An in vitro study of oncogenesis of primary cervical cells by human papillomavirus 16 and cigarette smoke condensate

Yang, Xiaolong (1995) An in vitro study of oncogenesis of primary cervical cells by human papillomavirus 16 and cigarette smoke condensate. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (23MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Previous epidemiological studies indicated that cigarette smoking females are at increased risk of developing cervical cancer. However, because of the confounding variables of these studies, and since other studies have given conflicting results, convincing evidence is lacking. Furthermore, the molecular role of cofactors, such as hormones, in the multistage carcinogenic process is still unclear. -- To examine the role of human papillomavirus (HPV) and cigarette smoking in the carcinogenesis of cervical cancer, I studied two HPV16 immortalized endocervical cell lines previously established in this lab, HEN-16 and HEN-16-2. Both lines were treated with cigarette smoke condensate (CSC) at 75, 100, 125 μg/ml. After 6-12 months' treatment with CSC, 10⁷ cells of treated and untreated immortalized cells with equal passages were injected into female nude mice. Four to six weeks later, only CSC-treated cells but not CSC-untreated immortalized cells formed palpable tumors, which were subsequently used to derive tumor cell lines, HEN-16T and HEN-16-2T. -- Further characterization of the immortalized cell lines and CSC-transformed cell lines indicated that the CSC-treated tumorigenic cells a) displayed distinct morphologies in monolayer and organotypic (raft) cultures; b) proliferated faster in DMEM, a medium containing physiological calcium levels; c) showed in vitro anchorage-independency; d) contained and expressed similar levels of HPV16; e) expressed similar levels of some cellular genes associated with enhanced malignancy, c-myc, H-ras, p53, WAF1, GADD45, GADD153, and fibronectin, compared with immortalized cells. However, f) HEN-16T and HEN-16-2T expressed higher levels of B-myb and PCNA; and g) obtained enhanced resistance to growth inhibition by tansforming growth factor-β1 (TGF-β1) and retinoic acid (RA) . On the other hand, the two immortalized cell lines displayed higher levels of p53, B-myb, PCNA and lower levels of Wafl and fibronectin, compared with primary endocervical cells. -- In addition, two novel cDNAs, designated PA4 and PA9, which were specifically expressed at higher levels in immortalized cells and primary endocervical cells, respectively, were identified and cloned using differential display assays. Further characterization of these two novel cDNAs will be very helpful for us to fully understand the molecular pathogenesis of cervical cancer. -- In summary, this study provided the first in vitro evidence that cigarette smoke can enhance the risk of developing cervical cancer in HPV-infected patients. Furthermore, the in vitro system will be very useful to investigate the mechanism of multistep carcinogenesis of cervical cancer.

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