Immune Checkpoint Molecules in Hodgkin Lymphoma and Other Hematological Malignancies.

Immune checkpoints such as PD-1/PD-L1, CTLA-4, LAG-3, TIM-3, and TIGIT play critical roles in regulating anti-tumor immunity and are exploited by hematological malignancies to evade immune surveillance. While classic Hodgkin lymphoma (HL) demonstrates notable responsiveness to immune checkpoint inhibitors (ICIs), which is attributed to genetic alterations like chromosome 9p24.1 amplification, the responsiveness of non-Hodgkin lymphoma (NHL), acute myeloid leukemia (AML), and multiple myeloma (MM) remain inconsistent and generally modest. In NHL, the heterogeneous immune microenvironment, particularly variations in tumor-infiltrating lymphocytes and PD-L1 expression, drives differential ICI outcomes. AML shows limited responsiveness to monotherapy, but the combination of monotherapy with hypomethylating agents yield encouraging results, particularly in selected patient subsets. Conversely, MM trials have largely failed, potentially due to genetic polymorphisms influencing checkpoint signaling pathways and the inherently immunosuppressive bone marrow microenvironment. Both intrinsic tumor factors (low tumor mutational burden, impaired antigen presentation, IFN-γ pathway alterations) and extrinsic factors (immunosuppressive cells and alternative checkpoint upregulation) contribute significantly to primary and acquired resistance mechanisms. Future strategies to overcome resistance emphasize combination therapies, such as dual checkpoint blockade, epigenetic modulation, and reprogramming the tumor microenvironment, as well as biomarker-driven patient selection, aiming for precision-based, tailored immunotherapy across hematological malignancies.