Anthocyanins and flavonoids derived from Clitoria ternatea L. flower inhibit bladder cancer growth via suppressing fatty acid synthesis mediated by SREBP1 pathway

Abstract

Clitoria ternatea L. flowers are used as traditional herbal medicines and are known for their advanced pharmacological activities. Flavonoids and anthocyanins reportedly contribute to the therapeutic properties of C. ternatea flowers; however, their potential anti-bladder cancer effects and molecular mechanisms remain unknown. In this study, flavonoid- and anthocyanin-rich samples from C. ternatea flowers (DDH) are prepared via macroporous resin-based extraction coupled with an efficient and reliable two-dimensional UPLC-DAD-MS/MS method. In vitro and in vivo studies reveal that DDH can inhibit bladder cancer cell growth and enhance the anti-bladder cancer activity of cisplatin. RNA-seq combined with KEGG analysis reveals that fatty acid synthesis is closely related to the anti-bladder cancer effect of DDH. Furthermore, DDH dose-dependently reduces cellular fatty acid levels in bladder cancer cells, and the addition of fatty acids significantly mitigates DDH-induced cell growth inhibition. Subsequent findings reveal that DDH downregulates sterol regulatory element-binding protein 1 (SREBP1), a key transcriptional regulator of de novo fatty acid synthesis in cancer cells, and its downstream targets (FASN, SCD1, and ACC). Additionally, this study demonstrates that gallic acid not only enhances the stability of DDH but also synergistically potentiates its anti-bladder cancer activity. Our study suggests that targeting the SREBP1 pathway is an effective strategy in bladder cancer therapy, and the ability of DDH to induce cell death by inhibiting the SREBP1 pathway and its good tolerance in mice make it a promising strategy for preventing and treating bladder cancer.

1. Introduction

The incidence and mortality rates of bladder cancer, a malignant urological tumor, are increasing annually. The Global Cancer Statistics 2022 report estimated that there were 614,000 new cases and 220,000 deaths worldwide associated with bladder cancer in 2022 [1]. A prominent metabolic alteration observed in cancer is the reprogramming of lipid metabolism. Lipids not only are important components of biological membranes but are also involved in cellular energy metabolism and storage as well as in intracellular signaling [2]. Tumor cells increase lipid metabolism, particularly fatty acid synthesis, to meet their needs for rapid proliferation, survival, migration, invasion, and metastasis [3]. Sterol regulatory element-binding protein 1 (SREBP1) is a key transcriptional regulator of de novo fatty acid synthesis in cells and regulates the expressions of key enzymes involved in lipid synthesis, such as stearoyl-CoA desaturase 1 (SCD1), fatty acid synthase (FASN), and acetyl-CoA carboxylase (ACC) [4]. Emerging evidence indicates that inhibiting the SREBP1 pathway can suppress intracellular fatty acid synthesis, thereby reducing the proliferation of tumor cells [3,4]. The abnormal hyperactivity of lipid metabolism in bladder cancer is closely linked to its development, progression, and drug resistance [5–7]. Hence, targeting SREBP1 pathway-mediated fatty acid synthesis holds promise as a strategy for treating bladder cancer.

Clitoria ternatea L. is a common plant in the Sipsongpanna region of Yunnan, China, and its blue flowers are known for their advanced health benefits, such as anti-inflammatory, antioxidant, and anti-obesity effects [8–10]. The primary active constituents of C. ternatea flowers are flavonoids and anthocyanins [11–13]. Reportedly, flavonoids and anthocyanins from plant sources are promising agents for inhibiting the proliferation of various tumor cells, such as hepatocellular carcinoma, lung cancer, and bladder cancer [14,15]. However, whether flavonoids and anthocyanins from C. ternatea flowers can inhibit the proliferation of bladder cancer cells as well as their underlying mechanism of action remain unclear.