this study. According to in vitro experiments, both CaB and non-CaB urines had comparable effect on cell toxicity, proliferation, adhesion, invasion and colonies formation ability in four cell lines, HTB9, RT4, T24 and UMUC3, while RT4 was the most sensitive to urine toxicity. After evaluating the relationship between basic physiochemical parameters and cytotoxicity, we found out that there were strong negative correlations between pH value and 24 hours death rate for the 4 CaB cell lines (HTB9 r = -0.6651, p<0.001; RT4 r = -0.8335, p<0.001; T24 r = -0.4924, p<0.001; UMUC3 r = -0.7066, p<0.001). Osmolarity, urine Cr and PO4 all had weakly or moderately positive correlations with CaB cells on 24 hours death rate. CaB patients who developed recurrence had more alkaline urine than those who did not develop recurrence. In the urine sample with the highest cytoxicity, high concentrations of IL-6 and IFN-gamma were found. Conclusions Our study confirmed that there was not statistically significant difference in cytotoxicity between CaB and non-CaB urines. However, we identified some parameters that could have an impact on cytotoxicity towards CaB cells. Modifying certain urine characteristics peri-operatively may induce cytotoxicity, avoid tumour re-implantation, and reduce the chance of cancer recurrence.