Human papillomavirus and p16 expression in inverted papillomas of the urinary bladder

Human Papillomaviruses (HPVs) have been found in association with benign and malignant growth of epithelia. The cell cycle inhibitor p16^Ink4a has been shown to be overexpressed in HPV-positive cervical pre-malignant and malignant lesions, probably as a result of pRB targeting by the viral E7 protein. Inverted papillomas of the urinary bladder are epithelial tumors considered to be of benign nature. In this report we analyze the expression of p16^Ink4a and the presence of HPV sequences in inverted papillomas and in non-tumoral bladder controls. Our results show no association of HPV infection and inverted papillomas. Further, no correlation between p16 overexpression and HPV positivity was found. We conclude that HPV does not play an indispensable role in the development of urinary bladder inverted papillomas and that overexpression of p16^Ink4a does not correlate with HPV infection in these tumors.     

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。     

Human papillomavirus type 16 E6 induces cervical cancer cell migration through the p53/microRNA-23b/urokinase-type plasminogen activator pathway

Deregulation of microRNA (miRNA or miR) expression in human cervical cancer is associated frequently with human papillomavirus (HPV) integration. miR-23b is often downregulated in HPV-associated cervical cancer. Interestingly, urokinase-type plasminogen activator (uPA), the miR-23b target, is detected in cervical cancer, but not in normal cervical tissues. Thus, the importance of miR-23b and uPA in HPV-associated cervical cancer development is investigated. In this study, the high-risk subtype HPV-16 E6 oncoprotein was found to decrease the expression of miR-23b, increase the expression of uPA, and thus induce the migration of human cervical carcinoma SiHa and CaSki cells. uPA is the target gene for miR-23b as the miR repressed uPA expression and interacted with the 3'-untranslated region of uPA mRNA. The tumor suppressor p53 is known to be inactivated by HPV-16 E6. A consensus p53 binding site is detected in the promoter region of miR-23b, whereas p53 trans-activated and also interacted with the miR's promoter. Therefore, p53 is believed to mediate the HPV-16 E6 downregulation of miR-23b. From the above, miR-23b/uPA are confirmed to be involved in HPV-16 E6-associated cervical cancer development.     

A subset of head and neck squamous cell carcinomas exhibits integration of HPV 16/18 DNA and overexpression of p16INK4A and p53 in the absence of mutations in p53 exons 5-8

Besides well-known risk factors such as tobacco use and alcohol consumption, oncogenic human papillomavirus (HPV) infection also has recently been suggested to promote head and neck tumorigenesis. HPV is known to cause cancer by inactivation of cell cycle regulators p53 and pRb via expression of viral oncoproteins E6 and E7. This indicates that p53 mutations are not a prerequisite in HPV-induced tumor development. However, discrepancy exists with respect to the frequency of head and neck squamous cell carcinomas (HNSCC) harboring DNA of oncogenic HPV and the fraction of these tumors showing p53 mutations. In our study, we examined the frequency of HNSCC demonstrating HPV 16/18 integration as identified by fluorescence in situ hybridization (FISH) and investigated their p53 (mutation) status by immunohistochemistry and single-strand conformation polymorphism (SSCP) analysis of exons 5-8. Paraffin-embedded, archival biopsy material from 27 premalignant mucosal lesions and 47 cases of HNSCC were analyzed. Ten of the 47 (21%) HNSCC unequivocally exhibited HPV 16 integration, including 8 of 12 (67%) tonsillar carcinomas. This is supported by the immunohistochemical detection of p16(INK4A) overexpression in all 10 HPV-positive tumors. Although FISH is considered to be less sensitive than PCR-based methods for HPV detection, our data clearly demonstrate clonal association of HPV with these tumors, as illustrated by the presence of integrated HPV 16 in both the primary tumor and their metastases in 2 patients. In contrast, HPV 16/18 DNA could not be detected in the premalignant lesions. In 30 of 47 (64%), HNSCC accumulation of p53 was observed, including 8 of the 10 HPV-positive carcinomas. However, in none of the latter cases could mutations in exons 5-8 be identified, except for a polymorphism in codon 213 of exon 6 in one patient. Evaluation of clinical data revealed a significant inverse relation between tobacco use with or without alcohol consumption, and HPV positivity of the tumors.     

人乳头瘤病毒感染和p53基因突变与宫颈癌的关系

目的：探讨人乳头瘤病毒１６ 和１８ 型及抑癌基因ｐ５３ 突变对宫颈的致癌作用以及 Ｈ Ｐ Ｖ 感染与ｐ５３ 基因突变的相关性。方法：采用聚合酶链反应（ Ｐ Ｃ Ｒ） 技术和限制性酶切片段多态性分析（ Ｒ Ｆ Ｌ Ｐ） 技术对３４ 例原发性宫颈癌组织及３０ 例正常宫颈组织 Ｈ Ｐ Ｖ１６ ,１８ 型 Ｄ Ｎ Ａ 及抑癌基因ｐ５３ 的突变进行了检测。结果： Ｈ Ｐ Ｖ１６ ,１８ Ｄ Ｎ Ａ 在宫颈癌的总阳性率为６４７ ％ （２２／３４） ,正常宫颈组织只有６７ ％ 阳性,８例宫颈癌组织出现ｐ５３ 基因第６ 外显子突变,其中２ 例为 Ｈ Ｐ Ｖ１６ Ｄ Ｎ Ａ 阳性、１ 例 Ｈ Ｐ Ｖ１８ Ｄ Ｎ Ａ 阳性。结论：宫颈癌的发病与 Ｈ Ｐ Ｖ 感染及ｐ５３ 基因突变有关,宫颈癌组织中ｐ５３ 基因突变与 Ｈ Ｐ Ｖ 感染无关。     

Alteration of the CDKN2/p16 gene is not required for HPV-positive uterine cervical cancer cell lines

To determine whether alterations of the CDKN2/p16 might be involved in HPV-positive cervical cancers, we examined for alterations of this gene and function of the protein p16 to interact with CDK4 in 5 cervical cancer cell lines. No alteration of this gene was detected. Proteins for p16 and CDK4 were normally expressed and function of p16 to interact with CDK4 was not abrogated in these cell lines. These cell lines were human papillomavirus (HPV)-positive and carried wild-type p53. These findings suggest that phosphorylation of pRb by CDK4 is not critical in the carcinogenesis or in the establishment of HPV-positive cervical cancer cell lines, since HPV E6 or E7 viral-transforming proteins inactivate p53 and pRb tumor suppressor protein function, resulting in deregulated progression of the cell cycle.     

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.     

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.     

Functional interaction of p53 with HPV18 E6, c-myc and H-ras in 3T3 cells.

Wild-type (wt) p53 has been suggested to be the product of a tumor-suppressor gene. Recently, it has been shown that the E6 oncoproteins of human papillomavirus (HPV) types 16 and 18, like the SV40 large T antigen, are physically associated with wt p53. We have investigated the functional interaction of wt p53 with the viral oncogene products of HPV16 and 18 and with cellular oncogenes by transfection of NIH3T3 cells with p53 wt alone or with several oncogene(s). We found that over-expression of HPV18 E6, c-myc or activated H-ras, like SV40 large T, can partially overcome the growth-inhibitory effect of wt p53 in NIH3T3 cells, while HPV16 E6 and E7, HPV18 E7, k-fgf, c-fos and mutant (mt) p53 do not. Further studies indicate that HPV18 E6 and c-myc can overcome the antiproliferative effect, but not the antitransforming effect, of wt p53, while activated H-ras can overcome both the antiproliferative and antitransforming effects of wt p53. These data show evidence of a functional interaction between HPV18 E6 and wt p53, and suggest that the cooperation of HPV E6 and cellular oncogenes c-myc and H-ras, which are activated in several cases of human cervical cancers, may be necessary to overcome completely the anti-oncogenic function of p53 in the development of these tumors.     

BAG3 down-modulation sensitizes HPV18 HeLa cells to PEITC-induced apoptosis and restores p53

BAG3 is a multi-functional component of tumor cell pro-survival machinery, and its biological functions have been largely associated to proteasome system. Here, we show that BAG3 down-modulation resulted in reduced cell viability and enhanced PEITC-induced apoptosis largely more extensively in HeLa (HPV18⁺) rather than in C33A (HPV⁻) cervical carcinoma cell lines. Moreover, we demonstrate that BAG3 suppression led to a decrease of viral E6 oncoprotein and a concomitant recovery of p53 tumor suppressor, the best recognized target of E6 for proteasome degradation. E6 and p53 expression were modulated at protein level, since their respective mRNAs were unaffected. Taken together our findings reveal a novel role for BAG3 as host protein contributing to HPV18 E6-activated pro-survival strategies, and suggest a possible relevance of its expression levels in drug/radiotherapy-resistance of HPV18-bearing cervical carcinomas.     

HPV16 E6-mediated stabilization of ErbB2 in neoplastic transformation of human cervical keratinocytes

Whether ErbB2 receptor tyrosine kinase contributes to cervical cancer is controversial. We have examined the effects of E6 and E7 genes of human papillomaviruses type 16 (HPV-16) on ErbB2 expression in primary human cervical keratinocytes (HCK) immortalized with hTERT (HCK1T). In E6-positive cells (HCK1T-E6 and HCK1T-E6E7), ErbB2 expression levels increased with the cell density. HCK1T-E6E7 showed impaired contact inhibition and anchorage-independent growth in soft agar which were abrogated with introduction of ErbB2-specific short hairpin RNA (shRNA) or an ErbB2 specific inhibitor AG825. Furthermore, increased ErbB2 expression was also observed in HPV16 positive cervical cancer cell lines and this was diminished by introduction of HPV16E6- or E6AP-shRNA. At post-confluence cell densities, ErbB2 protein was stabilized in the presence of E6 whereas increased ErbB2 expression was not obvious with E6 mutants incapable of degrading p53. Furthermore, introduction of p53-shRNA to HCK1T resulted in increased ErbB2 protein stability, indicating possible ErbB2 regulation through p53. Finally, we showed that tumor formation of ErbB2-shRNA introduced SiHa cells were almost abolished. Taken together, these data indicate an important role of ErbB2 regulation by HPV16 E6 in oncogenic transformation of human cervical keratinocytes.     

Reversal of Resistance towards Cisplatin by Curcumin in Cervical Cancer Cells

Epigenetic regulators like histone deacetylases (1 and 2), and viral onco-proteins (E6/E7) are known to beoverexpressed in cervical cancer cells. The present study was designed to investigate the effect of curcumin onHDACs (1 and 2) and HPV E6/E7 in the cervical cancer cell line SiHa and a drug resistant clone SiHaR (derivedfrom SiHa). It was further intended to investigate whether curcumin could sensitize the cells towards cisplatininduced cell killing by modulation of multi drug resistant proteins like MRP1 and Pgp1. Curcumin inhibitedHDACs, HPV expression and differentially increased acetylation and up-regulation of p53 in SiHa and SiHaR,leading to cell cycle arrest at G1-S phase. Up-regulation of pRb, p21, p27 and corresponding inhibition of cyclinD1 and CDK4 were observed. Cisplatin resistance in SiHaR due to over-expression of MRP1 and Pgp1 wasovercome by curcumin. Curcumin also sensitized both the cervical cancer cells towards cisplatin induced cellkilling. Inhibition of HDACs and HPVs led to cell cycle arrest at G1/S phase by alteration of cell cycle regulatoryproteins. Suppression of MRP1 and Pgp1 by curcumin resulted in sensitization of cervical cancer cells, loweringthe chemotherapeutic dose of the drug cisplatin.     

Tumorigenesis in p27/p53- and p18/p53-double null mice: functional collaboration between the pRb and p53 pathways

Mice lacking both p18(Ink4c) and p27(Kip1) develop a tumor spectrum similar to pRb(+/-) mice, and loss of p53 function accelerates tumorigenesis in pRb(+/-) mice. We hypothesized that codeletion of either p18 or p27 in conjunction with p53 deletion will also accelerate tumorigenesis. Mice lacking both p18 and p53 develop several tumors not reported in either single null genotype, including hepatocellular carcinoma, testicular choriocarcinoma, hemangiosarcoma, leiomyosarcoma, fibrosarcoma, and osteosarcoma. Mice lacking both p27 and p53 exhibit a decreased lifespan and develop unique tumors, including papillary carcinoma of the colon, hemangiosarcoma, and leiomyosarcoma. In both p18/p53 and p27/p53 double null genotypes, the incidence and spectra of tissues that develop lymphoma are also increased, as compared to the single null genotypes. The development of p27/p53 double null colon tumors correlates with secondary changes in cell-cycle protein expression and CDK (cyclin-dependent kinase) activity, perhaps contributing to the progression of colorectal cancer. We concluded that p18 and p27 can, not only functionally collaborate with one another, but also can independently collaborate with p53 to modulate the cell cycle and suppress tumorigenesis in a tissue-specific manner.