DNA repair gene XPD and susceptibility to arsenic-induced hyperkeratosis

Chronic exposure to inorganic arsenic is known to cause non-melanocytic skin and internal cancers in humans. An estimated 50-70 million people in Bangladesh have been chronically exposed to arsenic from drinking water and are at risk of skin and other cancers. We undertook the first study to examine whether genetic susceptibility, as determined by the codon 751 SNP (A-->C) of the DNA repair gene XPD, influences the risk of arsenic-induced hyperkeratotic skin lesions, precursors of skin cancer, in a case-control study of 29 hyperkeratosis cases and 105 healthy controls from the same community in an area of Bangladesh. As expected, there was a monotonic increase in risk of hyperkeratosis in relation to urinary arsenic measures but the XPD genotype was not independently associated with the risk. However, the increase in hyperkeratosis risk in relation to urinary arsenic measures genotype was borderline significant for urinary total arsenic (P for trend=0.06) and statistically significant for urinary creatinine adjusted arsenic (P for trend=0.01) among subjects with the XPD A allele (AA) but not among subjects with the other XPD genotypes. Among AA carriers, the risk for the highest arsenic exposed group compared with the lowest was more than 7-fold for urinary total arsenic and about 11-fold for urinary creatinine adjusted arsenic. In conclusion, our findings suggest that the DNA repair gene XPD may influence the risk of arsenic-induced premalignant hyperkeratotic skin lesions. Future larger studies are needed to confirm this novel finding and investigate how combinations of different candidate genes and/or other host and environmental factors may influence the risk of arsenic induced skin and other cancers.