Poster Presentation 30th Lorne Cancer Conference 2018

Anti-tumour effects of Bacopaside II on colorectal cancer cells in vitro (#267)

Eric Smith 1 2 , Helen M Palethorpe 1 2 , Yoko Tomita 1 2 , Amanda R Townsend 2 3 , Timothy J Price 2 3 , Andrea J Yool 2 , Jennifer E Hardingham 1 2
  1. Molecular Oncology, Basil Hetzel Institute, The Queen Elizabeth Hospital, Woodville South, South Australia, Australia
  2. Adelaide Medical School, Adelaide Unisversity, Adelaide, South Australia, Australia
  3. Medical Oncology, The Queen Elizabeth Hospital, Woodville South, South Australia, Australia

Introduction: Bacopaside II is a triterpene saponin extracted from the medicinal herb Bacopa monnieri. Aquaporin-1 is a transmembrane pore-forming molecule that facilitates the rapid movement of water and small solutes across cell membranes. We have previously demonstrated that Bacopaside II can block aquaporin-1 water channels, and impair the in vitro migration of colon cancer cell lines that express comparatively high levels of aquaporin-1 (Pei et al., 2016). The aim of this study was to determine the effects of Bacopaside II on colorectal cancer cell growth in vitro.

Methods: Expression of aquaporin-1 in colon cancer cell lines HT-29, SW480, SW620 and HCT116 was determined by western immunoblot and quantitative real-time polymerase chain reaction. Analytical standard grade Bacopaside II was purchased from Sigma-Aldrich.  Cells were treated with either 0 (vehicle; 2% v/v methanol), 2.5, 5, 10, 15, 20 or 30 µM Bacopaside II. Cell growth was determined by crystal violet staining, metabolic activity by MTS assay, cell cycle analysis by propidium iodide (PI) staining, apoptosis by Annexin-V/PI staining and CellEvent Caspase 3/7 Green Detection Reagent, and autophagy by acridine orange staining.

Results: Aquaporin-1 expression was comparatively high in HT-29 and low in SW480, SW620 and HCT116 colon cancer cell lines. Treatment with Bacopaside II induced significant reductions in cell growth at ≥ 15 µM for SW480, SW620 and HCT116, and ≥ 20 µM for HT-29. Inhibition of cell growth was accompanied by one of two distinctive morphological changes within 24 hours, either cellular shrinkage and blebbing consistent with apoptosis at higher inhibitory doses, or the formation of large vacuoles suggestive of autophagy at lower inhibitory doses. Increases in Annexin-V staining and activation of caspase 3/7 confirmed induction of apoptosis. Propidium iodide staining demonstrated that Bacopaside II induced cell cycle arrest.

Conclusions: These results are the first to show that Bacopaside II inhibits colon cancer cell growth by inducing cell cycle arrest and apoptosis in vitro.

 

  1. PEI, J. V., KOURGHI, M., DE IESO, M. L., CAMPBELL, E. M., DORWARD, H. S., HARDINGHAM, J. E. & YOOL, A. J. 2016. Differential Inhibition of Water and Ion Channel Activities of Mammalian Aquaporin-1 by Two Structurally Related Bacopaside Compounds Derived from the Medicinal Plant Bacopa monnieri. Mol Pharmacol, 90, 496-507.