Development and Assessment of a General Theory of Cervical Carcinogenesis Utilizing a Severe Combined Immunodeficiency Murine–Human Xenograft Model

Abstract

Objective. Currently, we lack a theoretical explanation for why squamous cell cervical cancer develops predominantly in specific sites (i.e., along the squamocolumnar junction). We therefore implanted human cervical tissues containing the transformation zone in severe combined immunodeficiency (SCID) mice and studied morphology, steroid effects, gene expression, and human papillomavirus (HPV) factors.Methods. Normal and dysplastic human cervical tissues (3 ؋ 2 mm) were placed subcutaneously in SCID-beige mice and later assessed by in situ hybridization for HPV 16/18 DNA and by immunohistochemistry for expression of CD31, keratin, proliferating-cell nuclear antigen, HPV 16 E6, p53, and Notch-1 (a binary cell fate determination protein). Some normal tissues were implanted with either a 90-day release 1.7-mg 17␤-estradiol pellet or a 5-mg tamoxifen pellet; others were infected prior to implantation with human recombinant adenovirus 5 vector containing a human cytomegalovirus promoter-driven ␤-galactosidase gene and later assessed by X-gal staining.Results. Murine and human vessels formed anastomoses by 3 weeks. For at least 11 weeks, normal tissue retained the transformation zone and normal cell-type-specific keratin expression and exhibited normal proliferation; Notch-1 was present only in the basal cell layer. Dysplastic tissues exhibited koilocytosis, increased levels of cellular proliferation, and aberrant keratin, p53, and Notch-1 expression; HPV 16/18 DNA and HPV 16 E6 protein were detected for at least 6 weeks. Squamous metaplasia of normal cervical epithelium resulted from estrogen exposure, and a predominant columnar differentiation pattern was associated with tamoxifen administration. Through stable adenovirus infection, ␤-galactosidase was expressed for at least 6 weeks.Conclusions. This small manipulatable xenograft model maintains normal and dysplastic human cervical epithelium through neovascularization. Neoplastic tissue retains HPV 16/18 DNA and a premalignant phenotype, including elevated levels of cellular proliferation and aberrant keratin, p53, and Notch-1 expression. These attributes constitute essential features of a biologic model through which one may study HPV-mediated human disease and may be superior to cell culture and transgenic murine systems. Furthermore, this may serve as a model for gene therapy. Finally, we suggest that the normal cervical epithelium is maintained through putative interactions between the Notch locus and cell cycle growth regulators such as p53 and pRb. Neoplastic cervical epithelium may arise through disruption of this pathway. This theory may be testable in our animal model.

Green tea catechins for treatment of external genital warts

“…In addition to possessing antiviral [6][7][8] and immunostimulatory [9][10][11][12] properties, catechins also exhibit antitumor [13][14][15][16] and antioxidative 11,17 effects. There is also sufficient evidence for antiangiogenic activity.…”

“…Integration into the host genome, however, results in disruption of E2 and therefore loss of suppression of E6 and E7, resulting in disruption of p53 and pRB (retinoblastoma) signaling and oncogenesis. 6 The potential for integration and thus malignant transformation appears to vary among different HPV types, with HPV types 16 and 18 being most common in invasive lower genital tract cancers and HPV types 6 and 11 being associated Hastak et al 7 demonstrated that the EGCG-induced apoptosis in human prostate carcinoma cells is mediated through stabilization of p53 by phosphorylation on critical serine residues. Khafif et al 8 studied the effects of EGCG in an oral leukoplakia cell line and noted growth inhibition through a G 1 block that was induced with an increase in the underphosphorylated form of pRB.…”

Role of hormone cofactors in the human papillomavirus-induced carcinogenesis of the uterine cervix

“…For example, the mechanism by which the original squamocolumnar junction changes location after the onset of puberty may be due to swelling of the cervical stroma in response to hormonal stimulation and pregnancy is associated with more endocervical tissue moving out onto the ectocervix (Hendrickson and Kempson, 1997). The influence of estrogen exposure in the process of squamous metaplasia has also been shown in human TZ tissues implanted in SCID mice (Tewari et al, 2000).…”

New Strategies in Advanced Cervical Cancer: From Angiogenesis Blockade to Immunotherapy

“…Notch expression is associated with cell populations undergoing cell fate changes (e.g., columnar to squamous metaplasia at the transformation zone of the uterine cervix; ref. 35). The mammalian Notch genes (Notch-1 to -4) encode 300-kDa single pass transmembrane receptors.…”