Citral inhibits N‐nitrosodiethylamine‐induced hepatocellular carcinoma via modulation of antioxidants and xenobiotic‐metabolizing enzymes

Hepatocellular carcinoma (HCC) ranks the sixth position among various cancers worldwide. Recent research shows that natural and dietary compounds possess many therapeutic effects. Citral is a monoterpene aldehyde that contains geranial and neral. The present study was considered to study the role of citral against N‐nitrosodiethylamine (NDEA)‐induced HCC via modulation of antioxidants and xenobiotic‐metabolizing enzymes in vivo. NDEA‐alone‐administered group II animals profoundly showed increased tumor incidence, reactive oxygen species, liver marker enzyme levels, serum bilirubin levels, tumor markers of carcinoembryonic antigen, α‐fetoprotein, proliferative markers of argyrophilic nucleolar organizing regions, proliferating cell nuclear antigen (PCNA) expressions, phase I xenobiotic‐metabolic enzymes and simultaneously decreased antioxidants, and phase II enzymes levels. Citral (100 mg/kg b.w.) treatment significantly reverted the levels in group III cancer‐bearing animals when compared to group II cancer‐bearing animals. In group IV animals, citral‐alone administration did not produce any adverse effect during the experimental condition. Based on the results, citral significantly inhibits the hepatocellular carcinogenesis through restoring the antioxidants and phase II xenobiotic‐enzyme levels; thereby, it strongly proves as an antiproliferative agent against rat HCC.     

白藜芦醇下调肌球蛋白轻链激酶过表达抑制大鼠肝肿瘤增生

目的研究白藜芦醇(Res)通过影响肌球蛋白轻链激酶(MLCK)在肝脏中表达水平抑制原发性肝癌的增生。方法采用口服饮水中含0.9 mmol.L-1二乙基亚硝胺10周诱发原发性肝肿瘤;20周后,治疗组大鼠每天给予肌肉注射Res 50 mg.kg-16周;26周后,处死大鼠,计数肝表面癌结节数,称量和计算体重、肝重,肝/体重比,测定血清中甲胎蛋白的变化,观察大鼠肝脏的病理改变;用免疫组化和Westernblot法检测Res对MLCK的表达影响,用细胞凋亡试剂盒检测Res诱导肿瘤细胞的凋亡。结果 Res治疗组大鼠和模型组大鼠相比,体重增加,肝肿瘤结节数和肝/体重比和血清甲胎蛋白值减少或降低(P<0.05)。模型组大鼠肝组织MLCK的表达水平明显增加,而Res治疗可逆转MLCK的过表达水平,并诱导肿瘤细胞凋亡。结论 Res通过下调肝组织MLCK的表达水平诱导凋亡,抑制大鼠肝肿瘤细胞的增生。     

Chemopreventive evaluation of Tephrosia purpurea against N-nitrosodiethylamine-induced hepatocarcinogenesis in Wistar rats

Objectives The chemopreventive potential of Tephrosia purpurea extract (TPE) on N‐nitrosodiethylamine (NDEA)‐induced hepatocellular carcinoma (HCC) in Wistar rats was assessed. Methods HCC was induced by a single intraperitoneal injection of NDEA (200 mg/kg) followed by subcutaneous injections of CCl₄ (3 ml/kg per week) for six weeks. After administration of the carcinogen, 200 and 400 mg/kg TPE were administered orally once a day throughout the study. Key findings The levels of liver cancer markers, including α‐fetoprotein and carcinoembryonic antigen, were substantially increased by NDEA treatment. TPE treatment significantly reduced liver injury and restored the entire liver cancer markers. Additionally, TPE markedly normalized the activity of antioxidant enzymes, namely lipid peroxidation, reduced glutathione, catalase, superoxide dismutase, glutathione peroxidase and glutathione‐S‐transferase in the liver of NDEA‐treated rats. Treatment with TPE significantly reduced the nodule incidence and multiplicity in the carcinogen‐bearing rats. Histological observations of the liver tissues correlated with the biochemical observations. Conclusions These findings powerfully support that T. purpurea prevented lipid peroxidation, suppressed the tumour burden, and promoted enzymatic and nonenzymatic antioxidant defence systems during NDEA‐induced hepatocarcinogenesis. This might have been due to modulating the antioxidant defence status, which contributed to its anticarcinogenic potential.     

Apoptosis in stages of mouse hepatocarcinogenesis: failure to counterbalance cell proliferation and to account for strain differences in tumor susceptibility.

C3H/He and B6C3F1 show much higher liver cancer susceptibility than C57BL/6J mice. We studied the hypothesis that this difference might result from failure of apoptosis. Hepatocarcinogenesis was induced by a single dose of N-nitrosodiethylamine (NDEA), followed by phenobarbital (PB) for up to 90 weeks. We observed (1) earlier appearance of putative preneoplastic foci (PPF), hepatocellular adenoma (HCA), and carcinoma (HCC) in C3H/He than in C57Bl/6J mice and (2) an increase of hepatocellular DNA synthesis in C3H/He and C57Bl/6J mice, compared to normal liver, via PPF and HCA to HCC. PB enhanced DNA synthesis and growth of PPF, in the C3H/He strain only, and of HCA and HCC of both strains. Apoptoses were rare in unaltered livers as well as in preneoplastic lesions, but tended to increase in HCA and HCC of both strains. PB lowered apoptotic activity in PPF of C3H/He mice, but enhanced it in HCA and HCC of C57Bl/6J mice at late stages. In conclusion, the strain difference in growth rates of PPF and tumors is largely determined by higher rates of cell proliferation in C3H/He mice, with and without promotion by PB. Moreover, in C57Bl/6J mice the promoting effect of PB was restricted to HCA and HCC and was not seen in PPF. Apoptosis was generally low and was not a major cause of the strain difference in tumor susceptibility. In contrast with rat liver, inhibition of apoptosis appears to be a minor determinant of tumor promotion in mice.     

Diosmin abrogates chemically induced hepatocarcinogenesis via alleviation of oxidative stress,hyperproliferative and inflammatory markers in murine model

Hepatocellular carcinoma (HCC) is a global health problem and is fourth leading cause of cancer related deaths. Now-a-days new strategies have been accounted for the chemoprevention of liver cancer due to ineffective traditional treatments against HCC. In the present study, we have shown that diosmin attenuates 2-AAF induced hepatic toxicity and early tumor promotion markers (ODC, PCNA and Ki67), its chemopreventive efficacy against DEN initiated and 2-AAF promoted hyper-proliferation and hepatocarcinogenesis in Wistar rats. Hepatocarcinogenesis has been characterized by the presence of apparent hepatic nodules, hepatic proliferation, elevation in the levels of proliferation markers (PCNA and Ki67), and inflammatory markers (COX-2 and iNOS) in DEN and 2-AAF administered rats. Protective efficacy of diosmin has been investigated in terms of its potential in reducing the percentage of visible hepatic nodules and the restoration of early tumor markers (PCNA, Ki67 and ODC), oxidative stress biomarkers, serum cytotoxicity markers (AST, ALT and LDH), cell necrosis markers (NF-kappa B and TNF-α) and inflammatory markers (COX-2 and iNos). Our study demonstrates that the inhibition of cell proliferation and down regulation of inflammatory markers may be, at least in part, the underlying mechanisms related to the liver tumor inhibition by diosmin. The present study allows us to conclude that diosmin being a dietary supplement, could be used as chemopreventive agent to prevent hepatocarcinogenesis.     

Effect of 5-methoxypsoralen (5-MOP) on cell apoptosis and cell cycle in human hepatocellular carcinoma cell line.

The chemopreventive role of 5-methoxypsoralen (5-MOP) in the human hepatocellular carcinoma (HCC) cell line was investigated by studying the regulation of proliferation and apoptosis in HCC (J5) cells. Morphological analysis, cell viability assay, DNA analysis and cell-cycle analysis suggest that there are at least three modes of the suppressive effects shown by 5-MOP: (a) kills J5 cells directly; (b) induces apoptosis by arresting J5 cells at the G2/M phase in the cell cycle; (c) induces apoptosis through an independent pathway with cell-cycle arrest at 24-72 h of exposure. Further immunoblot analysis demonstrated that inhibition of cyclin B1 by 5-MOP may play an important role in G2/M arrest of J5 cells and provides an additional way to prevent cells from entering the M phase and undergoing apoptosis. 5-MOP therefore appears to exert its anticarcinogenic properties by cytotoxic effect, inducing apoptosis and inhibiting proliferation in the human hepatocellular carcinoma cell line.     

The protective mechanism of Nigella sativa against diethylnitrosamine‐induced hepatocellular carcinoma through its antioxidant effect and EGFR/ERK1/2 signaling

A wide variety of natural products have powerful chemopreventive effects due to their antioxidant, antimutagenic, and anti‐inflammatory activities that enable them to arrest cell proliferation in several cancer models. In the present study, we shed light on the protective mechanism of Nigella sativa extract against diethylnitrosamine (DENA)‐induced preneoplastic stage of hepatocellular carcinoma (HCC) in rats. We studied the extract effect on EGFR/ERK1/2 signaling pathway as one of the major signaling pathways controlling cell proliferation during hepatocarcinogenesis as well as the investigation of its antioxidant activity. The study also compared the effects of NSEE to those of (thymoquinone) TQ and silymarin as hepatoprotective substances. Rats received daily doses of NSEE (150, 250, 350 mg/kg BW), a dose per three alternative days/week of TQ (20 mg/kg BW) and a daily dose of silymarin (100 mg/kg BW). The doses were administered orally by gavage for 12 days before DENA and CCl₄ administration, and then the supply of NSEE, TQ or silymarin was continued until the end of the experiment (16 weeks). DENA administration activated EGFR/ERK1/2 signaling and caused a significant increase in P‐EGFR and P‐ERK1/2 as well as a significant up‐regulation of expression of target genes such as PCNA, c‐fos and Bcl2, which indicated the increase in cell proliferation. Furthermore, a significant elevation in alpha‐fetoprotein (AFP) and hepatic enzymes was observed in DENA‐treated rats in addition to a decrease in the antioxidant status. The protection with NSEE, TQ, or silymarin has the potential to inhibit the EGFR/ERK1/2 activation and improve the antioxidant status. Moreover, the action of NSEE against the hepatocarcinogenesis was supported by high antioxidant activity and the histopathological observations of the liver. These data suggest that NSEE has a chemopreventive role in DENA‐induced HCC through the inhibition of the EGFR/ERK1/2 signaling pathway and their target genes in addition to its role as an antioxidant.     

N-(methylamino)isobutyric acid inhibits proliferation of CFSC-2C hepatic stellate cells

Activation of hepatic stellate cells (HSCs) involves the induction of ECM protein synthesis and rapid cell proliferation. Thus, agents that interfere with either process could potentially mitigate the development of liver disease by reducing the synthesis of proteins associated with fibrosis or by reducing the number of activated HSC. Previously, we described that the non-metabolizable amino acid analog N-(methylamino)isobutyric acid (MeAIB) reduced hepatic collagen content of rats in a model of CCl(4)-induced liver injury, and in vitro studies using CFSC-2G cells indicated that MeAIB directly reduced collagen synthesis. However, the MeAIB-mediated reduction of hepatic collagen, in vivo, following liver injury was associated with a decrease in hepatic alpha-smooth muscle actin (alpha-SMA) which suggested that MeAIB also inhibited the activation of HSCs. Because HSC activation is inseparable from proliferation, the purpose of this study was to examine the effect of MeAIB treatment on the proliferation of HSCs in an in vitro model utilizing CFSC-2G cell cultures. In these studies, MeAIB effectively inhibited the proliferation of CFSC-2G cells by interfering with the progression of the cells through the G(1)-phase of the cell cycle which delayed entry into S-phase. MeAIB prevented the phosphorylation of p70S6 kinase (p70S6K) at Thr389 and reduced the phosphorylation at Thr421/Ser424. Because p70S6K is required for G(1)-cell cycle progression and is known to be regulated by nutrient availability, this correlates well with MeAIB interfering with the proliferation of CFSC-2G HSCs. In addition, the rate of protein synthesis was reduced by MeAIB treatment following mitogenic stimulation, which agrees with a p70S6K-mediated reduction in translation. These data are consistent with MeAIB inhibiting the proliferation of CFSC-2G cells by altering the mitogen activated pathway(s) leading to phosphorylation of p70S6K by a yet to be described mechanism.     

橘红素上调Cyclin B1和抑制ERK磷酸化诱导人胃癌AGS细胞周期阻滞

目的探讨橘红素对人胃癌AGS细胞增殖和周期的作用及其机制。方法采用MTT法观察橘红素对人AGS胃癌细胞增殖的作用;流式细胞仪检测橘红素对细胞周期的影响;Western blot检测橘红素对Cyclin B1、Cyclin D1、Cyclin E1和ERK、p-ERK蛋白表达的影响。结果橘红素可明显抑制AGS胃癌细胞的增殖(P<0.01),呈时间和剂量依赖性。橘红素作用于AGS细胞24 h,S期细胞百分比明显增高,与对照组比较差异有统计学意义(P<0.01);作用48和72 h,S期阻滞消失,G2/M期细胞百分比增高(P<0.05,P<0.01)。作用48 h,橘红素可上调Cyclin B1蛋白的表达(P<0.05,P<0.01),对Cyclin D1和Cyclin E1蛋白表达无明显影响;对ERK蛋白表达无影响,可降低p-ERK蛋白的表达(P<0.01),且呈剂量依赖性。结论橘红素可明显抑制人AGS胃癌细胞的增殖,使细胞阻滞于S期和G2/M期,主要机制可能是通过抑制ERK磷酸化和上调CyclinB1蛋白表达。     

Retinoic acid regulates cell cycle genes and accelerates normal mouse liver regeneration

All-trans retinoic acid (RA) is a potent inducer of regeneration. Because the liver is the principal site for storage and bioactivation of vitamin A, the current study examines the effect of RA in mouse hepatocyte proliferation and liver regeneration. Mice that received a single dose of RA (25 μg/g) by oral gavage developed hepatomegaly with increased number of Ki67-positive cells and induced expression of cell cycle genes in the liver. DNA binding data revealed that RA receptors retinoic acid receptor β (RARβ) and retinoid x receptor α (RXRα) bound to cell cycle genes Cdk1, Cdk2, Cyclin B, Cyclin E, and Cdc25a in mice with and without RA treatment. In addition, RA treatment induced novel binding of RARβ/RXRα to Cdk1, Cdk2, Cyclin D, and Cdk6 genes. All RARβ/RXRα binding sites contained AGGTCA-like motifs. RA treatment also promoted liver regeneration after partial hepatectomy (PH). RA signaling was implicated in normal liver regeneration as the mRNA levels of RARβ, Aldh1a2, Crabp1, and Crbp1 were all induced 1.5 days after PH during the active phase of hepatocyte proliferation. RA treatment prior to PH resulted in early up-regulation of RARβ, Aldh1a2, Crabp1, and Crbp1, which was accompanied by an early induction of cell cycle genes. Western blotting for RARβ, c-myc, Cyclin D, E, and A further supported the early induction of retinoid signal and cell proliferation by RA treatment. Taken together, our data suggest that RA may regulate cell cycle progression and accelerates liver regeneration. Such effect is associated with an early induction of RA signaling, which includes increased expression of the receptor, binding proteins, and processing enzyme for retinoids.     

4-氨基-2-三氟甲基苯基维甲酸酯对K562细胞分化和细胞周期的影响

目的本研究探讨新型维甲酸衍生物4-氨基-2-三氟甲基苯基维甲酸酯(4-amino-2-trifluoromethyl-phenyl retinate,ATPR)对K562细胞株的抑制增殖和诱导分化活性并对其机制进行研究。方法ATPR作用于K562细胞3d后,通过MTT法检测细胞的增殖,NBT还原实验法分析细胞的分化指标,瑞氏染色法在油镜下观察加药前后细胞形态学变化,FCM检测分析细胞周期,RT-PCR法检测cyclinE、cyclinD1、CDK2、CDK4、CDK6、p21cip1、p27kip1、p57kip2和PCNA mRNA的变化情况。Western blot法检测cyclin D1和CDK4蛋白表达的改变。结果ATPR呈浓度依赖性抑制K562细胞增殖的作用。ATPR诱导分化活性表现为NBT阳性细胞率增加,油镜下观察K562细胞有分化成熟的改变,G0/G1期细胞表达量增加,S期细胞表达量减少,呈G1期阻滞。RT-PCR检测发现cyclin E、cyclin D1、CDK2、CDK4、CDK6表达减少,PC-NA、P21cip1、P27kip1改变不明显,P57kip2表达增加。Western blot检测cyclin D1和CDK4蛋白表达减少。结论ATPR有较强的抑制K562细胞增殖并诱导其分化的活性,并通过上调P57kip2的表达,抑制Cyclin-CDK激酶复合物,发挥细胞周期阻滞的作用。     

Effects of diosgenin on cell proliferation induced by IGF-1 in primary human thyrocytes

Others and our previous studies showed that the increase of IGF-1 was involved in the formation of goiter. Our aim here was to evaluate the possible effects of diosgenin on cell proliferation induced by IGF-1 in primary human thyroid cells. The cells were treated with or without different concentrations of diosgenin in the present or absent of IGF-1 for 24, 48 and 72 h, respectively. Cell viability was determined by MTT, and cell proliferation was tested by EdU assay, and cell cycle analysis was performed by FACS. In addition, Cyclin D1 and B1 protein expression was tested by Western Blotting, respectively. We found that IGF-1 promoted cell cycle progression to S phase and increased the primary human thyroid cells proliferation. Diosgenin decreased the protein expression of cyclin D1 and resulted in cell G(0)/G(1) arrest. Importantly, when the human thyrocytes were exposed to diosgenin in the present of IGF-1, the IGF-1 inducing proliferation was significantly decreased and the proportion of the cells in G(0)/G(1) phase was increased, while that of S phase was decreased. This study shows that diosgenin inhibited cell proliferation, caused G(0)/G(1) arrest, and could inhibit cell proliferation induced by IGF-1 in primary human thyroid cells.     

Gene expression profiling reveals underlying molecular mechanisms of the early stages of tamoxifen-induced rat hepatocarcinogenesis

Tamoxifen is a widely used anti-estrogenic drug for chemotherapy and, more recently, for the chemoprevention of breast cancer. Despite the indisputable benefits of tamoxifen in preventing the occurrence and re-occurrence of breast cancer, the use of tamoxifen has been shown to induce non-alcoholic steatohepatitis, which is a life-threatening fatty liver disease with a risk of progression to cirrhosis and hepatocellular carcinoma. In recent years, the high-throughput microarray technology for large-scale analysis of gene expression has become a powerful tool for increasing the understanding of the molecular mechanisms of carcinogenesis and for identifying new biomarkers with diagnostic and predictive values. In the present study, we used the high-throughput microarray technology to determine the gene expression profiles in the liver during early stages of tamoxifen-induced rat hepatocarcinogenesis. Female Fisher 344 rats were fed a 420 ppm tamoxifen containing diet for 12 or 24 weeks, and gene expression profiles were determined in liver of control and tamoxifen-exposed rats. The results indicate that early stages of tamoxifen-induced liver carcinogenesis are characterized by alterations in several major cellular pathways, specifically those involved in the tamoxifen metabolism, lipid metabolism, cell cycle signaling, and apoptosis/cell proliferation control. One of the most prominent changes during early stages of tamoxifen-induced hepatocarcinogenesis is dysregulation of signaling pathways in cell cycle progression from the G(1) to S phase, evidenced by the progressive and sustained increase in expression of the Pdgfc, Calb3, Ets1, and Ccnd1 genes accompanied by the elevated level of the PI3K, p-PI3K, Akt1/2, Akt3, and cyclin B, D1, and D3 proteins. The early appearance of these alterations suggests their importance in the mechanism of neoplastic cell transformation induced by tamoxifen.     

Osthole induced apoptosis in human normal liver cells by regulating cell proliferation and endoplasmic reticulum stress

Osthole (Ost) is often used in treatment for cancer, inflammation and rheumatism in clinic. However, Ost‐induced liver injury has been reported. In this study, we aim to investigate the possible mechanism of Ost‐induced hepatotoxicity in human normal liver cells (L02). When cells were exposed to Ost, the cell viability was decreased and apoptosis rate increased, the intracellular markers of oxidative stress were changed. Simultaneously, Ost altered apoptotic related proteins levels, including Bcl‐2, Bax, Cleaved‐Caspase‐9/‐8/‐3, and Pro‐Caspase‐3/‐8. In addition, Ost enhanced the levels of endoplasmic reticulum (ER) stress proteins (GRP78/Bip, CHOP, Caspase‐4, IRE1α, PERK, JNK, P‐JNK, and ATF4), decreased the cell proliferation and cycle‐associated protein (Phospho‐Histone H3, P‐Cdc25C, Cdc25C, P‐Cdc2, Cdc2, and Cyclin B1) level. The results show that Ost has toxic effects on L02 cells. Furthermore, it induces apoptosis by inhibiting cell proliferation, arresting cell cycle at the G2/M phase and activating ER stress.     

P21-activated kinase 5 plays essential roles in the proliferation and tumorigenicity of human hepatocellular carcinoma

Aim： To investigate the roles of P21-activated kinase 5 （PAK5） in proliferation and tumorigenicity of human hepatocellular carcinoma （HCC）.
Methods： HCC and matched paraneoplastictis tissue samples were obtained from 30 patients. Human HCC cell lines SMMC7721, HepG2, Hep3B, SK-HEP-1, Huh-7, and liver cell line HL-7702 were examined. The expression of PAK5 gene was studied using real-time qPCR and Western blotting. Cell proliferation was quantified with the MTT assay. Cell cycle was analyzed with flow cytometry. The
tumorigenicity of Lv-shRNA-transfected HepG2 cells was evaluated in BALB/cA nude mice.

Results： The mRNA level of PAK5 was significantly higher in 25 out of 30 HCC samples compared to the matched paraneoplastic
tissues. The HCC cell lines showed varying expression of PAK5 protein, and the highest level was found in the HepG2 cells. PAK5 gene silencing in HepG2 cells markedly reduced the cell proliferation and colony formation, and induced cell cycle arrest in the G1 phase. Furthermore, PAK5 gene silencing suppressed the tumor formation in nude mice, and significantly decreased the expression of HCC-related genes Cyclin D1 and beta-catenin.

Conclusion： PAK5 may play essential roles in the initiation and progression of human HCC. Thus, it may be an effective therapeutic target or perhaps serve as a clinical diagnostic or prognostic marker in human HCC.     

Evaluation of hepatic and thyroid responses in male Sprague Dawley rats for up to eighty-four days following seven days of dietary exposure to potassium perfluorooctanesulfonate

In a prior 28-day dietary study in rats with 20 and 100 ppm K? PFOS, activation of PPARα and CAR/PXR were concluded to be etiological factors in K? PFOS-induced hepatomegaly and hepatic tumorigenesis. The objective of this study was to evaluate persistence/resolution of K? PFOS-induced, liver-related effects in male Sprague Dawley rats following a 7-day dietary exposure to K? PFOS at 20 or 100 ppm. Groups of 10 rats per treatment were observed on recovery Day(s) 1, 28, 56, and 84 following treatment. Changes consistent with hepatic PPARα and CAR/PXR activation noted on recovery Day 1 included: increased liver weight; decreased plasma cholesterol, alanine aminotransferase, and triglycerides; decreased liver DNA concentration and increased hepatocellular cytosolic CYP450 concentration; increased liver activity of acyl CoA oxidase, CYP4A, CYP2B, and CYP3A; increased liver proliferative index and decreased liver apoptotic index; decreased hepatocellular glycogen-induced vacuoles; increased centrilobular hepatocellular hypertrophy. Most effects resolved to control levels during recovery. Effects on plasma cholesterol, hepatocellular cytosolic CYP450 concentrations, liver apoptotic index, CYP3A, and centrilobular hepatocellular hypertrophy persisted through the end of the recovery period. Thyroid parameters (histology, apoptosis, and proliferation) were unaffected at all time points. Mean serum PFOS concentrations on recovery Day 1 were 39 and 140 μg/mL (20 ppm and 100 ppm K? PFOS, respectively), decreasing to 4 and 26 μg/mL by recovery Day 84. Thus, hepatic effects in male rats resulting from K? PFOS-induced activation of PPARα and CAR/PXR resolved slowly or were still present after 84-days following a 7-day dietary treatment, consistent with the slow elimination rate of PFOS.     

Stem cell research in hepatocellular carcinoma

The traditional view that adult human liver tumors, mainly hepatocellular carcinoma (HCC), arise from mature cell types has been challenged in recent decades. The results of several studies suggest that HCC can be derived from liver stem cells. There are four levels of cells in the liver stem cell lineage: hepatocytes, hepatic stem cells/oval cells, bone marrow stem cells and hepato-pancreas stem cells. However, whether HCC is resulted from the differentiation block of stem cells and, moreover, which liver stem cell lineage is the source cell of hepatocarcinogenesis remain controversial. In this review, we focus on the current status of liver stem cell research and their roles in carcinogenesis of HCC, in order to explore new approaches for stem cell therapy of HCC.     

Molecular pathway for thymoquinone-induced cell-cycle arrest and apoptosis in neoplastic keratinocytes

Thymoquinone (TQ), the most abundant constituent in black seed, was shown to possess potent chemopreventive activities against DMBA-initiated TPA-promoted skin tumors in mice. Despite the potential interest in TQ as a skin antineoplastic agent, its mechanism of action has not been examined yet. Using primary mouse keratinocytes, papilloma (SP-1) and spindle (I7) carcinoma cells, we studied the cellular and molecular events involved in TQ's antineoplastic activity. We show that non-cytotoxic concentrations of TQ reduce the proliferation of neoplastic keratinocytes by 50%. The sensitivity of cells to TQ treatment appears to be stage dependent such that papilloma cells are twice as sensitive to the growth inhibitory effects of TQ as the spindle cancer cells. TQ treatment of SP-1 cells induced G0/G1 cell-cycle arrest, which correlated with sharp increases in the expression of the cyclin-dependent kinase inhibitor p16 and a decrease in cyclin D1 protein expression. TQ-induced growth inhibition in I7 cells by inducing G2/M cell-cycle arrest, which was associated with an increase in the expression of the tumor suppressor protein p53 and a decrease in cyclin B1 protein. At longer times of incubation, TQ induced apoptosis in both cell lines by remarkably increasing the ratio of Bax/Bcl-2 protein expression and decreasing Bcl-xL protein. The apoptotic effects of TQ were more pronounced in SP-1 than in I7 cells. Collectively, these findings support a potential role for TQ as a chemopreventive agent, particularly at the early stages of skin tumorigenesis.     

自噬对肝癌HepG2细胞增殖及对细胞周期影响的研究

目的研究用诱导肝癌HepG2细胞自噬与抑制肝癌HepG2细胞自噬的方法检测自噬对肝癌HepG2细胞增殖的影响,阐明细胞自噬的发生与细胞周期的关系。方法常规培养肝癌HepG2细胞,应用MTT比色法和流式细胞仪检测肝癌HepG2细胞增殖抑制率及细胞周期各时相的变化。结果自噬诱导剂雷帕霉素组的肝癌HepG2细胞抑制率明显高于对照组（P〈0.05）,对照组的肝癌HepG2细胞抑制率明显高于自噬抑制剂3-MA组（P〈0.05）;流式细胞仪分析示自噬诱导剂雷帕霉素组细胞周期中G1期细胞增多,S期细胞减少,G2/M期细胞相对增多（P〈0.05）。自噬抑制剂3-MA组细胞周期中G1期细胞减少,S期细胞增多,G2/M期细胞相对减少（P〈0.05）。结论自噬对肝癌HepG2细胞增殖有抑制作用,自噬不利于肝癌HepG2细胞成活。肝癌HepG2细胞自噬的发生多停留在细胞周期的G1期。