Effect of PI3K-p110α Inhibitor Alpelisib in the Differentiation and Effector Functions of M-CSF and GM-CSF Macrophages.

Phosphatidylinositol-3-kinases (PI3Ks) are heterodimers of catalytic and regulatory subunits that regulate cell metabolism, activation, and survival. PI3K, particularly the p110α catalytic isoform, is frequently mutated in cancer, and highly specific inhibitors such as alpelisib are currently used in oncology and in PIK3CA-related overgrowth disorders. Given the relevance of macrophages in anti-tumor immunity, we examined the impact of alpelisib on murine monocytes' intracellular signaling and on in vitro differentiation, polarization, and effector functions of macrophages. Real-time qPCR (RT-qPCR) showed comparable relative expression of PI3K isoforms (p110α, p110β, p110δ, p110γ and p85) in bone marrow monocytes and in macrophages differentiated with macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF). However, alpelisib increased p110α, p110β, and p85 relative gene expression (2-3-fold) during M-CSF-dependent differentiation. Functionally, alpelisib-treated M-CSF macrophages displayed enhanced interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α) secretion and reduced IL-10 production after lipopolysaccharide (LPS) plus interferon gamma (IFN-γ) or LPS stimulation. In contrast, GM-CSF macrophages differentiated with alpelisib secreted lower levels of IL-6 and TNF-α and reduced inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) gene expression. Additionally, cytokine profiles (IL-2, IL-6, IFN-γ and IL-10) were altered when alpelisib-treated macrophages were cocultured with CD4+ T cells under either antigen-specific or polyclonal activation conditions, indicating that the inhibitor modifies both differentiation and subsequent effector interactions of the macrophages. Thus, alpelisib induces lasting effects on macrophage differentiation and function, with potential implications in tumor-associated macrophages that develop under M-CSF or GM-CSF-rich cancer microenvironments.