Oxidative stress and antioxidants in breast cancer: a double-edged sword

Breast cancer is a primary cause of cancer-related deaths among women globally. Timely diagnosis of breast cancer with effective treatment helps reduce mortality. Over the years, extensive research has linked oxidative stress, which results from the imbalance in Reactive Oxygen Species (ROS) and antioxidant homeostasis, to the formation of cancer cells. Oxidative stress can lead to carcinogenesis through its ability to alter genetic material (DNA), affect cellular signalling pathways and cell cycle regulation, promote angiogenesis and metastasis. Antioxidants are defence systems used to counteract ROS, thus ensuring ROS homeostasis in a cell. Examples of endogenous antioxidants include glutathione, catalase, and superoxide dismutase. Antioxidants can be obtained exogenously from plant sources or the diet. Examples of dietary antioxidants' sources include curcumin, brassinosteroids, gallocatechins, resveratrol, etc. Chemotherapy has some undesirable side effects which can negatively affect the quality of life of breast cancer patients, natural plant-based products rich in antioxidants have been shown to mitigate these side effects and therefore improve patients' quality of life. Various plants have been studied, and compounds having antioxidant properties have been identified that can help reduce the side effects of cancer treatment. The intake of dietary antioxidants has become important in cancer prevention and management. From various studies on ROS and antioxidants in breast cancer aetiology and treatment, there seems to be conflicting information suggesting contradictory roles of both ROS and antioxidants. Although ROS are seen to be involved in breast cancer formation, they are still used in treating cancer by inducing apoptosis. Some newer investigations have indicated certain antioxidants in promoting carcinoma. The concept of persistent oxidative stress in cancer cells, which supports tumour microenvironment (TME), is another phenomenon requiring more research. This review focuses on breast cancer, highlighting how oxidative stress contributes to its progression and evaluating the therapeutic potential of dietary antioxidants.