UGT1A6 and breast cancer: UGT1A6 also conjugates exogenous compounds which occur in the environment and in food, e.g., 4-ethylphenol or in drugs, e.g., acetaminophen (Harding et al., 1988; Bock and Kohle, 2005), which together with other UGT1A6 substrates have been suggested to affect breast cancer risk (Friis et al., 2008; Chen et al., 2011).