Baicalein Potentiated M1 Macrophage Polarization in Cancer Through Targeting PI3Kγ/ NF-κB Signaling

Abstract

Baicalein is one of the bioactive compounds extracted from Scutellaria baicalensis. Recent studies indicated the antitumor effects of baicalein, however, the underlying mechanisms are needed to be further determined. In this study, we found that baicalein could inhibit the tumor growth in mice models of breast cancer and melanoma and worked as an immunomodulator to promote the infiltration of tumor-associated macrophages (TAMs) and skew the TAMs towards the M1-like phenotype. Baicalein also induced M1-like phenotype polarization in THP-1-derived macrophages. Meanwhile, the expression of pro-inflammatory factors associated with M1 macrophages, including TNF-α, IL-1β, CXCL9 and CXCL10, were increased after baicalein treatment. Mechanistically, the RNA-seq data suggested that baicalein potentiated the M1 macrophage polarization via the NF-κB/TNF-α signaling pathway. ELISA and confocal microscopy assay confirmed that baicalein significantly induced the production of TNF-α and the activation of NF-κB, while TNF-α neutralization inhibited baicalein-induced macrophage polarization toward M1, and NF-κB P65 knock-down suppressed baicalein-induced TNF-α production in THP-1-derived macrophages. Phosphoinositide 3-kinase (PI3k) γ has been reported as a key molecule in macrophage polarization, and inhibition of PI3Kγ activates the NF-κB-related inflammatory signals. Our pharmacological network analysis predicted that PI3Kγ might be one of the major targets of baicalein. The results from the docking program and surface plasmon resonance (SPR) confirmed that baicalein displayed good binding activity to PI3Kγ. We further found that baicalein not only exhibited a direct inhibitory effect on the protein kinase activity of PI3Kγ, but also reduced the mRNA and protein expression of PI3Kγ, indicating that baicalein might be a novel PI3Kγ inhibitor. In summary, baicalein mediated the TAMs skewing to M1-TAMs, and then retarded tumor growth. These effects, at least in part, were linked to the PI3Kγ/NF-κB signaling.

Antitumor therapy for breast cancer: Focus on tumor‐associated macrophages and nanosized drug delivery systems

“…In the early stage of lung metastasis of BC, activation of NF‐κB in macrophages leads to a shift to anti‐tumor phenotype in the lung and results in the reduction of lung metastasis 115 . Some therapeutic drugs, such as baicalein, extracts of cordyceps sinensis, and cabazitaxel were demonstrated to inhibit BC growth by activating the NF‐kB signaling pathway and polarizing macrophages toward the M1 phenotype 116–118 . Notably, the activation of NF‐κB induced by ROS accumulation promotes PD‐L1 transcription in macrophages, resulting in immunosuppressive phenotypes 119 .…”

“…As well, the PI3K/AKT/mTOR signaling pathway participates in the transformation from M1‐type to M2‐type macrophages and has been considered as a promising target. Selective inhibition of P13K/AKT/mTOR in TAMs can decrease pro‐tumor macrophages and increase M1‐type macrophages 116,129–131 . MAPK signaling pathway has great effects on the regulation of macrophage polarization.…”

“… 115 Some therapeutic drugs, such as baicalein, extracts of cordyceps sinensis, and cabazitaxel were demonstrated to inhibit BC growth by activating the NF‐kB signaling pathway and polarizing macrophages toward the M1 phenotype. 116 , 117 , 118 Notably, the activation of NF‐κB induced by ROS accumulation promotes PD‐L1 transcription in macrophages, resulting in immunosuppressive phenotypes. 119 M‐CSF secreted by tumor cells activated the expression of VEGF through stimulation of the NF‐κB pathway in TAMs, contributing to angiogenesis and BC progression.…”

Anti-Inflammatory Mechanisms of Dietary Flavones: Tapping into Nature to Control Chronic Inflammation in Obesity and Cancer

“…Baicalein (50 mg/kg i.p. injected every other day) significantly delayed tumor growth and increased the percentage of M1 anti-tumor macrophages in both mouse xenografts of melanoma B16-F10 cells and murine mammary cancer 4T1 cells [ 201 ]. Likewise, vitexin (40 and 160 mg/kg/day i.p.…”

“…Apigenin in doses equivalent to human consumption in a healthy diet (20–50 μg/day via oral gavage) significantly reduced the growth of prostate cancers in mice, inhibited NF-κB p50 and p65 phosphorylation, and decreased phosphorylation and degradation of IκBα in a dose-dependent manner [ 197 ]. Interestingly, baicalein increased TNFα expression in M1 macrophages isolated from murine tumors via NF-κB pathway, phosphorylation of IκB, and nuclear translocation of p65 [ 201 ].…”