Effects of ginkgol C17:1 on cisplatin-induced autophagy and apoptosis in HepG2 cells

Plant-derived natural products and combination therapy in liver cancer

Liver cancer is one of the malignant cancers globally and seriously endangers human health because of its high morbidity and mortality. Plant-derived natural products have been evaluated as potential anticancer drugs due to low side effects and high anti-tumor efficacy. However, plant-derived natural products also have defects of poor solubility and cumbersome extraction process. In recent years, a growing numbers of plant derived natural products have been used in combination therapy of liver cancer with conventional chemotherapeutic agents, which has improved clinical efficacy through multiple mechanisms, including inhibition of tumor growth, induction of apoptosis, suppression of angiogenesis, enhancement of immunity, reversal of multiple drug resistance and reduction of side effects. The therapeutic effects and mechanisms of plant-derived natural products and combination therapy on liver cancer are reviewed to provide references for developing anti-liver-cancer strategies with high efficacy and low side effects.

Extraction, Purification, and Elucidation of Six Ginkgol Homologs from Ginkgo biloba Sarcotesta and Evaluation of Their Anticancer Activities

Ginkgols are active constituents from Ginkgo biloba L. (GB) and have pharmacological activities, such as antibacterial and antioxidant activities. In our previous report, only five ginkgols were separated. However, ginkgol C17:1 had two isomers, for which their separation, identification, and bioactivities have not yet been investigated. Hence, this research reports the successful isolation of six ginkgol homologs with alkyl substituents-C17:1-Δ¹², C15:1-Δ⁸, C13:0, C17:2, C17:1-Δ¹⁰, and C15:0-for the first time using HPLC. This was followed by the identification of their chemical structures using Fourier transform infrared (FTIR), ultraviolet (UV), gas chromatography and mass spectrometry (GC-MS), carbon-13 nuclear magnetic resonance (¹³C-NMR), and proton nuclear magnetic resonance (¹H-NMR) analysis. The results showed that two ginkgol isomers, C17:1-Δ¹² and C17:1-Δ¹⁰, were obtained simultaneously from the ginkgol C17:1 mixture and identified entirely for the first time. That aside, the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay showed that the six ginkgol homologs possessed significant antiproliferation effects against HGC and HepG2 cells. Furthermore, the ginkgols with unsaturated side chains (C17:2, C15:1-Δ⁸, C17:1-Δ¹², and C17:1-Δ¹⁰) exhibited more potent inhibitory effects than ginkgols with saturated side chains (C13:0, C15:0). In addition, unsaturated ginkgol C15:1-Δ⁸ showed the most potent cytotoxicity on HepG2 and HGC cells, of which the half-maximal inhibition concentrations (IC₅₀) were 18.84 ± 2.58 and 13.15 ± 2.91 μM, respectively. The IC₅₀ for HepG2 and HGC cells for the three unsaturated ginkgols (C17:1-Δ¹⁰, C17:2 and C17:1-Δ¹²) were ~59.97, ~60.82, and ~68.97 μM for HepG2 and ~30.97, ~33.81, and ~34.55 μM for HGC cells, respectively. Comparing the ginkgols' structure-activity relations, the findings revealed that the position and number of the double bonds of the ginkgols with 17 side chain carbons in length had no significant difference in anticancer activity.

Advances in the conventional clinical treatment for hepatoblastoma and therapeutic innovation

Background

Hepatoblastoma (HB) is a rare malignancy usually occurring in children under 3 years old. With advancements in surgical techniques and molecular biology, new treatments have been developed.

Data resources

The recent literatures on new treatments, molecular mechanisms and clinical trials for HB were searched and reviewed.

Results

Surgical resection remains the main option for treatment of HB. Although complete resection is recommended, a resection with microscopical positive margins (R1) may have similar 5-year overall survival and 5-year event-free survival (EFS) rates after cisplatin chemotherapy and the control of metastasis, as only once described so far. Indocyanine green-guided surgery can help achieve precise resection. Additionally, associating liver partition and portal vein ligation for staged hepatectomy can rapidly increase future liver remnant volume compared with portal vein ligation or embolization. Cisplatin-containing chemotherapies slightly differ among the guidelines from the International Childhood Liver Tumors Strategy Group (SIOPEL), Children’s Oncology Group (COG) and Chinese Anti-Cancer Association Pediatric Committee (CCCG), and the 3-year EFS rate of patients in SIOPEL and CCCG studies was recently shown to be higher than that in COG studies. Liver transplantation is an option for patients with unresectable HB, and successful cases of autologous liver transplantation have been reported. In addition, effective inhibitors of important targets, such as the mTOR (mammalian target of rapamycin) inhibitor rapamycin, β-catenin inhibitor celecoxib and EpCAM (epithelial cell adhesion molecule) inhibitor catumaxomab, have been demonstrated to reduce the activity of HB cells and to control metastasis in experimental research and clinical trials.

Conclusion

These advances in surgical and medical treatment provide better outcomes for children with HB, and identifying novel targets may lead to the development of future targeted therapies and immunotherapies.

Role of autophagy in alcohol and drug-induced liver injury

Alcohol-related liver disease (ALD) and drug-induced liver injury (DILI) are common causes of severe liver disease, and successful treatments are lacking. Autophagy plays a protective role in both ALD and DILI by selectively removing damaged mitochondria (mitophagy), lipid droplets (lipophagy), protein aggregates and adducts in hepatocytes. Autophagy also protects against ALD by degrading interferon regulatory factor 1 (IRF1) and damaged mitochondria in hepatic macrophages. Specifically, we will discuss selective autophagy for removal of damaged mitochondria and lipid droplets in hepatocytes and autophagy-mediated degradation of IRF1 in hepatic macrophages as protective mechanisms against alcohol-induced liver injury and steatosis. In addition, selective autophagy for removal of damaged mitochondria and protein adducts for protection against DILI is discussed in this review. Development of new therapeutics for ALD and DILI is greatly needed, and selective autophagy pathways may provide promising targets. Drug and alcohol effects on autophagy regulation as well as protective mechanisms of autophagy against DILI and ALD are highlighted in this review.

Inhibiting SUMO1-mediated SUMOylation induces autophagy-mediated cancer cell death and reduces tumour cell invasion via RAC1

Post-translational modifications directly control protein activity and, thus, they represent an important means to regulate the responses of cells to different stimuli. Protein SUMOylation has recently been recognised as one such modification, and it has been associated with various diseases, including different types of cancer. However, the precise way that changes in SUMOylation influence the tumorigenic properties of cells remains to be fully clarified. Here, we show that blocking the SUMO pathway by depleting SUMO1 and UBC9, or by exposure to ginkgolic acid C15:1 or 2-D08 (two different SUMOylation inhibitors), induces cell death, also inhibiting the invasiveness of tumour cells. Indeed, diminishing the formation of SUMO1 complexes induces autophagy-mediated cancer cell death through increasing the expression of Tribbles pseudokinase 3 (TRIB3). Moreover, we found that blocking the SUMO pathway inhibits tumour cell invasion by decreasing RAC1 SUMOylation. These findings shed new light on the mechanisms by which SUMO1 modifications regulate the survival, and the migratory and invasive capacity of tumour cells, potentially establishing the bases to develop novel anti-cancer treatments based on the inhibition of SUMOylation.

Ginkgolic Acids Impair Mitochondrial Function by Decreasing Mitochondrial Biogenesis and Promoting FUNDC1-Dependent Mitophagy

Ginkgolic acids (GAs) are found in the leaves, nuts, and testa of Ginkgo biloba and have been reported to exhibit antitumor, antibacterial, and pro-apoptotic activities. However, their role in mitochondrial function is still unclear. Our previous study showed that genes related to the mitochondria present significant changes in GA-treated mouse bone marrow stromal cells. We hypothesize that GAs may regulate mitochondrial function. Here, we found that GA treatment induced mitochondrial fragmentation, reduced mtDNA copy numbers and mitochondrial protein levels, and impaired mitochondrial adenosine 5'-triphosphate production and oxygen consumption. The GA-induced mitochondrial mass loss may be due to decreased mitochondrial biogenesis. In addition, abolishing autophagy by Atg7 knockout or the administration of an autophagy inhibitor can restore the GA-induced decrease in mitochondrial mass. Furthermore, FUNDC1 knockdown restored the GA-induced changes in mitochondrial mass reduction and mitochondrial membrane potential loss. Together, our studies demonstrated that GAs impaired mitochondrial function by decreasing mitochondrial biogenesis and promoting FUNDC1-dependent mitophagy.

Differential effects of ginkgol C17:1 on cisplatin-induced cytotoxicity: Protecting human normal L02 hepatocytes versus sensitizing human hepatoma HepG2 cells

Liver cancer is a major healthcare problem and one of the leading causes of cancer-associated mortality in the world. To date, chemotherapy remains a common method for treating cancer and cisplatin is one of the most widely used chemotherapeutics. However, owing to drug resistance and side effects, it is imperative to identify a novel approach to improve the anticancer effect of cisplatin. Auxiliary chemotherapy drugs with minor toxicity to normal cells may represent a novel strategy for cancer therapy. Previous studies have indicated that ginkgol C17:1 exhibits anticancer effects in liver cancer cells in vitro and in vivo. The antitumor activity of ginkgol C17:1 has been reported in combination with cisplatin in human liver cancer cells. Owing to the route of systemic administration, liver cancer cells and normal hepatocytes were exposed to chemotherapeutics and auxiliary chemotherapy drugs. However, the effects of ginkgol C17:1 in normal hepatocytes remain unclear. In the present study, the biological effects of ginkgol C17:1 alone and as co-treatment with cisplatin were compared in human hepatoma cells and normal hepatocytes. Consistently, the results confirmed that in human hepatoma HepG2 cells, ginkgol C17:1 or cisplatin alone induced autophagy and apoptosis. The co-treatment increased cisplatin-induced apoptosis and inhibited cisplatin-induced autophagy. In comparison, the treatments in human normal L02 hepatocytes indicated that ginkgol C17:1 alone induced autophagy, whereas cisplatin alone induced apoptosis. The co-treatment inhibited cisplatin-induced apoptosis, but enhanced autophagy in L02 cells. Further investigation revealed that the AMP-activated protein kinase/serine/threonine protein kinase ULK1 and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathways were involved in the underlying regulatory mechanisms. Taken together, the results of the present study provide the first evidence that ginkgol C17:1 protects normal hepatocytes against cisplatin-induced cytotoxicity while potentiating the anticancer effect of cisplatin chemotherapy. The differential effects on normal and cancer cells suggest that ginkgol C17:1 is a promising candidate for auxiliary chemotherapy.