Parietin is a pigment found in both rhubarb and lichens of the genus Caloplaca . Researchers at the Institute of Oncology at Winship Emory University have shown that the dye is also able to inhibit the growth of human cancer cell lines derived from lung and head and neck tumours implanted in mice. The researchers managed to obtain tumour cells from a patient suffering from acute lymphoblastic leukaemia - during their experiments and the application of different doses of the dye, the researchers found that it was able to kill half of the leukaemic cells in culture within 48 hours. These reports sow considerable optimism among patients struggling with oncological diseases, but more specialised research is still needed in this direction.