Promoter single nucleotide polymorphisms in pro-inflammatory cytokine genes in S. haematobium infected and the risk of prostate cancer development

Abstract

This thesis reports the findings of a thorough study to establish the role of the genetic variations in the pro-inflammatory genes and the risk of developing prostate cancer (PCa) in male individuals residing in a schistosomiasis endemic area of Murewa District in Zimbabwe. Genetic inclination and environmental factors are contributing factors that raise the risk of developing PCa. Single nucleotide polymorphisms of genes coding for the production of cytokines involved in innate immunity against schistosomiasis, might impact risk to developing PCa. The purpose of the study was assessing genetic variability in pro-inflammatory cytokines promoter positions IL-1β (-35T/C), IL-2 (350G/T), IL-4 (590T/C), IL-6 (-174G/C) and TNF- (-308G/A) due to S. haematobium infections as an indirect risk for male PCa development. We determined single nucleotide polymorphisms (SNPs) of pro-inflammatory cytokines of both schistosomiasis infected and uninfected individuals. The study was conducted with a total number of 40 samples. Urine filtration technique was used to detect S. haematobium eggs in the urine. PSA levels in the serum were qualitatively detected using ELISA. DNA extraction from the samples was performed using Qiagen DNA extraction kit. Promoter single nucleotide polymorphisms were determined in 5 different cytokine gene positions namely IL-1β (-35T/C), IL-2 (350G/T), IL-4 (590T/C), IL-6 (-174G/C) and TNF- (-308G/A) using ARMS-PCR. The data captured was analysed using SPSS, STATA and Graph pad prism. The S. haematobium prevalence estimate was 37.5%. The median age of the participants was 35 years (IQR; 25.5-59.5). The majority of the participants were of <40 years [n=25 (62.5%)] and >40 [n=15(37.5%)]. .Fourteen (35%) participants had no detected (0 ng/ml) PSA levels indicating no risk PCa development while 24(60%) had a low risk of developing PCa (median 37(IQR 28-65.5) and 2(5%) had a high risk of developing PCa (median 26.5(IQR 18-35) p value = 0.001. Most participants [n=25 (62.5%)] had a history of S. haematobium infection though there were no differences observed in PSA levels to those with or without a history of infection (p value = 0.760). Participants with the highest median number of eggs [28; IQR (18-38)] were not significantly different compared to low risk (0(0-6.5)) and high risk (28(18-38)) PSA levels; p=0.062. Participants with moderate to heavy infection intensity (≥11 eggs/10 mL of urine) did not associate (p=0.071) with high PSA levels. IL-1β (-35T/C), IL-2 (350G/T), IL-4 (590T/C), IL-6 (-174G/C) and TNF- (-308G/A) promoter SNPs were not associated with infection intensity. The prevalence of the genotypes for TNF- (-308G/A) AA (median 30), AG (median 0(IQR0-2) and GG (median 5.5(IQR 0-11), were 2.5 %, 32.5 % and 2.5 % in schistosomiasis positive participants, and 0 %, 60 % and 2.5 % in participants with no schistosome infection, respectively (p=0.344). The Kruskal Wallis Test on the medians of the promoter position IL-1β (-35T/C) genotypes CC 0, CT 0(0-9), TT 0(0-167) are not equal showing the lack of significance; p value = 0.793.The frequencies of the genotypes for the promoter position IL-2 (-350G/T) were TG, GG and TT, were 37.5 %, 0 % and 0 % in schistosomiasis infected individuals, and 57.5 %, 5 % and 0 % in individuals without schistosome infection, respectively. The Mann Whitney Test on the medians of the genotypes GG 0, GT 0(0-11) are not equal therefore not statistically significant; p = 0.352. There were significantly different (p value = 0.620)genotypes IL-4 (590T/C) TC, TT and CC, with frequencies of 35 %, 0 % and 2.5 % in schistosomiasis positive participants, and 55 %, 0 % and 7.5 % in participants who are schistosome infected, respectively. The Mann Whitney Test on the medians of the promoter position IL- 4 (-590 T/C) CC 0(0-5.5), TC 0(0-9) were not equal. The Kruskal Wallis Test on the medians of the gene promoter position IL-6 (-174 G/C) genotypes CC 11(0-11), GC 0, GG 0(0-4.5) are not equal which shows they are not significant; p value = 0.250. The density of the genotypes GC, CC and GG, were 12.5 %, 12.5 % and 12.5 % in participants without schistosome infection and 40 %, 5 % and 17.5 % in schistosomiasis infected participants, respectively. Male genital schistosomiasis and gene polymorphisms in the cytokine promoter positions IL-1β (-35T/C), IL-2 (350G/T), IL-4 (590T/C), IL-6 (-174G/C) and TNF- (-308G/A) are not associated with the emergency of PCa in older males residing in Murewa district, Mashonaland East, Zimbabwe.