WWOX expression in colorectal cancer-a real-time quantitative RT-PCR study

The WWOX gene is a tumour suppressor gene affected in various types of malignancies. Numerous studies showed either loss or reduction of the WWOX expression in variety of tumours, including breast, ovary, liver, stomach and pancreas. Recent study demonstrated that breast cancer patients exhibiting higher WWOX expression showed significantly longer disease-free survival in contrast to the group with lower relative WWOX level. This work was undertaken to show whether similar phenomena take place in colon tumours and cell lines. To assess the correlation of WWOX gene expression with prognosis and cancer recurrence in 99 colorectal cancer patients, we performed qRT-PCR analysis. We also performed analysis of WWOX promoter methylation status using MethylScreen method and analysis of loss of heterozygosity (LOH) status at two WWOX-related loci, previously shown to be frequently deleted in various types of tumours. A significantly better disease-free survival was observed among patients with tumours exhibiting high level of WWOX (hazard ratio = 0.39; p = 0.0452; Mantel-Cox log-rank test), but in multivariate analysis it was not an independent prognostic factor. We also found that although in colorectal cancer WWOX expression varies among patients and correlates with DFS, the exact mode of decrease in this type of tumour was not found. We failed to find the evidence of LOH in WWOX region, or hypermethylation in promoter regions of this gene. Although we provide the evidence for tumour-suppressive role of WWOX gene expression in colon, we were unable to identify the molecular mechanism responsible for this.