A new study suggests that lactate, a metabolic byproduct produced by cells during strenuous exercise, can rejuvenate immune cells that fight cancer. The finding could eventually be used to develop new strategies to augment the anti-tumor effect of cancer immunotherapies. "The lactate that we usually think of as a waste product appears to have a previously unrecognized role in fighting cancer," said Jinming Gao, Ph.D. To investigate, Dr. Gao gave lactate injections to mice with colon cancer or melanoma; other tumor-bearing mice received glucose injections. While glucose had little effect, tumor growth was significantly reduced in mice treated with lactate....