The deadliest form of brain cancer is making a comeback because tumors adapt to treatment by enlisting the help of nearby healthy tissue, researchers trying to find a cure for the disease have concluded, the journal Science reports.  The new study, conducted by an international team including experts from the University of Leeds, found that in response to treatment, high malignancy gliomas reshape the environment of the brain, potentially creating interactions with nearby neurons and immune cells in ways that protect the tumor cells and hide them from the body's defenses. The team also found that tumors of lower grade malignancy often develop a new mutation that allows the cells to start dividing faster, potentially promoting their transition to a higher grade form. Gliomas are rare brain tumors. Low-grade gliomas have a better survival rate than high-grade gliomas, but often progress to high-grade gliomas. More than 90% of patients with high-grade tumors die within five years. Current treatments include surgery, radiation therapy, and chemotherapy. Dr. Lucy Stead, associate professor of brain cancer biology at the University of Leeds Medical School and the study's lead UK researcher, notes that this study, which required a global effort to obtain enough glioma samples, gave them unprecedented insight into how these deadly tumors progress and whether they can be stopped. The researchers collected many glioma samples over time as they progressed from low to high grade, as well as before and after treatment. They then studied how the cells changed and adapted to see if they could find ways to stop them using new drugs. Mutation and previously unknown cell interactions could now be targeted with new drugs that would stop tumor cells from progressing and adapting to treatment. In this way, the research has opened up new avenues of study that could lead to more effective drugs that can be offered to patients.