Targeting tumor-intrinsic Nuclear Factor-kappa B signaling pathway for the discovery of anti-metastatic drug candidates from natural recourses

概要

Nuclear factor-Kappa B (NF-κB) is a ubiquitous transcription factor that constitutes a series of physiological and pathological cellular events including cell proliferation, apoptosis, and immune and inflammatory responses. NF-κB regulates a large number of inflammatory genes, such as TNF-α, IL-1β, IL-6, and COX-2. Both cell-intrinsic and extrinsic NF-κB activation contribute to cancer cell invasion and metastasis induces resistance to chemotherapy and affects the overall survival of patients. In breast cancer, hyperactivation of NF-κB was associated with large tumor size, negative estrogen, and progesterone receptor status, and implies aggressive biological behavior. Inhibition of NF-κB signaling has been shown to retard tumor formation and abrogate the migration, invasion, and metastasis capabilities of breast cancer through transcriptional regulation of multiple NF-κB downstream genes, such as MMPs and VEGF. Therefore, NF-κB is regarded as a promising therapeutic target in breast cancer.

In this study, we rationally identified five plant-derived compounds from Egyptian medicinal plants Commiphora wightii (myrrhanol A and myrrhanone A), Asphodelus microcarpus (Aloe-emodin and emodic-acid) as well as the developed synthetic derivative of E-guggulsterone (GSD-1) as potential NF-κB inhibitors for breast cancer therapy.

1. Identification of phytochemical constituents of Commiphora wightii by targeting tumor-intrinsic NF-κB activation as an anti-metastatic therapy in triple-negative breast cancer cells.
Traditional medicinal plants have been used for the treatment of a variety of diseases including cancer for several years. In this study, some valuable medicinal plant extracts were screened for their ability to inhibit NF-κB activity in 4T1 murine breast cancer cells. Three extracts out of nineteen were belonging to the medicinal plant Commiphora wightii (Guggul) possessed a strong potential to inhibit NF-κB activity. Within six isolated compounds from guggul, myrrh-triterpenes (myrrhanol A and myrrhanone A) strongly inhibited the constitutive NF-κB activity of 4T1 cells in a dose-dependent manner. Myrrh-triterpenes inhibited IκB-α degradation, subsequent p65 phosphorylation. Furthermore, in vitro invasion and migration of MDA-MB-231 and 4T1 cells, the ability of lung metastasis formation of 4T1 cells in vivo, and the expression of NF-κB regulatory gene product MMP-9 were markedly inhibited by treating myrrh-triterpenes. Given the association of TNF-α and TNFR1 to promote invasion and metastasis of breast cancer by acting on NF-κB-dependent pathway. We further confirmed that in treated 4T1 cells, mRNA expression of TNFR1 and TNF-α stimulated p65 were greatly down-regulated. Overall, these results demonstrated the potency of myrrhanol A or myrrhanone A as a promising therapeutic in metastatic TNBC and the underlying mechanism of its anti-metastatic function by targeting the intrinsic NF-κB as well as the inducible TNF-α/TNFR1/NF-κB pathways.

2. Synthetic E-guggulsterone derivative GSD-1 inhibits NF-κB signaling and suppresses the metastatic potential of breast cancer cells. （参考文献 1）
Guggulsterone (GS) is one of the major active phytosterol constituents in the gum resin of Commiphora wightii and is known for its medicinal effects. GSD-1 is a structurally-related synthetic GS derivative and strongly inhibits NF-κB activation induced by TNF-α. GSD-1 prevented the nuclear translocation of p65 through the blockade of IκB-α degradation and p65 phosphorylation, and further inhibited the activation of upstream kinases, including transforming growth factor-β activated kinase 1 (TAK1), IKKα, and IKKβ. Furthermore, GSD-1 inhibited the cell-intrinsic activation of NF-κB and exerted its direct anti-cancer and anti-metastatic effects in both murine and human breast cancer cells. This study demonstrated GSD-1 to be an effective compound to target NF-κB activation that has the potential for treating breast cancer growth and metastasis.

3. Inhibition of cell‐intrinsic NF-κB activity and metastatic abilities of breast cancer by aloe‐emodin and emodic‐acid isolated from Asphodelus microcarpus. （参考文献 2）
Anthraquinones are a major class of compounds naturally occurring in Asphodelus microcarpus. The pharmacological actions of anthraquinones in cancer cells are known to induce apoptosis or autophagy and revert multidrug resistance. Five anthraquinone-type analogs were isolated from the methanol extract of A. microcarpus leaves and identified as, emodin, rhein, physcion, aloe-emodin, and emodic acid. Among them, aloe-emodin and emodic-acid strongly inhibited the proliferation, cells- intrinsic NF-κB activity, and metastatic ability of breast cancer. Although aloe-emodin inhibited p38 and ERK phosphorylation, emodic-acid more markedly inhibited JNK, in addition to p38 and ERK phosphorylation. Both aloe-emodin and emodic-acid inhibited the secretion of the pro-tumorigenic cytokines IL-1β and IL-6, and VEGF and MMPs expression, and subsequently inhibited the invasive and migratory potential of 4T1 cells. Thus, our study demonstrated the effects of aloe-emodin and emodin- acid in controlling the migratory and invasive ability of 4T1 breast cancer cells, in addition to inhibiting NF-κB activity and the expression of its downstream target molecules.