Tumor Grade Determines PD-1/PDL-1 Expression

Endometrial carcinoma is the most common gynecologic cancer in the western world. Two types are usually described. Type I is the endometrioid and is usually estrogen dependent. Type II is usually more aggressive than type I and is estrogen independent. Type II endometrial cancer is usually characterized as high grade while type I as low intermediate and high grade. Ovarian carcinoma as opposed to endometrial carcinoma is not characterized by types but by different histological backgrounds. It is also divided into high and low grade tumors. Ovarian carcinoma is considered to be the most aggressive of all gynecological malignancies resulting in most yearly deaths. Our immune system usually responds to foreign intruders entering our body or formed inside and attacks it in order to destroy it. Cancer cells are considered to be foreign to the body hence the immune system is expected to destroy it . The immune mediated cells which are supposed to attack the cancer are called tumor infiltrating lymphocytes or "TILS". Many different cancers possess the ability to evade TILS in order to survive and grow. Many studies have demonstrated that the presence of large number of TILS improved cancer prognosis. One of these evasive methods is the PD-1/PDL-1 expression. The question whether more aggressive tumors possess better capabilities to evade an immune response via the PD-1/PDL-1 mechanism is currently unknown. All tumor types possess antigens on their cell surface which triggers an immune response to some extent. Even though, the tumor needs different methods in order to be able to avoid the immune system attack. TILS express the PD-1 receptor on their cell surface and when it binds to PDL-1 or PDL-2, the cells which express the ligand deactivate TILS hence deem the lymphocyte incapable of inducing programmed cell death. PDL-1 which is expressed on tumor cells to evade an immune response can be targeted by immunotherapy.