A23
Expression of the common fragile site tumour suppressor genes WWOX and FHIT is dysregulated following chemotherapy drug treatment
Szymon Janczar, Louise Coleman, Laila Safarfashandi, Carina Shortall, Riham Soliman, Hani Gabra, Adam Paige
Imperial College London, UK
Background
Common fragile sites (CFS) are genomic regions prone to instability and present in all individuals. CFS regions are targets of carcinogenic damage and exhibit deletions, translocations and rearrangements in many cancers. These often disrupt neighbouring genes and several CFS genes, e.g. WWOX and FHIT, have been confirmed as important tumour suppressors regulating apoptosis, cell adhesion and cell growth. Many chemotherapy drugs are DNA-damaging agents, and we hypothesise that these may also disrupt the expression of fragile site-associated tumour suppressor genes. This may contribute to the development of chemoresistant tumours.
Method
A2780 and SKOV3 ovarian cancer cells were treated with cisplatin or paclitaxel, and expression of the fragile site genes WWOX and FHIT examined by qRT-PCR and immunoblotting. Effect of WWOX expression on chemotherapy-induced apoptosis (caspase activation and annexin-V staining) was measured.
Results
The genotoxic chemotherapy agent cisplatin suppressed WWOX protein expression in both A2780 and SKOV3, and this persisted for at least several days. The mechanism likely involves the WWOX gene locus as no effect was observed on exogenous WWOX expression in transfected cells. Supporting this, suppression of WWOX mRNA by cisplatin was also observed, preceding protein loss. In contrast, exposure of these ovarian cancer cells to non-genotoxic chemotherapy (paclitaxel) did not affect WWOX expression. The FHIT tumour suppressor was also suppressed by cisplatin treatment in A2780 cells but was induced in SKOV3 cells, and FHIT was also induced by paclitaxel in A2780 cells. We have previously shown that WWOX induces apoptosis in detached but not adherent ovarian cancer cells. We are currently investigating the influence of WWOX expression on chemotherapy response.
Conclusion
Fragile site gene expression is dysregulated following chemotherapy drug treatment, resulting in disruption of the tumour suppressor genes WWOX and FHIT. Such a mechanism could contribute to induction of chemoresistant tumour.
