Heterotransplantation of human choriocarcinoma in nude mice. I. Morphologic and biologic characteristics

Development of an animal experimental model to study the effects of levonorgestrel on the human endometrium

BACKGROUND

This study was designed to develop an animal model to test the response of endometrium to local progestin delivery.

METHODS

Proliferative human endometrium was subcutaneously grafted in two groups of SCID mice that received, 2 days before, a subcutaneous estradiol (E(2)) pellet and, for half of them, an additional implant of levonorgestrel (LNG). Mice were sacrificed 1, 2, 3 or 4 weeks after endometrial implantation and grafts were histologically analysed. Proliferation, steroid hormone receptors, blood vessels and stromal decidualization in both groups (E(2) and LNG) were immunohistologically evaluated and compared with proliferative endometrium and endometrium from women with an LNG intrauterine device.

RESULTS

Grafts presented normal morphological endometrial characteristics. The expression of progesterone receptors was significantly decreased in glands and stroma of the LNG group as compared with the E(2) group at all times. A significant decrease was also observed in the stromal expression of estrogen receptor-alpha in the LNG group. At 4 weeks, the mean cross-sectional area of vessels was significantly higher after LNG treatment.

CONCLUSIONS

These morphological and immunohistochemical characteristics are similar to those observed in women treated with local LNG. This mouse model might facilitate further investigations needed to understand the mechanisms responsible for the breakthrough bleeding frequently observed in progestin users.

The SCID mouse: an experimental model for endometriosis

The purpose of this study was to validate the suitability of the severe combined immunodeficient (SCID) mouse as an experimental model for endometriosis, by defining the morphological and histological features of induced endometrial implants, and characterizing specific biochemical properties of these implants. Human secretory endometrial tissues were injected into the peritoneal cavity of SCID/SCID CB17 mature female mice. Successful peritoneal implantation was observed in 55 of 57 (96.5%) SCID mice and consisted of circumscribed elevated nodules. Haematoxylin-eosin staining of implanting lesions demonstrated the presence of endometrial glandular tissue in a mixed background of stromal and inflammatory cells. When progesterone was administered to mice, epithelial glands underwent well-defined secretory changes. Immunohistochemical analysis using polyclonal human pan-cytokeratin antibodies demonstrated selective positive staining in the glandular epithelium of the human implants with none in the surrounding stroma. In-situ hybridization analysis using complement component 3 cDNA radiolabelled riboprobes yielded significantly more intense signals in glands compared to stroma. As human endometrial implants in SCID mice were shown to retain specific histological, functional and biochemical properties, we conclude that the SCID mouse is an attractive animal model for the study of endometriosis.

Cell surface antigens of human trophoblast and choriocarcinoma defined by monoclonal antibodies

Six distinct cell surface antigens of human trophoblast and choriocarcinoma were defined with MAbs. The distribution of the antigens was determined by MHA assays on 150 tumor cell lines and normal cell cultures and by immunofluorescence tests with a wide range of normal adult and fetal tissues and a tumor panel. Antigen LK26 is expressed on all cultured choriocarcinoma, teratocarcinoma and renal cancer lines but is absent from most cell lines derived from other tumor types and from cultures of normal kidney epithelium and fibroblasts. LK26 expression in normal tissues is restricted to the trophoblast. No other adult or fetal tissue was found to express the antigen, but choriocarcinoma and teratocarcinoma tissues were LK26+. SV19 is expressed on cultured choriocarcinomas and teratocarcinomas and on subsets of breast and colon cancer lines, but not on 120 additional cultures tested. In tissues, SV19 is detected in normal placenta, mammary gland and colon epithelium as well as in tumors of breast, colon and lung. Two antibodies, AbSV63 and AbK8, react with PLAP and AbSV63 also reacts with the intestinal form of the enzyme. AbLK24 defines a heat-stable determinant present on choriocarcinoma and breast cancer cell lines but absent from most other cultured cells. It is expressed on a small range of normal and malignant epithelial tissues, including normal trophoblast, normal breast epithelium and urothelium and tumors derived from these tissues. One antigen, K66, showed a wide distribution on cultured epithelial cells but was not found in any normal or malignant tissue. Finally, S4, a previously described marker of normal and malignant kidney epithelial cells, was also expressed on the choriocarcinoma cell lines. Four of the antigens are glycoproteins that could be immunoprecipitated from radiolabelled extracts of choriocarcinoma cells: LK26 (Mr 35,000), SV19 (Mr 40,000), PLAP (Mr 68,000) and S4 (Mr 160,000). The highly restricted distribution of LK26, SV19, S4, and PLAP in normal tissues and their expression in tumors make these antigens potential diagnostic markers of gestational choriocarcinoma and germ-cell tumors and, possibly, targets for immunotherapy.

Ovarian tumour xenografts in the study of the biology of human epithelial ovarian cancer

Human epithelial ovarian tumours were successfully established as xenografts in nude mice in 54% of cases. An evaluation of the biological characteristics of tumours propagated in nude mice was carried out and the functions investigated included morphology, growth kinetics, cellular DNA content, cell surface antigen expression and sensitivity to chemotherapy. To allow a more detailed study of the influence of ploidy on biological behaviour, xenografted tumour with varying degrees of aneuploidy and tumours with a common ancestry but different ploidies were also established. Although this is a highly selective model system favouring the growth of biologically aggressive tumours the xenografts, in general, reflect many of the characteristics of the tumours from which they were derived and are likely to provide a useful model for investigating the biology of ovarian cancer.