Triptonide facilitates autophagy-mediated apoptosis in esophageal squamous cell carcinoma by targeting the AMPK-mTOR-ULK1 axis

Abstract

Triptonide (TN) is a small-molecule compound initially derived from Tripterygium wilfordii Hook. f used in traditional Chinese medicine. However, its potential antitumor mechanisms are still far from adequately understood. The purpose of this research is to elucidate the antitumor and pharmacological effects of TN on esophageal squamous cell carcinoma (ESCC). Functional assays, such as CCK-8 and colony formation assays, are used to evaluate the effects of TN on KYSE450 and KYSE510 cells. Subsequently, western blot analysis, Hoechst 33258 staining, flow cytometric analysis, autophagic flux detection, and transmission electron microscopy (TEM) are used to determine the effects of TN on apoptosis and autophagy in ESCC cells. Additionally, the autophagy inhibitor 3-methyladenine (3-MA) and the AMPK inhibitor dorsomorphin (Compound C, CC) are administered to explore the molecular mechanisms and crucial pathways in ESCC cells. Our findings provide strong evidence that TN induces autophagy-dependent apoptosis by targeting the AMPK-mTOR-ULK1 axis in ESCC cells. Collectively, this study sheds light on the anticancer mechanisms of TN in esophageal squamous cell carcinoma and suggests that TN is a promising candidate for the antitumor phytomedicine.

1. Introduction

Esophageal cancer has gradually become a serious international health issue, and its potential health impact is currently a highly topical focus of concern [1]. Esophageal cancer mainly consists of two histopathological subtypes, squamous cell carcinoma (SCC) and adenocarcinoma (AC) [2], of which SCC accounts for 90% of all cases of esophageal cancer globally and is highly prevalent in Asia, East Africa, and South America; however, AC is more common in developed countries and is the most common form of esophageal cancer in the US [3]. Esophageal cancer has the sixth highest overall global mortality rate and the seventh highest global incidence [4–6]. Therefore, owing to its high degree of malignancy, esophageal cancer should be prevented as early as possible. However, esophagectomy is a severe surgical treatment with potential dangers and complications [7]. Therefore, there is an urgent need to discover more dependable, efficient, and secure anticancer medications that can be utilized as alternatives or in addition to surgery to enhance treatment outcomes [8].

Natural products offer exceptional prospects for the discovery of innovative agents/active templates, particularly in the field of anticancer medication [9,10]. Chinese herbal medicines, the primary sources of natural products, are becoming increasingly popular owing to their remarkable therapeutic ability in biological systems. Therefore, we performed a comprehensive analysis to investigate the antitumor effects of these herbs on tumor cells. We investigated the antitumor effects and mechanisms of triptonide (TN), an ingredient obtained from the Chinese herb Tripterygium wilfordii Hook. f (TwHF). TwHF is extensively used to treat various dermatological and rheumatological disorders [11,12]. Owing to its combination therapy and new dosage form, the potential pharmacological activity of TwHF is currently a highly topical focus of concern [13]. TN not only possesses superior pharmacological properties, such as anti-inflammatory activity [14,15], antiandrogenic fertility [16] and antitumor properties [17], but is also less toxic than triptolide. Triptolide, which is also the main active ingredient in TwHF, is known as one of the most likely natural medicinal compounds to be developed into a modern drug [18,19]. TN has no noticeable toxic side effects at 20 times the effective dose in vivo [20]. However, studies on the inhibitory effect of TN on esophageal squamous cell carcinoma (ESCC) are lacking.