Abstract. Cancer is a major public health concern not only in developed countries, but also in developing countries. It is one of the leading causes of mortality worldwide. However, current treatments may cause severe side effects and harm. Therefore, recent research has been focused on identifying alternative therapeutic agents extracted from plant-based sources in order to develop novel treatment options for cancer. Strobilanthes crispa Blume is a plant native to countries including Madagascar and Indonesia. It has been used as an anti-diabetic, diuretic and laxative in traditional folk medicine. Furthermore, S. crispa has potential in treating cancer, as evidenced in previous studies. In the present study, the cytotoxic and apoptotic activities of S. crispa crude extracts were investigated in liver and breast cancer cell lines. Hexane, ethyl acetate, chloroform, methanol and water extracts prepared from the leaves, and stems of S. crispa were evaluated for their cytotoxicity on HepG-2 and MDA-MB-231 cells using an MTT assay. The anti-proliferative properties of stem hexane (SH) extract on both cell lines were analysed using cell doubling time determination and cell cycle analysis, while the apoptogenic properties was determined through the detection of caspase-8. Among the extracts tested, SH extract exhibited the lowest half maximal inhibitory concentrations in both the cell lines. The SH extract induced morphological changes in HepG-2 and MDA-MB-231 cells, and significantly delayed cell population doubling time. Furthermore, it altered cell cycle profile and significantly increased caspase-8 activity in HepG-2 cells, but not in MDA-MB-231 cells. In conclusion, the SH extract of S. crispa possesses potent anticancer properties and may be a suitable chemotherapeutic target. IntroductionCancer is characterized by uncontrolled growth and spreading of abnormal cells. It is one of the most life-threatening and challenging diseases of modern time, caused by a number of internal factors, including immune condition and inherited mutation, and external factors, including radiation, tobacco and chemical exposure (1). Liver, breast, colorectal, lung, cervical and nasopharyngeal cancer are the most prevalent cancer types in the modern age. The present study focused on liver and breast cancer due to their high occurrence rates. In 2006, hepatocellular carcinoma (HCC) was identified to account for 70-85% of total primary liver cancer types (2). HCC is primarily caused by chronic viral hepatitis B or C infection, iron overload, aflotoxin exposure, obesity, alcohol-associated cirrhosis and possibly non-alcoholic fatty liver disease (3,4). Breast cancer continues to be the leading cause of cancer-associated mortality among women (5), and the occurrence rate has increased in China and other Asian countries (6,7). Breast cancer can be categorized into two main types, ductal carcinoma and lobular carcinoma. Ductal carcinoma begins in the ducts that transport milk from the breast to the nipple, whereas lobular carcinoma starts i...