Growth and Differentiation Characteristics of Transformed Keratinocytes from Mouse and Human Skin in Vitro and in Vivo

Abstract

The altered phenotypic expression and chromosomal characteristics of mouse and human malignant keratinocyte lines have been studied in vitro and in vivo (in comparison with normal primary cultures). The cell lines exhibited different morphologic aspects that are probably more related to their respective degree of differentiation than to different stages in malignancy. Although all cell lines studied were deficient in some aspects of keratinization, certain basic structural and biochemical features were maintained, and these may serve as valid criteria for the identification of their epithelial nature. The altered expression of keratin proteins and morphologic differentiation can be modulated under in vivo growth conditions, but they cannot be reverted toward normality. Chromosomal alterations (in number and structure) occur early and are highly indicative criteria for malignancy, even though no tumor-specific aberrations have been identified. Two new approaches for evaluating characteristics of abnormal growth and differentiation in vitro, and of invasiveness in vivo, have been developed and have proved sensitive test methods for identifying malignant cells. While several abnormalities in growth and differentiation of cell lines in vitro are highly indicative of their malignant nature, the final proof that they are tumor cells still requires in vivo assay. The transplantation assay for studying cellular invasiveness not only improves the sensitivity of in vivo malignancy tests but has also proved to be a valuable model system for elucidating the modulation of differentiation by external influences.

Higher sensitivity of Adamts12-deficient mice to tumor growth and angiogenesis

“…The transplantation system is a highly sensitive tool to inspect the kinetic of early steps of host stromal response to tumor signals (Mueller and Fusenig, 2004;Jost et al, 2007Jost et al, , 2008. Malignant PDVA cells issued from carcinogen treatment of murine keratinocytes (Fusenig et al, 1983) precultured on a type I collagen gel were transplanted onto WT (n ¼ 14) and Adamts12-deficient mice (n ¼ 14). An early endothelial cell migration toward the tumor layer can be visualized through double immunostaining carried out to distinguish tumor cells (keratin positive) and vessels (CD31 positive cells or type IV collagenpositive basement membrane) .…”

Organotypic Collagen I Assay: A Malleable Platform to Assess Cell Behaviour in a 3-Dimensional Context

“…Here we present a method for production of a 3-dimensional matrix suitable for studies of invasive cell migration [6][7][8] . The matrix consists of collagen type 1 fibrils, which are contracted over a period of several days by primary human epidermal fibroblasts.…”

Angiogenesis Inhibition by Vascular Endothelial Growth Factor Receptor-2 Blockade Reduces Stromal Matrix Metalloproteinase Expression, Normalizes Stromal Tissue, and Reverts Epithelial Tumor Phenotype in Surface Heterotransplants

“…Cells were transplanted onto the dorsal muscle fascia of 7-to 9-week-old nude mice (Swiss/c nu/nu back-crosses) as monolayer cultures growing on collagen type I gels using a silicone chamber device (10,24,32). Transplants were dissected en bloc, embedded in TissueTek (Miles Laboratories, Elkhart, IN), and frozen in liquid nitrogen vapor for preparation of cryostat sections.…”