The present study revealed that estrogen induces cell proliferation of NSCLC cells in vitro [13], induces tumor formation in human tumor xenografts [12] and in urethane-induced NSCLC animal models [30], raising the question whether estrogen-induced ERβ even can promote lung cancer metastasis and the underlying mechanisms and signal transduction pathways activated. The gene discussed is ESR2; the disease is non-small cell lung carcinoma.