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Tham khảo tài liệu 'intraepithelial neoplasia part 12', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | AKNA as Genetic Risk Factor for Cervical Intraepithelial Neoplasia and Cervical Cancer 321 To study the genetic background and to explore the differences in individual cancer susceptibility a recent focus of research efforts has been on SNPs single nucleotide polymorphisms . SNPs are the most common known form of human genetic variation and are defined as stable single-base substitutions with a frequency of greater than 1 in at least one population Taylor et al. 2001 Meyer et al. 2008 . For cancer research the focus has been on SNPs that alter the function or expression of a gene to attempt to explain observed associations with a pathogenic mechanism. Indeed genetic polymorphisms in functionally critical genes such as immune response genes have been suggested as risk factors for the development of a variety of cancers including CC Taylor et al. 2001 Milam et al. 2007 . There are several reports about genes related to immune response e.g. MHC genes cytokine genes genes involved with cancer development e.g. p53 and CC susceptibility Glew et al. 1992 Haukin et al. 2002 Sierra-Torres et al. 2003 . Concerning HLA polymorphisms and the risk of CC discordant results have often been observed among different populations where the most consistent reports are for the DRB1 13 and DRB1 0603 alleles as a protection factor with OR 0.3-0.4 Hildesheim Wand 2002 Apple et al. 1994 Maciag et al. 2002 and increasing risk for the DQB1 03 and DRB1 1501-DQB1 0602 with OR 2.9 and for the DrB1 0301-DQB1 0201 haplotype which was associated with a two-fold reduction in risk for transient and persistent HPV infections. DRB1 1102-DQB1 0301 showed a lower risk effect only for persistence. DRB1 1602-DQB1 0502 and DRB1 0807-DQB1 0402 were associated with seven- and three-fold increases in risk for persistence respectively Hildesheim Wand 2002 Apple et al. 1994 Maciag et al. 2002 . More recently a study of CC cases that were HPV-16 positive and controls carried out in Mexican population showed .
