A breakthrough new study from Stanford University has homed in on a previously undiscovered signaling protein that, if effectively inhibited, may lead to new treatments for breast, ovarian, and other difficult-to-treat cancers.

Macrophages are immune cells that seek and destroy cancers in the human body, but cancer cells deploy a variety of strategies to hide from these hunters. One of these strategies is to express certain proteins that signal "don't eat me" to the macrophages.

Two of the earliest discovered signaling proteins used by cancer cells to hide from macrophages are PD-1 and CTLA-4. Initially uncovered in the 1990s, their discovery led to the development of exciting and novel cancer immunotherapies. Just last year the Nobel Prize in Medicine was awarded to the two scientists behind this amazing breakthrough.