Piper betle (PB) leaves (daun sirih in Malay language) extract has been demonstrated to have anticarcinogenic
activities in the experimental systems. It has been found the PB leaves extract could enhance the cytotoxic effect of other
anticancer drugs in cancer cells. The aim of this study is to investigate the combination effect of PB and 5-fluorouracil (5-FU)
in enhancing the cytotoxic potential using colon cancer cell lines.
We first examined the effect of PB leaves extract on colon cancer cells. Next, we examined whether PB leaves extract
could increase the sensitivity of the cells to 5-FU. Isobologram analysis was carried out to elucidate PB-5FU interaction.
Apoptotic features of the treated cells were then revealed by Annexin V/ PI stain. HPLC was performed to exclude any possible
chemical interaction between the compounds.
IC50 of 5-FU treated HT 29 and HCT 116 was 130.0µM and 12.5µM, respectively at 72 hours. IC50 of PB-treated HT
29 (200.0µg/ml) and HCT 116 cells (187.5µg/ml) was observed after 36 hours of treatment. In the presence of PB extract, the
cytotoxic effect of 5-FU was observed at a lower dose (12.5µM) and a shorter time (24 hours). HT 29 and HCT 116 cells
treated with 5-FU or PB alone induced a greater apoptosis effect compared to the combination treatment. Isobologram analysis
indicated PB and 5-FU interacted synergistically in HT 29 cells, but antagonistically in HCT 116 cells. Mixture of 5-FU and PB
sample did not show any interaction revealed by HPLC separation.
In the presence of PB, a lower dosage of 5-FU is required to achieve the maximum drug effect. PB works
synergistically with 5-FU in controlling cancer cell growth. However our current result showed this interaction may not solely
contribute to the apoptosis pathway. Further investigation should be performed to elucidate the possible mechanism.