The Proteomics of Colorectal Cancer: Identification of a Protein Signature Associated with Prognosis

Abstract

Colorectal cancer is one of the commonest types of cancer and there is requirement for the identification of prognostic biomarkers. In this study protein expression profiles have been established for colorectal cancer and normal colonic mucosa by proteomics using a combination of two dimensional gel electrophoresis with fresh frozen sections of paired Dukes B colorectal cancer and normal colorectal mucosa (n = 28), gel image analysis and high performance liquid chromatography–tandem mass spectrometry. Hierarchical cluster analysis and principal components analysis showed that the protein expression profiles of colorectal cancer and normal colonic mucosa clustered into distinct patterns of protein expression. Forty-five proteins were identified as showing at least 1.5 times increased expression in colorectal cancer and the identity of these proteins was confirmed by liquid chromatography–tandem mass spectrometry. Fifteen proteins that showed increased expression were validated by immunohistochemistry using a well characterised colorectal cancer tissue microarray containing 515 primary colorectal cancer, 224 lymph node metastasis and 50 normal colonic mucosal samples. The proteins that showed the greatest degree of overexpression in primary colorectal cancer compared with normal colonic mucosa were heat shock protein 60 (p<0.001), S100A9 (p<0.001) and translationally controlled tumour protein (p<0.001). Analysis of proteins individually identified 14-3-3β as a prognostic biomarker (χ2 = 6.218, p = 0.013, HR = 0.639, 95%CI 0.448–0.913). Hierarchical cluster analysis identified distinct phenotypes associated with survival and a two-protein signature consisting of 14-3-3β and aldehyde dehydrogenase 1 was identified as showing prognostic significance (χ2 = 7.306, p = 0.007, HR = 0.504, 95%CI 0.303–0.838) and that remained independently prognostic (p = 0.01, HR = 0.416, 95%CI 0.208–0.829) in a multivariate model.

Tumor suppressor gene &lt;italic&gt;NGX6&lt;/italic&gt; induces changes in protein expression profiles in colon cancer HT-29 cells

“…A recent proteomics study showed that ALDH1 was down-regulated in lymph node metastasis of colon carcinoma cells [28]. Our experiments showed that ALDH1 is significantly up-regulated in colon cancer cells transfected with NGX6, suggesting that NGX6 may up-regulate ALDH1 expression to inhibit oncogenesis and metastasis.…”

Reduced LIMK2 expression in colorectal cancer reflects its role in limiting stem cell proliferation

“…Similar to normal tissue, LIMK2 expression was relatively high in low grade adenomas but markedly decreased in high grade adenomas with low or high levels of dysplasia (figure 3A). We next stained a well-characterised TMA comprised of 650 patient samples of normal intestines and tissue from Dukes A to Dukes C tumours, as well as representative lymph node metastases 21. By assigning staining intensity scores from 1 (low) to 6 (high), we established that median staining intensity in normal intestines scored 5 with relatively little variation (figure 3B,C).…”

A Seven-Gene Signature Aggregates a Subgroup of Stage II Colon Cancers with Stage III

“…However, the heterogeneity in the use of adjuvant treatment procedures makes it difficult to compare previously published findings to ours regarding this issue. After analyzing paired normal and tumor DNA, two studies found the differentially-expressed genes to be prognostic factors (Duncan et al, 2008;O'Dwyer et al, 2011). Our study focused on primary tumor DNAs and histo-clinical parameters.…”