Induction of apoptosis of human gastric carcinoma SGC-7901 cell line by 5, 7-dihydroxy-8-nitrochrysin in vitro

Emerging cellular and molecular mechanisms underlying anticancer indications of chrysin

Chrysin has been shown to exert several beneficial pharmacological activities. Chrysin has anti-cancer, anti-viral, anti-diabetic, neuroprotective, cardioprotective, hepatoprotective, and renoprotective as well as gastrointestinal, respiratory, reproductive, ocular, and skin protective effects through modulating signaling pathway involved in apoptosis, oxidative stress, and inflammation. In the current review, we discussed the emerging cellular and molecular mechanisms underlying therapeutic indications of chrysin in various cancers. Online databases comprising Scopus, PubMed, Embase, ProQuest, Science Direct, Web of Science, and the search engine Google Scholar were searched for available and eligible research articles. The search was conducted by using MeSH terms and keywords in title, abstract, and keywords. In conclusion, experimental studies indicated that chrysin could ameliorate cancers of the breast, gastrointestinal tract, liver and hepatocytes, bladder, male and female reproductive systems, choroid, respiratory tract, thyroid, skin, eye, brain, blood cells, leukemia, osteoblast, and lymph. However, more studies are needed to enhance the bioavailability of chrysin and evaluate this agent in clinical trial studies.

Research Advances in the Correlation between Peroxisome Proliferator-Activated Receptor-γ and Digestive Cancers

Peroxisome proliferator-activated receptor-γ (PPARγ) is a class of ligand-activated nuclear transcription factors, which is a member of type II nuclear receptor superfamily. Previous studies demonstrate that PPARγ is expressed in a variety of tumor tissues and is closely associated with the proliferation and prognosis of digestive system tumors by its roles in mediation of cell differentiation, induction of cell apoptosis, and inhibition of cell proliferation.

SUMO-1 Gene Silencing Inhibits Proliferation and Promotes Apoptosis of Human Gastric Cancer SGC-7901 Cells

Background: It has been reported that blocking small ubiquitin-like modifier (SUMO) conjugation by silencing SUMO gene remarkably decreased tumor growth in vivo. However, few studies have examined the relationship between SUMO gene silencing and gastric cancer (GC). The study aims to explore the effects of SUMO-1 gene silencing on GC cell proliferation and apoptosis. Methods: GC cells were cultured and divided into 5 groups: the blank group (without any transfection or treatment), the empty vector group (transfected with empty vector), the shRNA-SUMO-1-1 group (transfected with shRNA-SUMO-1-1 plasmid), the shRNA-SUMO-1-2 group (transfected with shRNA-SUMO-1-2 plasmid), and the shRNA-SUMO-1-3 group (transfected with shRNA-SUMO-1-3 plasmid). Cell Counting Kit-8 (CCK-8) assay was performed to examine cell proliferation. Annexin V/PI staining combined with flow cytometry were used to detect cell apoptosis. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were employed to measure the mRNA and protein expressions of SUMO-1, P53, Bcl-2 and c-myc, respectively. Results: SUMO-1 mRNA and protein expressions were decreased after transfecting with shRNA-SUMO-1. Compared with the blank group, the shRNA-SUMO-1-1 group presented a remarkable decreased proliferation of SGC-7901 cells. Significant increase in cell apoptosis rate was observed. Bcl-2, c-myc and P53 expressions were declined after transfecting with shRNA-SUMO plasmid. Conclusion: Our study provided evidence that SUMO-1 gene silencing could decrease proliferation and promote apoptosis in GC cells.

Reversal of liver cancer-associated stellate cell-induced stem-like characteristics in SMMC-7721 cells by 8-bromo-7-methoxychrysin via inhibiting STAT3 activation

Hepatic stellate cells (HSCs) that are activated by human hepatocellular carcinoma (HCC) cells secrete a variety of cytokines, which are the main component of the HCC microenvironment. We aimed to determine whether 8-bromo-7-methoxychrysin (BrMC) could interfere in cross-talk of the human hepatic stellate cell line LX-2 and liver cancer stem-like cells (LCSLCs) to inhibit the characteristics of LCSLCs endowed with the capacity of sustaining human hepatocellular carcinoma (HCC) self-renewal and progression, and to identify its potential mechanism of action. We found that the levels of fibroblast activation protein (FAP) were augmented in LX-2 cells treated with the conditioned medium of LCSLCs (LCSLC-CM) compared to those cultured with routine medium, indicating that the LCSLC-CM can activate LX-2 cells to become liver cancer-associated stellate cells (LCAHSCs). Furthermore, sphere forming capability of SMMC-7721 cells was enhanced and stem cell-related protein expression was significantly increased following treatment with the conditioned medium of LCAHSCs (LCAHSC-CM). Moreover, the level of p-STAT3 was increased in LX-2 cells treated with LCSLC-CM and BrMC reduced expression of p-STAT3. Combination of BrMC and the selective inhibitor of STAT3 cucurbitacin I (JSI-124) synergistically suppressed the LCSLC characteristics in SMMC-7721 cells. Collectively, our data showed that BrMC inhibited the interaction between LX-2 cells and HCC-derived CSCs, and did so potentially through modulation of the STAT3 pathway. Future therapeutic strategies employing anti-CSC therapy should confirm the potential of cucurbitacin I (JSI-124) and BrMC as potent therapeutic agents.

8‑bromo‑7‑methoxychrysin induces apoptosis by regulating Akt/FOXO3a pathway in cisplatin‑sensitive and resistant ovarian cancer cells

8-bromo-7-methoxychrysin (BrMC), a novel chrysin analog, was reported to have anti-cancer activities. The aim of the present study was to investigate the molecular mechanism of 8-bromo-7-methoxychrysin (BrMC)-induced apoptosis via the Akt/forkhead box O3a (FOXO3a) pathway in cisplatin (DDP)-sensitive and -resistant ovarian cancer cells. The human ovarian cancer cell lines A2780 and A2780/DDP were cultured in vitro. Various molecular techniques were used to assess the expression of FOXO3a and B cell lymphoma 2 (Bcl-2)-interacting mediator of cell death (Bim) in cisplatin-sensitive and -resistant ovarian cancer cells. Different concentrations of BrMC induced apoptosis in cisplatin-sensitive and -resistant ovarian cancer cells. BrMC-induced apoptotic cell death occurred mainly by the activation of Akt, which was accompanied by the overexpression of transcription factor FOXO3a, with a concomitant increase in the expression levels of Bim. Silencing Bim expression by using small interfering RNA, attenuated the induction of apoptosis by BrMC treatment. The results indicated that BrMC-induced apoptosis in cisplatin-sensitive and -resistant ovarian cancer cells may occur via the regulation of Akt/FOXO3a, leading to Bim transcription.

Combination of chrysin and cisplatin promotes the apoptosis of Hep G2 cells by up-regulating p53

Cisplatin is a chemotherapy drug commonly used for the treatment of human cancers, however, drug resistance poses a major challenge to clinical application of cisplatin in cancer therapy. Recent studies have shown that chrysin, a natural flavonoid widely found in various plants and foods, demonstrated effective anti-cancer activity. In the present study, we found that the combination chrysin and cisplatin significantly enhanced the apoptosis of Hep G2 cancer cells. Combination of chrysin and cisplatin increased the phosphorylation and accumulation of p53 through activating ERK1/2 in Hep G2 cells, which led to the overexpression of the pro-apoptotic proteins Bax and DR5 and the inhibition of the anti-apoptotic protein Bcl-2. In addition, combination of chrysin and cisplatin promoted both extrinsic apoptosis by activating caspase-8 and intrinsic apoptosis by increasing the release of cytochrome c and activating caspase-9 in Hep G2 cells. Our results suggest that combination of chrysin and cisplatin is a promising strategy for chemotherapy of human cancers that are resistant to cisplatin.

Cytotoxicity of dietary flavonoids on different human cancer types

Flavonoids are ubiquitous in nature. They are also in food, providing an essential link between diet and prevention of chronic diseases including cancer. Anticancer effects of these polyphenols depend on several factors: Their chemical structure and concentration, and also on the type of cancer. Malignant cells from different tissues reveal somewhat different sensitivity toward flavonoids and, therefore, the preferences of the most common dietary flavonoids to various human cancer types are analyzed in this review. While luteolin and kaempferol can be considered as promising candidate agents for treatment of gastric and ovarian cancers, respectively, apigenin, chrysin, and luteolin have good perspectives as potent antitumor agents for cervical cancer; cells from main sites of flavonoid metabolism (colon and liver) reveal rather large fluctuations in anticancer activity probably due to exposure to various metabolites with different activities. Anticancer effect of flavonoids toward blood cancer cells depend on their myeloid, lymphoid, or erythroid origin; cytotoxic effects of flavonoids on breast and prostate cancer cells are highly related to the expression of hormone receptors. Different flavonoids are often preferentially present in certain food items, and knowledge about the malignant tissue-specific anticancer effects of flavonoids could be purposely applied both in chemoprevention as well as in cancer treatment.

Inhibition of cell growth by BrMC through inactivation of Akt in HER-2/neu-overexpressing breast cancer cells

We previously reported that chrysin (ChR) and its analogs induced cell cycle arrest and apoptosis in human estrogen receptor-positive/-negative breast cancer cells. However, it was unknown whether 8-bromo-7-methoxychrysin (BrMC), a novel synthetic ChR analog, inhibited the cell growth of human epidermal growth factor receptor 2 (HER-2)/neu-overexpressing breast cancers. In the present study, it was demonstrated that BrMC preferentially inhibited the cell viability of HER-2/neu-overexpressing MDA-MB-453 and BT-474 cells. Western blot analysis revealed that HER-2/neu expression and tyrosine phosphorylation were inhibited by BrMC in a concentration-dependent manner; whereas the proteasome inhibitor, MG-132, significantly prevented BrMC-induced HER-2/neu depletion and cell death in MDA-MB-453 cells. This directly indicated that BrMC-induced HER-2/neu depletion and cell growth inhibition was mediated by a proteasomal pathway. BrMC significantly downregulated the expression of cyclin D1, cyclin E and CDK4, followed by the suppression of protein kinase B phosphorylation and downstream effectors, GSK-3β and β-catenin. A colony formation assay also confirmed the growth-inhibitory effects of BrMC. Thus, these findings clearly demonstrate the anticancer activity of BrMC against human HER-2/neu-overexpressing breast cancer cells. Thus, these findings clearly demonstrate the anticancer activity of BrMC against human HER 2/neu-overexpressing breast cancer cells, and highlight BrMC as a promising candidate for breast cancer therapy.

8-bromo-5-hydroxy-7-methoxychrysin targeting for inhibition of the properties of liver cancer stem cells by modulation of Twist signaling

Emerging evidence has suggested that cancer stem cells with expression of surface biomarkers including CD133 and CD44 have more aggressive biological behavior, including epithelial-mesenchymal transition (EMT), which are closely related to invasion. The upregulation and nuclear relocation of the EMT regulator Twist1 have been implicated in the tumor invasion and metastasis of human hepatocellular carcinoma (HCC). In this study, we aimed to isolate and characterize a small population of CD133+ cells that existed in the HCC cell line SMMC-7721 by MACS and investigated the possible roles of 8-bromo-7-methoxychrysin (BrMC), a synthetic analogue of chrysin, in inhibiting the properties of CD133+ sphere-forming cells (SFCs) derived from the HCC cell line SMMC-7721, namely liver cancer stem cells (LCSCs). Based on the data, BrMC inhibited the proliferation, self-renewal and invasion of LCSCs in vitro and in vivo, downregulated the expression of the LCSC biomarkers CD133 and CD44 and induced EMT by downregulating the expression of Twist and β-catenin in LCSCs. BrMC potentiated the inhibition of LCSCs self-renewal after reduction of twist protein levels, which was attenuated when twist was overexpressed. This study not only provides an important experimental and theoretical basis for investigation of BrMC in LCSCs, but also helps in the development of effective therapeutic medicine for HCC.

7-difluoromethoxyl-5,4’-di-n-octylgenistein inhibits growth of gastric cancer cells through downregulating forkhead box M1

AIM: To investigate whether the 7-difluoromethoxyl-5, 4’-di-n-octylgenistein (DFOG), a novel synthetic genistein analogue, affects the growth of gastric cancer cells and its mechanisms.

METHODS: A series of genistein analogues were prepared by difluoromethylation and alkylation, and human gastric cancer cell lines AGS and SGC-7901 cultured in vitro were treated with various concentrations of genistein and genistein analogues. The cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The cells were incubated by DFOG at different concentrations. The growth inhibitory effects were evaluated using MTT and clonogenic assay. The distribution of the phase in cell cycle was analyzed using flow cytometric analysis with propidium iodide staining. The expression of the transcription factor forkhead box M1 (FOXM1) was analyzed by reverse transcription-polymerase chain reaction and Western blotting. The expression levels of CDK1, Cdc25B, cyclin B and p27^KIP1 protein were detected using Western blotting.

RESULTS: Nine of the genistein analogues had more effective antitumor activity than genistein. Among the tested analogues, DFOG possessed the strongest activity against AGS and SGC-7901 cells in vitro. DFOG significantly inhibited the cell viability and colony formation of AGS and SGC-7901 cells. Moreover, DFOG efficaciously arrested the cell cycle in G2/M phase. DFOG decreased the expression of FOXM1 and its downstream genes, such as CDK1, Cdc25B, cyclin B, and increased p27^KIP1 at protein levels. Knockdown of FOXM1 by small interfering RNA before DFOG treatment resulted in enhanced cell growth inhibition in AGS cells. Up-regulation of FOXM1 by cDNA transfection attenuated DFOG-induced cell growth inhibition in AGS cells.

CONCLUSION: DFOG inhibits the growth of human gastric cancer cells by down-regulating the FOXM1 expression.

5-allyl-7-gen-difluoromethoxychrysin enhances TRAIL-induced apoptosis in human lung carcinoma A549 cells

Background

5-allyl-7-gen-difluoromethoxychrysin (AFMC) is a novel synthetic analogue of chrysin that has been reported to inhibit proliferation in various cancer cell lines. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anti-cancer agent.

Methods

The cytotoxicity of A549 and WI-38 cells were determined using colorimetry. Apoptosis was detected by flow cytometry (FCM) after propidium iodide (PI) fluorescence staining and agarose gel electrophoresis. Caspase activities were evaluated using enzyme-linked immunosorbent assay (ELISA).The expressions of DR4 and DR5 were analyzed using FCM and western blot.

Results

Subtoxic concentrations of AFMC sensitize human non-small cell lung cancer (NSCLC) A549 cells to TRAIL-mediated apoptosis. Combined treatment of A549 cells with AFMC and TRAIL significantly activated caspase-3, -8 and -9. The caspase-3 inhibitor zDEVD-fmk and the caspase-8 inhibitor zIETD-fmk blocked the apoptosis of A549 cells induced by co-treatment with AFMC and TRAIL. In addition, we found that treatment of A549 cells with AFMC significantly induced the expression of death receptor 5 (DR5). AFMC-mediated sensitization of A549 cells to TRAIL was efficiently reduced by administration of a blocking antibody or small interfering RNAs against DR5. AFMC also caused increase of the Sub-G1 cells by TRAIL treatment and increased the expression levels of DR5 in other NSCLC H460 and H157 cell lines. In contrast, AFMC-mediated induction of DR5 expression was not observed in human embryo lung WI-38 cells, and AFMC did not sensitize WI-38 cells to TRAIL-induced apoptosis.

Conclusions

AFMC synergistically enhances TRAIL-mediated apoptosis in NSCLC cells through up-regulating DR5 expression.

Chrysin promotes tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induced apoptosis in human cancer cell lines

Chrysin exists widely in plants, honey and propolis. The anti-cancer property of chrysin has been demonstrated though the molecular mechanism is not clear. In this study, we found that pre-treatment with chrysin could promote the cell death induced by TRAIL according to the morphological changes and appearance of sub-G1 peak in four human cancer cell lines. In HCT-116 cells, the results of flow cytometry analysis showed that the percentage of sub-G1 reached (38.89 ± 3.78) % when pre-treatment of chrysin was used at 40 μM, but that was only (2.53 ± 0.10) % in the untreated group and (13.22 ± 0.20) % in TRAIL alone group. The differences between the combination and the untreated or TRAIL alone group were all significant (P<0.05) and dose-dependent effect was obvious. Similar results were obtained in CNE1 cells. In the search of molecular mechanisms, we found that pre-treatment with chrysin could increase TRAIL-induced degradation of caspase 3, caspase 8, PARP proteins. Z-VAD-fmk, which is a pan-caspase inhibitor, could inhibit the apoptosis enhanced by the combination of chrysin and TRAIL. All data indicate that chrysin can enhance the apoptosis induced by TRAIL, and the apoptosis is caspase-dependent and related to the activation of caspase 8.

8-bromo-7-methoxychrysin-induced apoptosis of hepatocellular carcinoma cells involves ROS and JNK

AIM: To investigate whether the apoptotic activities of 8-bromo-7-methoxychrysin (BrMC) involve reactive oxygen species (ROS) generation and c-Jun N-terminal kinase (JNK) activation in human hepatocellular carcinoma cells (HCC).

METHODS: HepG2, Bel-7402 and L-02 cell lines were cultured in vitro and the apoptotic effects of BrMC were evaluated by flow cytometry (FCM) after propidium iodide (PI) staining, caspase-3 activity using enzyme-linked immunosorbent assay (ELISA), and DNA agarose gel electrophoresis. ROS production was evaluated by FCM after dichlorodihydrofluorescein diacetate (DCHF-DA) probe labeling. The phosphorylation level of JNK and c-Jun protein was analyzed by Western blotting.

RESULTS: FCM after PI staining showed a dose-dependent increase in the percentage of the sub-G1 cell population (P < 0.05), reaching 39.0% ± 2.8% of HepG2 cells after 48 h of treatment with BrMC at 10 μmol/L. The potency of BrMC to HepG2 and Bel-7402 (32.1% ± 2.6%) cells was found to be more effective than the lead compound, chrysin (16.2% ± 1.6% for HepG2 cells and 11.0% ± 1.3% for Bel-7402 cell) at 40 μmol/L and similar to 5-flurouracil (33.0% ± 2.1% for HepG2 cells and 29.3% ± 2.3% for Bel-7402 cells) at 10 μmol/L. BrMC had little effect on human embryo liver L-02 cells, with the percentage of sub-G1 cell population 5.4% ± 1.8%. Treatment of HepG2 cells with BrMC for 48 h also increased the levels of active caspase-3, in a concentration-dependent manner. z-DEVD-fmk, a caspase-3-specific inhibitor, prevented the activation of caspase-3. Treatment with BrMC at 10 μmol/L for 48 h resulted in the formation of a DNA ladder. Treatment of cells with BrMC (10 μmol/L) increased mean fluorescence intensity of DCHF-DA in HepG2 cells from 7.2 ± 1.12 at 0 h to 79.8 ± 3.9 at 3 h and 89.7 ± 4.7 at 6 h. BrMC did not affect ROS generation in L-02 cells. BrMC treatment failed to induce cell death and caspase-3 activation in HepG2 cells pretreated with N-acetylcysteine (10 mmol/L). In addition, in HepG2 cells treated with BrMC (2.5, 5.0, 10.0 μmol/L) for 12 h, JNK activation was observed. Peak JNK activation occurred at 12 h post-treatment and this activation persisted for up to 24 h. The expression of phosphorylated JNK and c-Jun protein after 12 h with BrMC-treated cells was inhibited by N-acetylcysteine and SP600125 pre-treatment, but GW9662 had no effect. SP600125 substantially reduced BrMC-induced cell death and caspase-3 activation of HepG2 cells. N-acetylcysteine and GW9662 also attenuated induction of cell death and caspase-3 activation in HepG2 cells treated with BrMC.

CONCLUSION: BrMC induces apoptosis of HCC cells by ROS generation and sustained JNK activation.

Apoptotic effects of chrysin in human cancer cell lines

Chrysin is a natural flavonoid currently under investigation due to its important biological anti-cancer properties. In most of the cancer cells tested, chrysin has shown to inhibit proliferation and induce apoptosis, and is more potent than other tested flavonoids in leukemia cells, where chrysin is likely to act via activation of caspases and inactivation of Akt signaling in the cells. Moreover, structure-activity relationships have revealed that the chemical structure of chrysin meets the key structural requirements of flavonoids for potent cytotoxicity in leukemia cells. It is possible that combination therapy or modified chrysin could be more potent than single-agent use or administration of unmodified chrysin. This study may help to develop ways of improving the effectiveness of chrysin in the treatment of leukemia and other human cancers in vitro.

The effects of Stichopus japonicus acid mucopolysaccharide on the apoptosis of the human hepatocellular carcinoma cell line HepG2

In this study, the effects of Stichopus japonicus acid mucopolysaccharide (SJAMP) on the apoptosis of the human hepatocellular carcinoma cell line HepG2 were examined. The underlying mechanism was investigated by determining the effect of SJAMP on the expression of Bcl-2 and nm23-H1 genes in HepG2 cells. In vitro cultured HepG2 cells were treated with different concentrations of SJAMP. The dimethylthiazol (MTT) assay was used to determine the inhibition of cell proliferation. Expression of Bcl-2 and nm23-H1 genes was determined by Western blot analysis. The results showed that SJAMP inhibited the proliferation of HepG2 cells in a time- and dose-dependent manner, SJAMP induced apoptosis in HepG2 cells, and SJAMP decreased the expression of Bcl-2 and increased the expression of nm23-H1. We conclude that SJAMP inhibits the proliferation of HepG2 cells by inducing apoptosis. These results provide a theoretical basis for the utilization of SJAMP as a potential antitumor component for the treatment of hepatocellular carcinoma.

Induction of apoptosis in human liver carcinoma HepG2 cell line by 5-allyl-7-gen-difluoromethylenechrysin

AIM: To investigate the effect of 5-allyl-7-gen-difluoromethylenechrysin (ADFMChR) on apoptosis of human liver carcinoma HepG2 cell line and the molecular mechanisms involved.

METHODS: HepG2 cells and L-02 cells were cultured in vitro and the inhibitory effect of ADFMChR on their proliferation was measured by MTT assay. The apoptosis of HepG2 cells was determined by flow cytometry (FCM) using propidium iodide (PI) fluorescence staining. DNA ladder bands were observed by DNA agarose gel electrophoresis. The influence of ADFMChR on the proxisome proliferator-activated receptor γ (PPARγ), NF-κB, Bcl-2 and Bax protein expression of HepG2 cells were analyzed by Western blotting.

RESULTS: MTT assay showed that ADFMChR significantly inhibited proliferation of HepG2 cells in a dose-dependent manner, with little effect on growth of L-02 cells, and when IC₅₀ was measured as 8.45 &mgr;mol/L and 191.55 &mgr;mol/L respectively, the potency of ADFMChR to HepG2 cells, was found to be similar to 5-fluorouracil (5-FU, IC₅₀ was 9.27 &mgr;mol/L). The selective index of ADFMChR cytotoxicity to HepG2 cells was 22.67 (191.55/8.45), higher than 5-FU (SI was 7.05 (65.37/9.27). FCM with PI staining demonstrated that the apoptosis rates of HepG2 cells treated with 3.0, 10.0 and 30.0 &mgr;mol/L ADFMChR for 48 h were 5.79%, 9.29% and 37.8%, respectively, and were significantly higher when treated with 30.0 &mgr;mol/L ADFMChR than when treated with 30.0 &mgr;mol/L ChR (16.0%) (P < 0.05) and were similar to those obtained with 30.0 &mgr;mol/L 5-FU (41.0%). DNA agarose gel electrophoresis showed that treatment of HepG2 cells with 10.0 &mgr;mol/L ADFMChR for 48 h and 72 h resulted in typical DNA ladders which could be reversed by 10.00 &mgr;mol/L GW9662, a blocker of PPARγ. Western blotting analysis revealed that after 24 h of treatment with 3.0, 10.0, 30.0 &mgr;mol/L ADFMChR, PPARγ and Bax protein expression in HepG2 cells increased but Bcl-2 and NF-κB expression decreased; however, pre-incubation with 10.0 &mgr;mol/L GW9662 could efficiently antagonize and weaken the regulatory effect of 3.0, 30.0 &mgr;mol/L ADFMChR on PPARγ and NF-κB protein expression in HepG2 cells.

CONCLUSION: ADFMChR induces apoptosis of HepG2 cell lines by activating PPARγ, inhibiting protein expression of Bcl-2 and NF-κB, and increasing Bax expression.