SELENOS and cancer: An analysis of The Cancer Genome Atlas Program (TCGA) data displayed no overall associations of DIO1, DIO3, SELENOM, SELENOW, and SELENON with survival, when not incorporating serum Se (Additional file 1: Fig. S5), highlighting the need for consideration of both serum Se and tumour selenoprotein expression in order to ascertain effects of selenoprotein mRNA expression on prognosis.