Dibenzoxanthenes induce apoptosis and autophagy in HeLa cells by modeling the PI3K/Akt pathway

A new series of dibenzoxanthene derivatives 4a-4d (4a: 1-oxo-5-bromo-11-cyano-13c-methoxy-1,13c-dihydroxyl-dibenzo[a,kl]xanthene, 4b: 1-oxo-5-bromo-11-cyano-13c-ethoxy-1,13c-dihydroxyl-dibenzo[a,kl]xanthene, 4c: 1-oxo-5-bromo-11-cyano-13c-propoxy-1,13c-dihydroxyl-dibenzo[a,kl]xanthene and 4d: 1-oxo-5-bromo-11-cyano-13c-butoxy-1,13c-dihydroxyl-dibenzo[a,kl]xanthene) were synthesized and the molecular mechanisms of anti-cancer activities were investigated. These compounds showed excellent anti-tumor activity against A549, Eca-109, HeLa, HepG2 and SGC-7901 cell lines. Compounds 4a-4d could effectively inhibit the migration and invasion of HeLa cells in wound healing and transwell assays. Compounds induced the DNA damage and arrested in cell cycle distribution at G0/G1 phase. Apoptosis induced by compounds was detected using morphological observation of nuclear changes and FITC-Annexin V/PI staining. Additionally, compounds also induced the autophagy of HeLa cells through observing AO staining and upregulated the expression of LC3II and Beclin-1 proteins. Furthermore, treatment with autophagy inhibitor 3-methyladenine induced an obvious decrease in apoptotic rate in HeLa cells. This indicated that autophagy further promoted the HeLa cells apoptosis. Compounds 4a-4d enhanced the intracellular Ca²⁺ and ROS. Then the mitochondrial membrane potential of HeLa cells was depolarized and the cytochrome C was released from mitochondria into cytoplasm. Activities of the apoptotic factors Bcl-2, Bax, caspase-3 were measured using western blotting. After HeLa cells were exposed to compounds, the expressions of PI3K and Akt protein were decreased. Compounds exhibit anti-cancer activity via apoptosis and autophagy through inhibition of PI3K/Akt signaling pathway in HeLa cells.