Growth and differentiation of human papillomavirus type 31b positive human cervical cell lines

Human papillomavirus (HPV) containing cell lines derived from human cervical intraepithelial neoplasia (CIN) can offer valuable insights into the role of HPV in cervical neoplasia and can help in the understanding of the cellular changes that fuel the progression toward malignancy. We describe the growth and differentiation properties of an epithelial cell line established from a CIN I lesion. The cell line, designated as CIN 612, contains predominantly episomal copies of HPV 31b deoxyribonucleic acid (DNA). In vitro differentiation in a collagen raft system, growth characteristics, and episomal HPV DNA content of the CIN 612 cell line and two of its subclones were analyzed. Early passage CIN 612 cells differentiate in a manner which resembles the original low-grade intraepithelial lesion. On further passage, these cells exhibit increasingly poor differentiation in vitro. Two subclones with different growth characteristics and morphology were identified. A more rapidly growing, poorly differentiated subclone contains less episomal copies of viral DNA compared to a slower growing and better-differentiated subclone. Cell populations with similar growth characteristics yet different ploidy were observed. The CIN 612 cell line with its episomal copies of viral DNA shows promise for the development of an in vitro culture system for HPV 31b. The isolation of subclones with consistently different growth and differentiation properties in vitro creates an opportunity to identify the cellular events that lead to the progression from low-grade to high-grade cervical neoplasia.