Cancer of the cervix and the papilloma viruses

Virus manipulation of cell cycle

Viruses depend on host cell resources for replication and access to those resources may be limited to a particular phase of the cell cycle. Thus manipulation of cell cycle is a commonly employed strategy of viruses for achieving a favorable cellular environment. For example, viruses capable of infecting nondividing cells induce S phase in order to activate the host DNA replication machinery and provide the nucleotide triphosphates necessary for viral DNA replication (Flemington in J Virol 75:4475-4481, 2001; Sullivan and Pipas in Microbiol Mol Biol Rev 66:179-202, 2002). Viruses have developed several strategies to subvert the cell cycle by association with cyclin and cyclin-dependent kinase complexes and molecules that regulate their activity. Viruses tend to act on cellular proteins involved in a network of interactions in a way that minimal protein-protein interactions lead to a major effect. The complex and interactive nature of intracellular signaling pathways controlling cell division affords many opportunities for virus manipulation strategies. Taking the maxim "Set a thief to catch a thief" as a counter strategy, however, provides us with the very same virus evasion strategies as "ready-made tools" for the development of novel antivirus therapeutics. The most obvious are attenuated virus vaccines with critical evasion genes deleted. Similarly, vaccines against viruses causing cancer are now being successfully developed. Finally, as viruses have been playing chess with our cell biology and immune responses for millions of years, the study of their evasion strategies will also undoubtedly reveal new control mechanisms and their corresponding cellular intracellular signaling pathways.

Behavior of cervical intraepithelial neoplasia (CIN) associated with various human papillomavirus (HPV) types

201 cervical punch biopsies which showed CIN lesions and were obtained between 1967 to 1977 from Falu Hospital patients, with long-term follow-up data were examined histologically and by DNA typing for human papillomavirus (HPV). We used in situ hybridization for HPV types 6, 11, 16, 18, 31 and 33 and related our findings to the behaviour of the lesion (103 regressed spontaneously and 98 progressed, some of them to invasive cervical carcinoma). There was evidence of HPV infection in 75.6% (152/201) of these lesions on histological examination, and in 53.2% (107/201) on in situ DNA hybridization. Lesions positive for HPV by both methods occurred in the younger age group (Pearson's correlation coefficient, P = 0.008). HPV 16 was found in 51/152 (33.6%) of the HPV lesions, HPV in 12.5%, and HPV 33 in 8.5% HPV 16 was highly significantly (P = 0.0001), and HPV 18 and HPV 33 were significantly (P = 0.008 and P = 0.007, respectively) associated with increasing grades of CIN. Progression to invasive carcinoma was directly (and regression inversely) correlated with the severity of CIN in the first biopsy (P = 0.005). Almost 74% (17/23) of the HPV-CIN III lesions progressed, while only 25% of the HPV-NCIN lesions (6/24) did so. The progression rate was 84.6% for HPV 33 lesions and 52.9% for HPV 16. On the other hand, progression was less common with HPV 6 (25%), and HPV 31 (30.0%). Histological grade and HPV type appear to be of value as prognostic indices.

Prospective follow-up of cervical HPV infections: life table analysis of histopathological, cytological and colposcopic data

A total of 532 women with established cervical HPV infection have been prospectively followed (without treatment) since 1981 for a mean of 45 (SD 21) months. The patients were examined by colposcopy, PAP smears and/or punch biopsy every 6 months. The life-table method was applied to analyze the clinical course (i.e. regression and progression) of the HPV lesions, stratified by their colposcopic pattern, PAP smear findings and grade of CIN. During the follow-up, 107 (41.8%) of 256 patients with HPV-NCIN lesion in the first punch biopsy, experienced spontaneous regression. The corresponding proportions for HPV-CIN I, HPV-CIN II and HPV-CIN III lesions were 31.1%, 34.2%, and 20.7%, respectively. In the overall comparison between these four groups, the heterogeneity in the probability of regression was statistically significant (p = 0.0005). Clinical progression was also associated significantly with the histological grade of the lesions in the first biopsy. Progression rate was only 5.8% for HPV-NCIN lesions, as compared to 12.3% for HPV-CIN I, 20% for HPV-CIN II, and 55.2% for HPV-CIN III. The probability of progression varied significantly between the four groups (p less than 0.00001). Cumulative proportion of regression was 46% for patients with PAP smear class I, 84% with class II, and 82% for those with class III, cells, i.e. PAP smear was not of value in predicting the regression. However, PAP smears predicted clinical progression (p = 0.006 overall).(ABSTRACT TRUNCATED AT 250 WORDS)