Decidual-Like NK Cell Polarization: From Cancer Killing to Cancer Nurturing.

Natural killer (NK) cells accumulate at the fetal-maternal interface and represent 70% of immune cells in the decidua (dNK) at first-trimester pregnancy; they are immune-tolerant toward the semiallogenic fetus and are "nurturing" and nonkilling NK cells. A subset of NK cells in patients with cancer have features in common with dNK, which include expressing CD56, CD9, CD49a, and CXCR3, being poorly cytotoxic and proangiogenic, and mimicking the decidual nurturing role. In the oncologic patient, several factors can "decidualize" NK cells, turning them into immune-suppressant, growth-promoting proangiogenic cells. Here, we suggest ways to sharpen their blunted blades and intercept and curb their cancer-nurturing attitudes to restore their cytotoxic capabilities.