**Acknowledgements**

It was also reported that the prenylation together with the 41

30 Current Understanding of Apoptosis - Programmed Cell Death

observed sensitivity of MCF-7 breast cancer cells to the compound.

induction of apoptosis becomes a strategy for cancer drug discovery [18].

treated breast cancer cells and the Annexin V-FITC flowcytometric assays.

cells thus, halting its progression to immortality.

induced by Artonin E.

**5. Conclusion**

, 51

E had enhanced its affinity to the human estrogen receptor α. This affinity of Artonin E to the human estrogen receptor can be said to be mostly responsible for its better growth inhibition in MCF-7 cells observed in this study. Consistent with our findings, Obiorah et al. [13] discovered that ERα was exclusively responsible for the apoptosis induction of genistein, equol, and coumestrol, compounds which are structurally similar to Artonin E. They confirmed the phenomenon by a gene knockdown of ERα which prevented growth inhibition and apoptosis induced by these phytoestrogens. These support the involvement of the estrogen receptor in the growth inhibitory potential of Artonin E. Similarly, Turner et al. [14] also reported that prenylflavones show selectivity to estrogen receptors. Thus, it is of no doubt, that the affinity of Artonin E for the estrogen receptor is a possible basis for the

Various modes of cell death include apoptosis, necrosis and autophagy. However, from the results of this study, Artonin E provoked morphological features typical of apoptosis in the Artonin E treated breast cancer cells. In support of this, Carou et al. [15] and Gerl and Vaux [16], reported that apoptosis results in unique morphological changes including cell shrinkage, membrane alteration, DNA fragmentation and nuclear condensation. These features were observed in this study after treating the breast cancer cells with Artonin E. Succinctly, agents that trigger apoptosis are very essential in the management of cancer, giving that a unique hallmark of cancer cells is apoptosis evasion which is also implicated in its pathogenesis [17]. Hence,

A compromise in the phospholipid membrane asymmetry of a cell, results in the externalization of phosphatidylserine. To further strengthen the assessment of the apoptotic mode of cell death, annexin V FITC in combination with a DNA binding fluorochrome, PI were utilized [9, 19, 20]. In this study, Artonin E has been seen to significantly reduce the population of viable breast cancer cells in a concentration and time dependent manner while increasing the population undergoing apoptosis. Thus, treatment of breast cancer cells with Artonin E distorted the integrity of the lipid bilayer of the cancer cells, exposing their phospholipid as detected in this study. These observations qualifies apoptosis as the mode of cell death

Apoptotic endonucleases in the course of apoptosis, degrades chromosomal DNA into fragments [21]. This fragmented DNA can be visualized in a gel electrophoresis. In this study, after treating the cancer cells with Artonin E, its DNA was seen to have degraded into fragments in comparison to the untreated control. This DNA fragment induction by Artonin E, confirms apoptosis as the mode of cell death [22] which was also seen in the morphology of Artonin E

Artonin E inhibited the unregulated growth of breast cancer cells and induced apoptosis in the cancer cells. It produced enhanced cytotoxicity on the estrogen receptor positive MCF-7

vicinal diol groups in Artonin

We express our gratitude to the Universiti Putra Malaysia and all the staff of MAKNA-CANCER laboratory, UPM for their immense support in the success of this research. This study was co-supported by TETFund Nigeria, University Putra Malaysia and Ministry of Science, Technology and Innovation Malaysia (Vote No. 5450742).
