Reading Frame Of Human Papillomavirus Type Research Articles

Chromosomal abnormalities in HPV-16-immortalized oral epithelial cells

Human papilloma virus (HPV) type 16 has an established association with anogenital carcinoma, and to some extent with human oral squamous cell carcinoma. We hypothesize that HPV type 16 is capable of inducing chromosomal and cell cycle changes in cultured oral epithelial cells. Normal human oral epithelia] cells were immortalized with recombinant retrovirus containing the E6/E7 open reading frames of HPV type 16. These cells have been in culture for more than 350 passages and over 4 years. Flow cytometry demonstrated an average of 42% nuclear aneuploidy in HPV 16-immortalized cells; 16% in normal controls (probably tetrasomy). Cytogenetic analysis demonstrated significant progression of chromosomal abnormalities. Cells at early passage (p10) showed trisomy 20, with no other major changes. At passage 18, trisomy 1q and monosomy 13 were seen in addition to trisomy 20. At passage 61 there were two distinct cell populations ('a' and 'b'), with multiple chromosomal changes including trisomy 5q,14,20 in one line and 7p,9q,llq in the other. Both populations had monosomy 3p, with monosomy 8p in one population and monosomy 13 in the other. At passage 136, the cells were essentially identical to population 'b' of passage 61. At this passage, mutation of the p53 gene was detected at codon 273 of exon 8, with G to T conversion (Arg to Leu). This was absent in the normal cells from which this line was developed. Passage 262 contained the two major cell populations, each with a sub-group with additional chromosomal changes such as 10p monosomy. Cells from passages 217 and 305 were injected into nude mice a year apart. Both failed to produce tumors, as did normal cells. In conclusion, we present an HPV type 16-immortalized oral epithelial cell line (IHGK) with extensive and progressive chromosomal abnormalities, invasive growth in culture and yet no tumor formation in nude mice. We suggest that the question as to whether HPV alone can induce transformation is still open.

HPV Immortalization of Human Oral Epithelial Cells: A Model for Carcinogenesis

Human papillomavirus (HPV) has been implicated in the etiology of oral and cervical cancers. Normal oral epithelial cells at passage two were infected with recombinant retrovirus containing the E6/E7 open reading frames of HPV type 16. The G418-selected cells that were immortalized and express HPV 16 E6/E7 have been in culture for over 4 years and 350 passages. In contrast, the normal oral epithelial cells did not survive the culture environment beyond 7 to 9 passages. Fifteen clones were selected from the pooled population. By Northern blot analysis all clones demonstrated the presence of E6/E7 genes. Keratin expression of both normal and immortalized oral epithelial cells was studied in organotypic culture. Both cell types were positive with antibodies AE1, AE3, and 34BE12. Both were focally positive with AE8, which stains for keratin 13 (specific for oral and esophageal epithelial cells). The normal control cells were focally positive for filaggrin, while the HPV 16-immortalized cells (IHGK cells—immortalized human gingival keratinocytes) were negative. The IHGK cells were strongly positive with KS19.1, which stains the embryonal keratin K19, an indicator of premalignant or malignant changes, while the normal control cells were only lightly and focally positive. In conclusion, we present an oral epithelial cell line successfully immortalized with HPV E6/E7 which will facilitate further research on the involvement of HPV in oral carcinogenesis.