DNA methylation profiles in urothelial bladder cancer tissues and children with schistosomiasis from Eggua, Ogun State, Nigeria

Squamous cell carcinoma has been attributed to chronic schistosomiasis and is the predominant type of bladder cancer in schistosomiasis endemic areas. The aim of this study was to assess early promoter DNA methylation in selected genes implicated in schistosomiasis-associated bladder cancer (SABC). A total of 159 urine samples were collected from school-aged children in Eggua Community of Ogun State and examined by microscopy for Schistosoma haematobium eggs. From this sample, a subset of 34 (21.1%) urine samples positive for S. haematobium, age and sex-matched with negative urine control samples, and 16 formalin-fixed paraffin-embedded bladder cancer tissues obtained from the University College Hospital were subjected to DNA isolation and bisulphite DNA conversion. Quantitative methylation-specific PCR was used to determine the methylation status of APC, RARβ2, RASSF1A, and TIMP3 in the samples. High degrees of methylation of RARβ2(67.7%), RASSF1A (38.2%), and TIMP3(52.9%) was more common in urogenital schistosomiasis (UGS)-positive urine samples than negative urine (control) samples and in bladder cancer tissues. Promoter DNA methylation in the positive urine samples was 1.4-fold, 13.3-fold, 3.4-fold, and 3.8-fold higher in APC, RARβ2, RASSF1A, and TIMP3, respectively, than in the matched controls. The odds of promoter methylation were likely to increase with age group for APC (OR: 1.615) and TIMP3(OR: 2.000); sex for TIMP3(OR: 2.644); and haematuria for RARβ2(OR: 1.094), RASSF1A (OR: 1.143), and TIMP3(OR: 1.842), although there were no significant associations. Conclusions: Gene promoter DNA methylation in tumour suppressor genes was observed in schistosomiasis cases. Hence, promoter DNA methylation may occur during active schistosomiasis in children. This result may serve as an early non-invasive biomarker to detect and hint at the risk of developing SABC later in life.