ERBB4 and cancer: This result is similar to a number of other studies with EGFR/HER1, HER2, and HER3 in NSCLC cells [20,37,52,53,74], but because these NSCLC cancer cell lines were preselected due to at least one study reporting they contained HER4, our result differs from most studies with HER4, which generally show HER4 protein present in 30–40% of NSCLC cell lines [20,41,48,49,50,51,52,53,54,55,76], even though in PCR studies HER4 mRNA is present in almost all NSCLC cells [57].