Dauricine upregulates the chemosensitivity of hepatocellular carcinoma cells: Role of repressing glycolysis via miR-199a:HK2/PKM2 modulation

Highlights

• Dauricine upregulates the chemosensitivity of HCC cells.

• Dauricine reprograms glucose metabolism in HCC cells.

• Dauricine suppresses HK2 and PKM2 expression via inducing miR-199a.

Abstract

Dauricine (Dau) is a natural alkaloid exhibiting anti-proliferative activity against several different types of malignant cell. However, effects of Dau on hepatocellular carcinoma (HCC) cells and the underlying molecular mechanisms have remained to be fully elucidated. In this study, we found that Dau elevated the sensitivities of HCC cells to chemotherapeutic reagents, including cisplatin, sorafenib, and isoliensinine. Moreover, Dau promoted apoptosis of HCC cells triggered by these chemotherapeutic reagents. Consistently, in a xenograft mouse model, Dau sensitized HCC cells to sorafenib. In HCC cells, Dau dose-dependently inhibited glucose glycolysis and increased oxidative phosphorylation. Mechanistically, Dau downregulated the expression of hexokinase 2 (HK2) and pyruvate kinase M2 (PKM2). HK2 and PKM2 can be directly targeted by miR-199a. Dau dose-dependently increased miR-199a expression in HCC cells. Transfection of anti-miR-199a abrogated Dau-mediated suppression of HK2 and PKM2. Dau-induced metabolic shift was thereby severely crippled by anti-miR-199a. In addition, the incremental activity of Dau on sorafenib sensitivity of HCC cells was diminished in response to the transfection of anti-miR-199a. Taken together, our findings provided novel insights into the impact of Dau on HCC cells and supported considering Dau as an adjuvant reagent in the clinical treatment of HCC.

Introduction

Hepatocellular carcinoma (HCC) is the sixth-most common malignant worldwide, and the second leading cause of cancer-related mortality (Forner et al., 2012). Chemotherapy is the main strategy for the clinical treatment of middle-late stage HCC. An array of chemicals, such as sorafenib, cisplatin, and 5-fluorouracil, has been conventionally used in the chemotherapy of HCC. However, their prognosis can be severely affected by drug resistance. Therefore, it is imperative to search for novel chemical entities capable of elevating the chemosensitivity of HCC.

In mammalian cells, glycolysis and oxidative phosphorylation (OXPHOS) are two major metabolic pathways producing ATP. In untransformed cells, only approximately 10% of ATP originates from glycolysis, but this ratio is dramatically elevated to about 60% in malignant cells (Vander Heiden et al., 2009). In other words, even in the sufficient supply of oxygen, tumor cells prefer to generate ATP from glycolysis, rather than OXPHOS. Hexokinase 2 (HK2) and pyruvate kinase M2 (PKM2), the major isozymes of hexokinase and pyruvate kinase in tumors catalyzing rate-limiting reactions of glycolysis pathway, have been reported as critical contributors to aerobic glycolysis of malignant cells (Luo and Semenza, 2012; Vander Heiden, 2011). Increased glycolysis and upregulated expression of key enzymes of glycolysis pathway is frequently observed in HCC cells (Nie et al., 2015). This reprogrammed metabolism plays critical roles in drug resistance of HCC cells (Chen et al., 2015; Zhang et al., 2017).

Natural products constitute a group of chemicals with the potential of inhibiting HCC (Fan et al., 2017; Gunasekaran et al., 2017; Roh et al., 2016). Dauricine (Dau) is a natural alkaloid exhibiting anti-proliferative activity against an array of malignant cells (Wang et al., 2012; Yang et al., 2010). However, effect of Dau on HCC cells remains to be fully understood. Here, we reported that Dau is capable of elevating the chemosensitivity of HCC cells. Our further investigations were designed to explore the underlying molecular mechanisms.