Two immunologists, American James P. Allison and Japan's Tasuku Honjo, have been awarded the 2018 Nobel Prize in physiology or medicine for their work on a new approach to treating cancer.

The Nobel Assembly at the Karolinska Institute in Stockholm announced the winners on October 1, citing "their discovery of cancer therapy by inhibition of negative immune regulation."

"This year's Nobel Prize constitutes a landmark in our fight against cancer. The discovery made by the two Medicine Laureates takes advantage of the immune system's ability to attack cancer cells by releasing the brakes on immune cells," the assembly said.

Allison studied a protein that functions as a brake on the immune system. He realized the potential of releasing the brake and unleashing the body's immune cells to attack tumors, developing the concept into a new approach for treating cancer patients.

Separately, Honjo discovered a protein on immune cells and revealed that it can also operate as a brake, but with a different mechanism of action. Therapies based on his discovery have proven to be strikingly effective in the fight against cancer.

The two scientists will share the 9 million-Swedish-kronor ($1 million) prize.