[Expression level and application analysis of soluble costimulatory molecule B7-H3 in the serum of patients with colorectal cancer].

To investigate the expression level of costimulatory molecule B7-H3 in the tumor tissues and the level of soluble costimulatory molecule B7-H3 (sB7-H3) in the serum of patients with colorectal cancer (CRC), so as to evaluate the clinical value of sB7-H3 in auxiliary diagnosis of CRC. A cross-sectional study design was adopted. A total of 232 CRC patients, 87 patients with benign colorectal diseases, and 59 healthy subjects who were treated in Shanghai Eighth People's Hospital from January 2020 to December 2022 were selected. The levels of sB7-H3, CEA, CA199, CA724 and CA50 in the serum were detected. The receiver operating characteristic (ROC) curve was used to analyze the diagnostic value of sB7-H3 and the above-mentioned tumor markers for colorectal cancer (CRC). The expression levels of B7-H3 in CRC tissues and benign colorectal disease tissues were detected by immunohistochemistry. The relationship between the levels of sB7-H3 and clinicopathological features was analyzed statistically. The results showed that compared with the benign disease group or the healthy control respectively, the serum levels of sB7-H3, CEA, CA199, CA724 and CA50 in the CRC group were significantly increased, and the differences were statistically significant (<i>P<</i>0.05). In the CRC group, the serum levels of sB7-H3 showed a weak positive correlation with CA50, CEA and CA724 (the <i>r</i> values were 0.220, 0.217 and 0.182 respectively; the <i>P</i> values were 0.005,<0.001 and 0.024 respectively), and there was no significant correlation with CA199 (the <i>r</i> value was 0.162; the <i>P</i> value were 0.051). The areas under the curve (AUC) of sB7-H3, CEA, CA199, CA724 and CA50 for diagnosing CRC were 0.862, 0.774, 0.646, 0.677 and 0.644 respectively, and the cut-off values were 20.67 ng/ml, 10.74 U/ml, 3.17 ng/ml, 3.16 U/ml, and 22.55 U/ml, respectively. Taking 20.67 ng/ml as the cut-off value, the positive rate of sB7-H3 in CRC was 62.9%, which was significantly higher than that in patients with benign colorectal diseases (35.6%) and the healthy control group (10%) (<i>χ²</i>=81.995, <i>P<</i>0.001; <i>χ²=</i>103.56, <i>P</i><0.001). The positive rates of sB7-H3 and CEA in patients with pathological stages Ⅲ and Ⅳ were significantly higher than those in patients with stages Ⅰ and Ⅱ (<i>χ²</i>=82.876, <i>P<</i>0.001; <i>χ²</i>=22.617, <i>P</i><0.001). The positive rate of sB7-H3 in patients with pathological stages Ⅰ and Ⅱ was 56.2%, which was significantly higher than that of CEA (38%) (<i>χ²</i>=50.378, <i>P</i><0.001). Immunohistochemistry showed that B7-H3 positive staining was mainly distributed in the cytoplasm. The positive expression rate of B7-H3 in CRC (75.8%) was significantly higher than that in benign colorectal diseases (15.4%) (<i>χ²=</i>16.133, <i>P<</i>0.001). The serum level of sB7-H3 in CRC patients was positively correlated with the expression level of B7-H3 in tumor tissues (<i>r</i>=0.766, <i>P</i><0.001). The serum level of sB7-H3 was significantly correlated with distant metastasis and pathological stage of CRC (<i>W</i>=899, <i>P</i>=0.002; <i>H</i>=10.465, <i>P</i>=0.015). In conclusion, serum level of sB7-H3 may have certain clinical value in the auxiliary diagnosis of CRC.