Tumor-exposed NK cells (teNK cells) help breast cancer cells (red) form more metastatic tumors in mouse lungs (right) compared with healthy NK cells (hNK cells, center) or a control (left).
At first, the presence of NK cells (bottom row) restricts the growth of a tumor formed in the laboratory. But after 36 hours, the cancer cells reprogram the NK cells and the tumor starts to invade its surroundings.