The loss of the CBX7 gene expression represents an adverse prognostic marker for survival of colon carcinoma patients.

We have previously shown that CBX7 expression is associated with a more malignant phenotype in thyroid cancer. On this basis, we decided to investigate its possible prognostic value in colorectal cancer (CRC). CBX7 expression has been analysed by immunohistochemistry in tissue microarray (TMA) specimens obtained from a large series of sporadic CRC resections (n=1420). The CBX7 expression data have been correlated with several clinico-pathological parameters. CBX7 expression is reduced or absent in a significant number of CRC samples in comparison to the normal colonic mucosa and the loss of CBX7 expression correlates with a poor outcome of CRC (p<0.001). The block of CBX7 expression seems to occur at a transcriptional level since quantitative RT-PCR analysis showed a reduced CBX7-specific mRNA levels in CRC samples versus normal counterpart tissue (up to more than 50-fold). Finally, the restoration of CBX7 expression in two CRC cell lines reduces their proliferation rate suggesting a role of the loss of CBX7 expression in the progression step of colon carcinogenesis. Therefore, the data reported here indicate that the evaluation of CBX7 expression may represent a valid tool in the prognosis of colon cancer since a reduced survival of CRC patients is associated with the loss of CBX7 expression.