The antiproliferative and apoptosis inducing effects of Moringa oleifera aqueous leaf extract and its synthesised gold nanoparticles - modulation of oncogenes and tumour suppressor genes in human cancer cell lines.

Abstract

Cancer is one of the leading causes of global mortality. In South Africa (SA), the burden of cancer (lung and oesophageal) continues to increase. Moringa oleifera (MO), indigenous to India, is found widely in SA and used in traditional treatments of cancer. Gold nanoparticles (AuNP’s) are showing potential in cancer therapies and can be synthesised using plants extracts such as MO leaf extract (MOE). This study investigated the antiproliferative effect of MOE and AuNP’s synthesised from MOE (MLAuNP) in A549 lung and SNO oesophageal cancer cells. MO crude aqueous leaf extract was prepared and cytotoxicity (MTT assay) was assessed in A549, SNO cells and normal peripheral blood mononuclear cells (PBMCs) (24h). Oxidative stress, DNA fragmentation and apoptotic markers were determined. A one-pot green synthesis technique using MOE to synthesise MLAuNP was then conducted. A549, SNO cells and PBMCs were also exposed to MLAuNP and CAuNP to evaluate cytotoxicity and apoptotic markers. MOE was cytotoxic to A549 cells. MOE (IC50: 166.7μg/ml, 24h) significantly increased lipid peroxidation, decreased glutathione (GSH) and Nrf2 levels leading to DNA fragmentation. MOE induced apoptosis by significantly increasing p53, caspase-9, enhancing caspase-3/7 activities and Smac/DIABLO expression. MOE significantly cleaved PARP-1 into 89kDa and 24kDa fragments. MOE was not cytotoxic to PBMCs but in SNO cells (IC50: 389.2μg/ml, 24h), it significantly increased lipid peroxidation, DNA fragmentation, decreased GSH, catalase and Nrf2 levels. Apoptosis was confirmed by the significant increase in phosphatidylserine (PS) externalisation, caspase-9, enhanced caspase-3/7 activities and significant decrease in ATP levels. MOE significantly increased p53, Smac/DIABLO and cleavage of PARP-1, resulting in an increase in the 24kDa fragment. MLAuNP was successfully synthesised. MLAuNP and CAuNP were not cytotoxic to PBMCs, whilst its pro-apoptotic properties were confirmed in A549 (IC50: MLAuNP - 98.46μg/ml; CAuNP - 121.4μg/ml) and SNO (IC50: MLAuNP - 92.01μg/ml; CAuNP - 410.4μg/ml) cells. MLAuNP significantly increased caspase activity in SNO cells while MLAuNP significantly increased PS externalisation, mitochondrial depolarisation, caspase-9, caspase-3/7 activities and decreased ATP levels. Also, MLAuNP significantly increased p53, Bax, Smac/DIABLO, PARP-1 24kDa fragment and enhanced SRp30a levels. Conversely, MLAuNP significantly decreased Bcl-2,

Hsp70, Skp2, Fbw7α, c-myc levels and activated alternate splicing with caspase-9a splice variant being increased. These findings indicate that MOE exerts antiproliferative effects in cancerous A549 and SNO cells by increasing oxidative stress, DNA fragmentation and inducing apoptosis. MLAuNP also possessed antiproliferative properties in SNO cells and induced apoptosis in A549 cells by modulating oncogenes, tumour suppressor genes and activating alternate splicing of caspase-9. MOE and MLAuNP showed potential use as a complementary and alternative treatment for lung and oesophageal cancer. MOE fractionation studies are further recommended to identify the bioactive compounds responsible for the antiproliferative effect seen in A549 and SNO cells. In addition, membrane transport proteins as well as cell cycle analysis will provide further insight into MOE and MLAuNP antiproliferative effect.