Cancer cells are well known to require a constant supply of protein, lipid, RNA, and DNA via altered metabolism for accelerated cell proliferation. Targeting metabolic pathways is, therefore, a promising therapeutic strategy for cancers. Isoquercitrin (ISO) is widely distributed in dietary and medicinal plants and displays selective cytotoxicity to cancer cells, primarily by inducing apoptosis and cell cycle arrest. The aims of this study were to find out whether ISO could stabilize in a bladder-like acidic environment and inhibit bladder cancer cell proliferation by affecting their metabolism, and to investigate its molecular mechanism. In this study, the exposure of T24 bladder cancer cells to ISO (20–80 μM) decreased cell viability by causing ROS overproduction. This ROS change regulated the AMPK signaling pathway, and caused Caspase-dependent apoptosis as well as metabolism dysfunction. Metabolic alterations elevated metabolic pathway variation, which in turn destabilized lipid synthesis and altered anaerobic glycolysis. This linkage was proved by immunoblotting assay, and metabolomics as identified by UHPLC-QTOF-MS. Our findings provide comprehensive evidence that ISO influenced T24 bladder cancer cell metabolism, and that this process was mainly involved in activating the AMPK pathway. This study could lead to an understanding of how ISO suppresses bladder cancer cell growth, and whether the affected cancer metabolism is a common mechanism by which nutritional compounds suppress cancers.

•NB enhanced the antiproliferative activity of DCur.•DCur entered into the HepG2 cells by the pathway of TfR.•ROS was one cause of NB/DCur-induced cell cycle arrest in the G2/M phase.This study was to investigate whether natural borneol (NB) could enhance the anti-cancer effect of demethoxycurcumin (DCur) on HepG2 cell line by MTT assay, flow cytometry, and western blotting assay. Our results demonstrated that NB/DCur resulted in a significant decrease in cell viability due to pretreatment of NB enhancing the cellular uptake of DCur. Flow cytometric assay showed that NB/DCur-induced HepG2 cells growth inhibition was mainly caused by induction of G2/M arrest, as evidenced by accumulation of the G2/M cell population. Immunoblotting assay demonstrated that NB/DCur down-regulated expression levels of cdc2 and cyclin B1, which contributed to G2/M arrest. Moreover, NB/DCur elevated the level of intracellular reactive oxygen species (ROS), indicating that NB/DCur-induced G2/M arrest was achieved by triggered ROS-mediated DNA damage involving MAPK and Akt signaling pathways. Taken together, our results suggested that the combination of NB and DCur induced G2/M phase arrest in HepG2 through ROS overproduction. This study demonstrated that NB had the potential to be further developed into a chemosensitizer of DCur in the treatment of human cancers.

Curcumin (Cur), an active ingredient from the rhizome of the plant Curcuma longa, has wide anticancer activities. However, due to its poor solubility and hence poor absorption, Cur has limited clinical applications. It is therefore important to develop an effective method to improve its absorption. Natural borneol (NB), a terpene and bicyclic organic compound, has been extensively used as a food additive, and our previous studies show that it can improve the uptake of Cur in cancer cells. However, the anticancer mechanism of NB/Cur remains unclear. In this study, the effects of NB/Cur on HepG2 cells were investigated by proteomic analysis. The results showed that 32 differentially expressed proteins identified by matrix assisted laser desorption ionization time-of-flight mass spectrometry were significantly changed after NB/Cur treated HepG2 cells for 24 h. Moreover, 17 proteins increased and 12 proteins decreased significantly. Biological progress categorization demonstrated that the identified proteins were mainly associated with cell cycle and apoptosis (28.1%). Subcellular location categorization exhibited that the identified proteins were mainly located in nucleus (28.1%) and mitochondrion (21.9%). Among of all proteins, we selected three differential proteins (hnRNPC1/C2, NPM, and PSMA5), which were associated with the p53 pathway. Down-regulation of hnRNPC1/C2 and NPM contributed to the enhancement of phosphorylated p53. Activated p53 and down-regulation of PSMA5 resulted in an increase in p21 protein. Further studies showed that NB/Cur induced reactive oxygen species (ROS) generation, indicating that ROS might be upstream of the G2/M arrest signaling pathway. In summary, the results exhibited the whole proteomic response of HepG2 cells to NB/Cur, which might lead to a better understanding of its underlying anticancer mechanisms.

5-HMF is widely presented in foods and produced through the degradation of hexoses and Maillard reaction during heat treatment of foods containing reducing sugars and amino acids in an acid environment. However, controversial conclusions on the biological effects of 5-HMF have been drawn in previous studies. Therefore, the main aim of this study was to investigate the antioxidant and antiproliferative activities of 5-HMF. The 2,2′-azinobis-3-ethylbenzothiazolin-6-sulfonic acid (ABTS) assay, the 1,1-diphenyl-2-picryhydrazyl (DPPH) assay, and the hemolysis assay induced by 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) were performed to evaluate the antioxidant capacity of 5-HMF. The results showed that 5-HMF exhibited novel antioxidant activity by scavenging the ABTS and DPPH free radicals and inhibited the AAPH-induced hemolysis in a dose-dependent manner. In the hemolysis assay, the reduction of ROS and MDA contents and the increase in enzyme activities of SOD, CAT, and GPx were found in erythrocytes pretreated with 5-HMF, which demonstrated that 5-HMF could prevent the peroxidation from the source to protect the erythrocytes. The morphological changes of erythrocytes was also verified by observation using atomic force microscopy. The inhibitory effect of 5-HMF on human cancer cell proliferation was investigated by MTT assay, flow cytometric analysis, and the TUNEL and DAPI costaining assay. The results showed that 5-HMF displayed higher antiproliferative activity on human melanoma A375 cells than other cell lines. Further investigation on the action mechanisms revealed that 5-HMF could induce A375 cell apoptosis and G0/G1 cell cycle arrest. The A375 cell apoptosis that 5-HMF induced was characterized by a TUNEL and DAPI costaining assay. These findings suggest that 5-HMF could be developed as a novel natural antioxidant with potential applications in cancer chemoprevention.