Micronuclei in Cord Blood Lymphocytes and Associations with Biomarkers of Exposure to Carcinogens and Hormonally Active Factors, Gene Polymorphisms, and Gene Expression: The NewGeneris Cohort

Abstract

Background: Leukemia incidence has increased in recent decades among European children, suggesting that early-life environmental exposures play an important role in disease development.Objectives: We investigated the hypothesis that childhood susceptibility may increase as a result of in utero exposure to carcinogens and hormonally acting factors. Using cord blood samples from the NewGeneris cohort, we examined associations between a range of biomarkers of carcinogen exposure and hormonally acting factors with micronuclei (MN) frequency as a proxy measure of cancer risk. Associations with gene expression and genotype were also explored.Methods: DNA and protein adducts, gene expression profiles, circulating hormonally acting factors, and GWAS (genome-wide association study) data were investigated in relation to genomic damage measured by MN frequency in lymphocytes from 623 newborns enrolled between 2006 and 2010 across Europe.Results: Malondialdehyde DNA adducts (M1dG) were associated with increased MN frequency in binucleated lymphocytes (MNBN), and exposure to androgenic, estrogenic, and dioxin-like compounds was associated with MN frequency in mononucleated lymphocytes (MNMONO), although no monotonic exposure–outcome relationship was observed. Lower frequencies of MNBN were associated with a 1-unit increase expression of PDCD11, LATS2, TRIM13, CD28, SMC1A, IL7R, and NIPBL genes. Gene expression was significantly higher in association with the highest versus lowest category of bulky and M1dG–DNA adducts for five and six genes, respectively. Gene expression levels were significantly lower for 11 genes in association with the highest versus lowest category of plasma AR CALUX® (chemically activated luciferase expression for androgens) (8 genes), ERα CALUX® (for estrogens) (2 genes), and DR CALUX® (for dioxins). Several SNPs (single-nucleotide polymorphisms) on chromosome 11 near FOLH1 significantly modified associations between androgen activity and MNBN frequency. Polymorphisms in EPHX1/2 and CYP2E1 were associated with MNBN.Conclusion: We measured in utero exposure to selected environmental carcinogens and circulating hormonally acting factors and detected associations with MN frequency in newborns circulating T lymphocytes. The results highlight mechanisms that may contribute to carcinogen-induced leukemia and require further research.Citation: Merlo DF, Agramunt S, Anna L, Besselink H, Botsivali M, Brady NJ, Ceppi M, Chatzi L, Chen B, Decordier I, Farmer PB, Fleming S, Fontana V, Försti A, Fthenou E, Gallo F, Georgiadis P, Gmuender H, Godschalk RW, Granum B, Hardie LJ, Hemminki K, Hochstenbach K, Knudsen LE, Kogevinas M, Kovács K, Kyrtopoulos SA, Løvik M, Nielsen JK, Nygaard UC, Pedersen M, Rydberg P, Schoket B, Segerbäck D, Singh R, Sunyer J, Törnqvist M, van Loveren H, van Schooten FJ, Vande Loock K, von Stedingk H, Wright J, Kleinjans JC, Kirsch-Volders M, van Delft JHM, NewGeneris Consortium. 2014. Micronuclei in cord blood lymphocytes and associations with biomarkers of exposure to carcinogens and hormona...

The influence of single nucleotide polymorphisms on the association between dietary acrylamide intake and endometrial cancer risk

“…These 2 CYP2E1 SNPs are in the intronic region of the gene and thus do not affect the protein code, but they may be in linkage disequilibrium with variants that are causative. It was shown that the allelic variants of both genes and specifically their combination were associated with an increase in micronuclei (MN) count in binucleated lymphocytes, a marker of DNA damage and an established risk marker for carcinogenesis 6 . CYP2E1 metabolizes several other compounds than acrylamide, e.g., ethanol, benzene, nitrosamines, and acetaminophen 7 , and the enzyme bioactivates these compounds and thus increases their MN-forming potential.…”

Fetal exposure to dietary carcinogens and risk of childhood cancer: what the NewGeneris project tells us: Table 1

“…In addition, polymorphisms in the epoxyhydrolase 1/2 (EPHX1/2) and cytochrome p450 2E1 (CYP2E1) genes coding for metabolic enzymes, which may bioactivate precarcinogenic chemicals, seem to be associated with the micronuclei frequencies. 11 In conclusion, although the evidence is still limited, our data suggest some genetic predisposition to risk of childhood cancer associated with fetal exposure to dietary carcinogens.…”

“…15 We found significant associations between particular features of micronuclei and exposure to oxidative fat metabolites and dioxins and PCBs, predominantly in the highest quarters of exposure. 11 To investigate further the molecular mechanisms underlying carcinogenic events in utero we determined global gene expression levels in 120 Norwegian neonates in relation to fetal exposure to acrylamide and dioxins. While exposure did not seem to differ between the sexes, we discovered important sex-specific differences in genomic responses, in particular associated with effects on cell cycle and the immune system.…”

“…Expression levels were significantly lower for seven genes in those with highest exposure to dioxins compared with the lowest category. 11 The affected genes have roles in cell cycle regulation and apoptosis, which are generic processes involved in carcinogenesis.…”

The polymorphism rs2480258 within CYP2E1 is associated with different rates of acrylamide metabolism in vivo in humans

“…GA is also carcinogenic in animal studies (Beland et al 2015) and shown to be genotoxic (Rice 2005). Perhaps this explains why rs2480258 genotypes were associated with cytogenetic damages and risk of differentiated thyroid carcinoma (DTC) in human studies (Merlo et al 2014;Pellè et al 2016). AA and GA are detoxified through conjugation with glutathione (GSH), forming mercapturic acids, Nacetyl-S-(2-carbamoylethyl)-cysteine and N-acetyl-S-(2-hydroxy-2-carbamoylethyl)-cysteine (Fennell and Friedman 2005;Fuhr et al 2006).…”