Hinokitiol inhibits vasculogenic mimicry activity of breast cancer stem/progenitor cells through proteasome-mediated degradation of epidermal growth factor receptor

Abstract

Abstract. Hinokitiol, alternatively known as β-thujaplicin, is a tropolone-associated natural compound with antimicrobial, anti-inflammatory and antitumor activity. Breast cancer stem/progenitor cells (BCSCs) are a subpopulation of breast cancer cells associated with tumor initiation, chemoresistance and metastatic behavior, and may be enriched by mammosphere cultivation. Previous studies have demonstrated that BCSCs exhibit vasculogenic mimicry (VM) activity via the epidermal growth factor receptor (EGFR) signaling pathway. The present study investigated the anti-VM activity of hinokitiol in BCSCs. At a concentration below the half maximal inhibitory concentration, hinokitiol inhibited VM formation of mammosphere cells derived from two human breast cancer cell lines. Hinokitiol was additionally indicated to downregulate EGFR protein expression in mammosphere-forming BCSCs without affecting the expression of messenger RNA. The protein stability of EGFR in BCSCs was also decreased by hinokitiol. The EGFR protein expression and VM formation capability of hinokitiol-treated BCSCs were restored by co-treatment with MG132, a proteasome inhibitor. In conclusion, the present study indicated that hinokitiol may inhibit the VM activity of BCSCs through stimulating proteasome-mediated EGFR degradation. Hinokitiol may act as an anti-VM agent, and may be useful for the development of novel breast cancer therapeutic agents. IntroductionCancer stem/progenitor cells (CSCs) are a subpopulation of cancer cells with the characteristics of tumor initiation (1), resistance to therapy (2) and metastasis (3). In breast cancer, breast CSCs (BCSCs) have been identified as cells with cluster of differentiation (CD)24 -CD44 + surface markers (4) or with high intracellular aldehyde dehydrogenase activity (5). BCSCs may additionally be enriched by cultivation in a serum-free, non-adherent environment, known as the mammosphere, which is a floating clump composed of breast cancer cells (6,7). In addition to tumor initiation and chemoresistant properties, BCSCs have also been indicated to exhibit vasculogenic mimicry (VM) activity (8), defined as the formation of perfusable, matrix-rich and vasculogenic-like networks by tumor cells, without involvement of endothelial cells (9). A previous study demonstrated that the VM activity of BCSCs is regulated by epidermal growth factor receptor (EGFR) signaling (8).Hinokitiol, alternatively known as β-thujaplicin, is a tropolone-associated natural compound isolated from heartwood cupressaceous plants (10), and has been widely used as an antimicrobial agent in toothpastes, cosmetics and food (11). In addition to antimicrobial activity, hinokitiol has been reported to possess anti-inflammatory (12,13) and antitumor Hinokitiol inhibits vasculogenic mimicry activity of breast cancer stem/progenitor cells through proteasome-mediated degradation of epidermal growth factor receptor

Long Non-Coding RNA HOXA-AS2 Regulates Malignant Glioma Behaviors and Vasculogenic Mimicry Formation via the MiR-373/EGFR Axis

“…An in vitro study by Lee et al [55] demonstrated that inhibiting EGFR phosphorylation or EGFR knockdown suppresses VM formation in breast cancer stem/progenitor cells (BCSCs). In addition, Tu et al [56] confirmed that hinokitiol decreases EGFR protein stability, leading to the destruction of VM in BCSCs. EGFR also regulates glioma VM formation.…”

An Overview of Vasculogenic Mimicry in Breast Cancer

“…Hinokitiol is also a natural compound with antitumor properties. In cells obtained from mammospheres, it was demonstrated that hinokitiol diminishes levels of the EGFR protein by increasing its proteasome-mediated degradation and, consequently, inhibits VM (73).…”

Hypoxia promotes vasculogenic mimicry formation by vascular endothelial growth factor A mediating epithelial‐mesenchymal transition in salivary adenoid cystic carcinoma

“…7 VM had been found to evaluate in various aggressive cancers, including colorectal cancer, 8 breast cancer, 9 melanoma, 10 and head and neck squamous cell carcinoma, 11 suggesting that it was a novel hallmark of cancer. 7 VM had been found to evaluate in various aggressive cancers, including colorectal cancer, 8 breast cancer, 9 melanoma, 10 and head and neck squamous cell carcinoma, 11 suggesting that it was a novel hallmark of cancer.…”