APOBEC-mediated mutagenesis may also be increased in the case of a reduced expression or the loss of protein activity of the tumour suppressor fragile histidine triad protein (FHIT), and higher levels of APOBEC-mediated mutagenesis were observed from TCGA lung adenocarcinoma tumours that had both increased A3B expression and the loss of FHIT protein expression (figure 4) [134,175,176]. Here, FHIT is linked to lung adenocarcinoma.