Molecular mechanism of the cytotoxic activity of Pogostemon quadrifolius (Benth.)

Abstract

The study entitled “Molecular mechanism of the cytotoxic activity of Pogostemon quadrifolius (Benth.)” was carried out in the Department of Plant Biotechnology, College of Agriculture, Vellayani, Thiruvananthapuram during 2021 - 2022. The objective of this study was to evaluate the cytotoxic effect of P. quadrifolius (Benth.) leaf extract on cancer cells and to elucidate its action on genes of apoptotic pathway. P. quadrifolius (Benth.) is a shrub belonging to the family Lamiaceae and there are preliminary reports on antiproliferative effect of P. quadrifolius (Benth.) leaf extract in chronic myelogenous leukemia cancer cells and prostate cancer cells. However, the molecular mechanism of its cytotoxicity is not yet understood. P. quadrifolius (Benth.) leaves were dried and then extracted with methanol, 53.2 mg/g of crude extract was obtained from powdered leaf sample. Cytotoxic effect of the leaf extract was evaluated by MTT assay in human lung (A549), breast cancer cell line (MDA-MB -231) and normal cell line HEK 293. The extract showed dose dependent reduction in cell survival percentage and IC 50 values were found to be 48.01 µg/ml and 75.38 µg/ml for lung and breast cancer respectively, while it was non-toxic towards normal cells in the above dosage. The leaf extract also inhibited the colonyforming ability of cancer cells in the clonogenic assay which was indicative of the extract’s ability to affect cell survival and proliferation. DNA isolated from the methanolic leaf extract treated cells when subjected to DNA fragmentation assay was seen sheared which is an indication of apoptosis in those cells. Expression profiling of the key apoptotic genes BAX, CASPASE 3, CASPASE 9, PARP and BCL2 showed upregulation of BAX, CASPASE 9 and CASPASE 3 in the treated cells. The antiapoptotic genes BCL2 and PARP1 were downregulated and also the BAX/ BCL2 ratio was found to be greater than 1 which confirms that active apoptosis is happening in cancer cells upon treatment with leaf extract. Cytotoxic effect of methanolic leaf extract of P. quadrifolius (Benth.) on lung and breast cancer cells were elucidated and the gene expression analysis revealed that the mechanism of cytotoxicity is via apoptosis. The findings suggest that the leaf extract of P. quadrifolius (Benth.) can be a potent candidate for development of cancer chemotherapeutics after further advanced research.