p53和HPV—16、18E6蛋白在宫颈癌的表达

目的探讨宫颈癌中抑癌基因p53蛋白与HPV-16、18癌基因E6蛋白的表达及其意义.方法采用SP免疫组织化学方法,检测68例宫颈癌和8例慢性宫颈炎上皮组织中p53和HPV-16、18E6蛋白的表达.结果68例宫颈癌中有17例p53蛋白和60例HPV-16、18E6蛋白呈阳性表达,阳性率分别为25.0%和88.2%.p53蛋白阳性表达与组织学类型有关,其阳性率在宫颈腺癌中为83.3%和宫颈鳞癌中为17.2%,有极显著性差异(P＜0.01);p53蛋白表达也与临床分期相关,该蛋白阳性表达率随着临床分期上升而增高.p53表达同肿瘤分化程度,淋巴结转移无关(P＞0.05).HPV-16、18E6蛋白在宫颈癌组织中的表达同肿瘤分化程度、淋巴结转移、组织学类型和临床分期无关(P＞0.05).在慢性宫颈炎上皮组织中均无p53和HPV-16、18E6蛋白表达.结论p53蛋白阴性和弱阳性表达以及HPV-16、18E6蛋白过度表达与宫颈癌发生有关,但在宫颈腺癌和临床分期升高的宫颈癌组织中,p53蛋白阳性表达的增强可能是p53基因突变的结果,或者与其他细胞蛋白结合,阻止了HPV-16、18E6蛋白对p53蛋白的降解作用,使p53蛋白稳定性增加和阳性表达水平提高.     

Proteasome inhibition mediates p53 reactivation and anti-cancer activity of 6-Gingerol in cervical cancer cells

Human papilloma virus (HPV) expressing E6 and E7 oncoproteins, is known to inactivate the tumor suppressor p53 through proteasomal degradation in cervical cancers. Therefore, use of small molecules for inhibition of proteasome function and induction of p53 reactivation is a promising strategy for induction of apoptosis in cervical cancer cells. The polyphenolic alkanone, 6-Gingerol (6G), present in the pungent extracts of ginger (Zingiber officinale Roscoe) has shown potent anti-tumorigenic and pro-apoptotic activities against a variety of cancers. In this study we explored the molecular mechanism of action of 6G in human cervical cancer cells in vitro and in vivo. 6G potently inhibited proliferation of the HPV positive cervical cancer cells. 6G was found to: (i) inhibit the chymotrypsin activity of proteasomes, (ii) induce reactivation of p53, (iii) increase levels of p21, (iv) induce DNA damage and G2/M cell cycle arrest, (v) alter expression levels of p53-associated apoptotic markers like, cleaved caspase-3 and PARP, and (vi) potentiate the cytotoxicity of cisplatin. 6G treatment induced significant reduction of tumor volume, tumor weight, proteasome inhibition and p53 accumulation in HeLa xenograft tumor cells in vivo. The 6G treatment was devoid of toxic effects as it did not affect body weights, hematological and osteogenic parameters. Taken together, our data underscores the therapeutic and chemosensitizing effects of 6G in the management and treatment of cervical cancer.     

HPV-18 E6*I modulates HPV-18 full-length E6 functions in a cell cycle dependent manner

The E6 ORFs of the high-risk Human Papillomavirus (HPV) Types 16 and 18 have been shown to encode (besides the full-length product) several truncated forms, termed E6*. We have reported previously that the HPV-18 E6*I protein interacts with the full-length E6 protein as well as with the ubiquitin ligase E6-AP and, as a result of this, E6* can inhibit E6-mediated degradation of p53. Moreover, ectopic expression of the HPV-18 E6*I protein has an antiproliferative effect in cervical cancer-derived cell lines. These results led us to investigate further the modulatory functions of E6*I on E6. Using epitope tagged versions of the 2 proteins we have analyzed the sub-cellular distribution of the full-length HPV18 E6 and HPV18 E6*I, as well as their respective cellular abundance during the cell cycle, and show specific upregulation of E6*I during G2/M. We also investigated the effect of E6*I overexpression in cell lines derived from cervical tumors, with respect to the expression levels of E6 target proteins, such as p53, hDlg and Scribble and find a corresponding increase in p53 expression also during G2/M. In addition we show that the overexpression of E6*I reduces the amount of E6 in the insoluble nuclear and membrane fractions of the cell. E6 levels can, however, be restored by the addition of a specific proteasome inhibitor, suggesting that the interaction between E6 and E6*I leads to the destabilization of a subset of the E6 protein. These results suggest that the E6*I protein can function as a fine regulator of the full-length E6 protein by direct interaction that leads both to changes in its cellular abundance as well as its distribution during particular phases of the cell cycle.     

Therapeutic potential of an adenovirus expressing p73 beta, a p53 homologue, against human papilloma virus positive cervical cancer in vitro and in vivo

Human papilloma virus (HPV) infection is the most important risk factor for cervical cancer development. p53 based gene therapy is not suitable for cervical cancer because HPV oncoprotein E6 inactivates p53 protein by targeting it for ubiquitin mediated degradation. Here we evaluated the efficiency of Ad-p73, a replication deficient adenovirus expressing p73beta a p53 homologue, to inhibit the growth of HPV positive cervical cancer cells in vitro using tissue culture system and in vivo using human xenografts in nude mice. Ad-p73, but not Ad-p53 (p53 adenovirus), inhibited the growth in vitro of three different HPV positive cervical cancer cell lines, HeLa, ME180, and SiHa, efficiently, which correlated with stable expression of functional p73 protein. However, the growth of a HPV negative cervical cancer cell line, C33A, was inhibited equally by both Ad-p73 and Ad-p53. In addition, we show that Ad-p73 preinfected HeLa cells and HCT116 E6 cells, an E6 stable cell line, failed to form tumors in nude mice unlike Ad-p53 or Ad-LacZ preinfected cells. Moreover, Ad-p73, but not Ad-p53, inhibited completely the growth of already established tumors of HeLa or HCT116 E6 cells. Furthermore, the ability of p73 to inhibit the growth of these tumors correlated with the stable expression of p73 protein with the concomitant induction of its target gene p21(WAF1/CIP1) and induction of apoptosis in tumor cells. These results suggest that Ad-p73 inhibits efficiently the growth in vitro and tumorigenicity and tumor growth in vivo of HPV positive cervical cancer cells and that p73-based approach should be explored as a potential therapeutic model for the treatment of cervical cancer.     

HPV E6,p53与宫颈癌的关系及其在基因治疗中的应用

目前宫颈癌的发病率仍居全世界妇女常见恶性肿瘤的第二位.高危型人乳头瘤病毒（high-risk Human Papillomavirus,HR-HPV）感染是宫颈癌及其癌前病变最主要的诱因之一.抑癌基因p53能够有效地抑制细胞增殖和促进细胞凋亡,人类近半数的肿瘤都与p53基因的突变和失活有关,HPV E6蛋白降解p53蛋白,是宫颈癌发生的前提.选择性杀伤p53功能缺失的肿瘤细胞,同时保护正常细胞,发展HPV疫苗及联合用药是临床肿瘤免疫学家进行宫颈癌基因治疗的目标.     

宫颈鳞癌HPV16感染及其与c-myc p53表达的关系

目的：探讨HPV16在宫颈鳞癌发生发展中的作用及其与c-myc、p53表达产物之间的关系。方法：采用原位杂交和免疫组化方法检测了18例慢性宫颈炎、28例CIN、4例宫颈浸润性腺鳞癌和55例宫颈浸润性鳞癌HPV16 E6 DNA及其蛋白和c-myc、p53蛋白的表达情况。结果：浸润性宫颈癌。HPV16 E6 DNA及其蛋白、p53蛋白阳性率明显高于慢性宫颈炎组，c-myc蛋白阳性率则明显低于慢性宫颈炎组。p53蛋白阳性率与HPV16 E6 DNA的检出率之间无负相关关系。结论：宫颈鳞癌的发生发展可能与HPV16 E6 DNA的检出及c-myc、p53蛋白的表达异常相关。     

Radioimmunotherapy with an antibody to HPV16 E6 oncoprotein is effective in experimental cervical tumor expressing low levels of E6

Purpose

HPV16 is associated with ∼50% of all cervical cancers worldwide. The E6 and E7 genes of oncogenic HPV types, such as HPV16, are necessary for the HPV transforming function and tumorogenesis making them ideal targets for novel treatments. Radioimmunotherapy employs systemically administered radiolabeled monoclonal antibodies (mAbs) that bind to tumor-associated antigens. Previously we demonstrated in mice that radioimmunotherapy targeting viral antigens with mAb to HPV16 E6 suppressed CasKi cervical tumors expressing high levels of E6 (∼600 copies of HPV per cell). However, that study opened the question whether radioimmunotherapy can suppress the growth of cervical tumors with low E6 and E7 expression, such as may be seen in patients.

Experimental Design

We evaluated the expression of E6 in patients'' tumors and in the SiHa cell line expressing low levels of E6 and E7 (1–2 copies of HPV per cell) and found them comparable. We initiated SiHa tumors in nude mice, radiolabeled C1P5 mAb to E6 with a beta-emitter 188-Rhenium (¹⁸⁸Re) and treated tumor-bearing mice with: (1) 200 µCi ¹⁸⁸Re-C1P5 alone; (2) proteasome inhibitor MG132 alone; (3) MG132 followed by 200 µCi ¹⁸⁸Re-C1P5; (4) unlabeled C1P5; (5) 200 µCi ¹⁸⁸Re-18B7 (isotype-matching control mAb); (6) no treatment. ¹⁸⁸Re-C1P5 alone and in combination with MG-132 significantly retarded tumor growth compared to all control groups.

Conclusions

Our data demonstrate the possibility to suppress tumor growth by targeting viral antigens even in cervical tumors with low E6 expression and provide additional evidence for the potential usefulness of radioimmunotherapy targeting HPV-related antigens in the clinic.Key words: cervical cancer, viral antigens, E6 oncoprotein, radioimmunotherapy, 188-rhenium     

Chemoradiation of cervical cancer cells: targeting human papillomavirus E6 and p53 leads to either augmented or attenuated apoptosis depending on the platinum carrier ligand

Recent clinical trials comparing concurrent chemotherapy and radiation with radiation alone in cervical cancer have shown that chemoradiation reduces the risk of death by 30-50%. Despite the clinical success, treatment responses at the cellular level are still inadequately explored. A key event in cervical carcinogenesis is the disruption of p53 tumor suppressor pathway by human papillomavirus (HPV) E6 oncogene. We found that regardless of the HPV type in SiHa (HPV 16+) CaSki (HPV 16+), HeLa (HPV 18+), and UT-DEC-1 (HPV 33+) cell lines, cisplatin, carboplatin, and a novel platinum compound, oxaliplatin, activated a p53 reporter and reduced the HPV E6 mRNA. Carboplatin and oxaliplatin treatment led also to stabilization of p53, whereas none of the platinums changed p73 levels. After irradiation (IR) alone, a decrease in HPV E6 mRNA levels and an activation of the p53-reporter were detected in SiHa, CaSki, and HeLa cells, but not in UT-DEC-1 cells. Concomitant platinum treatment and IR led to poly(ADP-ribose) polymerase cleavage as a sign of caspase-3 activation and apoptosis. Clonogenic survival was enhanced by expressing a dominant negative p53 or ectopic HPV16 E6 in SiHa and HeLa cells treated with IR, carboplatin, or oxaliplatin or with a combination of IR + carboplatin or oxaliplatin. In contrast, dominant negative p53 or ectopic HPV 16 E6 sensitized the cells to cisplatin. Pt chemotherapeutics and radiation had a synergistic cytotoxic effect as determined by Bliss independence criterion. Taken together, p53 has a significant role in the cellular response to chemoradiation treatment in cervical cancer cell lines, but p53 activity may have a dramatically different effect on cell survival depending on the platinum carrier ligand.     

宫颈腺癌p53、HPV16/18-E6蛋白和ER的表达及其临床意义

目的　探讨宫颈腺癌组织中 p5 3蛋白、HPV16 / 18 E6蛋白及ER的表达及其临床意义。 方法　采用免疫组织化学S P法对 6 3例宫颈腺癌组织进行p5 3蛋白、HPV16 / 18 E6蛋白及ER检测。结果　 6 3例宫颈腺癌中p5 3、HPV16 / 18 E6蛋白和ER阳性表达率分别为为 5 2 .3%、31.7%和 4 9.2 %。p5 3表达与肿瘤病理分级、临床分期 (Ⅰ、Ⅱ、Ⅲ期 )有关。HPV16 / 18 E6、ER的表达与宫颈腺癌的病理学分级、临床分期无关 ,但与 p5 3表达呈负相关 (P <0 .0 1) ,HPV16 / 18 E6、ER在宫颈腺癌中的表达呈正相关 (P <0 .0 1)。结论　随宫颈腺癌组织病理分级和临床分期增高p5 3阳性表达率逐渐增高 ,可能与 p5 3突变有关 ,部分宫颈腺癌的发病可能与HPV16 / 18 E6蛋白过度表达有关。部分宫颈腺癌可能属于激素依赖性 ,雌激素可能有协同HPV致癌的作用。     

Inhibition of E6 induced degradation of p53 is not sufficient for stabilization of p53 protein in cervical tumour derived cell lines.

The E6 proteins derived from tumour associated papillomavirus types target the cellular tumour suppressor protein p53 for ubiquitin mediated degradation. In cell lines derived from cervical tumours the p53 protein is present in very low amounts, but it can be activated by appropriate DNA damaging agents, indicating that functional p53 is present within these lines. Recent studies have also shown that different polymorphic forms of the p53 protein are differentially susceptible to E6 mediated degradation. Therefore we have been interested in analysing the effects of different HPV E6 proteins upon p53 levels in a variety of cervical tumour derived cell lines. We show that inhibition of E6 mediated degradation of p53 frequently results in increased levels of p53 expression. However, there are notable exceptions to this where increased p53 levels are only obtained following DNA damage and proteasome inhibition. We also show in E6 expressing cells, that as well as p53 being targeted for degradation, the localization of p53 to the nucleus is also inhibited, consistent with previous observations which indicate that degradation of p53 is not essential for E6 mediated inhibition of p53 function. These results have important implications for any potential therapies which might aim to block E6 mediated degradation of p53.     

喉癌组织中HPV16／18E6、p53和EZH2的表达及其相关性分析

目的 检测HPV16／18E6、p53和EZH2在喉鳞状细胞癌（喉癌）组织中的表达,探讨它们在肿瘤发生发展过程中的相互作用。方法 采用免疫组化En Vision法检测78例喉癌、15例癌旁正常组织、20例声带息肉中HPV16／18E6、p53和EZH2蛋白的表达情况,分析它们的表达与喉癌临床病理特征之间的关系以及三者之间的相关性。结果 喉癌组织、癌旁正常组织、声带息肉中HPV16／18E6蛋白的阳性表达率分别为47.4％（37／78）、20.0％（3／15）和0（0／20）;p53蛋白阳性表达率为60.3％（47／78）、33.3％（5／15）和0（0／20）;EZH2蛋白阳性表达率为65.4％（51／78）、40.0％（6／15）和5.0％（1／20）,差异均具统计学意义（P＜0.05）。HPV16／18E6、EZH2的阳性表达率均随肿瘤T分期升高而增高（P＜0.05）;淋巴结转移组HPV16／18E6、p53阳性表达率高于无淋巴结转移组（P＜0.05）;p53阳性表达率随分化程度升高而增高（P＜0.05）。p53和EZH2阳性表达表达一致（kappa值=0.451,P＜0.05）。结论 HPV16／18E6、p53和EZH2蛋白表达与喉癌的发生关系密切。EZH2过表达与p53失活有关,二者在促进喉癌发展过程中发挥重要作用。     

The cytotoxicity of chemotherapy drugs varies in cervical cancer cells depending on the p53 status

Metastatic cervical cancer remains a clinical problem. The development of more efficient treatment modalities and the optimal use of chemo- and radiotherapy require better understanding of their impact on regulation of cell survival and apoptosis, but the issue is insufficiently explored. Human papillomavirus (HPV) E6 protein is present in nearly all cervical cancers, targeting the p53 tumor suppressor protein for degradation. We studied the role of p53 in mediating the cytotoxic effects of 31 chemotherapy compounds. SiHa cervical cancer cells, carrying wild type (wt) p53 and HPV16 genome, were stably transfected with dominant negative p53 (DDp53) or ectopic HPV16 E6 in order to inhibit p53 function. The effects of chemotherapy drugs in these cells were compared to the effects in cells retaining endogenous residual p53 activity. Twenty-ight out of 31 drugs reduced the amount of E6 mRNA, but only some induced marked p53 activation. In clonogenic cell survival experiments, the presence of DDp53 and ectopic E6 either increased or decreased cytotoxicity, depending on the drug. The decrease of E6 mRNA was necessary, but not sufficient event in the p53 activation by chemotherapy. The impact of p53 on clonogenic cell survival varied between 0-60%, indicating that p53 plays an important, but not crucial role in response to chemotherapy. The finding that chemosensitivity varies depending on the p53 status may have clinical implications, since early stage cervical cancer cells usually carry wt p53, whereas p53 mutations are frequently found in advanced disease.     

HPV18E6基因沉默对宫颈癌Hela细胞生长和凋亡的影响

目的：观察RNA干扰法沉默HPV18E6基因表达对宫颈癌Hela细胞牛长和凋亡的影响，探索宫颈癌基因治疗的新途径。方法：针对HPV18E6 mRNA序列合成一对60bp的编码siRNA的DNA模板和一对60bp的非特异性对照DNA模板，构建pSUPER—siRNA和pSUPER—com重组质粒，瞬时转染Hela细胞；采用RT—PCR法检测质粒转染后细胞HPV18E6基因表达的变化，用蛋白免疫印迹法检测转染后Hela细胞p53、p21、Bcl-2和Bax蛋白表达变化，以细胞计数法检测细胞生长情况，Hoechest／PI双荧光活细胞染色法检测细胞凋亡。结果：pSUPER—siRNA质粒转染能有效降低HPV18E6在mRNA水平的表达，转染后48小时，抑制效率达70％以上；转染后细胞053、p21和Bax蛋白表达显著增加，Bcl-2蛋白表达减少。RNA干扰法沉默HPV18E6基因表达后，Hela细胞增殖受到明显抑制，细胞凋亡率明显增加。结论：pSUPER—siRNA质粒转染可有效抑制HPV18E6在人宫颈癌Hela细胞中的表达，抑制Hela细胞生长并促进其凋亡。以HPV18E6为靶点的RNA干扰技术可望成为宫颈癌基因治疗的新途径。     

Upregulation of p18Ink4c expression by oncogenic HPV E6 via p53-miR-34a pathway

Binding of p53 to miR-34a promoter activates the expression of tumor-suppressive miR-34a. Oncogenic human papillomavirus (HPV) infection downregulates miR-34a expression through viral E6 degradation of p53. In our report, we found that miR-34a specifically targets p18Ink4c, a CDK4 and CDK6 inhibitor induced by E2F transactivation. HPV18(+) HeLa cells with ectopic miR-34a expression or by E6 siRNA knockdown-induced expression of endogenous miR-34a exhibited a substantial reduction of p18Ink4c in a dose-dependent manner, but had no effect on p16Ink4a, another member of CDK4/6 inhibitor family. In contrast, de novo infection by oncogenic HPVs of human keratinocyte-derived raft tissues increased p18Ink4c expression. Suppression of endogenous miR-34a in cell lines with a miR-34a inhibitor also increased p18Ink4c. We found that miR-34a suppresses the expression of p18Ink4c by binding to a specific seed match in the 5' UTR of p18Ink4c. Further investigation found remarkable increase of p18Ink4c in cervical precancer lesions and cervical cancer. Immunohistochemical staining of cervical tissue arrays showed increased expression of p18Ink4c in 68% of cervical cancer, 8.3% of chronic cervical inflammation and 4.8% of normal cervix. Although p18Ink4c inhibits cell proliferation in general and regulates E2F1 expression in HCT116 cells, it appears not to function as a tumor suppressor in cervical cancer cells lacking an intact G1 checkpoint because of viral E7 degradation of pRB. In summary, our study demonstrates an intimate connection among oncogenic HPV E6, p53, miR-34a and p18Ink4c and identifies p18Ink4c as a possible biomarker for cervical cancer.