Isoliquiritigenin Induces Growth Inhibition And Apoptosis Through Downregulating Arachidonic Acid Metabolic Network Via The Deactivation Of PI3K/Akt In Human Breast Carcinoma

Purpose Herbal flavonoid isoliquiritigenin(ISL) has previously been reported to be a strong suppresser of the COX-2pathway as well as an inducer of apoptosis in multiple kinds of tumor cell types. The present study was undertaken to examine the effects of isoliquiritigenin on the key enzymes in arachidonic acid metabolic network in human breast cancer cells and its antitumor mechanisms.Methods Growth inhibitory and apoptotic inductive potential of isoliquiritigenin against two human breast cancer cell lines were analyzed. Relative mRNA concentrations of PLA2, COX-1, COX-2,5-LOX, FLAP, and CYP4Allwere examined using qPCR in both MDA-MB-231and MCF-7cells. The levels of PGE2, LTB4and20-HETE were analyzed using commercial enzyme immunoassay (EIA) kit and liquid chromatograpy mass spectrometry (LC/MS/MS), respectively. Western blot analysis, Akt kinase activity assay, release of Cytochrome c assay, and Caspase activity assay were conducted to elucidate the mechanism involved. The in vivo effects of isoliquiritigenin were tested in human tumor xenografts model.Results Treatment with isoliquiritigenin resulted in a decrease of cell viability,5-bromo-2’-deoxyuridine (BrdU) incorporation, and clonogenic ability, and significant induction of apoptosis in both MDA-MB-231and MCF-7cell lines. Isoliquiritigenin not only significantly inhibited mRNA expression of arachidonic acid-metabolizing enzymes (PLA2, COX-2and CYP4A11) but also decreased their products (PGE2and20-HETE) in human breast cancer cell lines. PGE2, LTB4and WIT003reverse isoliquiritigenin-induced apoptosis in human breast cancer cells. Furthermore, it downregulated levels of phospho-PI3K, phospho-Akt (Thr308), phospho-Bad (Ser136), and BcI-xL expression, thereby activation of Caspase cascades and eventually cleavage of poly (ADP-ribose) polymerase (PARP). Relative resistance to isoliquiritigenin-induced apoptosis was observed when pretreated with Caspase inhibitors or infected with adenoviral vectors containing the constitutively active Akt. In nude mice xenografts model study, isoliquiritigenin exhibited potent anticancer activity against breast carcinoma without major side effects, together with induction of apoptosis, decrease in eicosanoids levels, and downregulation of intratumoral phospho-Akt (Thr308) level, cleavage of Caspase-3and PARRConclusion Isoliquiritigenin induces growth inhibition and apoptosis through downregulating arachidonic acid metabolic network via the deactivation of PI3K/Akt in human breast carcinoma.