A62
The antagonists of chemokine receptor CXCR4 inhibit growth of ovarian cancer cells by inducing mitotic catastrophe and G2/M arrest
Joseph Kwong1, Hagen Kulbe1, Donald Wong2, Walter Korz2, Fran Balkwill1
1Centre for Cancer and Inflammation, Institute of Cancer, Barts and The London School of Medicine and Dentistry, London, UK, 2Chemokine Therapeutics Corp, Vancouver, Canada
Since CXCL12-CXCR4 signalling influences the development of primary ovarian tumours and metastasis, we have targeted the signalling in ovarian cancer using CXCR4 antagonists CTCE-9908 and AMD3100. CTCE-9908 is a small peptide antagonist of CXCR4, whereas AMD3100 is a bicyclam non-peptide antagonist of CXCR4.
In the present study, we evaluated the activity of these antagonists in ovarian cancer in vitro. Treatment with CTCE-9908 inhibited growth of CXCR4-positive ovarian cancer cells at the concentration of 100 µg/ml. AMD3100 inhibited growth of ovarian cancer cells at the concentration of 10 µg/ml. These antagonists did not show any significant effect on the growth of immortalized non-transformed ovarian epithelial cells.
We further showed that the growth inhibition by CTCE-9908 and AMD3100 was not caused by apoptosis or senescence. Instead, CTCE-9908 induced death in ovarian cancer cells by mitotic catastrophe. Using DNA content FACS analysis, we found that CTCE-9908 induced G2/M arrest and multi-nucleation in ovarian cancer cells. BrdU incorporation analysis showed that this multi-nucleation was a result of DNA re-replication. Using fluorescence and immuno-fluorescence labelling of DNA, p-MPM2 and a-tubulin, we observed that CTCE-9908 induced abnormal mitoses in ovarian cancer cells. This mitotic catastrophe was likely to be resulted from abnormal activity of various proteins at G2/M phase as Cdc2, Cdc25C, BubR1 and NUMA have been shown to be dys-regulated by CTCE-9908. The growth inhibition by AMD3100 was also caused by induction of G2/M arrest in ovarian cancer cells.
We did not observe any of these mechanisms of cell death and growth inhibition in ovarian cancer cells by CXCR4 inhibitory antibodies or CXCR4-targeting siRNA. We speculate that the binding of different types of antagonist to CXCR4 induces distinct intracellular signalling events in cancer cells. This is the first report elucidating the mechanisms of cell death and growth inhibition by CXCR4 antagonists in cancer cells.
