Do PD-1 and PD-L2 expressions have prognostic impact in hematologic malignancies?

PD-1 (programmed death-1) is an immune checkpoint receptor that modulates T-cell activity in peripheral tissues via interaction with its ligands, PD-L1 (programmed death-ligand 1) and PD-L2 (programmed death-ligand 2). Tumor cells upregulate PD-L1 or PD-L2 to inhibit this T lymphocyte attack. Our goal was to determine the PD-1 and PD-L2 expression rates of various hematologic malignancies, and evaluate whether PD-1 and PD-L2 expressions have an impact on prognosis.

For this purpose, pretreatment bone marrow biopsy specimens of 83 patients [42 multiple myeloma (MM), 21 acute leukemia, and 20 chronic lymphocytic leukemia (CLL)] were stained with monoclonal antibody immunostains of PD-1 and PD-L2.

As a result, the overall expression rate of PD-1 was 26.2%, 4.8%, and 60% in patients with MM, acute leukemia, and CLL, respectively, whereas the PD-L2 expression rate was 61.9%, 14.3%, and 10% in patients with MM, acute leukemia, and CLL, respectively.

Finally, we concluded that the role of the PD-1 pathway can be demonstrated by immunohistochemistry (IHC). Since we evaluated whether there is a correlation between the (IHC) results and survival of patients with MM, acute leukemia, and CLL, we could not demonstrate meaningful evidence that these markers have an impact on prognosis.