In addition, the positive correlation between expressions of these three estrogen receptors in tissue could be indirectly reflected in lung adenocarcinoma cell lines where the expression levels of three estrogen receptor in A549 cell line were all correspondingly higher than in PC9 cell line, and importantly, their expressions in PC9 cell line were also all correspondingly higher than in PC9-GR cell line (18). Here, ESR1 is linked to lung adenocarcinoma.