DPH6 and colorectal carcinoma: To assess if silencing of the genes involved in diphthamide biosynthesis confers resistance to DT, HCT116 colorectal cancer (CRC) cells, expressing intermediate levels of HBEGF, were chosen as a model and transduced with 18 different shRNAmir constructs, targeting the DPH2, DPH5, DPH6 and DPH7 transcripts (Supplementary Table 1).