Researchers have discovered a biological mechanism that could lead to a potential way to "tune up" the immune system's ability to kill cancer cells.In the study, published in the journal Proceedings of the National Academy of Sciences, they reported that a protein called Kruppel-like factor 2 (KFL2) is critical for expansion and survival of natural killer (NK) cells, a type of white blood cell that specifically recognise and destroy tumour cells.NK cell-mediated tumor therapy -- essentially, injections of NK cells -- is a cutting-edge technique currently used clinically. It can sweep the blood clean of cancer cells in leukemia patients. However, the remission is often short-lived.The protein reported in this study both limits immature NK cell proliferation and helps mature NK cells to be rich in interleukin 15 (IL-15), which is necessary for their continued survival."This is the same process likely used by cancer cells to avoid destruction by NK cells," said one of the researchers Eric Sebzda from Vanderbilt University Medical Centre in Tennessee, US.In particular, tumours may avoid immune clearance by promoting the destruction of the protein within the NK cell population, thereby starving these cells of IL-15.The researchers believe that the findings could lead to new cancer therapy.