INTRODUCTION
Lung cancer is a major cause of morbidity and mortality in the world (Ferlay et al. 2010; Ridge et al. 2013). Lung cancer initiates when cells in the lung grow extensively forming a tumour, lesion or nodule. It is divided into two main classifications, small cell lung cancer and non-small cell lung cancer (NSCLC). The NSCLCs include squamous cell carcinomas, adenocarcinomas, and large cell carcinomas. Squamous cell carcinoma is commonly found in men and is correlated with history of smoking. According to the National Cancer Registry Report 2007-2011, lung cancer was reported to be the third most common cancer in Malaysia affecting men predominantly (Azizah et al. 2016).
Generally, oxidative stress was implicated to be a causative factor for cancer development. Long term exposure to oxidative stress causes oxidative modifications to macromolecules such as DNA, lipid 209and protein resulting in damages of cell structure and function (Poyton et al. 2009; Hussain et al. 2003). High levels of reactive oxygen species (ROS) produced by metabolic pathways also stimulate mutations and oncogenes formation leading to development of cancer cells (Fang et al. 2009; Trachootham et al. 2009; Waris & Ahsan 2006). On the other hand, few cancer treatment such as chemotherapy and radiotherapy utilises ROS for cancer elimination. Increased oxidative stress induced by these treatments may also cause further DNA damage and mutations leading to the development of drug-resistance in tumour cells. Hence, proper evaluation of anticancer strategies aimed to modulate levels of ROS are warranted (Gorrini et al. 2013).
Previous studies proved that Gelam honey contains high contents of phenols, mineral, protein, free amino acid, enzymes, and vitamins. These compounds provide different biological properties including antioxidant, anticancer, anti-diabetic, anti-inflammatory and improved wound healing (Putri Shuhaili et al. 2016; Hussein et al. 2011) free radicals scavenging activities (Hussein et al. 2011). Phenolic compounds in honey such as caffeic acid, chrysin, phenyl ester, galangin, kaempferol, antioxidants, amino acids, and protein mediate antiproliferative effect towards cancer cells by inducing antioxidant effects, stimulation of TNF-α, induction of apoptosis and inhibition of lipoprotein oxidation (Tonks et al. 2001). Previous research reported that Gelam honey from Malaysia provided anti-cancer properties by inhibiting of cell proliferation and DNA damage as well as inducing of apoptosis of human osteosarcoma and cervical cancer cells (Tahir et al. 2015). Gelam honey has been proposed to reduce oxidative damage through modulation of the endogenous antioxidant enzyme activities (Sahhugi et al. 2014). Since, Gelam honey has been shown to possess both anti-cancer and antioxidants properties, the purpose of this study is to determine whether Gelam honey can attenuate or augment the oxidative damages in stress induced lung cancer cells.
MATERIALS & METHODSA549 CELL LINE CULTURE
In this study, 3 different passages of A549 lung cancer cell were used. A cryovial of A549 stock was thawed in 37