TGF-β1/SMAD SIGNALING PATHWAY MEDIATES p53-DEPENDENT APOPTOSIS IN HEPATOMA CELL LINES

Objective To determine whether transforming growth factor betal (TGF-β1)/Smad signaling pathway mediates p53-dependent apoptosis in hepatoma cell lines.Methods Three human hepatic carcinoma cell lines, HepG2, Huh-7, and Hep3B, were used in this study.TGF-β1-induced apoptosis in hepatic carcinoma cell lines was analyzed using TUNEL assay.For identifying the mechanism of apoptosis induced by TGF-β1, cell lines were transfected with a TGF-β1-inducible luciferase reportor plasmid containing Smad4 binding elements.After transfection, cells were treated with TGF-β1, then assayed for luciferase activity.Results The apoptosis rate of HepG2 cell lines (48.51%± 8.21%) was significantly higher than control ( 12.72%±2.18%, P<0.05).But TGF-β1 was not able to induce apoptosis of Huh-7 and Hep3B cell lines.The relative luciferase activity of TGF-β1-treated HepG2 cell lines (4.38) was significantly higher than control (1.00, P< 0.05).But the relative luciferase activity of TGF-β1-treated Huh-7 and Hep3B cell lines less increased compared with control.Conclusions HepG2 cells seem to be highly susceptible to TGF-β1-induced apoptosis compared with Hep3B and Huh-7 cell lines.Smad4 is a central mediator of TGF-β1 signaling transdution pathway.TGF-β1/Smad signaling pathway might mediate p53-dependent apoptosis in hepatoma cell lines.

The role of Dectin-1/Raf-1 signal cascade in innate immune of human corneal epithelial cells against Aspergillus fumigatus infection

AIM： To investigate the expression of the v-raf-1murine leukemia viral oncogene homolog 1（Raf-1） and its role in the innate immune response of human corneal epithelial cells（HCECs） infected by Aspergillus fumigatus.METHODS： HCECs were cultured in vitro.They were randomly divided into 4 groups,including control group,Aspergillus fumigatus group,GW5074（an inhibitor of Raf-1） group and Laminarin [an inhibitor of Dendriti-cell-associated C-type lectin 1（Dectin-1）] group.The protein expression level of total Raf-1 and p-Raf-1 was measured by Western blot.The expression of IL-6 and IL-8 m RNA in each group was detected by real-time polymerase chain reaction.RESULTS： In Aspergillus fumigatus group,total Raf-1 protein levels in HCECs remained unchanged at 5,15,30 and 45min after infection,while p-Raf-1 expression was significantly enhanced at 30 min after infection compared with control group.However,the expression of p-Raf-1 was apparently declined after treated with GW5074 or Laminarin compared with Aspergillus fumigatus group.The expression levels of IL-6,IL-8 m RNA were significantly increased after stimulation with fumigatus compared with control group.Pre-treated with GW5074 significantly inhibited Aspergillus fumigatus-induced upregulation of IL-8 and IL-6.CONCLUSION： Aspergillus fumigatus stimulation can elevate the expression of p-Raf-1 in HCECs in vitro.Dectin-1/Raf-1 signal pathway may play a role on regulating the expression of inflammatory cytokines,including IL-6 and IL-8.

YWHAH activates the HMGA1/PI3K/AKT/mTOR signaling pathway by positively regulating Fra-1 to affect the proliferation of gastric cancer cells

Fos-related antigen 1(Fra-1)is a nuclear transcription factor that regulates cell growth,differentiation,and apoptosis.It is involved in the proliferation,invasion,apoptosis and epithelial mesenchymal transformation of malignant tumor cells.Fra-1 is highly expressed in gastric cancer(GC),affects the cycle distribution and apoptosis of GC cells,and participates in GC occurrence and development.However,the detailed mechanism of Fra-1 in GC is unclear,such as the identification of Fra-1-interacting proteins and their role in GC pathogenesis.In this study,we identified tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein eta(YWHAH)as a Fra-1-interacting protein in GC cells using co-immunoprecipitation combined with liquid chromatography-tandem mass spectrometry.Experiments showed that YWHAH positively regulated Fra-1 mRNA and protein expression,and affected GC cell proliferation.Whole proteome analysis showed that Fra-1 affected the activity of the high mobility group AT-hook 1(HMGA1)/phosphatidylinositol-4,5-bisphosphate 3-kinase(PI3K)/protein kinase B(AKT)/mechanistic target of rapamycin(mTOR)signaling pathway in GC cells.Western blotting and flow cytometry confirmed that YWHAH activated HMGA1/PI3K/AKT/mTOR signaling pathway by positively regulating Fra-1 to affect GC cell proliferation.These results will help to discover new molecular targets for the early diagnosis,treatment,and prognosis prediction of GC.

TTF1调控ERK信号转导通路的作用

[目的]探讨TTF1调控ERK信号转导通路的作用.[方法]建立人肝癌HepG2裸鼠移植瘤模型,取40只随机分为阴性对照组、紫杉醇组、TTF1小剂量组、TTF1中剂量组及TTF1大剂量组,每组各为8只,药物干预21 d后处死裸鼠,采用Western blot技术检测肿瘤组织ERK1/2和p-ERK1/2蛋白表达.[结果]TTF1对人肝癌HepG2裸鼠移植瘤的生长有抑制作用;ERK1/2蛋白表达未见明显变化,p-ERK1/2蛋白表达随着TTF1剂量的升高而减少.[结论]TTF1对肿瘤生长有抑制作用,其机制可能与通过调节ERK信号转导通路有关.

Enhancive effect of N,N'-dinitrosopiperazine on inducing precancerous lesion on nasal and/or nasopharyngeal epithelia of TgN(p53mt-LMP1)/HT mice

Objective： To investigate the enhancive effect ofN, N′-dinitrosopiperazine （DNP） on induced carcinogenesis in nasal and/or nasopharyngeal epithelia among TgN（p53mt-LMP1）/HT transgenic mice to examine the underlying mechanism for the development of nasopharyngeal carcinoma （NPC）. Methods： TgN（p53mt-LMP1）/HT transgenic mice and the same strain of C57BL/6J wild-type mice both at the age of 5 months were randomly divided into 2 groups in parallel, respectively, i.e., TgN（p53mt-LMP1）/HT cancerous lesion-inducing group （T1）, TgN（p53mt-LMP1）/HT control group （TC）, C57BL/6J cancerous lesion-inducing group （CI）, and C57BL/6J control group （CC）. TI and CI mice were treated only with DNP for 16 weeks, twice each week, while TC and CC mice were given the same volume of saline as controls.At the end of treatment, animals were sacrificed to collect epithelial tissue samples from nasal cavity and nasopharynx for pathohistological evaluation by hacmatoxylin and eosin （HE） staining and for determination on the expression ofTRAF2, c-Jun, and p 16 by immunohistochemistry. Results： Atypical hyperplasia was more significant in the samples of TI than in those of TC, CI, and CC, with the rates of lesions being 90%, 10%, 0, and 0 （P〈0.01） respectively, though DNP was used alone in a much shortened inducing period at less dosage and without the use of carcinogenic promoter 12-0-tetradecanoylphorbol-13-acetate as usual. The expressions of tumor necrosis factor （TNF） receptor-associated factor 2 （TRAF2） and c-Jun in these samples were significantly up-regulated in TI （P〈0.0 I）, while tbe expression of p16 was significantly lower in TI than in the other groups （P〈0.01）. Conclusion： TgN（p53mt-LMPI）/HT mice hold inherited constitutional defect in immune surveillance function, which can be aggravated by environmental carcinogens, such as DNP used even though in a much less strength. The enhanced carcinogenesis-inducing effect of DNP on TgN（p53mt-LMP1）/HT mice should be closely associated with abnormal signaling of activator protein-1 （AP-1） pathway, especially up-regulated expressions of TRAF2 and c-Jun, and down-regulated expression of p l6.

G protein b_1λ_2 subunits purification and their interaction with adenylyl cyclase

A preliminary study on the interaction of G protein (guanine triphosphate binding pro- tein) b1g2 subunits and their coupled components in cell signal transduction was conducted in vitro. The insect cell lines, Sf9 (Spodoptera frugiperda) and H5 (Trichoplusia ni ) were used to express the recombinant protein Gb1g2. The cell membrane containing Gb1g2 was isolated through affinity chromatography column with Ni-NTA agarose by FPLC method, and the highly purified protein was obtained. The adenylyl cyclase 2 (AC2) activity assay showed that the purified Gb1g2 could signifi-cantly stimulate AC2 activity. The interaction of b1g2 subunits of G protein with the cytoplasmic tail of various mammalian adenylyl cyclases was monitored by BIAcore technology using NTA sensor chip, which relies on the phenomenon of surface plasmon resonance (SPR). The experiments showed the direct binding of Gb1g2 to the cytoplasmic tail C2 domain of AC2. The specific binding domain of AC2 with Gb1g2 was the same as AC2 activity domain which was stimulated by Gb1g2.