Lophira alata Suppresses Phorbol Ester-Mediated Increase in Cell Growth via Inhibition of Protein Kinase C-α/Akt in Glioblastoma Cells

Abstract

Background: Medicinal plants serve as sources of compounds used to treat other types of cancers. The root of the plant Lophira alata (Ochnaceae) has been used as a component of traditional herbal decoctions administered to cancer patients in southwestern Nigeria. However, the mechanism of the cytotoxic effects of Lophira alata alone or in the presence of phorbol ester has not been investigated in brain tumor cells. Objective: This study was aimed at examining the cytotoxic potential of the methanolic fraction of Lophira alata root on malignant glioma invasive cellular growth and survival. Method: The methanolic fraction of Lophira alata (LAM) was subjected to high-performance liquid chromatography to determine the fingerprints of the active molecules. The antiproliferative effects of Lophira alata were assessed using the MTT and LDH assays. Protein immunoblots were carried out to test the effects of Lophira alata, alone or in the presence of phorbol ester, on survival signaling pathways such as Akt, mTOR, and apoptotic markers such as PARP and caspases. Results: The methanolic fraction of Lophira alata (LAM) induced a concentration-dependent and time-dependent decrease in glioma cell proliferation. In addition, LAM attenuated phorbol ester-mediated signaling of downstream targets such as Akt/mTOR. Gene silencing using siRNA targeting PKC-alpha attenuated LAM-mediated downregulation of Akt. In addition, LAM induced both PARP and caspase cleavages. The HPLC fingerprint of the fraction indicates the presence of flavonoids. Conclusion: LAM decreases cell proliferation and induces apoptosis in glioma cell lines and thus could serve as a therapeutic molecule in the management of gliomas.