The Mechanism of Ca²⁺ Movement in the Involvement of Baicalein-Induced Cytotoxicity in ZR-75-1 Human Breast Cancer Cells

Abstract

Baicalein (5,6,7-trihydroxyflavone) (1) has been found to be active against a wide variety of cancer cells. However, the molecular mechanism underlying the effects of 1 on the induction of Ca(2+) movement and cytotoxicity in human breast cancer cells is unknown. This study examined the relationship between 1-induced Ca(2+) signaling and cytotoxicity in ZR-75-1 human breast cancer cells. The in vitro investigations reported herein produced the following results: (i) Compound 1 increased intracellular Ca(2+) concentration ([Ca(2+)]i) in a concentration-dependent manner. The signal was decreased by approximately 50% by removal of extracellular Ca(2+). (ii) Compound 1-triggered [Ca(2+)]i increases were significantly suppressed by store-operated Ca(2+) channel blockers 2-aminoethoxydiphenyl borate (2-APB) and the PKC inhibitor GF109203X. (iii) In Ca(2+)-free medium, compound 1-induced [Ca(2+)]i increases were also inhibited by GF109203X. Furthermore, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (TG) or 2,5-ditert-butylhydroquinone (BHQ) abolished 1-induced [Ca(2+)]i increases. Inhibition of phospholipase C (PLC) with U73122 abolished 1-induced [Ca(2+)]i increases. (iv) Compound 1 (20-40 μM) caused cytotoxicity, increased reactive oxygen species (ROS) production, and activated caspase-9/caspase-3. Furthermore, compound 1-induced apoptosis was significantly inhibited by prechelating cytosolic Ca(2+) with BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester) or by decreasing ROS with the antioxidant NAC (N-acetylcysteine). Together, baicalein (1) induced a [Ca(2+)]i increase by inducing PLC-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via PKC-dependent, 2-APB-sensitive store-operated Ca(2+) channels. Moreover, baicalein (1) induced Ca(2+)-associated apoptosis involved ROS production in ZR-75-1 cells.

Mitochondria in Neuroprotection by Phytochemicals: Bioactive Polyphenols Modulate Mitochondrial Apoptosis System, Function and Structure

“…Curcumin increased Ca 2+ influx into cells, depolarized ∆Ψm, released Cytc, and activated caspases in human hepatocellular carcinoma cells [161]. Honokiol (5,3′-dially-2,4′-dihydroxybiphenyl), eugenol (4-ally-2-methoxyphenol), gallic acid, and baicalein caused phospholipase C-dependent Ca 2+ release from the endoplasmic reticulum (ER) and Ca 2+ influx into cells through the transient receptor potential channel melastatin 8, or PKC-dependent channel in human glioblastoma and breast cancer cells [162,163,164]. Morusin (an extended 5,2′,4′-trihydroxyflavone) induced cell death by VDAC-mediated Ca 2+ overload in epithelial ovarian cancer [165].…”

Baicalin suppresses proliferation, migration, and invasion in human glioblastoma cells via Ca²⁺-dependent pathway

“…Moreover, the release of Ca 2+ from the ER to cytosol is dependent on the PLC pathway. 33 Increase in the free Ca 2+ concentrations always leads to aggravated ER stress and the disturbance of mitochondrial membrane potential, thus leading to mitochondrial apoptosis. 34 Hoyer-Hansen et al demonstrated that unwanted cytoplasmic Ca 2+ led to autophagy via the activation of CaM-dependent kinase kinase-β and inhibition of mTOR.…”

Baicalein, unlike 4-hydroxytamoxifen but similar to G15, suppresses 17β-estradiol-induced cell invasion, and matrix metalloproteinase-9 expression and activation in MCF-7 human breast cancer cells

“…Baicalein (5,6,7-trihydroxyflavone) is the primary flavonoid derived from Scutellaria baicalensis Georgi, whose structure is composed of a three-ring flavone backbone with phenolic hydroxyl at the 5' , 6' , and 7' position. Several studies have revealed that baicalein possesses antitumor activity in breast cancer and exhibits anti-estrogenic activity (20)(21)(22). In our previous study, it was demonstrated that baicalein is able to suppress E2 enhanced migration, adhesion and invasion of breast cancer cells and interferes with E2 or G-1 induced GPR30 signaling activation (23).…”