New research suggests cancer may do something utterly unexpected: send molecular signals that help the brain defend itself against Alzheimer’s disease. For decades, scientists have noticed a strange pattern. People diagnosed with cancer are statistically less likely to develop Alzheimer’s and people with Alzheimer’s are less likely to get cancer. It looked like a coincidence. Now, a mouse study offers a biological explanation. Researchers implanted human lung, prostate, and colon tumors into mic