Daniel Oyugi, PhD

Anticancer Potential of Vernonia amygdalina Extracts

Vernonia amygdalina (VA) is a tropical African plant of the Asteraceae family used as a dietary supplement and a medicinal herb for many diseases and infections. Some of the well-known therapeutic uses of VA include treating gastrointestinal -disorders, sexually transmitted diseases, amoebic dysentery, malaria and other parasitic and microbial infections. Previously, we identified, through bioassay-guided extraction processes, the activity markers of VA fractions in breast cancer cells. These markers were useful in the standardization and quality determination of VA samples. Several secondary metabolites were detected in the fractions, all of which have been reported to possess pharmacological properties in a variety of neoplastic diseases. Additionally, we have shown, by [3H]-thymidine incorporation assay, that VA leaf extracts inhibit growth and proliferation of cancer cells, in vitro. Previous studies have also shown that low concentrations of VA leaf extracts exerts a dose-dependent growth inhibition of human breast cancer cells, and induces apoptosis, in vitro. Although these reports testify to the therapeutic potential of VA on cancer, the mechanisms underlying its cell growth inhibition and apoptosis induction are not well understood. In preliminary studies, we found that VA disrupts organization of microtubule, a structural protein involved in many cellular processes including growth and division. In this study, therefore, we propose to: (1) Determine if organization of microtubule in VA-treated cells show disruption leading to cell cycle arrest. This will be necessary to assess whether assembly or disassembly of tubulin protofilaments are due to VA compounds. Additionally, this will allow for the measurement of DNA content, as well as analysis of expression levels of cyclins. (2) Establish if DNA in VA treated cells show damage resulting in mitotic arrest. This will be important in monitoring DNA strand breaks and repair response due to VA treatment, and also to assess DNA content. (3) Determine if treated cells undergo apoptosis, by assessing whether nuclear and DNA fragmentation, as well as activation of pro-apoptotic genes and accumulation of Reactive Oxygen Species, are due to compound treatment. Specifically, it will allow for detection, quantification and identification of localization patterns of genes and proteins involved in programmed cell death. In addition to assessing the fundamental mechanism of VA activity in cancer, this work will also provide the natural product community with (a) a toolbox of ideas on the pivotal molecular targets important in cell survival and death, (b) an impetus to further explore interactions between compound and target, focusing on Structure-Activity Relationships, particularly on compound binding site, binding selectivity and binding affinity to target molecules, and (c) a basis to examine potential role of natural products in promoting target-mediated drug delivery and alleviation of likely resistance.