PD-L1 and PD-1 in immune regulation and their implications in blood cancers

Because of emerging opportunities for cancer immunotherapy, the capacity to suppress the immune system in order to cure and eradicate cancer is currently a topic of intense study. When the bone marrow microenvironment is exposed to immune suppression, leukemia cells result in the immune system's inability to eliminate malignant cells. To get a better understanding of the immunological possibilities associated with leukemia, clinical trials have explored immunotherapy techniques such as T cell activators, checkpoint inhibitors, antibody medicinal molecules, and cell treatments. One of the most important immune pathways is the programmed cell death 1 (PD1) protein. PD1 is expressed on the surface of T-cells and controls immune reactions. CD274, B7–H1, or PD-L1 are expressed by cells of the myeloid lineage, including macrophages, dendritic cells, effector CD8⁺ T cells, tumor cells, and tumor-associated suppressor cells. Expression of PD-L1 molecule in cancer has been associated to worse prognosis and resistance to anti-cancer therapies in several malignancies. In this review, we update on the expression of PD-1 molecule in malignant hematological tumor cells and describe these molecules which inhibit the immune response to cancer cells. We provide an overview of the current scientific advancements, the significance of immunotherapy strategies and highlighting the potential for further development in targeting this specific molecule. Additionally, ascertaining if PD-1/PD-L1 can be a reliable prognostic for blood cancer diagnosis.