NFE2L2 and breast carcinoma: Since GSK-3β is negatively regulated by the PI3K/Akt axis via phosphorylation at Serine 9 (Ser 9) [32], and (+)-usnic acid was shown to inhibit Akt activity in breast cancer cells [33], we speculated whether (+)-usnic acid interferes with Nrf2 expression via the PI3K/Akt pathway in LUSC cells.