Abstract:Objective To investigate the expression of immunoglobulin-like transcript 3 (ILT3) in colorectal cancer tissues and colorectal cancer cell lines, and the correlations with the clinicopathological factors and prognosis, and to reveal the clinical significance of ILT3 abnormal expression in colorectal cancer. Methods The mRNA and protein expressions of ILT3 in colorectal cancer cell lines SW480, SW620, HT-29 and human normal intestinal epithelial cell line FHC were detected by real-time fluorescence quantitative PCR and Western blotting, and the differences were analyzed. Immunohistochemistry was used to detect the expressions of ILT3 in 85 colorectal cancer tissues and 30 adjacent normal tissues. The correlations between the expression of ILT3 and clinicopathological factors and prognosis were analyzed. Results The relative expressions of ILT3 mRNA in cancer cell lines SW480, SW620, HT-29 and the normal intestinal epithelial cells line FHC were 10.813±3.289, 4.391±0.622, 1.481±0.055 and 1.000±0.000 respectively, with a significant difference (F=21.846, P<0.001). Compared with the normal intestinal epithelial cell line FHC, the relative expressions of ILT3 mRNA in cancer cell lines SW480 and SW620 were significantly higher, with a statistically significant difference (P<0.001, P=0.038), and the relative expression of ILT3 mRNA in cancer cell HT-29 was higher, but the difference has no statistical significance (P=0.734). The relative expressions of ILT3 protein in cancer cell lines SW480, SW620, HT-29 and normal intestinal epithelial cells line FHC were 1.838±0.651, 1.763±0.222, 1.449±0.200 and 0.628±0.263 respectively, with a statistically significant difference (F=6.320, P=0.017). Compared with the normal intestinal epithelial cell line FHC, the relative expressions of ILT3 protein in cancer cell lines SW480, SW620, HT-29 were significantly higher, with a statistically significant difference(P=0.005, P=0.007, P=0.030). ILT3 was mainly expressed in the membrane and (or) cytoplasm. In 85 cases of colorectal cancer tissues, 55 cases (64.7%) have ILT3 high expressions, which were significantly higher than those in the adjacent normal tissues (16.7%, 5/30), with a significant difference (χ2=20.508, P<0.001). The high expression of ILT3 was related to lymph node metastasis (χ2=4.684, P=0.030) and TNM staging (χ2=4.684, P=0.030), but it was not related to age (χ2=0.927, P=0.336), gender (χ2=0.078, P=0.780), tumor location (χ2=0.249, P=0.618), tumor size (χ2=1.813, P=0.178) and tumor differentiation (χ2=0.807, P=0.369). The median overall survival of patients with high ILT3 expression was significantly shorter than that of patients with low ILT3 expression (45.0 months vs. 74.0 months), with a significant difference (χ2＝17.907, P<0.001). Conclusion The expressions of ILT3 in colorectal cancer cells are higher than those in the normal intestinal epithelial cell line, the expressions of ILT3 in colorectal tissues are higher than those in the adjacent normal tissues, which are correlated with lymph node metastasis and TNM staging. Patients with high expressions of ILT3 indicate poor clinical prognosis. The expression of ILT3 may serves as a new target for diagnosis, treatment and prognosis of colorectal cancer.

Key words:Colorectal neoplasms,Prognosis,Immunoglobulin like transcription factor 3