Strong prognostic value of SLAMF7 protein expression in patients with lymph node-positive breast cancer.

Breast cancer (BC) in women is the second most commonly diagnosed type of cancer worldwide, and the leading cause of cancer-related mortality among women. To date, surgery is the main treatment option, often combined with other (neo)adjuvant therapeutic modalities to treat this malignancy and prevent relapse. Despite the invasive aspects of the majority of these therapeutic interventions and their associated side-effects, these treatments are still unable to effectively cure this disease and prevent relapse. Thus, there is an urgent need for the identification of more relevant biomarkers for more effective theranostics. Signaling lymphocytic activation molecule F7 (SLAMF7) is a glycosylated cell surface protein that plays a critical role in immune cell functions under both healthy conditions and in cancer. It is specifically targeted by elotuzumab for the treatment of multiple myeloma. The present retrospective study aimed to investigate the expression patterns of SLAMF7 and evaluate its associations with clinicopathological features, including the survival outcomes of patients with BC. The protein expression of SLAMF7 in BC was investigated in 278 lymph node-positive formalin-fixed and paraffin-embedded (FFPE) tissue blocks using tissue microarray and immunohistochemistry techniques. The results revealed a significant association between cytoplasmic SLAMF7 protein expression and several clinicopathological parameters, particularly age at diagnosis (P<0.007), tumor invasion (P<0.008) and vascular invasion (P=0.05). Kaplan-Meier analysis revealed that the overexpression of SLAMF7 was a strong positive prognosticator of both disease-free and disease-specific survival in the patients with BC (log-rank P=0.001 and P=0.008, respectively). This suggests that patients with SLAMF7 protein expression have a higher survival rate and a lower recurrence rate. On the whole, the present study demonstrated that a weak or no SLAMF7 expression was a powerful prognosticator of poor survival outcomes associated with both tumor and vascular invasion. Therefore, elotuzumab (as SLAMF7monoclonal antibody therapy) may be a promising option for targeted therapy worthy of clinical testing in patients with BC.