Overexpression of B7-H4 is associated with infiltrating immune cells and poor prognosis in metastatic colorectal cancer

Metastasis commonly occurs in colorectal cancer (CRC) patients and confers a poor prognosis. B7-H4, an immune checkpoint molecule, has been found to be expressed in numerous tumor tissues and play critical roles in tumor progression. However, B7-H4 expression and its prognostic significance in different metastases from CRC remain unclear. In the present study, we screened a novel mouse anti-human B7-H4 monoclonal antibody (mAb) which exhibited a higher degree of recognition and sensitivity than the commercial reagent in immunohistochemistry (IHC). Using this antibody, overall 110 metastatic and paired primary lesions of CRC were analyzed for their expression of B7-H4, CD8 and CD68. Our results showed that expression of B7-H4 and CD68 in metastastic lesions was significantly higher than that in matched primary lesions (P = 0.0016, P < 0.0001). We also found a significant increase of CD68-positive immune cell infiltration in the B7-H4 high expressing metastases (P = 0.041). Moreover, upregulated B7-H4 in metastatic lesions was correlated with poor prognosis of patients (P = 0.014), while in primary lesions, B7-H4 combined with CD8 was associated with the overall survival (OS) (P = 0.043). Further, B7-H4 expression in metastatic lesions was significantly correlated with hazard ratio (HR) both in univariate and multivariate analysis. Altogether, B7-H4 in metastatic lesions is promising to be a potential prognostic indicator of CRC, and may promote tumor progression and metastasis of this cancer.