Apoptotic potential role of Agave palmeri and Tulbaghia violacea extracts in cervical cancer cells

Cervical cancer, a gynaecological malignant disorder, is a common cause of death in females in Sub-Saharan Africa, striking nearly half a million of lives each year worldwide. Currently, more than 50 % of all modern drugs in clinical use are of natural products, many of which have an ability to control cancer cells (Madhuri and Pandey, Curr Sci 96:779-783, 2009; Richter, Traditional medicines and traditional healers in South Africa, 2003). In South Africa, plants used to treat cancer are rare even though majority of our population continue to put their trust in traditional medicine. In this study we aimed to screen Agave palmeri (AG) and Tulbaghia violacea (TV) for potential role in inducing cell death in cervical cancer cell lines HeLa and ME-180, and in normal human fibroblast cell line KMST-6 cell lines. To achieve this, AG and TV crude extracts were utilized to screen for apoptosis induction, inhibition of cell proliferation followed by elucidation of the role of Bax, Bcl-2, p53, Rb, RBBP and Mdm2 genes in cervical cancer. In brief, plant leaves and roots were collected, crushed and methanolic extracts obtained. Different concentrations of the stock extracts were used to treat cancer cells and measure cell death using the [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay and flow cytometry. Western blot was applied to measure gene expression at protein level using RBBP6, p53, Mdm2, Rb, Bax, Bcl-2 and β-actin mouse monoclonal primary antibodies (IgG) and goat anti mouse coupled with horseradish peroxidase secondary antibody from Santa Cruz Biotechnology and real time-PCR was used for mRNA expression level. Plant extracts of AG and TV were time (24 h) and dose (50, 100, 150 μg/ml) dependent in their induction of cell death with an IC₅₀ ~ 150 μg/ml. A further mixed respond by several genes was observed following treatment with the two plant extracts where RBBP6 was seen to be spliced in cancer cells while Bax was induced and Bcl-2 was inhibited with the levels of p53 remaining the same. The two plant extracts do induce cell death, in a p53 independent manner.