Activin A-Mediated Polarization of Cancer-Associated Fibroblasts and Macrophages Confers Resistance to Checkpoint Immunotherapy in Skin Cancer

Targeting tumor‑associated macrophages: Critical players in tumor progression and therapeutic strategies (Review)

Tumor‑associated macrophages (TAMs) are essential components of the tumor microenvironment (TME) and display phenotypic heterogeneity and plasticity associated with the stimulation of bioactive molecules within the TME. TAMs predominantly exhibit tumor‑promoting phenotypes involved in tumor progression, such as tumor angiogenesis, metastasis, immunosuppression and resistance to therapies. In addition, TAMs have the potential to regulate the cytotoxic elimination and phagocytosis of cancer cells and interact with other immune cells to engage in the innate and adaptive immune systems. In this context, targeting TAMs has been a popular area of research in cancer therapy, and a comprehensive understanding of the complex role of TAMs in tumor progression and exploration of macrophage‑based therapeutic approaches are essential for future therapeutics against cancers. The present review provided a comprehensive and updated overview of the function of TAMs in tumor progression, summarized recent advances in TAM‑targeting therapeutic strategies and discussed the obstacles and perspectives of TAM‑targeting therapies for cancers.

Novel insights and new therapeutic potentials for macrophages in pulmonary hypertension

Inflammation and immune processes underlie pulmonary hypertension progression. Two main different activated phenotypes of macrophages, classically activated M1 macrophages and alternatively activated M2 macrophages, are both involved in inflammatory processes related to pulmonary hypertension. Recent advances suggest that macrophages coordinate interactions among different proinflammatory and anti-inflammatory mediators, and other cellular components such as smooth muscle cells and fibroblasts. In this review, we summarize the current literature on the role of macrophages in the pathogenesis of pulmonary hypertension, including the origin of pulmonary macrophages and their response to triggers of pulmonary hypertension. We then discuss the interactions among macrophages, cytokines, and vascular adventitial fibroblasts in pulmonary hypertension, as well as the potential therapeutic benefits of macrophages in this disease. Identifying the critical role of macrophages in pulmonary hypertension will contribute to a comprehensive understanding of this pathophysiological abnormality, and may provide new perspectives for pulmonary hypertension management.

Inhibition of anti-tumor immunity by melanoma cell-derived Activin-A depends on STING

The transforming growth factor-β (TGF-β) family member activin A (hereafter Activin-A) is overexpressed in many cancer types, often correlating with cancer-associated cachexia and poor prognosis. Activin-A secretion by melanoma cells indirectly impedes CD8+ T cell-mediated anti-tumor immunity and promotes resistance to immunotherapies, even though Activin-A can be proinflammatory in other contexts. To identify underlying mechanisms, we here analyzed the effect of Activin-A on syngeneic grafts of Braf mutant YUMM3.3 mouse melanoma cells and on their microenvironment using single-cell RNA sequencing. We found that the Activin-A-induced immune evasion was accompanied by a proinflammatory interferon signature across multiple cell types, and that the associated increase in tumor growth depended at least in part on pernicious STING activity within the melanoma cells. Besides corroborating a role for proinflammatory signals in facilitating immune evasion, our results suggest that STING holds considerable potential as a therapeutic target to mitigate tumor-promoting Activin-A signaling at least in melanoma.