Low-dose ionizing radiation exposure and risk of leukemia: results from 1950-1995 Chinese medical X-ray workers’ cohort study and meta-analysis

Background:It has been well-established that acute radiation exposures increase the risk of leukemia.However,it is still unknown whether these leukemia risk estimates could be extrapolated to occupational populations who receive repeated low-dose radiation exposure.The purpose of this study was to estimate quantified associations between low-dose radiation exposures and leukemia.Methods:The Chinese medical X-ray worker study(CMXW)included 27,011 medical X-ray workers employed at major hospitals in 24 provinces in China from 1950 to 1980,and a control population of 25,782 physicians matched by hospital,who were unexposed to X-ray equipment.Poisson regression models were used to esti-mate the excess relative risk(ERR)and excess absolute risk(EAR)for the incidence of leukemia associated with cumulative doses.A meta-analysis of the published literature on low-dose occupational radiation exposure and leukemia risk was also conducted.Results:The incidence rates of leukemia in X-ray workers and the control group were 6.70 and 3.39 per 100,000 person-years,respectively.Among X-ray workers,the average cumulative red bone marrow dose was 0.046 Gy.We found a positive relationship between 2-year lagged cumulative red bone marrow dose and risk of leukemia excluding chronic lymphocytic leukemia(CLL)(ERR=0.66 per 100 mGy,90%CI:0.09,1.53;EAR=0.29 per 104 PY-100 mGy,90%CI:0.07,0.56).The excess risk was largely driven by myeloid leukemia(ERR=1.06 per 100 mGy,90%CI:0.22,2.51).Based on the meta-analysis,the pooled ERR at 100 mGy was 0.19(95%CI:0.08,0.31).Conclusion:This study provides strong evidence of a positive and linear doseresponse relationship between cu-mulative red bone marrow dose and the incidence of non-CLL leukemia.

Impact of mTOR gene polymorphisms and gene-tea interaction on susceptibility to tuberculosis

BACKGROUND mTOR gene is a key component of the PI3K/Akt/mTOR signaling pathway,and its dysregulation is associated with various diseases.Several studies have demonstrated that tea drinking is a protective factor against tuberculosis(TB).This study was designed to explore five single nucleotide polymorphisms(SNPs)of mTOR in the Han population of China to determine how their interactions with tea drinking affect susceptibility to TB.AIM To investigate if the polymorphisms of mTOR gene and the gene-tea interaction are associated with susceptibility to TB.METHODS In this case-control study,503 patients with TB and 494 healthy controls were enrolled by a stratified sampling method.The cases were newly registered TB patients from the county-level centers for disease control and prevention,and the healthy controls were permanent residents from Xin'ansi Community,Changsha city.Demographic data and environmental exposure information including tea drinking were obtained from the study participants.We genotyped five potentially functional SNP sites(rs2295080,rs2024627,rs1057079,rs12137958,and rs7525957)of mTOR gene and assessed their associations with the risk of TB using logistic regression analysis,and marginal structural linear odds models were used to estimate the gene-environment interactions.RESULTS The frequencies of four SNPs(rs2295080,rs2024627,rs1057079,and rs7525957)were found to be associated with susceptibility to TB(P<0.05).Genotypes GT(OR 1.334),GG(OR 2.224),and GT+GG(OR 1.403)at rs2295080;genotypes CT(OR 1.562)and CT+TT(OR 1.578)at rs2024627,genotypes CT(OR 1.597),CC(OR 2.858),and CT+CC(OR 1.682)at rs1057079;and genotypes CT(OR 1.559)and CT+CC(OR 1.568)at rs7525957 of mTOR gene were significantly more prevalent in TB patients than in healthy controls.The relative excess risk of interaction between the four SNPs(rs2295080,rs2024627,rs1057079,and rs7525957)of mTOR genes and tea drinking were found to be-1.5187(95%CI:-1.9826,-1.0547,P<0.05),-1.8270(95%CI:-2.3587,-1.2952,P<0.05),-2.3246(95%CI:-2.9417,-1.7076,P<0.05)and-0.4235(95%CI:-0.7756,-0.0714,P<0.05),respectively,which suggest negative interactions.CONCLUSION The polymorphisms of mTOR(rs2295080,rs2024627,rs1057079,and rs7525957)are associated with susceptibility to TB,and there is a negative interaction between each of the four SNPs and tea drinking.