Dr. Stacy Norton was only 7 years old when her mother died of colon cancer, one of several family members struck by aggressive tumors at unusually young ages.

Decades later, Norton rolled up her sleeve to help test if a new kind of vaccine might protect her and her own children from cancer.

The Houston doctor is among an estimated 1 million Americans who have Lynch syndrome, a faulty gene passed from a parent that puts them at extremely high risk of colorectal cancer and more vulnerable to certain other cancers, too.