Natural Killer Cell Defects in Breast Cancer: A Key Pathway for Tumor Evasion.

As the most important innate immune component cancers invader, natural killer (NK) cells have a magnificent role in antitumor immunity without any prior sensitization. Different subsets of NK cells have distinct responses during tumor cell exposure, according to their phenotypes and environments. Their function is induced mainly by the activity of both inhibitory and activating receptors against cancerous cells. Since the immunosuppression in the tumor microenvironment of breast cancer patients has directly deteriorated the phenotype and disturbed the function of NK cells, recruiting compensatory mechanisms indicate promising outcomes for immunotherapeutic approaches. These evidences accentuate the importance of NK cell distinct features in protection against breast tumors. In this review, we discuss the several mechanisms involved in NK cells suppression which consequently promote tumor progression and disease recurrence in patients with breast cancer.