Abstract
In the present study, we investigated the mechanisms of chamaejasmine action on human HEp-2 larynx carcinoma cells, which possess constitutively active Akt. Results indicated that chamaejasmine showed more notable anticancer activity than apigenin against HEp-2, PC-3, NCI-H1975, HT-29 and SKOV-3. Moreover, chamaejasmine presented most significantly inhibition towards HEp-2, with IC₅&sub0; values of 1.92 µM. Treatment of HEp-2 cells with chamaejasmine (1-4 μM) resulted in significant dose-dependent decrease in Akt phosphorylation at Serine473. Chamaejasmine-mediated dephosphorylation of Akt resulted in inhibition of its kinase activity, which was confirmed by reduced phosphorylation of proapoptotic proteins BAD and glycogen synthase kinase-3, essential downstream targets of Akt. Inactivation of Akt seems to be associated with downregulation of insulin-like growth factor receptor 1 protein level and inhibition of its autophosphorylation upon chamaejasmine treatment. Exposure to chamaejasmine significantly induced caspase-9 and caspase-3 activity. In vivo, chamaejasmine intake through gavage resulted in inactivation of Akt and induction of apoptosis in HEp-2 tumors. These results suggest that Akt inactivation and dephosphorylation of BAD is a critical event, at least in part, in chamaejasmine-induced HEp-2 cells apoptosis.