Anthraquinone compounds have been shown to induce apoptosis in different cancer cell types. Effects of chrysophanol, an anthraquinone compound, on cancer cell death have not been well-studied. The goal of this study was to examine if chrysophanol had cytotoxic effects and if such effects involved apoptosis or necrosis in J5 human liver cancer cells. Chrysophanol induced necrosis in J5 cells in a dose- and time-dependent manner. Non-apoptotic cell death was induced by chrysophanol in J5 cells and was characterized by caspase independence, delayed externalization of phosphatidylserine and plasma membrane disruption. Blockage of apoptotic induction by a general caspase inhibitor (z-VAD-fmk) failed to protect cells against chrysophanol-induced cell death. The levels of ROS production and loss of mitochondrial membrane potential (ΔΨm) were also determined to assess the effects of chrysophanol. However, reductions in ATP levels and increases in LDH activity indicated that chrysophanol stimulated necrotic cell death. In summary, human liver cancer cells treated with chrysophanol exhibited a cellular pattern associated with necrosis and not apoptosis.

Resveratrol is known to be an effective chemo-preventive phytochemical against multiple tumor cells. However, the increasing drug resistance avoids the cancer treatment in oral cavity cancer. In this study, we investigated the oral antitumor activity of resveratrol and its mechanism in cisplatin-resistant human oral cancer CAR cells. Our results demonstrated that resveratrol had an extremely low toxicity in normal oral cells and provoked autophagic cell death to form acidic vesicular organelles (AVOs) and autophagic vacuoles in CAR cells by acridine orange (AO) and monodansylcadaverine (MDC) staining. Either DNA fragmentation or DNA condensation occurred in resveratrol-triggered CAR cell apoptosis. These inhibitors of PI3K class III (3-MA) and AMP-activated protein kinase (AMPK) (compound c) suppressed the autophagic vesicle formation, LC3-II protein levels and autophagy induced by resveratrol. The pan-caspase inhibitor Z-VAD-FMK attenuated resveratrol-triggered cleaved caspase-9, cleaved caspase-3 and cell apoptosis. Resveratrol also enhanced phosphorylation of AMPK and regulated autophagy- and pro-apoptosis-related signals in resveratrol-treated CAR cells. Importantly, resveratrol also stimulated the autophagic mRNA gene expression, including Atg5, Atg12, Beclin-1 and LC3-II in CAR cells. Overall, our findings indicate that resveratrol is likely to induce autophagic and apoptotic death in drug-resistant oral cancer cells and might become a new approach for oral cancer treatment in the near future.

Epigallocatechin gallate (EGCG) is a green tea polyphenol that presents anticancer activities in multiple cancer cells, but no available report was addressed for the underling molecular mechanism of cytotoxic impacts on drug-resistant oral squamous cell carcinoma cells. In the present study, the inhibitory effects of EGCG were experienced on cisplatin-resistant oral cancer CAR cells. EGCG inhibited cell viability in a time- and concentration-dependent manner by a sulforhodamine B (SRB) assay. EGCG induced CAR cell apoptosis and autophagy by 4',6-diamidino-2-phenylindole (DAPI) dye, acridine orange (AO) staining and green fluorescent protein (GFP)-tagged LC3B assay, respectively. EGCG also significantly enhanced caspase-9 and caspase-3 activities by caspase activity assay. EGCG markedly increased the protein levels of Bax, cleaved caspase-9, cleaved caspase-3, Atg5, Atg7, Atg12, Beclin-1, and LC3B-II, as well as significantly decreased the expression of Bcl-2, phosphorylated AKT (Ser473) and phosphorylation of STAT3 on Tyr705 by western blotting in CAR cells. Importantly, the protein and gene expression of multidrug resistance 1 (MDR1) were dose-dependently inhibited by EGCG. Overall, downregulation of MDR1 levels and alterations of AKT/STAT3 signaling contributed to EGCG-induced apoptosis and autophagy in CAR cells. Based on these results, EGCG has the potential for therapeutic effect on oral cancer and may be useful for long-term oral cancer prevention in the future. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 845-855, 2017.

Autophagy, a double-edged sword for cell survival, is the research object on 2016 Nobel Prize in Physiology or Medicine. Autophagy is a molecular mechanism for maintaining cellular physiology and promoting survival. Defects in autophagy lead to the etiology of many diseases, including diabetes mellitus (DM), cancer, neurodegeneration, infection disease and aging. DM is a metabolic and chronic disorder and has a higher prevalence in the world as well as in Taiwan. The character of diabetes mellitus is hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and failure of producing insulin on pancreatic beta cells. In T2DM, autophagy is not only providing nutrients to maintain cellular energy during fasting, but also removes damaged organelles, lipids and miss-folded proteins. In addition, autophagy plays an important role in pancreatic beta cell dysfunction and insulin resistance. In this review, we summarize the roles of autophagy in T2DM.

In recent years, glycative stress from exogenous or endogenous advanced glycation end products (AGEs) and highly reactive dicarbonyls has gained great attention for its putative effects on cancer development. AGEs are a group of compounds formed from the complex chemical reaction of reducing sugars with compounds containing an amino group. AGEs bind to and activate the receptor for AGEs (RAGE), which is a predominant modulator of inflammation-associated cancer, and AGEs induce reactive oxygen species that are an important regulator of the hallmarks of cancer. Dicarbonyls, which are formed during glycolysis, lipid oxidation, or protein degradation, include glyoxal, methylglyoxal, and 3-deoxyglucosone and are regarded as major precursors of AGEs. These dicarbonyls not only fuel the AGE pool in living organisms but also evoke carbonyl stress, which may contribute to the carbonylative damage of carbohydrates, lipids, proteins, or DNA. Carbonylative damage then leads to many lesions, some of which are implicated in the pathogenesis of cancer. In this review, studies regarding the effects of AGEs and dicarbonyls on cancer onset or progression are systematically discussed, and the utilization of AGE inhibitors and dicarbonyl scavengers in cancer therapy are noted.

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Oral cancer is a serious and fatal disease. Cisplatin is the first line of chemotherapeutic agent for oral cancer therapy. However, the development of drug resistance and severe side effects cause tremendous problems clinically. In this study, we investigated the pharmacologic mechanisms of YC-1 on cisplatin-resistant human oral cancer cell line, CAR. Our results indicated that YC-1 induced a concentration-dependent and time-dependent decrease in viability of CAR cells analyzed by MTT assay. Real-time image analysis of CAR cells by IncuCyte™ Kinetic Live Cell Imaging System demonstrated that YC-1 inhibited cell proliferation and reduced cell confluence in a time-dependent manner. Results from flow cytometric analysis revealed that YC-1 promoted G0/G1 phase arrest and provoked apoptosis in CAR cells. The effects of cell cycle arrest by YC-1 were further supported by up-regulation of p21 and down-regulation of cyclin A, D, E and CDK2 protein levels. TUNEL staining showed that YC-1 caused DNA fragmentation, a late stage feature of apoptosis. In addition, YC-1 increased the activities of caspase-9 and caspase-3, disrupted the mitochondrial membrane potential (AYm) and stimulated ROS production in CAR cells. The protein levels of cytochrome c, Bax and Bak were elevated while Bcl-2 protein expression was attenuated in YC-1-treated CAR cells. In summary, YC-1 suppressed the viability of cisplatin-resistant CAR cells through inhibiting cell proliferation, arresting cell cycle at G0/G1 phase and triggering mitochondria-mediated apoptosis. Our results provide evidences to support the potentially therapeutic application of YC-1 on fighting against drug resistant oral cancer in the future.

Fenofibrate, a peroxisome proliferator-activated receptor alpha (PPARα) agonist and lipid-lowering agent, has been used worldwide for treatment of hyperlipidemia. The clinical trials demonstrate that fenofibrate possesses multiple pharmacological activities, including antitumor effects. However, the precise mechanisms in oral squamous cell carcinoma (OSCC) remain unclear. In this study, we investigated the anticancer effects of fenofibrate on the migration and invasion of human oral cancer CAL 27 cells. Fenofibrate inhibited the cell migration and invasion of CAL 27 cells by the wound healing and Boyden chamber transwell assays, respectively. In addition, fenofibrate reduced the protein expressions of MMP-1, MMP-2, MMP-7, and MMP-9 by Western blotting and inhibited enzyme activities of MMP-2/-9 using gelatin zymography assay. Results from immunoblotting analysis showed that the proteins of p-LKB1 (Ser428), LKB1, p-AMPKα (Thr172), p-AMPKα1/α2 (Ser425/Ser491), p-AMPKβ1 (Ser108), and AMPKγ1 were upregulated by fenofibrate; the levels of p-IKKα/β (Ser176) and p-IκBα were reduced in fenofibrate-treated cells. Also, fenofibrate suppressed the expressions of nuclear NF-κB p65 and p50 by immunoblotting and NF-κB DNA binding activity by EMSA assay. The anti-invasive effect of fenofibrate was attenuated by compound C [an adenosine 5'-monophosphate-activated protein kinase (AMPK) inhibitor] or dominant negative form of AMPK (DN-AMPKα1). Thus, fenofibrate considerably inhibited metastatic behaviors of CAL 27 cells might be mediated through blocking NF-κB signaling, resulting in the inhibition of MMPs; these effects were AMPK-dependent rather than PPARα signaling. Our findings provide a molecular rationale, whereby fenofibrate exerts anticancer effects and additional beneficial effects for the treatment of cancer patients. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 866-876, 2016.