Finally, high‐performance liquid chromatography (HPLC) analysis detected dopamine secretion from various lung cancer cell lines grown in vitro (Fig. 1A) while RNAseq analysis of patients in the NCI‐MD study showed that transcript levels of both TH and DDC, key enzymes involved in the conversion of tyrosine to dopamine, are increased in lung cancer, suggesting a mechanism by which dopamine production is increased in lung cancer cells (Fig. S2J). This evidence concerns the gene DDC and lung cancer.