Molecular mechanisms of ZD1839-induced G1-cell cycle arrest and apoptosis in human lung adenocarcinoma A549 cells

Epithelial growth factor receptor (EGFR) has been proposed as a target for anticancer therapy. ZD1839 (Iressa) is a quinazoline derivative that selectively inhibits the EGFR tyrosine kinase activity and is under clinical use in cancer patients. However, the molecular mechanisms involved in ZD1839-mediated anticancer effects remain largely uncharacterized. In this study, exposure of human lung adenocarcinoma A549 cells to ZD1839 caused G1 arrest, and subsequently induced apoptosis. Moreover, ZD1839 increased the protein levels of p27(KIP1) and retinoblastoma-related Rb2/p130 while decreased the expression of cyclin-dependent kinase-2 (CDK2), CDK4, CDK6 and cyclin-D1, cyclin-D3. In vitro kinase assay showed that ZD1839 decreased these CDKs expression in A549 cells, leading to significantly reduce their kinase activities. In addition, ZD1839-induced death of A549 cells with characteristics of apoptosis including apoptotic morphological changes, DNA fragmentation and enhancement of TUNEL-positive cell. These events were accompanied by a marked increase of Fas protein expression, and activation of caspase-2, -3, -8. Co-treatment of cells with Fas antagonist antibody significantly blocked ZD1839-induced apoptosis. Caspase-8 and caspase-3 inhibitors, but not a caspase-9 inhibitor, were also capable of restoring cell viability. Our results indicate that downregulation of the expression and function of CDK2, CDK4, CDK6, cyclin-D1 and cyclin-D3, as well as upregulation of p27(KIP1) and pRb2/p130, are strong candidates for the cell cycle regulator that arrests ZD1839-treated A549 cells at G1 phase. Furthermore, upregulation of Fas appears to play a major role in the initiation of ZD1839-induced apoptosis, activation of caspase-8/caspase-3 cascade is involved in the execution phase of this death program.     

Participation of cyclin D1 deregulation in TNP-470-mediated cytostatic effect: involvement of senescence

Inhibition of angiogenesis is becoming one promising, alternative approach to stop tumor from growth and spreading to distant organs. TNP-470, an analog of fumagillin, possesses potent anti-angiogenic effects with minimal toxicity in animal tumor models and is now in the phase III of human cancer trial. Although TNP-470 induced endothelial cell cycle arrest at G1 phase via p53 and p21(Cip1), the underlying mechanism of the cytostatic effect of TNP-470 on endothelial cells remains limited. We have found that TNP-470 did not only induce p53 and p21(Cip1) but also cyclin D1 in the basic fibroblast growth factors (bFGF)-treated endothelial cells. The TNP-470-mediated increase of cyclin D1 protein was due to the enhanced expression of mRNA. The induced cyclin D1 formed a complex with cyclin-dependent kinase4 (CDK4) and p21(Cip1). The ability of cyclin D1-associated CDK4 to phosphorylate retinoblastoma (Rb) protein was, however, reduced in the same cells. TNP-470 also significantly increased senescence-associated-beta-galactosidase activity (SA-gal), hallmark of cells undergoing senescence. Interestingly, the effect of increased cyclin D1 protein mimicked by overexpression of cyclin D1 increased the sensitivity of human umbilical vein endothelial cells (HUVECs) to TNP-470. In summary, the cytostatic effect of TNP-470 on endothelial cells is in part mediated by induction of senescence and cyclin D1 is a key molecule participating in this event.     

Role of BCL-2 and cell cycle regulatory proteins for corticosensitivity assessment in childhood acute lymphoblastic leukaemia

Results of treatment in childhood acute lymphoblastic leukaemia (ALL) remain unsatisfactory because relapses occur even after high-dose chemotherapy. Corticosensitivity is used in numerous therapeutic trials as a prognostic factor for treatment choice. The aim of this study was to evaluate the role of cell cycle regulatory protein expression before and during the first 48 h of corticotherapy for predicting corticosensitivity. Fifty-two children presenting with ALL were studied at diagnosis and during the first 48 h of treatment for cell proliferation and apoptosis level by measurement of DNA content, and for expression of several cell proliferation regulatory proteins by means of Western blot. Glucocorticoids induced a significant decrease in the percentage of cells in S-phase and in CDK1, CDK4 and CDK6 expression and an increase in the percentage of cells in subG1 peak. Two criteria for corticosensitivity were used: (i) the number of blast cells after 7 d of treatment with a threshold at 1 x 109/l (usual criterion), (ii) the J8/J1 blast cell ratio, which is independent from initial leucocytosis. Bcl-2 expression at diagnosis was the best predictive variable for the usual corticosensitivity criterion in B- and T-cell ALL. For the second criterion, in B-cell ALL, p21waf1 expression at diagnosis was the sole (albeit poorly) predictive variable, whereas bcl-2 remained of high interest in T-cell ALL. Interestingly, these proteins, bcl-2 and p21waf1, are associated with prolonged cell lifespan and their increased expression is often linked to poor response to cytotoxic drugs. Such preliminary results call for subsequent studies on large independent sets of T-cell and B-cell lineage ALL in order to confirm the J8/J1 blast cell ratio value as well as the role of bcl-2 and p21waf1 expression in predicting corticosensitivity.     

Inhibition of MG-63 cell cycle progression by synthetic vitamin D3 analogs mediated by p27, Cdk2, cyclin E,and the retinoblastoma protein

Progression through eukaryotic cell division cycle is regulated by synergistic activities of both positive and negative regulatory factors. The active form of vitamin D₃ (1α,25(OH)₂D₃, 1,25D) and a number of its synthetic analogs have been shown to arrest cells in the G₁ phase of the cell cycle. In the present study, 1α,25(OH)₂D₃ and the analogs KH1060, EB1089, and CB1093 were used to study the mechanism of the cell cycle arrest and to compare the effectiveness of these compounds in human MG-63 osteosarcoma cells. The 20-epi analogs KH1060 and CB1093, as well as the 20-normal analog EB1089, were found to be more potent than 1α,25(OH)₂D₃ in inhibiting cell proliferation and arresting the MG-63 cells in the G₁ phase. These analogs were more active than 1α,25(OH)₂D₃ in increasing the cyclin dependent kinase inhibitor p27 protein levels (approximately 2.3-2.5-fold compared to 1α,25(OH)₂D₃) by both increasing its formation and decreasing its degradation rate. The increased p27 formation was accompanied by stabilization of binding of nuclear proteins to the Sp1+NF-Y responsive promoter region of the p27 gene. The increase in p27 protein levels and the simultaneous decrease in cyclin E protein levels was accompanied by decreased Cdk2 kinase activity, retinoblastoma (Rb) protein hypophosphorylation and, finally, cell cycle arrest in the G₁ phase. In summary, the analogs KH1060, EB1089, and CB1093 keep Rb protein in its growth-suppressing, hypophosphorylated form and prevent cell cycle progression through the restriction point. Therefore, these synthetic vitamin D₃ analogs may be potential candidates for treating diseases, where cell cycle regulation is needed.     

复方苦参注射液对荷DMS153裸鼠移植瘤的抑瘤作用及STAT3、MMP9表达的影响

目的:观察复方苦参注射液(compound Kushen injection,CKI)对荷DMS153小细胞肺癌裸鼠移植瘤的抑瘤作用,并初步探讨其作用机制与STAT3、MMP9表达的关系。方法:建立荷DMS153裸鼠移植瘤模型。实验分为对照组、CKI低中高剂量干预组、顺铂干预组,共5组,每组10只裸鼠。CKI低中高干预组每天予以不同剂量CKI干预［1.0、2.0和4.0 ml/（kg·d）］,顺铂（DDP）干预组予以顺铂干预（第1、3、5天给药4.8 mg/kg）,每天观察移植瘤生长情况,并测量肿瘤体积,各实验组裸鼠在第29天处死取材。qPCR和Western blotting法检测肿瘤中STAT3和MMP9的mRNA和蛋白表达水平。结果:相比于对照组,CKI不同剂量干预均能不同程度抑制肿瘤的生长（P<0.05）,其中高剂量组抑制作用最为明显;与对照组相比,DDP干预亦能够显著抑制移植瘤生长（P<0.05）,与CKI高剂量干预组相比差异具有统计学意义（P<0.05）。与对照组相比,CKI不同剂量干预均能不同程度抑制移植瘤中STAT3和MMP9的mRNA转录和蛋白表达水平（P<0.05）,其中高剂量组抑制最为显著;CKI不同剂量干预组STAT3和MMP9的mRNA转录呈显著正相关（Pearson相关系数为0.912>0,P=0.044＜0.05）;CKI不同剂量干预组STAT3和MMP9的蛋白表达水平均呈显著正相关（Pearson相关系数为0.990>0,P=0.005＜0.05）;与对照组相比,DDP干预亦能够显著抑制移植瘤组织中STAT3和MMP9的mRNA转录和蛋白表达（P<0.05）,与CKI高剂量干预组相比差异亦具有统计学意义（P<0.05）。结论:CKI能够有效抑制荷DMS153小细胞肺癌裸鼠移植瘤的生长,且高剂量组抑瘤作用较优;CKI抗小细胞肺癌的作用机制可能与其调控STAT3和MMP9的基因和蛋白表达有关。     

Cell-cycle regulatory proteins in human wound healing

Proper healing of mucosal wounds requires careful orchestration of epithelial cell migration and proliferation. To elucidate the molecular basis of the lack of cellular proliferation in the migrating 'epithelial tongue' during the re-epithelialization of oral mucosal wounds, the expression of cell-cycle regulators critical for G(1)-phase progression and S-phase entry was here analysed immunohistochemically. Compared to normal human mucosa, epithelia migrating to cover 2- or 3-day-old wounds made either in vivo or in an organotypic cell culture all showed loss of the proliferation marker Ki67 and cyclins D(1) and A, and reduced expression of cyclins D(3) and E, the cyclin D-dependent kinase 4 (CDK4), the MCM7 component of DNA replication origin complexes and the retinoblastoma protein pRb. Among the CDK inhibitors (CKIs), p16ink4a and p21Cip1 were moderately increased and decreased, respectively, whereas the abundance of most of the CKIs, including p27Kip1, p57Kip2, p15ink4b and p18ink4c, was relatively maintained in the migrating epithelial tongue. These data indicate that downmodulation of several G(1)/S-phase cyclins and a relative excess of CKIs may cooperate to ensure the quiescent state of migrating keratinocytes during wound healing.     

细胞周期调控与白血病

细胞周期是细胞生命活动的基本过程,由细胞周期素（cyclin）依次激活相应的细胞周期蛋白激酶（CDK）推动,而多种细胞周期蛋白依赖性激酶抑制因子（CKI）通过在不同的作用点抑制CDK活性,对细胞周期起着负调控的作用。本文就以上各个因素在细胞周期中的作用和白血病发病中以上各细胞周期因子的改变进行综述。     

复方苦参注射液影响HL-60细胞迁移的机制研究

目的探讨复方苦参注射液(CKI)影响HL-60细胞迁移的机制。方法选取HL-60细胞株作为研究对象,根据不同加药方案分为粒细胞集落刺激因子(G-CSF)组(40ng/mL)、CKI组(0.5ng/mL)、G-CSF和CKI联合加药组和空白对照组,共培养48h后采用蛋白质印迹法(WB)和逆转录聚合酶链反应(RT-PCR)分别检测微小RNA-146a(miR-146a)、趋化因子CXC受体4(CXCR4)等信使RNA(mRNA)、CXCR4蛋白表达变化情况;同时采用Transwell小室检测CKI、G-CSF作用前后细胞迁移率变化情况。结果 (1)与空白对照组相比,基质细胞衍生因子-1α(SDF-1α)能促进HL-60细胞的迁移[(2.01±0.13)比(1.05±0.10),P0.05],而CKI组、G-CSF组、CKI联合GCSF组均能阻断HL-60细胞向SDF-1α迁移[(1.50±0.04)、(1.68±0.08)、(1.27±0.02)比(2.01±0.13),P0.05]。(2)与空白对照组相比,CKI、G-CSF处理HL60细胞后,CXCR4的mRNA、蛋白表达均受抑[(0.75±0.10)、(0.47±0.09)比(1.00±0.08),P0.05];与CKI组、G-CSF组相比,CIK联合GCSF组CXCR4的mRNA蛋白表达受抑更明显[(0.24±0.04)比(0.47±0.09)、(0.75±0.10),P0.05]。(3)与空白对照组比较,G-CSF、CKI处理HL-60细胞后,miR-146a表达显著上调[(5.59±0.46)、(3.53±0.39)比(1.03±0.11),P0.01];而联合加药组上调更明显[(6.76±0.54)比(5.59±0.46)、(3.53±0.39),P0.05]。结论 CKI能协同G-CSF上调miR-146a表达,通过降低HL-60细胞表面的CXCR4表达而阻断CXCR4/SDF-1α信号轴,最终导致HL-60细胞体外迁移能力明显下降。     

Gaseous nitrogen oxides stimulate cell cycle progression by retinoblastoma phosphorylation via activation of cyclins/Cdks [correction].

Nitrogen oxides (NOx) are important indoor and outdoor air pollutants. Many studies have indicated that NOx gas causes lung tissue damage by its oxidation properties and its free radicals. In a previous study we demonstrated that NOx gas induced proliferation of human lung fibroblast MRC-5 cells. In this study we show that NOx gas stimulates MRC-5 cell proliferation by retinoblastoma (Rb) phosphorylation via activation of cyclin-cell division protein kinase (cdk) complexes [correction]. Western blot and immunoprecipitation data showed that NOx gas increased the expressions of cyclinA/cdk2, cyclinD1/cdk4, and cyclinE/cdk2 complexes in the cells at 9 h after treatment. The levels of phospho-Rb were also increased and cdk inhibitors (CKIs) p27 and p16 were apparently decreased. These data suggested that NOx gas stimulates cell-cycle progression by Rb phosphorylation via activation of cyclin-cdk complexes and inhibition of CKIs. In conclusion, the NOx-gas that induced lung fibroblast cell proliferation by stimulation of cell-cycle progression may contribute to lung fibrosis by NOx pollutants.     

细胞周期依赖性激酶抑制剂P27、P21在人角膜上皮的表达研究

目的　探讨细胞周期依赖性激酶抑制剂 (CKI) P2 7、P2 1在角膜上皮细胞的表达情况。方法　应用 SP免疫组化法 ,检测 P2 7、P2 1等细胞周期依赖性激酶抑制剂和增殖细胞核抗原 (PCNA)在角膜上皮不同部位的表达情况。结果　角膜缘上皮区 PCNA呈阳性表达 ,主要位于基底细胞层 ,中央区角膜上皮内未见阳性表达 ,差异有显著意义 (P <0 .0 1) ;P2 7、P2 1在中央区角膜上皮内呈阳性表达 ,角膜缘上皮内未见阳性表达 ,差异均有显著意义(P <0 .0 1)。结论　细胞周期依赖性激酶抑制剂 P2 7、P2 1和 PCAN在角膜上皮不同部位的表达差异 ,提示在角膜缘上皮基底层内存在着一群有较高的增殖能力、处于 G1 期的细胞群 ,即干细胞