Shiuan Chen, Ph.D., working in lab (IMAGE) City of Hope Caption City of Hope in Southern California is now recruiting patients for a Phase 2 clinical trial to investigate whether pills containing white button mushroom extract could regulate the immune system, affecting prostate-specific antigen (PSA) levels to either remain stable or decline. Heightened levels of PSA in men may indicate the existence of prostate tumors. Credit City of Hope Usage Restrictions Please use credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.