Scientists have identified the genes in cancer cells that are required in order for cancer immunotherapies to work. If clinical studies validate the findings, it could eventually help to tailor more effective treatments for patients based on the genetic profiles of cancer tumors.

What they did: Researchers used CRISPR gene editing to knock out the function of each of a human melanoma cell's 19,000 genes — and then tested whether the modified cancer cells could be destroyed by immune cells. They found about 100 genes in the cancer cells that, when their function was lost, made cells resistant to immunotherapies. Some were previously implicated but others were unknown to have had a role.

How it works: Cancer immunotherapies leverage the body's own immune T cells to destroy tumors. They're used to treat late-stage melanoma, bladder, neck and other cancers — with varying success. Why some tumors are susceptible and others are not is a question of intense interest for doctors and scientists who want to see immunotherapies work in more patients.

Next steps: "If we can truly understand mechanisms of resistance to immunotherapy, we might be able to develop new therapeutics," NCI's Nicholas Restifo said in a press release. "In fact, in the future, this knowledge could speed the development of a new category of drugs that can circumvent these escape mechanisms of tumor cells and help patients experience complete responses."