B7–H3 Ligand Expression by Primary Breast Cancer and Associated With Regional Nodal Metastasis

In Brief Objective: B7 ligand family members have been shown to be important immunoregulatory factors in host tumor immune responses. We hypothesized that B7–H3, a coinhibitory factor, is expressed by primary breast cancer cells and associated with metastasis to regional tumor-draining lymph nodes. Experimental Design: American Joint Committee on Cancer stage I to III primary breast cancers (n = 82) and normal breast specimens (n = 17) were assessed for B7–H3 expression using paraffin-embedded archival tissues. B7–H3 expression by breast cancer cells was assessed by a quantitative real-time reverse transcription-polymerase chain reaction, and B7–H3 protein expression was evaluated using immunohistochemistry. Results: B7–H3 mRNA expression was detected in 32 of 82 (39%) primary breast tumors but not in normal breast tissues (P = 0.0029). B7–H3 expression in primary tumors significantly correlated with increasing tumor size, American Joint Committee on Cancer stage, and lymphovascular invasion (P< 0.0001, P< 0.0001, P = 0.0071). B7–H3 expression was highly correlated to sentinel lymph node and overall number of lymph nodes with metastasis P = 0.003, and P = 0.004, respectively). In a multivariate analysis, B7–H3 mRNA expression of the primary tumor significantly predicted metastasis to regional lymph nodes (P = 0.021, and P = 0.023, respectively). Antibody staining analysis of paraffin-embedded archival tissue breast tumors and flow cytometry of breast cancer cell lines demonstrated B7–H3 protein expression. Conclusions: B7–H3 protein expressed by primary breast cancer cells is a tumor progression factor and is associated with extent of regional nodal metastasis. Prediction of extent of regional nodal metastasis in breast cancer patients on primary tumor diagnosis would identify high-risk patients. B7-H3 a protein associated with immune tolerance was identified in breast cancer cells. The presence of B7-H3 in breast primary tumors is associated with advances to regional nodal metastasis.