Prognosis significance of indoleamine 2, 3-dioxygenase, programmed death ligand-1 and tumor-infiltrating immune cells in microenvironment of breast cancer

Introduction: The immune microenvironment plays an increasingly important role in predicting the prognosis of multiple tumors and selecting patients for immunotherapy trials. We studied the expression of indoleamine 2, 3-dioxygenase (IDO) and programmed death ligand-1 (PD-L1), detected the proportion of tumor-infiltrating immune cells (TIIs), and further analyzed the association of these immunological characteristics with the dinicopathological parameters and prognosis of breast cancer patients. Methods: Immunohistochemical staining for IDO, PD-L1, CD4, CD8, Foxp3, CD20, CD56 and CD68 expression in breast cancer tissues was carried out. IDO and PD-L1 expression were scored by extent in tumor cells. TIIs expressing CD4, CD8, Foxp3, CD20, CD56 or CD68 were evaluated by positive count. Clinicopathological characteristics and follow-up were recorded. Results: The frequencies of IDO-high-expressing and PD-L1-expressing tissue were 33.77% and 24.68%, respectively. The co-expression of IDO and PD-L1 was identified in 16/77 (20.78%) of cases. IDO high expression, CD4(+) T cells and CD56(+) cells were most frequently observed in patients with tumor-draining lymph nodes (TDLNs) metastasis. Immune cells were more common in non-luminal breast cancer than in luminal breast cancer. In survival analysis, PFS were not associated with high levels of IDO and PD-L1, nor were TIIs. However, CD20 and CD68 were significant risk factors for prognostic after adjusting covariates by COX regression. IDO(high)Foxp3(high)T patients had a tendency with shorter progression-free survival. Conclusions: Although we found a limited prognostic effect of TIIs on survival in breast cancer patients, IDO combined with TIIs can help to evaluate the prognosis of patients.