Immunohistochemical results of HER2/neu protein expression assessed by rabbit monoclonal antibodies SP3 and 4B5 in colorectal carcinomas.

HER2/neu is an efficient target for cancer therapy. However, reports about its overexpression rate in colorectal carcinomas showed wide variability. This study aims to investigate HER2/neu expression in colorectal carcinomas using these two rabbit monoclonal HER2/neu antibodies, and to clarify the relationship between protein overexpression and gene amplification of HER2/neu and their clinicopathologic importance. Tissue microarray was performed from sections of 106 cases colorectal carcinomas. Their clinical data, including gender, age, stage, recurrence, lymph node metastasis, and follow-ups were collected. Immunohistochemistry for rabbit monoclonal antibody SP3 and 4B5 were performed, Fluorescent in situ hybridization was applied to detect the amplification of HER2/neu gene. The HER2/neu overexpression of (2+ and 3+) in our results were seen in 7.5% (8/106) for 4B5 and 3.8% (4/106) for SP3 respectively, the HER2/neu amplification was in 2.8% (3/106). All cases of overexpression for SP3 were included by those for 4B5. Both antibodies stained 3 cases of HER2/neu 3+, and FISH confirmed HER2/neu amplification did occurred in these cases. In our study, 4B5 was more sensitive to detect HER2/neu of colorectal carcinoma than SP3. 2.8% patients with colorectal patients might benefit from anti-HER2/neu therapy.