Human tissue validation of potential biomarkers for colorectal cancer


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Shahram Ibrahim1, Karen Reed2, Abeer Hammoudi1, Alan Clarke2, Mark Pritchard1, John Jenkins1
1University of Liverpool, Liverpool, UK, 2University of Cardiff, Cardiff, UK

Background

Colorectal cancer is the second leading cause of cancer-related death in the UK. Biomarkers which allow earlier non-invasive detection of disease or which predict response to therapy would greatly aid disease management. Mutations in the WNT pathway are regarded as the key drivers of sporadic colorectal cancer development. The adenomatous polyposis coli (APC) gene regulates the WNT signaling pathway by mediating β-catenin degradation, therefore modulating intestinal homeostasis. We have previously performed a proteomic analysis of the changes which occur in the murine intestinal epithelium following deletion of the Apc gene (AhCre+Apcfl/fl mice). Several proteins demonstrated increased abundance and we hypothesised that some of these may represent potential biomarkers for human colorectal cancer. We have validated some of these using independent techniques in mouse and human samples and here present the results for: Prohibitin (PHB) a mitochondrial protein whose functions are not yet fully understood and Fatty acid binding protein 6 (FABP6) which is involved mainly in fatty acid metabolism.

Method

The expression patterns of PHB and FABP6 were assessed by immunohistochemistry in intestinal samples obtained from AhCre+Apcfl/fl mice and ApcMin/+ mice aged 1, 3 and 6 months (5-10 mice/group) and validated in human colorectal cancer tissue samples (3-5 independent samples per tumour stage). WNT activity was assessed using nuclear localisation of Beta catenin.

Results

PHB showed mild if any change during the early stages of colorectal tumourigenesis, but demonstrated clear upregulation in the more advanced stages such as polyp cancers and Dukes' A and B stages. On the other hand FABP6 showed much stronger changes during the early stages of tumourigenesis and reduced expression in more advanced lesions.

Conclusion

FABP6 and PHB showed altered expression in murine and human intestinal/colonic tumours and as such represent promising potential biomarkers of the different stages of colorectal tumourigenesis.