The positive response to tamoxifen in ERa-positive breast cancer patients is usually of a short duration as many
of the patients eventually develop resistance. Our preliminary results show that aloe emodin extracted from
the leaves of the Aloe barbadensis Miller demonstrated a cytotoxicity that is selective to ERa-positive breast
cancer cells (MCF-7), but not to ERa-negative breast cancer cells (MDA-MB-231) and to the control cells (MCF-
10A). The objective of this study was to test the hypothesis that aloe emodin may enhance the response of
MCF-7 cells to treatment with tamoxifen. MCF-7 cells were treated with aloe emodin alone, tamoxifen alone
or a combination of emodin and tamoxifen, at their respective IC50 concentrations and at different time points
of 24 hours, 48 hours and 72 hours. The respective IC50s were the concentrations of aloe emodin and tamoxifen
required to achieve 50% inhibition of the cells in the study. Cell viability and apoptosis were determined using
trypan blue exclusion and DNA fragmentation assays, respectively. The involvement of RAS/MEKs/ERKs genes
of MAPK signalling pathways with aloe emodin was determined using QuantiGene 2.0 Plex assay. Data was
evaluated using the one-way ANOVA test. Our findings showed that aloe emodin enhanced the cytotoxicity of
tamoxifen on MCF-7 cells through apoptosis by downregulation of MEK1/2 genes. Our research may provide a
rational basis for further in vivo studies to verify the efficacy of a combination of aloe emodin and tamoxifen
on the viability of ERa-positive-breast cancer cells.