Indole-3-carbinol enhances anti-proliferative, but not anti-invasive effects of oxaliplatin in colorectal cancer cell lines.

The primary aim of this study was to determine whether combination of the chemopreventive agent indole-3-carbinol (I3C) with oxaliplatin would decrease proliferative index and invasive potential of human colorectal tumour cells. Combination of the agents resulted in a 170-fold decrease in proliferative capacity in SW480 and SW620 cell lines, which was approximately 6-fold greater than for oxaliplatin alone. Decreased proliferation was attributed to enhanced S-phase cell cycle arrest for SW480, and increased apoptosis for SW620 cells. The combined agents resulted in significantly increased E-cadherin levels in SW480 cells, and beta-catenin levels in both cell lines (assessed by in-cell westerns). In SW480 cells confocal microscopy revealed an increase in membrane-associated beta-catenin levels, with oxaliplatin treatments enhancing nuclear export and cytoplasmic localisation. In SW620 cells, all treatments increased membrane localisation of E-cadherin. Whilst both oxaliplatin and I3C decreased invasive capacity of SW480 cells, this was not further enhanced by the combined treatment.