TRPM7通过PI3K/AKT/ERK信号途径影响脑胶质瘤细胞增殖、上皮-间质转化

目的 探讨沉默M型顺时受体电位通道7（melastatin transient receptor potential channel 7,TRPM7）对脑胶质瘤细胞增殖、上皮-间质转化的影响及其作用机制。方法 采用qRT-PCR和Western blot检测TRPM7在人正常星形胶质HA1800细胞株以及脑胶质瘤细胞株（U251、U87、U373）中的表达。将U251细胞分为U251组（未转染的U251细胞）、U251/shNC组、U251/shTRPM7组,然后采用qRT-PCR和Western blot检测TRPM7的表达,细胞克隆形成实验检测细胞增殖能力;Transwell实验检测细胞迁移和侵袭能力;细胞免疫荧光实验检测E-cadherin和Vimentin表达情况;Western blot检测PI3K/AKT/ERK信号途径相关蛋白的表达情况。结果 与HA1800细胞比较,TRPM7在脑胶质瘤细胞系中高表达（P<0.05）;沉默TRPM7后,U251细胞中TRPM7表达降低（P<0.001）,细胞增殖、迁移和侵袭能力明显下降（P<0.01）;E-cadherin表达增加（P<0.001）,Vimentin表达降低（P<0.01）;PI3K蛋白表达水平下调（P<0.01）,AKT和ERK1/2蛋白磷酸化程度明显降低（P<0.01）。结论 沉默TRPM7可抑制U251细胞增殖、迁移和侵袭能力及上皮-间质转化,其作用机制可能与激活PI3K/AKT/ERK信号途径有关。     

Induction of apoptosis in human leukemia cells by the tyrosine kinase inhibitor adaphostin proceeds through a RAF-1/MEK/ERK- and AKT-dependent process

Effects of the tyrphostin tyrosine kinase inhibitor adaphostin (NSC 680410) have been examined in human leukemia cells (Jurkat, U937) in relation to mitochondrial events, apoptosis, and perturbations in signaling and cell cycle regulatory events. Exposure of cells to adaphostin concentrations > or =0.75 microM for intervals > or =6 h resulted in a pronounced release of cytochrome c and AIF, activation of caspase-9, -8, and -3, and apoptosis. These events were accompanied by the caspase-independent downregulation of Raf-1, inactivation of MEK1/2, ERK, Akt, p70S6K, dephosphorylation of GSK-3, and activation of c-Jun-N-terminal kinase (JNK) and p38 MAPK. Adaphostin also induced cleavage and dephosphorylation of pRb on CDK2- and CDK4-specific sites, as well as the caspase-dependent downregulation of cyclin D1. Inducible expression of a constitutively active MEK1 construct markedly diminished adaphostin-induced cytochrome c and AIF release, JNK activation, and apoptosis in Jurkat cells. Ectopic expression of Raf-1 or constitutively activated (myristolated) Akt also significantly attenuated adaphostin-induced apoptosis, but protection was less than that conferred by enforced activation of MEK. Lastly, antioxidants (e.g., L-N-acetylcysteine; L-NAC) opposed adaphostin-mediated mitochondrial dysfunction, Raf-1/MEK/ERK downregulation, JNK activation, and apoptosis. However, in contrast to L-NAC, enforced activation of MEK failed to block adaphostin-mediated ROS generation. Together, these findings demonstrate that the tyrphostin adaphostin induces multiple perturbations in signal transduction pathways in human leukemia cells, particularly inactivation of the cytoprotective Raf-1/MEK/ERK and Akt cascades, that culminate in mitochondrial injury, caspase activation, and apoptosis. They also suggest that adaphostin-related oxidative stress acts upstream of perturbations in these signaling pathways to trigger the cell death process.     

Inhibition of the mitogen activated protein kinase pathway potentiates radiation-induced cell killing via cell cycle arrest at the G2/M transition and independently of increased signaling by the JNK/c-Jun pathway

The ability of low dose ionizing radiation (2 Gy) to modulate the activities of the mitogen activated protein kinase (MAPK) and c-Jun NH2-terminal kinase (JNK1) cascades in human monocytic leukemia (U937/pREP4) cells and in cells over-expressing dominant negative c-Jun (TAM67) (U937/TAM67) was investigated. Radiation exposure caused prolonged ( approximately 1 h) MAPK activations in U937 cells. In contrast, low dose irradiation weakly modulated JNK1 activity in these cells. Inhibition of the MAPK pathway by use of the specific MEK1/2 inhibitor (10 microM PD98059) in both U937/pREP4 and U937/TAM67 cells prior to radiation exposure permitted strong prolonged radiation-induced activations of JNK1. Expression of TAM67 decreased the ability of radiation to cause apoptosis compared to control transfected cells. However, combined MEK1/2 inhibition and radiation exposure in both cell types caused a large decrease in suspension culture growth and a large increase in apoptosis, when compared to either treatment alone. Reduced proliferation after combined irradiation and PD98059 treatment in both cell types correlated with prolonged cell cycle arrest in G2/M phase. Prolonged growth arrest was abolished when MEK1/2 inhibitor was removed 6 h following irradiation, which was associated with a reduction in apoptosis. The ability of MEK1/2 inhibition to cause prolonged G2/M growth arrest was reduced in U937 cells stably transfected with a p21Cip-1/WAF1 antisense construct (U937/p21AS). This data correlated with an enhancement of radiation-induced apoptosis and a reduced ability of MEK1/2 inhibition to potentiate apoptosis. Collectively our data demonstrate that inhibition of MEK1/2 function increases the radiation sensitivity of U937 cells, independently of c-Jun function, and decreases the ability of these cells to recover from the radiation-induced G2/M cell cycle checkpoint arrest. In addition, our data also demonstrate that the ability of MEK1/2 inhibition to potentiate radiation-induced cell death in U937 cells in part requires an ability of cells to express low levels of p21Cip-1/WAF1.     

The mechanism of geranylgeraniol-induced apoptosis involves activation, by a caspase-3-like protease, of a c-jun N-terminal kinase signaling cascade and differs from mechanisms of apoptosis induced by conventional chemotherapeutic drugs

In the present study, we investigated the effects of geranylgeraniol (GGO), a potent inducer of apoptosis in various lines of human tumor cells, on signal transduction cascades involved in apoptosis in human leukemia cells. GGO strongly induced the activation of c-Jun N-terminal kinase (JNK/SAPK) within 2 h in U937 and K562 cells, while neither ERK nor p38 was activated to any considerable extent during GGO-induced apoptosis. Transient expression of a constitutively active mutant form of mitogen-activated protein kinase kinase 1 (MEKK1), deltaMEKK1, or of deltaMEKK1-green fluorescent protein (GFP) in K562 cells activated JNK, but not a caspase-3-like protease, and was insufficient to induce cell death but rendered cells susceptible to GGO-induced cell death. Stable expressions of deltaMEKK1-GFP in U937 cells gave similar results. In contrast to VP-16-induced apoptosis, GGO-induced activation of JNK was almost completely inhibited by benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone (Z-DEVD) and by benzyloxycarbonyl-Asp-CH2OC[O]-2,6,-dichlorobenzene (Z-Asp), indicating that the JNK-activation step is located downstream of the caspase signaling pathway in GGO-induced apoptosis. Moreover, apoptosis induced by GGO was significantly inhibited in two lines of cells with a dominant-negative deletion mutation in c-Jun, indicating a requirement for JNK signaling. In addition, unlike the effects on other inducers of apoptosis, the activation of JNK and of the caspase-3-like protease by GGO was significantly delayed by 12-O-tetradecanoylphorbol-13-acetate (TPA), suggesting that the site of inhibition by TPA might be located upstream of the protease and JNK in the GGO-induced apoptotic signaling pathway.     

Acetyl derivative of quercetin 3-methyl ether-induced cell death in human leukemia cells is amplified by the inhibition of ERK

Flavonoids are polyphenolic compounds that are ubiquitously in plants and display a vast array of biological activities. Here we have studied the effect of the phenylbenzo-gamma-pyrone-derivative quercetin 3-methyl ether tetracetate (QD), obtained by acetylation of the natural product quercetin 3-methyl ether, on cell viability of human leukemia HL-60 and U937 cell lines. The results show that QD was cytotoxic and induced G2-M phase cell cycle arrest on both cell lines and it was a potent apoptotic inducer on HL-60 cells. QD-induced apoptosis is (i) mediated by caspase activation, since it was prevented by the non-specific caspase inhibitor z-VAD-fmk, (ii) associated with cytochrome c release and (iii) triggered in Bcl-2 over-expressing U937 cells. The treatment of HL-60 and U937 cells with QD also induces the activation of the mitogen-activated protein kinases (MAPKs) pathway, including c-Jun N-terminal kinase, p38 mitogen-activated protein kinase and extracellular signal-regulated kinases (ERK) 1/2. Inhibition of c-Jun N-terminal kinase by SP600125 and of p38 mitogen-activated protein kinase by SB203580 had no influence on QD-mediated apoptosis. In contrast, inhibition of ERK1/2 with the pharmacologic inhibitors U0126 or PD98059, together with QD, resulted in an important enhancement of apoptosis. Cells are sensitized to QD-mediated apoptosis after blocking ERK1/2, which suggests that inhibition of this pathway is a valuable strategy to increase the sensitivity of human leukemia HL-60 cells toward QD.     

Coadministration of histone deacetylase inhibitors and perifosine synergistically induces apoptosis in human leukemia cells through Akt and ERK1/2 inactivation and the generation of ceramide and reactive oxygen species

Interactions between histone deacetylase inhibitors (HDACIs) and the alkyl-lysophospholipid perifosine were examined in human leukemia cells. Coadministration of sodium butyrate, suberoylanilide hydroxamic acid (SAHA), or trichostatin with perifosine synergistically induced mitochondrial dysfunction (cytochrome c and apoptosis-inducing factor release), caspase-3 and -8 activation, apoptosis, and a marked decrease in cell growth in U937 as well as HL-60 and Jurkat leukemia cells. These events were associated with inactivation of extracellular signal-regulated kinase (ERK) 1/2 and Akt, p46 c-jun-NH2-kinase (JNK) activation, and a pronounced increase in generation of ceramide and reactive oxygen species (ROS). They were also associated with up-regulation of Bak and a marked conformational change in Bax accompanied by membrane translocation. Ectopic expression of Bcl-2 delayed but was ultimately ineffective in preventing perifosine/HDACI-mediated apoptosis. Enforced expression of constitutively active mitogen-activated protein kinase kinase (MEK) 1 or myristoylated Akt blocked HDACI/perifosine-mediated ceramide production and cell death, suggesting that MEK/ERK and Akt inactivation play a primary role in these phenomena. However, inhibition of JNK activation (e.g., by the JNK inhibitor SP600125) did not attenuate sodium butyrate/perifosine-induced apoptosis. In addition, the free radical scavenger N-acetyl-L-cysteine attenuated ROS generation and apoptosis mediated by combined treatment. Finally, the acidic sphingomyelinase inhibitor desipramine attenuated HDACI/perifosine-mediated ceramide and ROS production as well as cell death. Together, these findings indicate that coadministration of HDACIs with perifosine in human leukemia cells leads to Akt and MEK/ERK disruption, a marked increase in ceramide and ROS production, and a striking increase in mitochondrial injury and apoptosis. They also raise the possibility that combining these agents may represent a novel antileukemic strategy.     

Involvement of cell cycle regulatory proteins and MAP kinase signaling pathway in growth inhibition and cell cycle arrest by a selective cyclooxygenase 2 inhibitor, etodolac, in human hepatocellular carcinoma cell lines

Recent studies have shown that selective cyclooxygenase-2 (COX-2) inhibitors induce growth inhibition and cell cycle arrest in hepatocellular carcinoma (HCC) cell lines. However, the mechanism by which COX-2 inhibitors regulate the cell cycle and whether or not growth signal pathways are involved in the growth inhibition remain unclear. In this study, we investigated the mechanisms of growth inhibition and cell cycle arrest by etodolac, a selective COX-2 inhibitor, in HCC cell lines, HepG2 and PLC/PRF/5, by studying cell cycle regulatory proteins, and the MAP kinase and PDK1-PKB/AKT signaling pathways. Etodolac inhibited growth and PCNA expression and induced cell cycle arrest in both HCC cell lines. Etodolac induced p21WAF1/Cip1 and p27Kip1 expression and inhibited CDK2, CDK4, CDC2, cyclin A and cyclin B1 expression, but did not affect cyclin D1 or cyclin E. HGF and 10% FBS induced ERK phosphorylation, but phosphorylation of p38, JNK and AKT was down-regulated by etodolac. PD98059, a selective inhibitor of ERK phosphorylation, induced growth inhibition, the expression of p27Kip1 and cell cycle arrest. In conclusion, p21WAF1/Cip1, p27Kip1, CDK2, CDK4, CDC2, cyclin A, cyclin B1 and the MAP kinase signaling pathway are involved in growth inhibition and cell cycle arrest by a selective COX-2 inhibitor in HCC cell lines.     

Growth-stimulatory activity of TIMP-2 is mediated through c-Src activation followed by activation of FAK,PI3-kinase/AKT,and ERK1/2 independent of MMP inhibition in lung adenocarcinoma cells

Tissue inhibitors of metalloproteinases (TIMPs) control extracellular matrix (ECM) homeostasis by inhibiting the activity of matrix metalloproteinases (MMPs), which are associated with ECM turnover. Recent studies have revealed that TIMPs are implicated in tumorigenesis in both MMP-dependent and MMP-independent manners. We examined a mechanism by which TIMP-2 stimulated lung adenocarcinoma cell proliferation, independent of MMP inhibition. The stimulation of growth by TIMP-2 in A549 cells required c-Src kinase activation. c-Src kinase activity, induced by TIMP-2, concomitantly increased FAK, phosphoinositide 3-kinase (PI3-kinase)/AKT, and ERK1/2 activation. Selective knockdown of integrin α3β1, known as a TIMP-2 receptor, did not significantly change TIMP-2 growth promoting activity. Furthermore, we showed that high TIMP-2 expression in lung adenocarcinomas is associated with a worse prognosis from multiple cohorts, especially for stage I lung adenocarcinoma. Through integrated analysis of The Cancer Genome Atlas data, TIMP-2 expression was significantly associated with the alteration of driving genes, c-Src activation, and PI3-kinase/AKT pathway activation. Taken together, our results demonstrate that TIMP-2 stimulates lung adenocarcinoma cell proliferation through c-Src, FAK, PI3-kinase/AKT, and ERK1/2 pathway activation in an MMP-independent manner.     

黑色素瘤中癌基因B-RafV600E对B-Raf/ERK/Mps1负反馈抵抗作用的机制

目的 明确癌基因B-Raf^V600E在Mps1和B-Raf^WT/MEK/ERK通路之间自动调节的负反馈回路中抵抗作用的具体机制。方法 （1）Sbcl2转染B-RafWT和Mps1-KD,Western blot方法检测p-ERK水平;（2）向B-Raf野生型SK-MEL31、Sbcl2、WM35细胞及V600E突变型SK-MEL28、A375细胞中过表达Mps1,Western blot方法检测p-ERK水平;（3）在SK-MEL31、Sbcl2、WM35细胞中敲低AKT,转染Mps1,Western blot方法检测p-ERK水平;（4）在SK-MEL31、Sbcl2、WM35细胞中敲低内源性B-Raf,过表达外源性Raf^V600E,Western blot方法检测p-AKT水平;敲低SK-MEL-28、A375细胞中Raf^V600E,Western blot方法检测p-AKT水平。结果 （1）Mps1激酶和B-Raf^WT/MEK/ERK通路之间的自动负反馈通路不依赖Mps1激酶的活性;（2）在野生型SK-MEL31、Sbcl2、WM35细胞中外源性Mps1的表达可诱导AKT磷酸化,抑制ERK活性;V600E突变型SK-MEL28、A375细胞中外源性Mps1的表达不能诱导AKT磷酸化,亦不影响ERK活性。（3）敲低野生型黑色素瘤细胞中的AKT后,Mps1和B-Raf^WT/MEK/ERK之间的负反馈作用消失。（4）癌基因B-Raf^V600E通过抑制AKT的磷酸化,进而抵抗Mps1激酶与B-Raf/MEK/ERK通路之间的负反馈调节作用。结论 Mps1和B-Raf^WT/MEK/ERK通路之间的自动负反馈通路不依赖Mps1激酶的活性,且癌基因B-Raf^V600E对B-Raf/MEK/ERK/Mps1负反馈通路的抵抗作用是通过抑制AKT的磷酸化实现的。     

紫杉醇联合紫草素对U87脑胶质瘤细胞的作用及机制初探

目的:探讨紫杉醇联合紫草素通过协同作用杀伤人脑胶质瘤的作用。方法:将不同浓度的紫杉醇与紫草素单药及两种药物半量联合作用于胶质瘤细胞后，用CCK-8法检测细胞增殖抑制率，用划痕实验和Transwell法检测细胞生物学行为（迁移与侵袭）的影响，流式细胞技术检测细胞周期及凋亡率，Western-blot测定细胞外调节蛋白激酶（ERK）的蛋白表达。结果:紫杉醇与紫草素对胶质瘤细胞株U87细胞增殖具有抑制作用，且呈时间和剂量依赖性，并且发挥协同作用。紫杉醇与紫草素单独以及联合应用抑制U87细胞迁移与侵袭。两种药物联合应用促进U87细胞凋亡，紫草素组G1期的RNA含量增多，紫杉醇组及联合应用组的G2期RNA含量显著增高。Western-blot结果显示两者联合应用时，p-ERK蛋白表达降低。结论:与紫杉醇或紫草素单用组相比，两者半量联用通过协同作用能显著抑制U87胶质瘤细胞增殖、迁移、侵袭能力，促进细胞凋亡，阻滞细胞周期。紫杉醇与紫草素的协同效应机制与二者联合应用抑制p-ERK蛋白表达相关。     

beta-Sitosterol induces G2/M arrest, endoreduplication, and apoptosis through the Bcl-2 and PI3K/Akt signaling pathways

β-Sitosterol (SITO) is a potentially valuable candidate for cancer chemotherapy, however the cellular and molecular mechanisms responsible for its anti-cancer activity are unknown. Therefore, we attempted to elucidate the mechanisms responsible for SITO-induced anti-proliferation in human leukemia cells. Treatment with SITO increased caspase-3 activation and DNA fragmentation in U937 and HL60 cells. This effect was associated with significant G₂/M arrest and endoreduplication. We also demonstrated that SITO treatment significantly increases levels of polymeric -tubulin and promoted microtubule polymerization. We next elucidated that ectopic expression of Bcl-2 accelerates endoreduplication in U937 cells. Furthermore, the specific Bcl-2 inhibitor, HA14-1, prevented endoreduplication through G₂ phase arrest. Interestingly, SITO treatment did not significantly promote endoreduplication or decrease cell viability in Bcl-2 null K562 cells. SITO treatment also induced a gradual increase of phosphatidyl-inositol 3-kinase (PI3K) and Akt phosphorylation. Treatment with the selective PI3K/Akt inhibitor LY29004 completely blocked endoreduplication and apoptosis in the presence of SITO. In addition, treatment with SITO-induced phosphorylation of extracellular signal-regulated protein kinase (ERK), however significance of ERK activation in the execution of apoptosis and endoreduplication is unknown. These results suggest that SITO induces endoreduplication by promoting spindle microtubule dynamics through the Bcl-2 and PI3K/Akt signaling pathways.     

Rap2b基因真核表达载体构建及其对NIH3T3细胞P38通路的影响

目的构建pcDNA3.1-Rap2b真核表达载体,以外源基因Rap2b转染NIH3T3细胞,以了解该基因对NIH3T3细胞AKT、ERK、JNK和P38信号转导通路的影响,为探讨该基因在人肺癌发生中的作用提供实验依据。方法构建人Rap2b真核表达载体pcDNA3.1-Rap2b并稳定转染NIH3T3细胞,利用Western blot方法对转染的细胞进行AKT、ERK、JNK和P38磷酸化蛋白及总蛋白表达水平检测。结果转染pcDNA3.1-Rap2b质粒的细胞与转染空质粒pcDNA3.1的细胞相比,其AKT、ERK、JNK磷酸化蛋白表达水平差异无统计学意义（P＞0.05）,而P38磷酸化蛋白表达水平明显上调（P＜0.05 ）。结论Rap2b基因外源性高表达可能对P38通路有活化作用,对JNK、ERK、AKT通路无活化作用。     

Berberine-antiproliferative activity in vitro and induction of apoptosis/necrosis of the U937 and B16 cells

Berberine, an isoquinoline plant alkaloid, is widely distributed in plants used in the traditional Chinese medicine. It displays a wide range of biological activities and the mechanism of action. Our previous studies of the anticancer activity of berberine against the cancer cell lines HeLa and L1210 were extended to the human tumour U937 cell line and the murine melanoma B16 cell line growing in vitro. Cytotoxicity was measured by the growth inhibition assay and by the cell morphology monitoring. The in vitro cytotoxic studies were complemented by the cell cycle analysis and determination of apoptotic DNA fragmentation. Berberine acted cytotoxically on both tumour cell lines. The melanoma B16 cells were much more sensitive to berberine treatment than the U937 cells. The value of IC(100) was below 100 microg/ml for the U937 cells and below 1 microg/ml for the B16 cells. As for both cell lines under the long-term influence the values of IC(50) were found to be less than 4 microg/ml. No effect of berberine on the cell cycle profile of the U937 and B16 cells was detected, however, berberine induced apoptosis of the U937 cells. On the other hand, cell lysis/necrosis of the berberine-treated B16 cells was observed as the result of the integrity damage of the cytoplasmic membrane.     

miR-152在急性髓系白血病患者骨髓和细胞系中的表达及生物学功能的初步研究

目的:检测miR-152在急性髓系白血病(AML)患者骨髓和细胞系中的表达水平。初步研究miR-152在急性髓系白血病中的生物学功能。方法:收集急性髓系白血病患者40例,非恶性血液病对照组20例,提取骨髓有核细胞;培养U937、Kasumi-1、THP-1三种急性髓系白血病细胞系。RT-PCR检测miR-152的表达水平。分别对U937细胞系和Kasumi-1细胞系转染miR-152 mimics和inhibitor,CCK-8法检测U937细胞及Kasumi-1细胞增殖情况,Annexin V/PI流式实验检测细胞凋亡,流式细胞术检测细胞周期。结果:miR-152在急性髓系白血病患者骨髓及细胞系中较非恶性血液病对照组表达明显下降。U937细胞系转染miR-152 mimics后,增殖受抑制,细胞凋亡增加,细胞阻滞在G0-G1期;Kasumi-1细胞系转染miR-152 inhibitor后,增殖增加,细胞凋亡减少,G0-G1期细胞减少。结论:miR-152在急性髓系白血病患者骨髓及细胞系中的表达水平均较正常对照组显著降低。miR-152在急性髓系白血病中起抑癌基因的作用,过表达miR-152可以抑制细胞增殖,促进凋亡。     

胚胎发育相关基因精子转录本在白血病细胞系中的表达及其调节

 目的 探讨胚胎发育相关基因（EDAG）在白血病细胞中的调控机制。方法 用半定量RT-PCR方法检测白血病细胞系中EDAG精子转录本EDAG-t的表达;使用不同的分化诱导剂诱导K562和U937细胞分化,检测EDAG-t的表达改变情况。结果 在白血病细胞系K562和U937中也可检测到EDAG-t的表达;使用不同的分化诱导剂诱导K562和U937细胞分化,发现EDAG精子转录本和造血转录本的表达都会随细胞分化而下调,但它们的下调步伐不一致,总的说来,EDAG-t的减弱较EDAG-h慢。结论 EDAG精子转录本在白血病细胞中的异常表达值得进一步研究。     

Apoptosis triggered by vitexin in U937 human leukemia cells via a mitochondrial signaling pathway

Vitexin, a lignan compound, has been shown to exert apoptotic actions on human breast cancer cell lines and to have anti-inflammatory activities. Nevertheless, there is currently no study addressing the effects of vitexin on the induction of apoptosis in U937 human leukemia cells. The aim of this study was to determine the anticancer effects and molecular mechanisms of vitexin on U937 leukemia cells. We showed that vitexin can potently induce programmed cell death in U937 leukemia cell growth as well as morphological changes that were examined by MTT assay and phase contrast microscopy, respectively. The DNA content and the levels of mitochondrial membrane potential (?Ψm) were determined by flow cytometric analysis. The cell cycle arrest-regulated and apoptosis-associated protein levels were measured by western blotting. Vitexin-triggered apoptosis was accompanied by a decrease of the level of ?Ψm and the percentage of viability and provoked apoptosis in U937 cells. The downregulation of the protein level for Bcl-2 with the simultaneous upregulation of caspase-3 and -9 protein expression in U937 cells were observed after treatment with vitexin. Therefore, our data provide a potential mechanism for the chemopreventive activity of vitexin, and we suggest that vitexin may serve as a therapeutic agent for the treatment of human leukemia.     

白细胞介素-24 delE5对人类白血病细胞系K562的抑制作用

 目的　探索白细胞介素（IL）-24 delE5对人类白血病细胞系K562的抑制作用。方法　用TPA诱导白血病细胞系U937和HL-60向单核-巨噬细胞分化后,检测mda-7／IL-24及其选择性剪接体IL-24 delE5的表达。构建IL-24 delE5真核表达载体,稳定转染K562细胞。通过MTT法、集落形成实验、流式细胞术、Annexin-Ⅴ／PI检测及动物实验,观察IL-24 delE5对K562细胞增殖、集落形成、细胞周期、凋亡及体内致瘤性的影响;同时与mda-7／IL-24进行比较。结果　在TPA诱导分化的U937和HL-60细胞中发现IL-24 delE5的表达。稳定转染IL-24 delE5的K562增殖及集落形成明显下降,与空载体相比,G0／G1期细胞比例由（24.46±3.99）%增至（42.69±3.04）%,细胞周期阻滞于G0／G1期,体内实验证实K562细胞移植瘤生长明显被抑制。与mda-7／IL-24相比,上述各实验结果差异均无统计学意义。结论　IL-24 delE5与mda-7／IL-24一样对人类白血病细胞系K562具有明显的体内外抑制作用,该作用可能与IL-24 delE5所引起细胞周期G0／G1期阻滞有关。     

Shikonin and its derivatives inhibit the epidermal growth factor receptor signaling and synergistically kill glioblastoma cells in combination with erlotinib

Overexpression and mutation of the epidermal growth factor receptor (EGFR) gene play a causal role in tumorigenesis and resistance to treatment of glioblastoma (GBM). EGFR inhibitors such as erlotinib are currently used for the treatment of GBM; however, their efficacy has been limited due to drug resistance. New treatment strategies are therefore urgently needed. Shikonin, a natural naphthoquinone, induces both apoptosis and necroptosis in human glioma cells, but the effectiveness of erlotinib‐shikonin combination treatment as well as the underlying molecular mechanisms is unknown yet. In this study, we investigated erlotinib in combination with shikonin and 14 shikonin derivatives in parental U87MG and transfected U87MG.ΔEGFR GBM cells. Most of the shikonin derivatives revealed strong cytotoxicity. Shikonin together with five other derivatives, namely deoxyshikonin, isobutyrylshikonin, acetylshikonin, β,β‐dimethylacrylshikonin and acetylalkannin showed synergistic cytotoxicity toward U87MG.ΔEGFR in combination with erlotinib. Moreover, the combined cytotoxic effect of shikonin and erlotinib was further confirmed with another three EGFR‐expressing cell lines, BS153, A431 and DK‐MG. Shikonin not only dose‐dependently inhibited EGFR phosphorylation and decreased phosphorylation of EGFR downstream molecules, including AKT, P44/42MAPK and PLCγ1, but also together with erlotinib synergistically inhibited ΔEGFR phosphorylation in U87MG.ΔEGFR cells as determined by Loewe additivity and Bliss independence drug interaction models. These results suggest that the combination of erlotinib with shikonin or its derivatives might be a potential strategy to overcome drug resistance to erlotinib.