抑癌基因p16INK4a与p53抑制白血病细胞株生长作用的比较

目的比较野生型p16INK4a、p53抑癌基因的表达对白血病细胞株K562和HL60的生长抑制。方法采用脂质体介导野生型p16INK4a、p53抑癌基因转染K562、HL60细胞并进行G418筛选,免疫印渍检测p16INK4a、p53基因的表达,通过细胞生长曲线检测细胞活力,流式细胞仪进行细胞DNA周期分析及细胞凋亡分析,采用联苯胺氧化试验检测K562细胞的分化。结果转染后p53、p16INK4a在K562及HL60细胞中表达;与对照细胞相比,实验组细胞生长受到明显的抑制,G1期细胞数增加,S期细胞减少。与p16INK4a相比,抑癌基因p53使细胞表达Annexin V增加,显示出更强的致凋亡现象,尤其在HL60细胞株。结论抑癌基因p16INK4a、p53能有效抑制白血病细胞株的生长,可能更适合复发、难治性白血病的基因治疗。     

共表达p53、p16基因真核表达载体的构建及其在K562细胞中的表达

[目的]构建p53、p16基因真核表达载体,观察其在K562细胞中的表达。[方法]设计并构建包含野生型p53cDNA、p16cDNA的真核双表达载体pBudCE4．1-53—16,脂质体法转染K562白血病细胞,用间接免疫细胞化学法、Western blot等方法鉴定外源性p53及p16的表达情况。[结果]构建成功p53、p16基因双表达真核载体,体外成功转染入K562细胞,检测到K562细胞外源性p53、p16蛋白的表达。[结论]重组质粒pBudCE4．1-53-16体外转染K562细胞后．目的基因能够在细胞中同时表达,为进一步研究两种基因用于肿瘤治疗奠定基础。     

野生型p53基因蛋白在氨肽酶抑制剂诱导人白血病细胞株K562细胞凋亡的实验研究

目的研究野生型p53基因蛋白对国产氨肽酶抑制剂乌苯美司(ubenimex)诱导人白血病细胞凋亡的影响及其作用机制。方法真核转导试剂FuGEMNE^TM6转导入K562细胞，免疫组化法检测细胞p53蛋白的表达，DNA片段原位末端标记及流式细胞仪(FCM)检测细胞凋亡，Rhodamin(Rh)123染色后，FCM检测细胞线粒体跨膜电位。结果p53基因cDNA转导的细胞p53蛋白表达增加；p53基因转导能促进ubenimex诱导K562细胞凋亡并增加ubenimex诱导的K562细胞线粒体跨膜电位(△ψm)的下降。结论野生型p53基因转导能促进ubenimex诱导K562细胞凋亡，并可能参与线粒体信号传导通路的调控。     

野生型p53对白血病K562细胞中心体过度复制的抑制作用

背景与目的：肿瘤组织细胞中p53基因突变或缺失是导致非整倍体的发生和基因组不稳定的主要原因之一：最近研究发现慢性粒细胞白血病（chronic myelogenous leukemia．CML）各期患者均有中心体异常,且异常的程度与临床分期有关。急变期显示更为严重的中心体异常。本研究建立携野生型p53基因的CML急变K562细胞株．以研究该细胞内野生型p53基因表达后p53信号转导通路对K562细胞中心体的影响。方法：用HEK293细胞扩增重组p53野生型、突变型及空载腺病毒载体,联合polybrene分别感染K562细胞;未接受感染的细胞作为空白对照。流式细胞术检测重组腺病毒载体感染效率,Western blot检测P53蛋白表达。间接免疫荧光染色后用激光共聚焦计数K562细胞中心体的变化。Westernblot检测p53信号转导通路下游效应分子生长阻滞和DNA损伤应答基因Gadd45a（growtharrest and DNA damage）、BubRl（Bublrelated）、AuroraA的表达。结果：成功建立携野生型p53基因的K562细胞株．腺病毒载体感染效率达60％以上,野生型p53可在K562细胞中持续表达。感染72h后,携野生型p53基因的K562细胞中中心体数量异常（n〉2）的细胞比例降至（0．38＋0．02）％,与空白对照组（0．71＋0．14）％比较其差异有统计学意义（P〈0．05）;Westernblot结果发现p53信号转导通路下游效应分子Gadd45a、BubRl表达分别上调93％、88％．而AuroraA的表达下降56％（P值均〈0．05）。结论：重组腺病毒介导的野生型p53基因能够在白血病K562细胞中持续表达：野生型P53蛋白可能通过转录激活-依赖途径上调Gadd45a、BubR1表达以及转录激活-非依赖途径使AuroraA的表达下降,从而抑制K562细胞中心体的过度复制。     

p53基因对胶质瘤细胞系U251生长抑制作用的研究

背景与目的：肿瘤抑制基因p53是调节多种与细胞周期、凋亡、DNA修复等有关基因表达的转录因子。p53基因在大约30％的胶质瘤中发生突变，在胶质瘤的发生和发展中起重要作用。本文主要探讨野生型p53基因过表达对脑胶质瘤细胞系U251细胞生长抑制的机制。方法：通过p53腺病毒表达载体pAdCMV-p53及空载体pAdCMV-lacZ分别感染U251细胞系，RT-PCR及Westem blot方法检测转染效率；并通过MTT检测生长抑制率、流式细胞仪检测细胞周期及TUNEL检测分析细胞凋亡等指标观察p53基因对U251细胞生长的影响。结果：MOI为100时，野生型p53基因的过表达可引起U251细胞G0、G1期阻滞、诱导U251细胞凋亡以及引起U251细胞生长抑制。结论：p53基因可以通过细胞周期G0、G1期阻滞及诱导细胞凋亡抑制胶质瘤细胞系U251的生长。     

野生型p53基因转染对卵巢癌细胞生长及药物敏感性影响

目的：探讨野生型p53基因转染对人卵巢癌细胞株SKOV-3的体外生长及裸鼠体内致瘤性抑制作用。并了解p53基因与SKOV-3细胞对顺铂敏感性之间的关系。方法：利用脂质体介导,将含有人野生型p53cDNA的真核表达质粒pCB6-p53导入SKOV-3细胞中,观察该细胞体外生长和裸鼠体内致瘤性改变;应用流式细胞仪检测细胞周期及凋亡情况,MTT法检测细胞药物敏感性改变。结果：免疫组化法证实外源性p53基因在阳性细胞克隆稳定存在;转染野生型p53基因的SKOV-3细胞体外生长速率下降,裸鼠体内致瘤性丧失;G1/G0期细胞百分比（81.5%)和凋亡细胞百分比（11%）增高;p53表达阳性的SKOV-3细胞对顺铂的敏感性明显增强。结论：野生型p53基因转染能使SKOV-3细胞出现生长抑制和对顺铂的化疗敏感性增强。     

野生型p53基因转染对卵巢癌细胞生长及药物敏感性影响

目的:探讨野生型p53基因转染对人卵巢癌细胞株SKOV-3的体外生长及裸鼠体内致瘤性抑制作用,并了解p53基因与SKOV-3细胞对顺铂敏感性之间的关系.方法:利用脂质体介导,将含有人野生型p53cDNA的真核表达质粒pCB6-p53导入SKOV-3细胞中,观察该细胞体外生长和裸鼠体内致瘤性改变;应用流式细胞仪检测细胞周期及凋亡情况,MTT法检测细胞药物敏感性改变.结果:免疫组化法证实外源性p53基因在阳性细胞克隆稳定存在;转染野生型p53基因的SKOV-3细胞体外生长速率下降,裸鼠体内致瘤性丧失;G1/G0期细胞百分比(81.5%)和凋亡细胞百分比(11%)增高;p53表达阳性的SKOV-3细胞对顺铂的敏感性明显增强.结论:野生型p53基因转染能使SKOV-3细胞出现生长抑制和对顺铂的化疗敏感性增强.     

p16基因治疗对肝癌细胞生物学行为的影响

背景与目的：p16基因是原发性肝癌（hepatocellular carcinoma,HCC）中失活频率很高的抑癌基因之一,应是治疗HCC的理想靶基因。本研究的目的是探讨转入野生型p16cDNA对肝细胞性肝癌细胞生物学行为的影响。方法：用我们构建的p16基因的逆转录病毒表达载体pcLXSN-p16,分别感染p16蛋白表达阴性与表达阳性的肝癌细胞株SNU-449与HepG2.2.15,筛选出稳定的表达株,对转基因后肿瘤细胞的生物学行为进行观察。结果：p16蛋白表达阴性的SNU-449细胞转入野生型p16基因后,细胞生长速度明显减慢,G0-G1期细胞明显多于转基因前,其裸鼠首次接种成瘤率（可在一定程度上反映瘤细胞对组织的侵袭能力）、在裸鼠体内的生长速度以及对裸鼠的致死性均低于未转基因者。而p16蛋白表达阳性的HepG2.2.15细胞转入外源p16cDNA后,其生长状况及细胞周期则未发现有明显改变。就SNU-449与HepG2.2.15细胞株而言,转入p16cDNA均未能诱导细胞凋亡。结论：转入外源野生型p16基因可抑制p16蛋白表达阴性的肝癌细胞的生长并降低其侵袭能力,但对p16蛋白表达阳性的肝癌细胞的生长则无影响。     

p53和Bcl-2 mRNA表达在三七皂苷R1诱导HL-60细胞凋亡中的作用

目的：探讨三七皂苷R1诱导HL-60细胞凋亡的作用机制.方法：采用MTT比色法观察三七皂苷R1对人白血病细胞株HL-60细胞增殖的抑制作用.采用流式细胞术检测细胞凋亡改变,并以RT-PCR检测凋亡调节基因p53、Bcl-2的表达.结果：三七皂苷R1能明显抑制人白血病细胞株HL-60细胞的生长,且呈时间和浓度依赖性.三七皂苷R1作用后人白血病细胞株HL-60细胞呈现凋亡特征,流式细胞术显示凋亡细胞比例升高.RT-PCR检测可见p53 mRNA表达显著增加,而Bcl-2 mRNA表达减少.结论：三七皂苷R1能诱导人白血病细胞株HL-60细胞凋亡,其作用可能与凋亡调节基因p53的上调和Bcl-2的下调有关.     

食管鳞癌中hMLH1、E-cadherin、p16^INK4a基因启动子甲基化及其意义

背景与目的:目前认为抑癌基因启动子甲基化导致转录抑制是恶性肿瘤发生的重要机制之一,hgLH1、E-cadherin及p16INK4a基因在多种恶性肿瘤中都已被证实存在较高频率的甲基化.本研究通过检测食管鳞癌组织及癌旁组织中hMLH1、E-cadherin,p16INK4a基因启动子甲基化的发生情况,探讨hMLH1、E-cadherin、p16INK4a基因启动子甲基化在食管鳞癌发生发展中的作用.方法:采用酚-氯仿法提取105例食管鳞癌组织及癌旁组织的基因组DNA,应用甲基化特异性PCR对所提DNA进行hMLH1、E-cadherin、p16INK4a基因甲基化检测.采用EnVison免疫组织化学二步法对癌组织中上述3种基因蛋白表达进行检测.结果:癌组织中E-cadherin、hMLH1、p16INK4a基因启动子甲基化的阳性率分别为57.1%(60/105)、20.9%(22/105)和50.5%(53/105),而癌旁食管组织中相应的3个基因的甲基化率分别为10.5%(11/105)、1.9%(2/105)和7.6%(8/105),均显著低于癌组织.E-cadherin(P=0.021)及p16INK4a(P=0.026)基因甲基化与蛋白表达缺失密切相关,而hMLH1基因甲基化与蛋白表达无显著相关性.E-cadherin基因启动子甲基化与淋巴结转移有关(P=0.016),p16INK4a基因启动子甲基化与低分化癌有关性(P=0.024).hMLH1基因甲基化与各项临床病理特征均无关.结论:食管鳞癌中p16INK4a基因启动子甲基化与相应蛋白表达缺失密切相关,且在低分化癌中更多见;E-cadherin基因启动子甲基化与相应蛋白质表达缺失有相关性,并且有淋巴结转移多见的显著特征,这2个基因的甲基化位点与食管鳞癌密切相关.hMLH1基因甲基化可能并不直接参与食管鳞癌的发生、发展.     

腺病毒介导野生型p53基因对人白血病细胞系HL-60、K_(562)生长的抑制作用

目的探索肿瘤抑制基因ｐ５３对人白血病细胞系的生长抑制作用和促凋亡作用。方法选用含野生型ｐ５３基因的重组腺病毒载体,体外感染人白血病细胞系ＨＬ－６０、Ｋ５６２。通过细胞生长曲线,ＤＮＡ检测及流式细胞仪分析检测转染细胞的增殖受抑制和细胞凋亡的发生。结果ＰＣＲ检测转染后ＨＬ－６０和Ｋ５６２细胞ｐ５３ｃＤＮＡ表达。转染后Ａｄ／ｐ５３病毒对ＨＬ－６０细胞和Ｋ５６２细胞的生长有抑制作用。随着Ａｄ／ｐ５３病毒浓度加大,ＨＬ－６０和Ｋ５６２细胞的ＯＤ值越低即生长抑制程度越大。经Ａｄ／ｐ５３病毒转染的ＨＬ－６０和Ｋ５６２细胞均有明显的细胞凋亡峰出现,对照细胞则无。细胞周期分析无明显异常发现。结论重组腺病毒载体介导的野生型ｐ５３基因在体外对人白血病细胞系ＨＬ－６０和Ｋ５６２的生长有抑制作用,能导致细胞凋亡的发生。     

外源性野生型p53基因抑制裸小鼠体内人白血病细胞的生长

目的探讨野生型ｐ５３基因对体内生长的白血病细胞的抑制作用。方法采用直接注射法向裸小鼠体内ＨＬ６０－ｎ和Ｋ５６２－ｎ细胞移植瘤注射编码人野生型ｐ５３的重组逆转录病毒，使其在这两种细胞中表达，并导致其编程性细胞死亡。结果裸小鼠在接种ＨＬ６０－ｎ或Ｋ５６２－ｎ细胞后２４ｈ，于接种部位连续７天注射编码野生型ｐ５３的逆转录病毒，移植瘤发生的潜伏期较对照组明显延长。结论直接注射转移野生型ｐ５３基因能有效地抑制裸小鼠体内人白血病细胞的生长。     

Loss of p16INK4a expression is associated with vascular endothelial growth factor expression in squamous cell carcinoma of the esophagus

Vascular endothelial growth factor (VEGF) expression has been suggested to correlate with intratumoral microvessel density, tumor advancement and prognosis in esophageal squamous cell carcinoma (ESCC). Previous studies have showed that disruption of cell cycle regulator p16 is related to oncogenesis and tumor progression in ESCC. We hypothesized that VEGF expression in ESCC is reflected by abnormalities in the p16(INK4a) gene. To clarify the regulatory role of p16(INK4a) in VEGF expression in vitro, we transferred the p16(INK4a) gene into a p16(INK4a)-deleted ESCC cell line and observed changes in VEGF expression. Furthermore, we immunohistochemically assessed the expression of the cell cycle regulators (p16, p53 and RB) and VEGF in 90 surgically resected specimens of ESCC. Introduction of p16(INK4a) cDNA by the p16 expression vector significantly suppressed cell proliferation in the p16(INK4a)-deleted cell line TE8 (p < 0.0001). VEGF secretion by TE8 cells transfected with the p16(INK4a) vector was significantly suppressed as compared to non-transfected TE8 cells (p < 0.0001) and TE8 cells transfected with a control vector (p = 0.0015). The immunohistochemical studies of ESCC primary tumor specimens showed that loss of p16 expression was significantly correlated with VEGF-positive expression (p = 0.0004). The cumulative postoperative survival rate in the group with p16-positive and VEGF-negative expression was significantly higher than in the other groups. Neither p53 nor RB expression had any impact on outcome. Aberrant p53 expression tended to be associated with VEGF expression, but the trend did not reach statistical significance. Our study demonstrated that VEGF expression was correlated with p16 expression in ESCC. Our results suggest that p16 may have a regulatory role in VEGF expression in ESCC.     

Adenovirus-mediated p16INK4a gene expression radiosensitizes non-small cell lung cancer cells in a p53-dependent manner

We examined the influence of adenovirus-mediated wild-type p16INK4a (Ad/p16) expression on the radiation sensitivity of NSCLC cell lines, all of which lacked constitutive p16INK4a but each of which varied in p53 status: A549 (-p16INK4a/ +pRb/wt-p53), H322 (-p16INK4a/ +pRb/mt-p53), and H1299 (-p16INK4a/ +pRb/deleted-p53). The in vitro clonogenic survival results indicate that Ad/p16 enhanced the radiosensitivity of A549 but not H322 or H1299. Further analysis indicated that the apoptosis induced by combination therapy using Ad/p16 plus irradiation was dependent on the endogenous p53 status of the cancer cells. We performed Western blotting to analyse the p53 protein expression of A549 cells treated with either Ad/p16 or Ad/Luc. Endogenous p53 protein levels were higher in A549 cells transfected with Ad/p16 than in those transfected with Ad/Luc. Furthermore, when wt-p53 protein expression was restored in H1299 using Ad/ p53, Ad/p16 stabilized p53 protein expression and radiosensitized the cells. These results suggest that Ad/ p16-induced stabilization of p53 protein may play an important role in Ad/p16 mediated radiosensitization by enhancing or restoring apoptosis properties. Thus, Ad/ p16 plus radiation in combination may be a useful gene therapy strategy for tumors that have wt-p53 but nonfunctional p16INK4a.     

外源性野生型p53基因在K562－n细胞表达的意义

目的研究外源性野生型ｐ５３基因在红白血病细胞表达的意义。方法采用重组逆转录病毒载体介导的方法将人野生型ｐ５３基因ｃＤＮＡ转移入Ｋ５６２－ｎ细胞，用形态学、流式细胞仪和联苯胺染色试验检测转基因后的Ｋ５６２－ｎ细胞。结果野生型ｐ５３基因可以诱导Ｋ５６２－ｎ细胞编程性细胞死亡和分化的形态特征，且伴有细胞周期Ｇ１期的生长阻滞。结论野生型ｐ５３基因能抑制人红白血病细胞生长的某些机制。     

Involvement of p53 in oroxylin A‐induced apoptosis in cancer cells

Oroxylin A, a naturally occurring monoflavonoid extracted from Scutellariae radix, exhibits anticancer activity and induces apoptosis in human hepatocellular carcinoma HepG2 cells according to our previous data. In this study, we investigate whether p53 is involved in oroxylin A‐triggered viability inhibition and apoptosis induction in cancer cells. In a panel of different cancer cell lines, more potent inhibitory effects of oroxylin A were observed in wtp53 cells than those in mtp53 or p53‐null cells. Moreover, p53‐siRNA‐transfected HepG2 cells showed lower levels of apoptosis induced by oroxylin A than control‐siRNA‐transfected cells. Likewise, after oroxylin A treatment, p53‐null K‐562 cells displayed promoted apoptosis rate when transfected with wtp53 plasmid. Western blot and real‐time RT‐PCR assay revealed that oroxylin A markedly upregulated p53 protein expression in HepG2 and p53‐overexpressing K‐562 cells, but had no influence on p53 mRNA synthesis. Furthermore, after co‐treatment with cycloheximide, oroxylin A still exerted a little effect on p53 expression. The negative regulator of p53, MDM2 protein was detected, and downregulated expression was observed. In the presence of MG132, an inhibitor of proteasome‐mediated proteolysis, no change in p53 expression was obtained. Additionally, the antioxidant N‐acetyl‐L‐cysteine could obviously abrogate p53 stabilization triggered by oroxylin A. Therefore, it is summarized that oroxylin A stabilized p53 expression and induced apoptosis at the posttranslational level via downregulating MDM2 expression and interfering MDM2‐modulated proteasome‐related p53 degradation. This indicated that oroxylin A could be served as a potential, novel agent candidate for cancer therapy. © 2009 Wiley‐Liss, Inc.     

H-, K- and N-Ras inhibit myeloid leukemia cell proliferation by a p21WAF1-dependent mechanism

Mutated ras genes are frequently found in human cancer. However, it has been shown that oncogenic ras inhibits growth of primary cells, through pathways involving p53 and the cell cycle inhibitors p16INK4a and p19ARF. We have analysed the effect of the ectopic expression of the three mammalian ras genes on the proliferation of K562 leukemia cells, which are deficient for p53, p16INK4a, p15INK4b and p19ARF genes. We have found that high expression levels of both wild-type and oncogenic H-, K- and N-ras inhibit the clonogenic growth of K562 cells. Induction of H-rasV12 expression in K562 transfectants retards growth and this effect is accompanied with an increase of p21WAF1 mRNA and protein levels. Furthermore, p21WAF1 promoter is activated potently by oncogenic ras and less pronounced by wild-type ras. This induction is p53-independent since a p21WAF1 promoter devoid of the p53 responsive elements is still activated by Ras. Finally, inhibition of p21WAF1 expression by an antisense construct partially overcomes the growth inhibitory action of oncogenic H-ras. Altogether, these results indicate that the antiproliferative effect of ras in myeloid leukemia cells is associated to the induction of p21WAF1 expression and suggest the existence of p19ARF and p16INK4a-independent pathways for ras-mediated growth inhibition.     

G1 checkpoint protein and p53 abnormalities occur in most invasive transitional cell carcinomas of the urinary bladder.

The G1 cell cycle checkpoint regulates entry into S phase for normal cells. Components of the G1 checkpoint, including retinoblastoma (Rb) protein, cyclin D1 and p16INK4a, are commonly altered in human malignancies, abrogating cell cycle control. Using immunohistochemistry, we examined 79 invasive transitional cell carcinomas of the urinary bladder treated by cystectomy, for loss of Rb or p16INK4a protein and for cyclin D1 overexpression. As p53 is also involved in cell cycle control, its expression was studied as well. Rb protein loss occurred in 23/79 cases (29%); it was inversely correlated with loss of p16INK4a, which occurred in 15/79 cases (19%). One biphenotypic case, with Rb+p16- and Rb-p16+ areas, was identified as well. Cyclin D1 was overexpressed in 21/79 carcinomas (27%), all of which retained Rb protein. Fifty of 79 tumours (63%) showed aberrant accumulation of p53 protein; p53 staining did not correlate with Rb, p16INK4a, or cyclin D1 status. Overall, 70% of bladder carcinomas showed abnormalities in one or more of the intrinsic proteins of the G1 checkpoint (Rb, p16INK4a and cyclin D1). Only 15% of all bladder carcinomas (12/79) showed a normal phenotype for all four proteins. In a multivariate survival analysis, cyclin D1 overexpression was linked to less aggressive disease and relatively favourable outcome. In our series, Rb, p16INK4a and p53 status did not reach statistical significance as prognostic factors. In conclusion, G1 restriction point defects can be identified in the majority of bladder carcinomas. Our findings support the hypothesis that cyclin D1 and p16INK4a can cooperate to dysregulate the cell cycle, but that loss of Rb protein abolishes the G1 checkpoint completely, removing any selective advantage for cells that alter additional cell cycle proteins.     

苦瓜蛋白在K562/A02细胞生长抑制和凋亡中的作用及其机制研究

目的:研究苦瓜蛋白(momordin)诱导人慢性粒细胞白血病耐药细胞株K562/A02的凋亡及作用机制.方法:采用CCK-8法检测细胞生长抑制率,FCM法和细胞形态学检测细胞凋亡,FCM法检测P-糖蛋白(P-glycoprotein, P-gp)、p53、bcl-2和caspase-3蛋白表达水平,并运用caspase-8活性检测试剂盒检测caspase-8的活性.结果:苦瓜蛋白能抑制K562/A02耐药细胞的生长且呈剂量依赖关系,并能诱导细胞凋亡,能使P-gp、p53和bcl-2的表达下降,而使caspase-3和caspase-8活性增强.结论:苦瓜蛋白可逆转耐药细胞株K562/A02的细胞凋亡受抑性,主要机制可能与其下调p53、P-gp和bcl-2的表达以及提高caspase活性有关.