The results indicate that most NSCLC cells have high levels of mRNA for NRG1 (interacts with HER3 and HER4) and NRG3 (interacts only with HER4), but not NRG2 (interacts with HER3) or NRG4 (interacts only with HER4). This evidence concerns the gene NRG3 and non-small cell lung carcinoma.