NR2E3 and cancer: The difference in sensitivity between the U2OS cancer and hTERT-RPE1 fibroblast cell lines prompted us to also test the sensitivity in additional fibroblast cell lines MRC5-SV2 and 16HBE14o, both of which did not show a differential response when exposed to the pyrimidine synthesis inhibitors pyrazofurin or brequinar nor RNR inhibition with HU (Supplementary Fig. 5A).