Investigation of the association between the internal dose levels of environmental pollutants and disease in human breast cancer

In this thesis, a possible relation between initiation and/or progression of breast cancer and persistent organic pollutants (POPs), as well as correlation between blood and breast tissue levels of POPs were investigated. In addition, it was evaluated whether genetic polymorphisms in enzymes possibly catalyse either phase I and phase II biotransformation reactions of POPs in vivo represent a risk factor for breast cancer. In order to perform these, breast tumour tissues from patients who undergone tumour surgery and healthy breast tissues from individuals, who undergone breast reduction surgery, as well as blood samples from both groups were collected. In total concentrations of 32 POP derivatives were determined in these samples by gas chromatography electron capture detection (GC-ECD). Genomic DNAs were isolated from each blood sample and genetic variations of phase I enzyme CYP1A1, and phase II enzymes GSTP1, GSTM1 and GSTT1 that expected to catalyse biotransformation of POP derivatives, and DNA oxidative damage repair enzyme hOGG1 were analysed by PCR-RFLP. Significantly higher POP concentrations were observed when compared between control and cancer groups, which suggested a possible relation between breast cancer and POP exposure. For 9 POP derivatives, positive correlations were determined between blood and tissue concentrations and it was concluded that blood levels of these POPs can be used as surrogate for predicting tissue concentrations of the same compounds. It was concluded that genetic variations in CYP1A1 and GSTT1, which were expected to catalyse POPs biotransformation, may be risk factors for breast cancer. In addition, it was determined in all groups that both age and cigarette smoking may also be risk factors for initiation and/or progression of breast cancer.