Human papillomavirus infection and TP53 gene mutation in primary cervical carcinoma

A fully defined static suspension culture system for large-scale human embryonic stem cell production

Human embryonic stem cells (hESCs) play an important role in regenerative medicine due to their potential to differentiate into various functional cells. However, the conventional adherent culture system poses challenges to mass production of high-quality hESCs. Though scientists have made many attempts to establish a robust and economical hESC suspension culture system, there are existing limitations, including suboptimal passage methods and shear force caused by dynamic stirring. Here, we report on an efficient large-scale culture system, which enables long-term, GMP grade, single-cell inoculation, and serial expansion of hESCs with a yield of about 1.5 × 10⁹ cells per 1.5-L culture, while maintaining good pluripotency. The suspension culture system was enlarged gradually from a 100-mm dish to a 1.8-L culture bag with methylcellulose involvement to avoid sphere fusion. Under the optimal experimental protocol, this 3D system resolves current problems that limit mass production and clinical application of hESCs, and thus can be used in commercial-level hESC production for cell therapy and pharmaceutics screening in the future.

Phenotypic features with p53 alterations related to human papillomavirus and prognostic evaluation in cervical cancer

Cervical cancer is one of the most common tumor affecting women worldwide. Human papillomavirus (HPV) was found to have a causal relationship with cervical cancer and its precursors. The interaction between HPV E6 protein and p53 was identified in in vitro studies. The aim of the study was to evaluate the prevalence of p53 alterations related to HPV infection and the prognostic significance of p53 alterations in cervical cancer. Studies were identified by a MEDLINE search, and all relevant articles were retrieved from 1991 to March 2004. The prevalence of p53 mutations is a rare event in cervical cancer. The correlation between p53 mutations and HPV or prognosis is controversial. Loss of heterozygosity (LOH) of p53 is more commonly found in cervical cancer and is related with the prognosis of this disease. There is no significant correlation between p53 polymorphism and development of cervical cancer. The p53 mutations were not commonly found in cervical cancer. LOH of p53 may contribute to the progression of this malignancy. p53 polymorphism failed to be an independent prognostic factor in predicting the outcome of patients with cervical cancer. Further, epidemiologic surveys should be undertaken in larger populations and in different geographical regions.

Role of human papillomavirus in the carcinogenesis of squamous cell carcinoma and adenocarcinoma of the cervix

Human papillomavirus (HPV) infection is the most common sexually transmitted disease, with more than 80% of the population infected at some time in their life. In rare cases, this infection may lead to cervical cancer. Virtually all squamous cell carcinomas and the overwhelming majority of adenocarcinomas of the cervix are HPV positive. HPV integration in the genome will lead to inactivation of the p53 pathway and the Rb pathway. Integration is essential for the onset of cervical carcinogenesis, but is probably not sufficient for progression to invasive cervical cancers. It is likely that several cofactors, such as environmental, viral and host-related factors, are necessary for the development of cervical cancer. There are several similarities and differences between the two major histological types. This article will address the role of HPV in cervical carcinogenesis as well as the molecular biology involved in the process.

Human papillomavirus infection and p53 protein expression in vulvar intraepithelial neoplasia and invasive squamous cell carcinoma

The etiopathogenesis of vulvar intraepithelial neoplasia (VIN III) and invasive squamous cell carcinoma are largely unknown. Since there are few studies on Brazilian patients, our purpose was to determine the frequency of human papillomavirus (HPV) infection and the expression of p53 in these lesions, and associate them with other factors such as age, morphological subtypes, multicentric and multifocal disease. Thirty-eight cases of VIN III, nine of superficially invasive carcinoma, and 55 of invasive vulvar carcinoma were retrospectively evaluated from 1983 to 1995 for the presence of HPV by immunohistochemistry and in situ hybridization, and for p53 protein expression by immunohistochemistry on paraffin sections. All cases for whom material (slides and paraffin blocks) and clinical data were available were included. HPV and p53 were detected in 57.9 and 21.1% of the VIN III lesions, 33.3 and 66.7% of superficially invasive carcinomas, and 7.3 and 58.2% of invasive squamous cell carcinomas, respectively. HPV infection was associated with younger age in the VIN III and invasive carcinoma groups. In the latter, HPV infection was associated with the basaloid variant. p53 expression rate was higher in superficially invasive and invasive lesions and was not related to HPV infection. Our findings are similar to others and support the hypothesis that there are two separate entities of the disease, one associated with HPV and the other unrelated, with p53 inactivation possibly being implicated in some of the cases.

The role of TP53 in Cervical carcinogenesis

Functional loss of the tumor suppressor p53 by alterations in its TP53 gene is a frequent event in cancers of different anatomical regions. Cervical cancer is strongly linked to infection by high-risk human papillomavirus (HPV) types. The viral oncoprotein E6 has the ability to associate with and neutralize the function of p53. E6 interacts with a 100-kDa cellular protein, termed E6 associated protein (E6AP; also called ubiquitin-protein ligase E3A or UBE3A), which functions as an ubiquitin protein ligase. The dimeric complex then binds p53 and E6AP catalyzes multi-ubiquitination and degradation of p53. The ability to promote p53 degradation is an exclusive property of E6 from the high-risk HPV types. Indeed, the low-risk E6 proteins lack this activity, although they can bind p53. Consistent with the E6 function of the high-risk HPV types, the majority of cervical cancer cells have a wild-type p53 gene, but the protein levels are strongly decreased. Several independent studies have shown that in a small percentage of cervical tumors the p53 gene is mutated. However, this event appears to be unrelated to the presence or absence of HPV infection and the nature of the tumor.

P53 immunohistochemical expression: messages in cervical carcinogenesis

AIMS

The pattern of p53 expression was studied in pre-invasive and invasive cervical carcinoma in an attempt to clarify its role in cervical carcinogenesis.

METHODS

A total of 234 invasive cervical carcinomas (152 squamous cell carcinomas, 61 adenocarcinomas and 21 adenosquamous carcinomas) and 16 cervical intraepithelial neoplasia (CIN) I, six CIN II and 25 CIN III were immunohistochemically studied for p53.

RESULTS

p53 was detected more frequently in CIN and invasive carcinoma (100% of CIN I, 74.2% CIN II + III and 70.1% invasive carcinoma) compared with benign cervices (P< 0.001); however, only three squamous cell carcinomas, 11 adenocarcinomas and two adenosquamous carcinomas exhibited p53 expression in >75% of tumour nuclei. Six of the 11 adenocarcinomas and both adenosquamous carcinomas were poorly differentiated compared with one of the three squamous carcinomas. p53 immunoreactive cells were randomly distributed in invasive carcinoma, confined to the lower third of the epithelium in CIN I, reached the middle third in 20% of CIN II and upper third in 16.6% of CIN III.

CONCLUSIONS

Assuming that p53 immunoreactivity indicates gene mutation when the majority (> 75%) of neoplastic cells express p53, p53 mutations would seem uncommon in cervical carcinogenesis. Nonetheless, glandular malignancies, in particular poorly differentiated variants, may show a higher frequency of mutation. p53 was detected more frequently in CIN I compared with CIN II/III and invasive carcinoma which may be due to p53 protein degradation following interaction with high risk human papillomavirus E6 protein in CIN II/III and invasive carcinoma.

The molecular biology of cervical cancer

Cervical cancer remains a major worldwide health problem, especially in developing countries. Over the last few decades many advancements have been made in determining the molecular genetics of the development of cancer. This paper attempts to summarize the major disturbances in cellular function known to date to play a role in the development of cervical cancer. The role of human papillomavirus (HPV) infection in the development of cervical cancer is a major player in the genetic abnormalities described thus far. The effects of HPV E6 and E7 on important cell cycle genes are discussed. As oncogenes and tumor suppressor genes have been described in the different types of cancer, their possible role in cervical cancer has been investigated. The possible role of angiogenesis and angiogenic factors is described. Because of the importance of HPV infection in the development of cervical cancer, the role of the body's immune function in this cancer is also under study, and the results of these findings are summarized. Although a complete paradigm of the development of cervical cancer from normal cervical epithelium is not yet known, continued study in this area will hopefully lead to a defined progression of molecular and immunologic abnormalities that cause the disease. The goal would be to use this information to help prevent and/or treat cervical cancer in the future.

Low frequency of p53 mutations in cervical carcinomas among Brazilian women

Human papillomavirus (HPV) infections of the high-risk types are strongly linked to the development of cervical carcinoma. The HPV oncoproteins E6 and E7 are thought to play a crucial role in this process through their interactions with the p53 protein and the retinoblastoma susceptibility gene product pRb, respectively. E6 binds to p53 protein promoting its degradation. This is considered to contribute to the oncogenesis of HPV-associated anogenital cancer. On the other hand, in HPV-negative cervical carcinoma, p53 mutations are thought to have a role in the transformation process. A total of 122 HPV-positive cervical carcinoma tissue samples were evaluated for the presence of mutations in exons 5-8 of the p53 gene by single-stranded conformation polymorphism analysis and DNA sequencing. Only four missense point mutations were detected. These findings suggest that other mechanisms independent of p53 inactivation may play a role in the genesis of cervical carcinomas.

Differences in K-ras codon 12 mutation frequency between "high-risk" and "low-risk" HPV-infected samples

OBJECTIVES

The current study was designed to determine the association between K-ras point mutations and the presence of high- and low-risk HPV types in noncancerous samples.

METHODS

One hundred fifty-five noncancerous cytological samples from genital specimens positive for HPV-6, -16, or -18 were analyzed for codon 12 ras point mutations. DNA samples were subjected to nested PCR for the detection of HPV genome. Mutations at the first and second bases of K-ras codon 12 were detected using specific enriched PCR.

RESULTS

Eleven percent of the HPV-positive samples analyzed showed mutation in K-ras codon 12 (17 of 155). Mutations were detected in 8 of 53 HPV-16- (15%) and 8 of 38 HPV-18-positive samples (21%). Nevertheless, when HPV-6-positive samples were screened for K-ras mutations only 1 of 64 samples was found mutated (1.56%). Statistical analysis using the chi(2) test showed a highly significant difference (chi(2) = 9.865, P < 0.01) when the rate of mutation for samples positive for high-risk HPV types (16 and 18) was compared with the frequency found in low-risk-infected samples (HPV-6).

CONCLUSION

These results could be considered an indicator of the association between K-ras codon 12 mutations and the presence of high-risk HPV types.

Molecular abnormalities associated with endocrine tumors of the uterine cervix

Objective. We studied the molecular abnormalities involved in the pathogenesis of endocrine tumors of the uterine cervix. Methods. We obtained DNA from precisely microdissected archival tissue from 15 endocrine tumors of the uterine cervix, consisting of 5 carcinoids (1 typical, 4 atypical), 2 large cell neuroendocrine carcinomas, and 8 small cell carcinomas. We investigated the presence of high-risk (types 16 and 18) and intermediate-risk (types 31 and 33) human papilloma virus (HPV) sequences, TP53 and K-ras gene mutations, and loss of heterozygosity (LOH) at 9 genes/chromosomal regions, including 3p14.2/FHIT, 3p14-p21, 3p21, 3p22-p24, 5q21-q22/APC-MCC region, 9p21/CDKN2, 11q23/MEN1, 13q/RB, and 17p/TP53. Results. HPV sequences were detected in 8 (53%) tumors, HPV 16 in 2 cases, and HPV 18 in 2 cases. LOH at 9p21 (43%) and localized 3p deletions (47%) were the most frequent allelic losses found. Allelic losses at 5q21-q22/APC-MCC region, 11q23/MEN1, and 13q/RB were infrequent. TP53 gene mutations were detected in 7 (47%) tumors (1 atypical carcinoid and 6 carcinomas). HPV sequences were demonstrated in 4 of the 7 cases with TP53 gene mutations. No K-ras mutations were detected. Conclusion. The molecular changes present in endocrine tumors of the uterine cervix have distinct features. They incorporate those present in the neuroendocrine tumors of the lung (high frequency of TP53 gene abnormalities and 9p21 deletions) with those detected in squamous cell carcinomas of the cervix (high-risk HPV sequences and localized 3p deletions).