Background: Securidaca1 and 2 are plant-derived substances isolated from African medicinal plant S. longipedunculata, using new bioactivity-guided method partly described in Obasi et al. (2017). Our previous report suggested that certain fractions from this plant root were able to activate apoptosis in cervical cancer cell lines. Generally, over 90% of cervical cancer has been associated with high-risk human papilloma virus (HPV), whose etiologic molecule E6 oncoprotein is involved in the process of carcinogenesis. The purpose of this study, therefore, is to investigate the proapoptotic potentials of these substances and their ability to block cell survival mechanism, via antiapoptotic effectors of PI3K-AKT downstream.

Experimental Procedure: Two cervical cancer cell lines (Caski and BU25TK), positive with HPV were used for the investigation. Cells were treated with the plant-derived substances and the IC50 was determined by MTT assay. Fluorescence microscopy (Annexin V-FITC, MPC and PI staining) was used to investigate autophagy/apoptosis, while relevant genes were analyzed by RT-qPCR.

Results: Reduced cell proliferation was earlier achieved in dose- and time-dependent manner by fractions retaining Securidaca1 and 2, with IC50 of 7.03 and 16.39 (μg/mL) respectively on Caski cells. Late apoptosis was also activated on cells treated with securidaca1 fraction, while the securidaca2 in contrast indicated early apoptosis. Analysis by RT-qPCR revealed a fold-change expression of antiapoptotic proteins, MCL-1 and BCL2L1, more pronounced in securidaca1. Interestingly, the AKT-3 was significantly inhibited, correlating with low expression of MCL-1, BCL2L1, VEGFA and CDH-1. Data analysis suggests the most likely activation of apoptosis via PTEN regulated PI3K-AKT pathway and respondent downstream (mTOR/ NF-kB).

Conclusion: The ability of Securidaca1 and 2 to kill tumor cells and induce apoptosis in manner involving multiple regulatory pathways enhances their potential against possible resistance and makes them attractive as candidates for anticancer development.

Citation Format: Titus C. Obasi, Cornelia Braicu, Heiko Noack, Ioana Berindan-Neagoe, Bjorn Junker, Radu N. Oprean. Securidaca1 and 2 induced apoptosis: A PI3K-AKT dependent pathway in cervical cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2673.