OBJECTIVETo detect the expression of fibroblast activation protein(FAP) in colorectal cancer tissue, and to investigate the association between expression of FAP with pathological parameters.

METHODSFifty-five cancer tissues and 50 normal colorectal samples were examined using immunohistochemistry with anti-FAP polyclonal antibody. The distribution of positive cells in different tissues, and associations of positive cell number with tumor staging, lymph node metastasis and tumor invasion were investigated to evaluate the effects of FAP on pathological progress in colorectal cancer.

RESULTSNo FAP expression was observed in 50 normal colorectal tissue samples. FAP positive cells were seen in carcinoma associated fibroblasts(CAFs), and in few colorectal cancer cells. The numbers of FAP positive cells in tissue samples of TNM III(-IIII((40.1±15.9) was significantly greater than that of TNMI(-II( (18.3±7.7)(P<0.01). Furthermore, the number of FAP positive cells in tissue samples with lymph node metastasis (44.4±13.3) was also significantly higher than those without lymph node metastasis (18.5±8.1)(P<0.01). Significant positive correlations were found between the number of FAP-positive cells with the tumor TNM staging and lymph node metastasis(r=0.544 and r=0.793, respectively)(P<0.01). The number of FAP-positive cells was 25.2±8.9 in T2, 32.41±19.30 in T3, and 29.2±16.5 in T4. The association between number of positive cells and depth of invasion was not statistically significant(P>0.05).

CONCLUSIONSThe FAP mainly expresses in CAFs locating in colorectal cancer tissues. The number of FAP positive cells is positively correlated with TNM staging of colorectal cancer and lymph node metastasis.