Anticarcinogenic Effects of the Ethanolic Extract of Salix aegyptiaca in Colon Cancer Cells: Involvement of Akt/PKB and MAPK Pathways

Abstract

The bark from Salix species of plants has been traditionally consumed for its antiinflammatory properties. Because inflammation frequently accompanies the progress of colorectal cancer (CRC), we have evaluated the anticancer properties of the ethanolic extract from the bark (EEB) of S. aegyptiaca, a Salix species endogenous to the Middle East, using HCT-116 and HT29 CRC cell lines. Fresh bark from S. aegyptiaca was extracted with ethanol, fractionated by solvent-solvent partitioning and the fractions were analyzed by tandem mass spectrometry. Catechin, catechol, and salicin were the most abundant constituents of the extract. Interestingly, EEB showed the highest anticancer effect in the colon cancer cells followed by its fractions in ethyl acetate and water, with catechin, catechol, and salicin showing the least efficacy. EEB could strongly reduce the proliferation of the cancer cells, but not of CCD-18Co, normal colon fibroblast cell line. Accompanying this was cell cycle arrest at G1/S independent of DNA damage in the cancer cells, induction of apoptosis through a p53 dependent pathway and an inhibition of PI3K/Akt and MAP Kinase pathways at levels comparable to known commercial inhibitors. We propose that the combination of the polyphenols and flavonoids in EEB contributes toward its potent anticarcinogenic effects.

[Supplementary materials are available for this article. Go to the publisher's online edition of Nutrition and Cancer for the following free supplemental resource(s): Supplementary Figure 1 and Supplementary Figure 2.]

ACKNOWLEDGMENTS

The authors would like to thank Dr. Ihsan Gursel at the Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey for the use of the flow cytometry facility and Dr. Tamay Şeker at the Middle East Technical University (METU) Molecular Biology and Biotechnology Central Lab for the tandem MS experiments. Dr. Ozlen Konu, Dr. Uygar Tazebay, Dr. Betul Ozdemir Soyler, and Dr. Elif Erson-Bensan are thanked for sharing resources. Dr. Mesut Muyan is gratefully acknowledged for critically reading the manuscript. This work was funded by METU Scientific Research Fund (Project no. BAP-2008-07-02-04) and the Turkish Academy of Sciences Young Scientist award (TÜBA-GEBİP) to Sreeparna Banerjee. Shabnam Enayat is supported by a TÜBİTAK bursary for international students (TÜBİTAK-BİDEB 2215).