Metastatic mouse melanoma cells have a high affinity for the basement membrane and the ability to degrade it; these properties may allow tumor cells to invade the membrane and disseminate. In this study it was found that the metastatic potential of mouse melanoma cells varied when the cells were exposed in culture to fibronectin or laminin. After removal of fibronectin or exposure to laminin, the cells had an increased affinity for basement membrane collagen, were more invasive of basement membranes in vitro, and produced more lung colonies in vivo. These changes are correlated with and may be due to an increase in the laminin-binding capacity of the tumor cell surface.

NIH/3T3 cells transfected with DNA from malignant human tumors produced experimental and spontaneous metastases in nude mice. In contrast, parent or spontaneously transformed NIE/3T3 cells failed to metastasize. The transfected clones contained either activated c-Harvey-ras or N-ras oncogenes. A representative clone (T71-17SA2) which was used to assess selected cellular and host factors relevant to the metastatic process produced lung metastases in 100% of the NIH nude mice recipients, secreted augmented levels of type IV collagenase, and invaded human amnion basement membrane in vitro. Expression of the metastatic phenotype was not related to decreased sensitivity to natural killer cells or macrophage-mediated cytotoxicity. Analysis of the cellular DNA from the T71-17SA2 transfectant and its corresponding metastases, both of which contained activated N-ras oncogenes, revealed a twofold increase in the N-ras-specific DNA sequences in the metastatic cells. Thus, transfection with human tumor DNA containing activated ras oncogenes can induce the complete metastatic phenotype in NIH/3T3 cells by a mechanism apparently unrelated to immune cell killing.

Second-passage rat embryo cells were transfected with a neomycin resistance gene and the activated form of the c-Ha-ras I gene, or with these two genes plus the adenovirus type 2 E1a gene. Foci of morphologically transformed cells were observed in both cases; however, the frequency of transformation was at least ten times higher with two oncogenes than with the ras gene alone. All the transformed cell lines gave rise to rapidly growing tumors when injected subcutaneously into nude mice. All but one of the cell lines transformed by the ras oncogene alone formed metastatic nodules in the lungs of animals that had been injected subcutaneously with transformed cells. When transformed cells were injected intravenously, all the ras single-gene transformants gave rise to many metastatic lung nodules. In contrast, cell lines transformed with ras and E1a did not generate metastases after subcutaneous injection and gave rise to very few metastatic lung nodules after intravenous injection. These data demonstrate that a fully malignant cell with metastatic potential, as measured in an immunodeficient animal, can be obtained from early passage embryo cells by the transfection of the ras oncogene alone.

Abstract. Human and murine tumor cells contain cell surface receptors for the basement membrane glycoprotein laminin. Since a biologic role for the receptor had not previously been demonstrated, we explored the possibility that the laminin receptor may be involved in hematogenous metastases formation.Preincubation of metastatic murine melanoma cells with syngeneic whole laminin followed by tail vein injection increased tumor cell retention in the lung and strongly stimulated metastases formation. The domain of the laminin molecule responsible for stimulating metastases was identified. Laminin is a cross-shaped molecule with three short arms and one long arm. All arms have globular end regions. Purified protease-derived fragments of laminin were prepared which (a) lacked only the long arm of the molecule (alpha fragment) or, (b) lacked both the long arm and the globular end regions of the short arms (C, fragment). Both types of fragments contained the laminin receptor binding region. The fragments had opposite effects on metastases. The alpha fragment stimulated metastases formation to the same extent as whole laminin. In contrast, the C, fragment greatly reduced or abolished metastases formation in a dose-dependent manner. The C, fragment also inhibited tumor cell attachment to whole amnion basement membrane in vitro. We conclude that intact globular end regions on the short arms (but not the long arm) of the cell surface receptor-bound laminin molecule are necessary for stimulating metastases by the intravenous route.

The major protein components of shell scute of desert tortoises have amino acid composition and antigenic features of beta keratins. Scute protein composition may be altered in tortoises with certain systemic illnesses.