35), transforming growth factor alpha (TGF‐α), heparin‐binding EGF‐like growth factor (HB‐EGF), and betacellulin (BTC), whereas amphiregulin (AREG), epiregulin (EREG), and epigen (EPGN) are intrinsically low‐affinity ligands (reviewed in Ref. 34). Because EGFR in humans (aka Her1 and ErbB1) is at the heart of signals for growth and proliferation, it is frequently mutated and/or over‐expressed and thus hyper‐activated in human cancers,36 including non‐small cell lung cancer (NSCLC)37 and glioblastoma multiforme38. For this reason, EGFR is an important target of anticancer therapy.39 Here, BTC is linked to lung cancer.