Correlation between colorectal cancer Bcl-2 expression and tumour clinicopathological variables

The aim of our study was to elucidate whether and in a what way applying two slightly different immunohistochemical procedures effects Bcl-2 protein detection as well as its relationship to colorectal cancer clinicopathological features. A series of 74 primary colorectal cancers was investigated for expression of the Bcl-2 protein. Two immunohistochemical procedures: first with antigen retrieval using a microwave (art-), second with antigen retrieval by use pressure pot (art+) pre-treatment, were applied in each cancer case. Formalin-fixed, paraffin embedded tissues were treated with ant-Bcl-2 antibody (Dako No M 0887). Bcl-2 (art+) immunostaining was positive in 48 (64.9%) cases of colorectal cancers whereas Bcl-2 (art-) immunohistochemical reaction was positive only in 15 (20%) colorectal tumours. A significant, positive correlation was observed between Bcl-2 (art+) expression and localization of the tumour in the rectum (p = 0.007). At the same time a statistically significant positive correlation between tumour Bcl-2 (art-) expression and colon tumour pT stage (p = 0.007), rectum tumour differentiation grade (p = 0.04) and Bcl-2 (art-) protein immunostaining in lymph node metastases (p < 0.000001) was observed. This data suggest that the type of procedure for antigen retrieval to detection of Bcl-2 protein by immunohistochemical reaction, changes the study results and should be considered when comparing own results with the literature data.