Sutherlandia frutescens is a South African herbal remedy traditionally used for stomach problems, diabetes and lately to improve the overall health in cancer and HIV/AIDS patients. The in vitro influence of crude S. frutescens extract was investigated in human breast adenocarcinoma (MCF-7) and normal non-tumorigenic breast epithelial (MCF-12A) cells after 48 h of exposure to S. frutescens extracts. Dose-dependent studies (1.0-2.0mg/ml) were conducted on cell numbers and viability by means of spectrophotometry. Morphological changes were determined with fluorescent and transmission electron microscopy (TEM). Cell cycle progression and apoptosis were analysed using flow cytometry and Agilent’s Human-1A Oligo Microarray slides with 20,173 known human 60-mer oligonucleotide probes were employed to study the differential effects of S. frutescens extracts on gene expression levels in both the MCF-7 and MCF-12A cells. A statistically significant decrease to 50% of malignant cell numbers was observed after 48 h of exposure to 1.0mg/ml S. frutescens extract in MCF-7 cells and 1.5mg/ml in MCF-12A. 48 h exposure to 1.5mg/ml S. frutescens revealed 21% viable MCF-7 and 78% viable MCF-12A cells compared to vehicle-treated control cells. Morphological characteristics of apoptosis and autophagy, including cytoplasmic shrinking, membrane blebbing and an increase in autophagic vacuoles were observed in both cell lines with the MCF-7 cells being more susceptible to autophagy and the MCF-12A cells more susceptible to apoptotic cell death. TEM confirmed ultrastructural characteristics of autophagy in both cell lines. Flow cytometry revealed a G2/M arrest with no increase in apoptosis in MCF-7 cells and a G2/M arrest with an increase in apoptosis in MCF-12A cells treated with 1.5mg/ml S. frutescens extract. Microarray analysis revealed differentially expressed genes involved in cell cycle progression including proliferating cell nuclear antigen (PCNA) and poly (ADP-ribose) polymerase (PARP2) in MCF-7 and topoisomerase I (TOPM1), DNA polymerase-sigma (POLS) in MCF-12A cells. This study contributes to the understanding of molecular mechanisms and cell signaling events associated with in vitro anticancer responses of S. frutescens, thus enabling researchers to focus on affected cellular mechanisms to identify and characterize active compounds from these extracts with subsequent evaluation as possible candidates for use in anticancer therapy.
Poster presented at the University of Pretoria Health Sciences Faculty Day, August 2007, Pretoria, South Africa.