Abstract: Objective To investigate the expression and clinical value of cancer⁃associated fibroblasts (CAFs) and programmed death⁃ligand 1 (PD⁃L1) in breast invasive ductal carcinoma. Methods A total of 121 surgical specimens of breast invasive ductal carcinoma were collected in the Second Affiliated Hospital of Nantong University who underwent modified radical mastectomy, from January 2019 to June 2021. The expression of CAFs and PD⁃L1 in breast cancer tissues were detected by using immunohistochemical staining, and the correlation of CAFs and PD⁃L1 with clinicopathological features was analyzed. Spearman correlation analysis was used to analyze the correlation between the expression of CAFs and PD⁃L1. The factors affecting the progression⁃free survival (PFS) were analyzed based on univariate and multivariate Cox analyses. Kaplan⁃Meier method was used to draw the survival curve and Log⁃rank test was used to compare the survival difference. Results CAFs was highly expressed in breast cancer tissues and were significantly correlated with tumor size, lymph node metastasis and TNM stage (all P<0.01). PD⁃L1 was highly expressed in breast cancer tissues, and was significantly correlated with lymph node metastasis, TNM stage and estrogen receptor (ER) expression(all P<0.01). The positive expression of CAFs was positively correlated with that of PD⁃L1 in breast cancer tissues (r=0.265, P=0.011). Univariate Cox analysis showed that histological grade, lymph node metastasis, TNM stage, ER positive expression and PD⁃L1 expression were all correlated with the prognosis of breast cancer (all P<0.05). Multivariate Cox analysis showed that positive PD⁃L1 expression was an independent risk factor for poor PFS (P<0.05). Survival analysis showed that there were statistically significant differences in 1⁃year PFS rate (100.00% vs 84.09%;  χ²= 11.115, P=0.001) and 3⁃year PFS rate (95.92% vs 79.55%; χ²=6.312, P=0.012) between the PD⁃L1 negative expression group and the PD⁃L1 positive expression group.   Conclusions CAFs and PD⁃L1 are highly expressed in breast cancer tissues, and PD⁃L1 is associated with poor prognosis. There may exist interplay between CAFs and PD⁃L1 in promoting the malignant progression of breast cancer, which is expected to become a new target for the immunotherapy of breast cancer.

Key words:  , Breast invasive ductal carcinoma, CAFs, PD?L1, Immunohistochemical staining, Immunotherapy