The Hodgkin Lymphoma Immune Microenvironment: Turning Bad News into Good

SIMPLE SUMMARY: Classic Hodgkin lymphoma (cHL) is one of the most enigmatic study models of the tumor microenvironment (TME), in which the Hodgkin–Reed Sternberg (HRS) cells are distributed throughout an abundant but ineffective immune ecosystem. The hyperactivation of HRS cells due to somatic mutations leads to complex interactions with the different subsets of immune cell populations, modeling the pathophysiology of the disease. There are remaining loose ends regarding the identification of the immune functional states in the cHL microenvironment and their influence on tumor cell survival. Here, we review the most relevant immune populations identified in the cHL context, focusing on integrative functional signatures. ABSTRACT: The classic Hodgkin lymphoma (cHL) tumor microenvironment (TME) is by far the most abundant component of tumors and is responsible for most of their biological and clinical characteristics. Recent advances in our knowledge of these networks in cellular interactions allow us to understand that the neoplastic Hodgkin and Reed Sternberg (HRS) cells, although they are in the minority, are the main architects of this dysregulated immune milieu. Here, we review the major changes that have happened in recent years: from TME as a helpless bystander, reflecting an ineffective immune response, to a dynamic tumor-promoting and immunosuppressive element. The HRS cells promote survival through interconnected intrinsic and extrinsic alterations, boosting pro-tumoral signaling pathways through genetic aberrations and autocrine growth signals, in parallel with abnormal cytokine secretion for the recruitment and selection of the best cell partners for this immunosuppressive TME. In turn, cHL is already proving to be the perfect model with which to address an immune checkpoint blockade. Preliminary data demonstrate the utility of druggable key signaling pathways in this ensemble, such as JAK-STAT, NF-κB, and others. In addition, myriad biomarkers predicting a response await validation by new in situ multiplex analytical methods, single-cell gene expression, and other techniques. Together, these components will define the functional phenotypes with which we will elucidate the molecular pathogenesis of the disease and improve the survival of patients who are refractory to conventional therapies.