Cancers are the most life-threatening conditions prevailing in the world (Jemal et al., 2007). Breast cancer is one of the leading causes of death among females. Its incidence is ever increasing, and it accounts for a major health problem in developing as well as developed nations. Two million new cases and half a million breast cancer-related deaths are recorded annually worldwide (Golubnitschaja et al., 2016). In India, the mortality caused by breast cancer has surpassed cervical cancer-related deaths (Malvia et al., 2017). It is a metastatic cancer spreading to bone, liver, lung, and brain, via blood or lymph, which further deteriorates the prognosis and accounts for its incurability.

Under normal conditions, cell death and proliferation occur in a balanced manner. In neoplastic tissues, cellular growth, division, and death are dysregulated. In fact, decisive cell death does not occur due to the lack of death signals (Thomadaki and Scorilas, 2006). Tumour cells are generally found to be resistant to apoptosis (Karin et al., 2002). Apoptosis dysregulation contributes remarkably to tumour pathogenesis by allowing the survival of neoplastic cells even in the presence of oxidative stress and hypoxia (Sadeghi et al., 2019). In cells, several proteins have pro-apoptotic or anti-apoptotic activities. The Bcl-2 protein family, which comprises of both pro-apoptotic and anti-apoptotic proteins, plays a key role in the regulation of apoptosis (Wang et al., 2016). Since cell survival or cell death depends upon the ratio of pro-apoptotic and anti-apoptotic proteins, any dysregulation at this level leads to uncontrolled proliferation of cells.

Various plant-derived products are being used as traditional folk medicines and food additives, which are known as herbal medicines. Cinnamomum cassia bark is the outer skin of evergreen tree, belonging to the Lauraceae family. Its extracts contain several active components such as essential oils (cinnamic aldehyde and cinnamyl aldehyde), tannin, mucus, and carbohydrates (Sadeghi et al., 2019). Their biological properties include antioxidative (Lee et al., 2003), antimicrobial, anti-inflammatory, antidiabetic (Khan et al., 2003), and antitumour activities (Schoene et al., 2005). Cinnamon can act as a therapeutic agent due to its antineoplastic effects by affecting different biochemical signalling pathways in cancer cells, including apoptosis. Since cancer cells are by and large resistant to apoptosis; hence, selective killing of cancer cells by promoting apoptosis using cinnamon provides an attractive and convincing way for the development of anticancer agents. As cinnamon has been demonstrated to possess antineoplastic properties, the current study was planned to evaluate the effect of cinnamon treatment on pro-apoptotic and anti-apoptotic genes in breast cancer cell line.