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Etude des facteurs de risque génétiques et des interactions gène-environnement dans les cancers différenciés de la thyroïde

Abstract : Context : Differentiated thyroid cancer (DTC) incidence is characterized by considerable geographic and ethnic variations. Particularly high incidence rates were observed in Melanesian women of New Caledonia. Except for the exposure to ionizing radiation in childhood and obesity, the role of other DTC risk factors is not clearly established. Genetic factors have been suggested to play an important role in DTC risk since epidemiological studies have shown that DTC has a higher familial relative risk than any other cancers. Linkage studies in multiple-case DTC families and candidate gene studies have identified polymorphisms in several genes but very few have been replicated so far. Genome-wide association studies (GWAS) also identified several DTC susceptibility loci with the most robust associations reported on the loci 9q22 and 14q13. Only few susceptibility loci were highlighted by GWAS and the identified variants were shown to account less than 10% of the DTC familial risk, emphasizing that much remains to be discoveredObjectives: The main objective of this work was to study the role of genetic risk factors and their interaction with environmental factors in DTC risk. More specifically, we aimed to: 1) replicate the association between DTC risk and polymorphisms reported in candidate gene and GWAS studies in 2 case-control studies conducted in Metropolitan France and New Caledonia; 2) identify potential causal variants of DTC risk in GWAS loci 9q22 and 14q13 using fine-mapping approach; 3) identify new genetic risk factors for DTC in women using pathway approach by pooling data from 2 case-control studies conducted in France and USA..Materials and methods: The analysis of the candidate genes and of the GWAS loci were based on a European population of 508 cases and 621 controls from 2 case-control studies conducted in metropolitan France (CATHY study) and in New Caledonia (NC study) and, a Melanesian population of 156 cases and 114 controls from the NC study. The pathway analysis was conducted in a first step on European women from the CATHY study (365 cases/376 controls) and from the Young-Thyr study (83 cases /93 controls) both conducted in metropolitan France. In a second step, we pooled the data from CATHY/Young-Thyr study and USRT/UTMDACC study (332 cases/443 controls) conducted in the United States.Results: In Europeans and Melanesians, we found no association with polymorphisms reported previously by candidate genes studies. However, we observed that among these genes, GSTM1 and GSTT1 may modulate the associations between DTC risk and obesity or alcohol consumption. Some polymorphisms identified in GWAS studies at loci 9q22, 14q13 and 2q35 were replicated in Europeans and in Melanesians. In the GWAS loci 9q22 and 14q13, we identify new variants that can be functionally related to DTC pathogenesis in Europeans and Melanesians. We also reported interactions between some of these variants and parity or tobacco smoking. The analysis of candidate pathways in European women showed interactions between alcohol consumption or tobacco smoking and genes involved in the metabolism of these compounds and, between age at first menarche or oral contraception and genes involved in biosynthesis and metabolism of sex steroid hormones.
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Catherine Ines Tcheandjieu Gueliatcha. Etude des facteurs de risque génétiques et des interactions gène-environnement dans les cancers différenciés de la thyroïde. Cancer. Université Paris Saclay (COmUE), 2017. Français. ⟨NNT : 2017SACLS064⟩. ⟨tel-02509609⟩

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