When surgeons remove a cancerous tumor, their goal is to get all of it. But that's tough. A pathologist must quickly examine the excised tissue to determine if all the cancer has been removed. It's not uncommon that later scans reveal cancerous tissue along the margins. That's why scientists are finding ways to 'light' up cancer cells to help surgeons see them during the operation.

The newest, a blue fluorescent dye called LUM015, has already been injected into fifteen patients who had surgery for breast cancer. None had a bad reaction.

LUM015 works because the dye is cut by an enzyme called cathepsins. In normal cells, cathepsins' job is to cut and degrade proteins; however in many tumors, cathepsins are made in higher amounts and sometimes secreted by the cell.

These extra cathepsins made by tumor cells also begin to digest something called ECM. This is extracellular matrix, a mesh of molecules that holds our cells in place. When ECM is gone, cells lose their ability to stay in one place and migrate into surrounding tissue, a hallmark of cancer called metastasis. Well, these extra cathepsins which are abundant on and around tumor cells can also cut the LUM015 dye causing them to light up in blue. A surgeon sees this when an imaging device is held over the area.

In experiments with mice the cancerous tissue glowed five times more brightly than normal tissue. Since the dye allowed surgeons to successfully remove the tumors of fifteen breast cancer patients, the goal now is to test LUM015 on fifty more patients to ensure its safety and effectiveness. Avoiding the need for more surgery spares patients not only physical pain but financial strain as well.