EGFR and lung adenocarcinoma: Little has been studied regarding anti-progesterone therapy in NSCLC, however, a recent preclinical study showed that PR contains a polyproline domain (PPD) that inhibits NSCLC cell proliferation and has a synergistic effect when given in combination with EGFR TKIs while another preclinical study demonstrated that progesterone can inhibit lung adenocarcinoma cell growth via membrane progesterone receptor alpha (49, 50).