Another explanation is the heterogenous distribution of selenoprotein gene expression within cells residing in the tumour and its microenvironment, as outlined in Fig. 1E. While DIO1 as an instance is mostly abundant in cancer cells, DIO2 shows nearly no expression in malignant cells, but rather in cancer associated fibroblasts, which may explain the lack of interaction for this member of the deiodinase family in our study. This evidence concerns the gene DIO1 and cancer.