RA-XII, a bicyclic hexapeptidic glucoside isolated from Rubia yunnanensis Diels, exerts antitumor activity by inhibiting protective autophagy and activating Akt-mTOR pathway in colorectal cancer cells. (10th February 2021)

• Record Type: Journal Article
• Authors: Wang, Jing; Wang, Jia; Li, Ling; Feng, Li; Wang, Yu-Rong; Wang, Zhe; Tan, Ning-Hua
• Is Part Of: Journal of ethnopharmacology. Volume 266(2020)
• Publication Date: 2021-02-10
• Subjects: Rubia yunnanensis Diels -- Cyclopeptide -- RA-XII -- Colorectal cancer -- Antitumor mechanism; ATGs autophagy-related proteins -- CQ chloroquine -- CTSB cathepsin B -- CTSD cathepsin D -- DMSO dimethyl sulfoxide -- FBS fetal bovine serum -- JC-1 5, 5′, 6, 6′-tetrachloro-1, 1′, 3, 3′-tetraethylbenzimidazolyl-carbocyanine iodide -- MDC monodansylcadaverine -- mTOR mammalian target of rapamycin -- siRNA small interfering RNA; Ethnopharmacology -- Periodicals; Pharmacognosy -- Periodicals; Herbs -- Periodicals; Herbs -- Periodicals; Pharmacognosy -- Periodicals; Pharmacognosie -- Périodiques; Herbes -- Périodiques; 615.1
• DOI: 10.1016/j.jep.2020.113438
• Languages: English
• ISSNs: 0378-8741

Abstract

Abstract: Ethnopharmacological relevance: The roots of Rubia yunnanensis Diels (Chinese name 'Xiao-Hong-Shen'), a traditional Chinese medicine native to Yunnan province (China), have a long history of use for treating several diseases, such as tuberculosis, rheumatism and cancers. A bicyclic hexapeptidic glucoside named RA-XII was isolated from R. yunnanensis, which has been reported to exert anti-inflammatory and antitumor activities. Aim of the study: This study was designed to investigate the antitumor activity and potential mechanism of RA-XII on colorectal cancer (CRC) cell lines. Materials and methods: Sulforhodamine B assay, clonogenic assay and cell cycle analysis were conducted to assess the anti-proliferative activity of RA-XII on CRC cells. GFP-LC3B plasmid transfection, MDC and AO staining assays, cathepsin activity assay, and siRNAs against several genes were used to investigate the effect of RA-XII on autophagy. Western blotting was used to examine the expression levels of proteins associated with cell cycle arrest, apoptosis and autophagy. Human CRC xenograft-bearing BALB/c nude mice were used to evaluate the antitumor effect of RA-XII in vivo . Results: RA-XII showed favorable antineoplastic activity in SW620 and HT29 cells in vitro and in vivo . RA-XII did not induce apoptosis indicated by no obvious changes on mitochondrial membrane potential and apoptosis-related marker proteins in SW620 or HT29 cells. Treatment of RA-XII inhibited the formation of autophagosomes, which is implied by the GFP-LC3 fluorescent dots, MDC-stained autophagic vesicles and LC3 protein expression. It was indicated that RA-XII suppressed autophagy by regulating several signaling pathways including mTOR and NF-κB pathways. Pharmacological or genetic inhibition of autophagy could enhance the cytotoxicity of RA-XII while autophagy inducer could rescue RA-XII-induced cell death. Besides, RA-XII could increase the susceptibility of CRC cells to bortezomib. Conclusion: Our study demonstrated that RA-XII exerted antitumor activity independent of apoptosis, and suppressed protective autophagy by regulating mTOR and NF-κB pathways in SW620 and HT29 cell lines, which suggested that RA-XII is a key active ingredient for the cancer treatment of Rubia yunnanensis and possesses a promising prospect as an autophagy inhibitor for CRC therapy. Graphical abstract: Image 1