Immunotherapy is a type of cancer treatment that uses the patient’s own cells to fight against cancer cancer cells. However, not all patients respond to this type of therapy. Our previous news report told about the rare story of a cancer patient who ultimately died from an “invisible” cancer cell created by an immunotherapy treatment. However, immunotherapy is still considered one of the most promising treatments and can be highly effective. An example is a 78-year-old patient with chronic lymphoblastic leukemia who underwent CAR-T cell treatment in 2018. The patient showed promising results two months after the first treatment and eventually went into remission (no evidence of cancer). According to the report on the case, the amazing response was due to the reproduction of a single CAR-T cell – one of billions that were put into the patient. This particular CAR-T cell had experienced change in a gene called TET2. Researchers found out that this change had somehow increased the “power” of the cancer killing cell. They are now looking into ways TET2 can play in improving immunotherapy for other patients.