Clinical relevance of natural killer cells in breast cancer

Breast carcinoma is the most common malignant disease in the female and one of the leading causes of death among women worldwide. Chronic inflammation and immunosuppressive environment achieved by the interaction of tumour and infiltrating immune cells are the hallmarks of cancers, including breast cancer. Natural killer cells are one of innate immune cells in tumour bed that possess great antitumour potential due to their ability to kill tumour cells without prior sensitization. They also play an important role in priming of type I immune responses and are considered to be main source of Interferon-γ. Unfortunately, antitumour activity of natural killer cells is often suppressed by pro-inflammatory cytokines secreted in tumour microenvironment and suppression of NK cells activity often correlates with therapy response and general outcome of patient with breast carcinoma. Different types of breast cancer are associated with different subsets of natural killer cells that possess different immunoregulatory function. Identification of specific tumour associated natural killer cell subset endowed with different functional capabilities might help practitioners in therapy decisions, therapy response monitoring, as well as in predicting overall prognosis of breast cancer patients. The purpose of this review is to give an overview of natural killer cells and their subsets, their role in pathogenesis of breast cancer and to discuss NK cells as potential useful therapy and prognostic tool for breast carcinomas.