Genistein potentiates the effect of arsenic trioxide against human hepatocellular carcinoma: role of Akt and nuclear factor-κB

Handan Ganle inhibits PI3K/Akt signaling pathway in liver fibrosis in rats

AIM: To investigate the role of the extracellular regulated protein kinases (ERK)1/2 pathway in genistein and 5-fluorouracil (5-FU)-induced cell cycle arrest in human hepatoma cells.

METHODS: The MTS method was used to assay cell proliferation. Cell cycle was detected by flow cytometry. The protein expression of total ERK1/2 and phospho-ERK1/2 was detected by Western blot.

RESULTS: Genistein and 5-FU, alone or in combination, inhibited proliferation of MHCC97-L cells. Genistein induced an S-phase arrest and slightly inhibited the expression of phospho-ERK1/2. ERK1/2 inhibitor could promote the inhibition of MHCC97-L cells by genistein, but had no significant effect on S-phase arrest. 5-FU alone or in combination with genistein arrested the cells in S phase and significantly activated ERK1/2. ERK1/2 inhibitor increased genistein and 5-FU-induced growth inhibition of MHCC97-L cells and S-phase arrest.

CONCLUSION: Genistein and 5-FU inhibit the proliferation of liver cancer cells by arresting the cell cycle. Inhibition of the ERK1/2 pathway can resist genistein-induced S phase arrest in liver cancer cells, but promote S phase arrest induced by 5-FU alone or in combination with genistein.

Sodium orthovanadate inhibits growth of human hepatocellular carcinoma cells in vitro and in an orthotopic model in vivo

The transition metal vanadium is widely distributed in the environment and exhibits various biological and physiological effects in the human body. As a well known vanadium compound, sodium orthovanadate (SOV) has shown promising antineoplastic activity in several human cancers. However, the effects of SOV on liver cancer are still unknown. In this study, for the first time, we showed that SOV could effectively suppress proliferation, induce G2/M cell cycle arrest and apoptosis, and diminish the mitochondrial membrane potential (MMP) of HCC cells in vitro. In addition, our in vitro results were recapitulated in vivo, showing that SOV exhibited a dose-dependent inhibition of growth of human HCC in an orthotopic model, evidenced by the reduction in tumor size, proliferation index and microvessel density, and increase in cell apoptosis. Most important, we found that SOV could inhibit autophagy in HCC cells in vitro and in vivo, which plays a prodeath role. Thus, our findings suggest that SOV could effectively suppress the growth of human HCC through the regulations of proliferation, cell cycle, apoptosis and autophagy, and thus may act as a potential therapeutic agent in HCC treatment.

Genistein and 5-FU inhibit apoptosis of human hepatocellular cancer cells by regulating Bax via p42/44 MAPK pathway

AIM: To explore whether genistein and 5-FU induce apoptosis of human hepatic cancer MHCC97-L cells by regulating Bax via the p42/44 MAPK pathway.

METHODS: MHCC97-L cells were treated with genistein, 5-FU, PD98059, genistein + 5-FU, PD98059 + genistein, PD98059 + 5-FU, or PD98059 + genistein + 5-FU, respectively. The density and morphology of MHCC97-L cells were observed under an inverted microscope. Apoptosis and cell death were detected after annexin V-FITC/PI staining under a fluorescence microscope. The expression of Bax protein was detected by Western blot.

RESULTS: All drug groups showed decreased cell density, cell death and debris, cell shrinkage or deformation, reduced cytoplasmic transparency, and vacuoles structure within the cells, with PD98059 + genistein + 5-FU group having the most obvious changes. Apoptotic cells and dead cells were detected in all drug groups. The relative expression of Bax protein was the highest in the genistein + 5-FU group, followed by the genistein, 5-FU, PD98059 + genistein + 5-FU, PD98059 + 5-FU, PD98059 + genistein, PD98059 and control groups. The expression of Bax protein in the PD98059 + genistein group was very close to that in the PD98059 group, but was significantly lower than that in the genistein group.

CONCLUSION: Genistein and 5-FU can induce the apoptosis of MHCC97-L cells and increase Bax expression possibly by regulating Bax mainly through the p42/44 MAPK pathway.

Targeting tumor ubiquitin-proteasome pathway with polyphenols for chemosensitization

The development of tumor drug resistance is one of the biggest obstacles on the way to achieve a favorable outcome of chemotherapy. Among various strategies that have been explored to overcome drug resistance, the combination of current chemotherapy with plant polyphenols as a chemosensitizer has emerged as a promising one. Plant polyphenols are a group of phytochemicals characterized by the presence of more than one phenolic group. Mechanistic studies suggest that polyphenols have multiple intracellular targets, one of which is the proteasome complex. The proteasome is a proteolytic enzyme complex responsible for intracellular protein degradation and has been shown to play an important role in tumor growth and the development of drug resistance. Therefore, proteasome inhibition by plant polyphenols could be one of the mechanisms contributing to their chemosensitizing effect. Plant polyphenols that have been identified to possess proteasome-inhibitory activity include (-)-epigallocatechins-3-gallate (EGCG), genistein, luteolin, apigenin, chrysin, quercetin, curcumin and tannic acid. These polyphenols have exhibited an appreciable effect on overcoming resistance to various chemotherapeutic drugs as well as multidrug resistance in a broad spectrum of tumors ranging from carcinoma and sarcoma to hematological malignances. The in vitro and in vivo studies on polyphenols with proteasome-inhibitory activity have built a solid foundation to support the idea that they could serve as a chemosensitizer for the treatment of cancer. In-depth mechanistic studies and identification of optimal regimen are needed in order to eventually translate this laboratory concept into clinical trials to actually benefit current chemotherapy.

Chemoprevention of head and neck squamous cell carcinoma through inhibition of NF-κB signaling

Nuclear factor-kappa B (NF-κB) transcription factors regulate cellular processes such as inflammation and cell survival. The NF-κB pathway is often activated with development and progression of head and neck squamous cell carcinoma (HNSCC). As such, NF-κB represents an attractive target for chemoprevention. HNSCC involves progression of lesions from premalignant to malignant, providing a window of opportunity for intervention with chemopreventive agents. Appropriate chemopreventive agents should be inexpensive, nontoxic, and target important pathways involved in the development of HNSCC. Several such agents that inhibit the NF-κB pathway have been investigated in HNSCC. Retinoids have been studied most extensively but have shown limited potential in human trials. Epidermal growth factor receptor inhibitors and PI3K-mTOR inhibitors may benefit a subset of patients. Other agents such as green tea extract and curcumin are appealing because they are generally regarded as safe. In contrast, there is evidence that Vitamin E supplementation may actually increase mortality of cancer patients. Repurposed drugs such as cyclooxygenase (COX) inhibitors and antidiabetic drugs are an emerging area of interest. Future research to develop agents with lower toxicity and higher specificity for the NF-κB pathway, and to target these therapies to individual patient genetic signatures should help to increase the utility of chemoprevention in HSNCC.

Antioxidant function of isoflavone and 3,3'-diindolylmethane: are they important for cancer prevention and therapy?

SIGNIFICANCE

Oxidative stress has been mechanistically linked with aging and chronic diseases, including cancer. In fact, oxidative stress status, chronic disease-related inflammation, and cancer occurred in the aging population are tightly correlated. It is well known that the activation of nuclear factor kappa B (NF-κB) plays important roles in oxidative stress, inflammation, and carcinogenesis. Therefore, targeting NF-κB is an important preventive or therapeutic strategy against oxidative stress, inflammation, and cancer.

RECENT ADVANCES

A variety of natural compounds has been found to reduce oxidative stress through their antioxidant activity. Among them, isoflavone, indole-3-carbinol (I3C), and its in vivo dimeric compound 3,3'-diindolylmethane (DIM) have shown their promising effects on the inhibition of NF-κB with corresponding reduction of oxidative stress.

CRITICAL ISSUES

It has been found that isoflavone, I3C, and DIM could inhibit cancer development and progression by regulating multiple cellular signaling pathways that are related to oxidative stress and significantly deregulated in cancer.

FUTURE DIRECTIONS

The antioxidative and anticancer effects of these natural agents make them strong candidates for chemoprevention and/or therapy against human malignancies. However, more clinical trials are needed to evaluate the effects of isoflavone and DIM for the prevention of cancer development and also for the treatment of cancer either alone or in combination with conventional cancer therapeutics.

Protective effects of hydroxytyrosol on liver ischemia/reperfusion injury in mice

SCOPE

Hydroxytyrosol (HT), a main phenolic compound in olive oil, has been proved to be a potent antioxidant and has beneficial effects on health. However, the effect of HT on oxidative liver damage, as seen in ischemia/reperfusion (I/R) injury, is unknown. Here, we examined whether HT could protect liver against I/R injury.

METHODS AND RESULTS

By using a mouse model, we found that HT administration protects against hepatic I/R injury, as indicated by the decreased levels of serum aminotransferase and less parenchymal necrosis and apoptosis. Serum levels of tumor necrosis factor-α, interleukin-6, macrophage inflammatory protein 2, as well as reactive oxygen species (ROS) content in liver tissues, were all decreased by HT, the latter correlated with the reduction of hepatic malondialdehyde (an index of oxidative stress) content and increased activities and expressions of liver antioxidant enzymes superoxide dismutase and catalase. The protective effect was also seen in isolated hepatocytes anoxia/reoxygenation assay.

CONCLUSION

HT exerts protective effects against hepatic I/R injury in mice, which might be associated with its anti-oxidative, anti-inflammatory, and anti-apoptotic properties. HT may be an effective hepatoprotective agent and a promising candidate for the treatment of liver I/R injury.

Therapeutic effect of coenzyme Q10 against experimentally-induced hepatocellular carcinoma in rats

The therapeutic potential of coenzyme Q10 was investigated in rats with hepatocellular carcinoma induced by trichloroacetic acid (0.5g/kg/day, p.o., for five days). Coenzyme Q10 treatment (0.4mg/kg/day, i.p.) was applied for four weeks following trichloroacetic acid administration. Coenzyme Q10 significantly suppressed lipid peroxidation, prevented the depletion of reduced glutathione and superoxide dismutase activity, and decreased the elevations of tumor necrosis factor-α and nitric oxide in liver tissue of rats with hepatocellular carcinoma. Also, the histopathological dysplastic changes induced by trichloroacetic acid in liver tissue were ameliorated by coenzyme Q10. Immunohistochemical analysis revealed that coenzyme Q10 significantly decreased the expression of hepPar-1, alpha-fetoprotein, inducible nitric oxide synthase, cyclooxygenase-2 and nuclear factor-κB in liver tissue of rats with hepatocellular carcinoma. It was concluded that coenzyme Q10 may represent a potential therapeutic option for liver carcinogenesis.

Interaction effects between genes involved in the AKT signaling pathway and phytoestrogens in gastric carcinogenesis: a nested case-control study from the Korean Multi-Center Cancer Cohort

SCOPE

To investigate whether genes involved in AKT/nuclear factor kappa B signaling and/or gene-environment interactions between the genes and phytoestrogens may be susceptible factors for gastric cancer.

METHODS AND RESULTS

The representative single nucleotide polymorphisms (SNPs) identified during the primary analysis (screening a total of 622 SNPs within ± 5 kbp of the 51 target gene locations) were further investigated in 317 matched case-control sets. The summary odds ratios (ORs) and 95% confidence intervals (CIs) for gastric cancer were calculated. Interaction effects between the SNPs and phytoestrogen biomarkers (genistein, daidzein, equol, and enterolactone) were computed. CDK1 rs4145643, FAS rs6586161, and FAS rs1468063 in the AKT signaling pathway presented significant genetic effects on gastric cancer (OR = 0.81 (95% CI: 0.66-0.99) for CDK1 rs4145643; OR = 1.27 (95% CI: 1.03-1.58) for FAS rs6586161; OR = 1.29 (95% CI: 1.03-1.56) for FAS rs1468063; Cochran Q statistics > 0.10). Risk alleles of FAS rs6586161, FAS rs1468063, MAP3K1 rs16886448, and MAP3K1 rs252902 showed significant interaction effects with enterolactone (p(interaction) < 0.05).

CONCLUSION

CDK1 and FAS genes involved in AKT signaling and influenced by anti-carcinogenic property of phytoestrogens can play a role as susceptible genetic factors in gastric carcinogenesis. FAS and MAP3K1 genes significantly interact with enterolactone, thereby modifying the individual's risk for gastric cancer.

Cyclooxygenase-2 (COX-2) mediates arsenite inhibition of UVB-induced cellular apoptosis in mouse epidermal Cl41 cells

Inorganic arsenic is an environmental human carcinogen, and has been shown to act as a co-carcinogen with solar ultraviolet (UV) radiation in mouse skin tumor induction even at low concentrations. However, the precise mechanism of its co-carcinogenic action is largely unknown. Apoptosis plays an essential role as a protective mechanism against neoplastic development in the organism by eliminating genetically damaged cells. Thus, suppression of apoptosis is thought to contribute to carcinogenesis. It is known that cyclooxygenase-2 (COX-2) can promote carcinogenesis by inhibiting cell apoptosis under stress conditions; and our current studies investigated the potential contribution of COX-2 to the inhibitory effect of arsenite in UV-induced cell apoptosis in mouse epidermal Cl41 cells. We found that treatment of cells with low concentration (5 μM) arsenite attenuated cellular apoptosis upon UVB radiation accompanied with a coinductive effect on COX-2 expression and nuclear factor-κB (NFκB) transactivation. Our results also showed that the COX-2 induction by arsenite and UVB depended on an NFκB pathway because COX-2 co-induction could be attenuated in either p65-deficient or p50-deficient cells. Moreover, UVB-induced cell apoptosis could be dramatically reduced by the introduction of exogenous COX-2 expression, whereas the inhibitory effect of arsenite on UVB-induced cell apoptosis could be impaired in COX-2 knockdown C141 cells. Our results indicated that COX-2 mediated the anti-apoptotic effect of arsenite in UVB radiation through an NFκB-dependent pathway. Given the importance of apoptosis evasion during carcinogenesis, we anticipated that COX-2 induction might be at least partially responsible for the co-carcinogenic effect of arsenite on UVB-induced skin carcinogenesis.

Antimetastatic effects of norcantharidin on hepatocellular carcinoma by transcriptional inhibition of MMP-9 through modulation of NF-kB activity

BACKGROUND

The rate of morbidity and mortality of hepatocellular carcinoma (HCC) in Taiwan has not lessened because of difficulty in treating tumor metastasis. Norcantharidin (NCTD) is currently used as an anticancer drug for hepatoma, breast cancer, and colorectal adenocarcinoma. NCTD possesses various biological anticancer activities, including apoptosis. However, detailed effects and molecular mechanisms of NCTD on metastasis are unclear. Thus, HCC cells were subjected to treatment with NCTD and then analyzed to determine the effects of NCTD on cell metastasis.

METHODOLOGY/PRINCIPAL FINDINGS

Modified Boyden chamber assays revealed that NCTD treatment inhibited cell migration and invasion capacities of HCC cells substantially. Results of zymography and western blotting showed that activities and protein levels of matrix metalloproteinase-9 (MMP-9) and urokinase plasminogen activator (u-PA) were inhibited by NCTD. Western blot analysis showed that NCTD inhibits phosphorylation of ERK1/2. Testing of mRNA level, quantitative real-time PCR, and promoter assays evaluated the inhibitory effects of NCTD on MMP-9 and u-PA expression in HCC cells. The chromatin immunoprecipitation (ChIP) assay for analyzing the genomic DNA sequences bound to these proteins was reactive to the transcription protein nuclear factor (NF)-kappaB, which was inhibited by NCTD. The expression of NF-kappa B was measured by western blot analysis, which revealed decreased nuclear-factor DNA-binding activity after NCTD treatment.

CONCLUSIONS

NCTD inhibited MMP-9 and u-PA expression through the phosphorylation of ERK1/2 and NF-kappaB signaling pathway which serves as a powerful chemopreventive agent in HCC cell metastasis.

Anti-hepatocellular carcinoma activity using human HepG2 cells and hepatotoxicity of 6-substituted methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate derivatives: in vitro evaluation, cell cycle analysis and QSAR studies

Hepatocellular carcinoma (HCC) is a highly complex cancer, resistant to commonly used treatments and new therapeutic agents are urgently needed. A total of thirty-two thieno[3,2-b]pyridine derivatives of two series: methyl 3-amino-6-(hetero)arylthieno[3,2-b]pyridine-2-carboxylates (1a-1t) and methyl 3-amino-6-[(hetero)arylethynyl]thieno[3,2-b]pyridine-2-carboxylates (2a-2n), previously prepared by some of us, were evaluated as new potential anti-HCC agents by studying their in vitro cell growth inhibition on human HepG2 cells and hepatotoxicity using a porcine liver primary cell culture (PLP1). The presence of amino groups linked to a benzene moiety emerges as the key element for the anti-HCC activity. The methyl 3-amino-6-[(3-aminophenyl)ethynyl]thieno[3,2-b]pyridine-2-carboxylate (2f) is the most potent compound presenting GI(50) values on HepG2 cells of 1.2 μM compared to 2.9 μM of the positive control ellipticine, with no observed hepatotoxicity (PLP1 GI(50) > 125 μM against 3.3 μM of ellipticine). Moreover this compound changes the cell cycle profile of the HepG2 cells, causing a decrease in the % of cells in the S phase and a cell cycle arrest in the G2/M phase. QSAR studies were also performed and the correlations obtained using molecular and 1D descriptors revealed the importance of the presence of amino groups and hydrogen bond donors for anti-HCC activity, and hydrogen bond acceptors for hepatotoxicity. The best correlations were obtained with 3D descriptors belonging to different subcategories for anti-HCC activity and hepatotoxicity, respectively. These results point to different molecular mechanisms of action of the compounds in anti-HCC activity and hepatotoxicity. This work presents some promising thieno[3,2-b]pyridine derivatives for potential use in the therapy of HCC. These compounds can also be used as scaffolds for further synthesis of more potent analogs.

Induction of cancer cell death by isoflavone: the role of multiple signaling pathways

Soy isoflavones have been documented as dietary nutrients broadly classified as "natural agents" which plays important roles in reducing the incidence of hormone-related cancers in Asian countries, and have shown inhibitory effects on cancer development and progression in vitro and in vivo, suggesting the cancer preventive or therapeutic activity of soy isoflavones against cancers. Emerging experimental evidence shows that isoflavones could induce cancer cell death by regulating multiple cellular signaling pathways including Akt, NF-κB, MAPK, Wnt, androgen receptor (AR), p53 and Notch signaling, all of which have been found to be deregulated in cancer cells. Therefore, homeostatic regulation of these important cellular signaling pathways by isoflavones could be useful for the activation of cell death signaling, which could result in the induction of apoptosis of both pre-cancerous and/or cancerous cells without affecting normal cells. In this article, we have attempted to summarize the current state-of-our-knowledge regarding the induction of cancer cell death pathways by isoflavones, which is believed to be mediated through the regulation of multiple cellular signaling pathways. The knowledge gained from this article will provide a comprehensive view on the molecular mechanism(s) by which soy isoflavones may exert their effects on the prevention of tumor progression and/or treatment of human malignancies, which would also aid in stimulating further in-depth mechanistic research and foster the initiation of novel clinical trials.

Arsenic and its combinations in cancer therapeutics

Arsenic is a metalloid that is considered to be a paradox in terms of its role both as a carcinogen and as a therapeutic agent. Chronic exposure to arsenic in drinking water has been linked with the development of various pathological conditions including cancer. Nevertheless, the therapeutic potential of arsenic and its derivatives in a variety of diseases have been exploited in the past. However, its role and mechanism of action as a therapeutic agent still remain an active area of research and investigation. Our ongoing work also suggests varied responses in cancer cells exposed to lower versus higher concentrations of arsenic. Furthermore, the arsenic combinations with chemopreventive or anticancer agents have been observed to sensitize the cell for cell-cycle arrest and cell death. Here, we have provided the account of recent updates on the mechanism of action of arsenic and its derivatives that lead to various disorders, and its role as a therapeutic agent both as a single agent as well as in combination chemotherapy.

Antitumor activity of sphingosine kinase 2 inhibitor ABC294640 and sorafenib in hepatocellular carcinoma xenografts

The balance between the pro-apoptotic lipids ceramide and sphingosine and the pro-survival lipid sphingosine 1-phosphate (S1P) is termed the "sphingosine rheostat". Two isozymes, sphingosine kinase 1 and 2 (SK1 and SK2), are responsible for phosphorylation of pro-apoptotic sphingosine to form pro-survival S1P. We have previously reported the antitumor properties of an SK2 selective inhibitor, ABC294640, alone or in combination with the multikinase inhibitor sorafenib in mouse models of kidney carcinoma and pancreatic adenocarcinoma. Here we evaluated the combined antitumor effects of the aforementioned drug combination in two mouse models of hepatocellular carcinoma. Although combining the SK2 inhibitor, ABC294640, and sorafenib in vitro only afforded additive drug-drug effects, their combined antitumor properties in the mouse model bearing HepG2 cells mirrored effects previously observed in animals bearing kidney carcinoma and pancreatic adenocarcinoma cells. Combining ABC294640 and sorafenib led to a decrease in the levels of phosphorylated ERK in SK-HEP-1 cells, indicating that the antitumor effect of this drug combination is likely mediated through a suppression of the MAPK pathway in hepatocellular models. We also measured levels of S1P in the plasma of mice treated with two different doses of ABC294640 and sorafenib. We found decreases in the levels of S1P in plasma of mice treated daily with 100 mg/kg of ABC294640 for 5 weeks, and this decrease was not affected by co-administration of sorafenib. Taken together, these data support combining ABC294640 and sorafenib in clinical trials in HCC patients. Furthermore, monitoring levels of S1P may provide a pharmacodynamic marker of ABC294640 activity.