Atraric acid and atranorin inhibit breast cancer energy metabolism and immune evasion through PI3K/AKT/Bcl-xL

Background: Breast Cancer (BC) is the most common Cancer among women worldwide, with 2.3 million new cases in 2022. Traditional Cancer treatments such as chemotherapyare limited by their cytotoxicity, underscoring the need to develop novel effective and less toxic drugs.

Purpose: Atraric acid (AA) was investigated as a potential alternative to the cytotoxic compound atranorin (ATR). The mechanisms underlying the Anticancer effects of AA on BC were explored.

Methods: The effects of AA and ATR in BC cells were evaluated using the 3-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide assay, transwell invasion assay, clonogenic assay, western blotting, immunoprecipitation, quantitative Real-Time PCR, seahorse glycolytic rate, cell mito assays, and flow cytometry. An orthotopic mouse model was used for in vivo bioluminescence imaging. Network pharmacology and molecular docking were used to identify potential targets and pathways of AA and ATR in BCs.

Results: AA and ATR significantly inhibited BC cell motility and proliferation by downregulating epithelial-mesenchymal transition markers including N-Cadherin, Snail, Slug, and Twist. AA and ATR suppressed p-AKT protein levels by disrupting the interaction between p-AKT and Bcl-xL, and AA was more effective than ATR. In addition, treatment with AA and ATR downregulated Akt phosphorylation, leading to decreased HK2 and VDAC1 levels, which suppressed glycolysis and ATP production. Both compounds inhibited the Wnt/β-catenin and STAT signaling pathways and had similar effects on glycolysis, although AA showed stronger inhibition of HK2. AA and ATR had comparable effects on decreasing Bcl-xL-mediated mitochondrial respiration. AA at 10 µg/ml suppressed CD44^high/CD24^high levels in BC and had a stronger effect than ATR on ICOSL, AhR, HVEM, IDO1, gal-9, and HVEM. Moreover, AA decreased immune evasion via PD-L1-mediated immune suppression and restores T cell activity. In an orthotopic BC mouse model, AA and ATR inhibited tumor growth and downregulated associated target genes in vivo.

Conclusion: AA and ATR inhibit BC cell growth, metabolism, and immune escape by targeting the Akt/Bcl-xL pathway, which is connected to STAT and β-catenin signaling. AA is a promising therapeutic alternative to ATR because of its lower cytotoxicity.

AKT/Bcl-xL; Atranorin; Atraric acid; Breast cancer; Cancer metabolism; Immune evasion.