Characterisation and protein expression profiling of annexins in colorectal cancer

Abstract

The annexins are family of calcium-regulated phospholipid-binding proteins with diverse roles in cell biology. Individual annexins have been implicated in tumour development and progression, and in this investigation a range of annexins have been studied in colorectal cancer. Annexins A1, A2, A4 and A11 were identified by comparative proteomic analysis to be overexpressed in colorectal cancer. Annexins A1, A2, A4 and A11 were further studied by immunohistochemistry with a colorectal cancer tissue microarray containing primary and metastatic colorectal cancer and also normal colon. There was significant increase in expression in annexins A1 (P=0.01), A2 (P<0.001), A4 (P<0.001) and A11 (P<0.001) in primary tumours compared with normal colon. There was increasing expression of annexins A2 (P=0.001), A4 (P=0.03) and A11 (P=0.006) with increasing tumour stage. An annexin expression profile was identified by k-means cluster analysis, and the annexin profile was associated with tumour stage (P=0.01) and also patient survival. Patients in annexin cluster group 1 (low annexin expression) had a better survival (log rank=5.33, P=0.02) than patients in cluster group 2 (high annexins A4 and A11 expression). In conclusion, this study has shown that individual annexins are present in colorectal cancer, specific annexins are overexpressed in colorectal cancer and the annexin expression profile is associated with survival.

Figure 1

Two-dimensional gels of (A) colorectal cancer and (B) normal colon mucosa. The circles labelled A1, A2, A4 and A11 correspond to the protein spots annexins A1, A2, A4 and A11, respectively (Coomassie blue-stained two-dimensional electrophoresis gel).

Figure 2

The immunohistochemical localisation of annexins in normal colon and colorectal cancer. Normal colon (A, C, E, G and I) and colorectal cancer (B, D, F, H and J). Annexin A1 (A and B), annexin A2 (C and D), annexin A4 (E and F), annexin A7 (G and H) and annexin A11 (I and J).

Figure 3

The mean intensity of expression of individual annexins in normal colon, primary colorectal cancer and lymph node metastasis.

Figure 4

Comparison of the mean intensity of annexin expression in Dukes C primary tumours and corresponding lymph node metastasis.

Figure 5

Patient survival in annexin cluster groups. There is a significant difference in survival between cluster group 1 (low annexin expression) and cluster group 2 (high annexins A2 and A11 expression, log rank=5.33; P=0.02).