Biomedical subjects

R Radinsky

Publications and source records attributed to R Radinsky.

44 records · Page 3Linked to original sources

PubMed1987

Amplification and rearrangement of the Kirsten ras oncogene in virus-transformed BALB/c 3T3 cells during malignant tumor progression.

Analyses of the cellular and viral Kirsten ras genes (c-Ki-ras and v-Ki-ras, respectively) during malignant tumor progression were performed by using Kirsten murine sarcoma virus-transformed BALB/c 3T3 cells that harbor a replication-defective provirus. After injection into athymic nude mice by four different routes, primary tumors and secondary lung metastases were isolated, adapted to in vitro growth, and analyzed for DNA levels and mRNA expression of both genes for comparison with the originally injected transformed cells and untransformed 3T3 cells. For all tumors (primary or secondary), the v-Ki-ras gene was amplified and v-Ki-ras mRNA expression was highly elevated above that observed in the original transformed cell population. In two of five lung metastases from the i.v. and footpad injection routes, rearranged Ki-ras DNA sequences were observed. Micrometastases from the s.c. route of injection did not display these alterations. Injection of footpad lung tumor cells with rearrangements into a second group of animals led to multiple lung metastases with even further rearrangements correlating with more effective lung colonization/growth ability (overt lung tumors in five of eight animals less than 20 days after injection). However, reinjection of an i.v. lung tumor with rearranged Ki-ras led to no further rearrangements in the lung microfoci tumors isolated greater than 40 days after injection. These data suggest (i) the significance of amplification and elevated expression of v-Ki-ras in tumor formation, (ii) correlation of this amplification with more effective tumor progression, and (iii) the selective advantage that cells with Ki-ras DNA sequence additions have in the formation of overt lung tumors.

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PubMed1986

Fibronectin binding to gangliosides and rat liver plasma membranes.

Binding of fibronectins to gangliosides was tested directly using several different in vitro models. Using an enzyme-linked immunoabsorbent assay (ELISA), gangliosides were immobilized on polystyrene tubes and relative binding of fibronectin was estimated by alkaline phosphatase activity of conjugated second antibody. Above a critical ganglioside concentration, the gangliosides bound the fibronectin (GT1b congruent to GD1b congruent to GD1a greater than GM1 much greater than GM2 congruent to GD3 congruent to GM3) in approximately the same order of efficiency as they competed for the cellular sites of fibronectin binding in cell attachment assays (Kleinman et al., Proc natl acad sci US 76 (1979) 3367). Alternatively, these same gangliosides bound to immobilized fibronectin. Rat erythrocytes coated with gangliosides GM1, GD1a or GT1b bound more fibronectin than erythrocytes not supplemented with gangliosides. Using fibronectin in which lysine residues were radioiodinated, an apparent Kd for binding to mixed rat liver gangliosides of 7.8 X 10(-9) M was determined. This value compared favorably with the apparent Kd for attachment of fibronectin to isolated plasma membranes from rat liver of 3.7 X 10(-9) M for fibronectin modified on the tyrosine residue, or 6.4 X 10(-9) M for fibronectin modified on lysine residues. As shown previously by Grinnell & Minter (Biochem biophys acta 550 (1979) 92), fibronectin modified on tyrosine residues did not promote spreading and attachment of CHO cells. It did, however, bind to cells. In contrast, lysine-modified fibronectin both bound to cells and promoted cell attachment. Plasma membranes isolated from hepatic tumors in which the higher gangliosides that bind fibronectin were depleted bound 43-75% less [125I]fibronectin than did plasma membranes from control livers. The findings were consistent with binding of fibronectins to gangliosides, including the same gangliosides depleted from cell surfaces during tumorigenesis in the rat.

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PubMed1986

Substratum contacts and cytoskeletal reorganization of BALB/c 3T3 cells on a cell-binding fragment and heparin-binding fragments of plasma fibronectin.

BALB/c 3T3 cells make both close contacts and tight-focal contacts (with associated microfilament stress fibers) on plasma fibronectin (pFN)-coated substrata. To resolve the importance of the heparan sulfate-binding or cell-binding activities of the pFN molecule in these adhesive responses, a cell-binding fragment (120K) (CBF) free of any heparan sulfate-binding activity was prepared from human pFN by chymotrypic digestion and isolated as described by Pierschbacher et al. (Cell 26 (1981) 259). These adhesive responses to CBF were also compared to those of the model heparan sulfate-binding protein, platelet factor-4 (PF4), or heparin-binding fragments (HBF) of pFN. On intact pFN, greater than 70% of the cells formed tight-focal contacts and associated stress fibers by 4 h, the latter staining with NBD-phallacidin. In contrast, cells spread differently on CBF and failed to form tight-focal contacts; staining with NBD-phallacidin was localized to spiky projections at the cell margin with no detectable stress fiber formation. On PF4 or HBF, cells failed to form tight-focal contacts but did spread well and formed long microfilament bundles in peripheral lamellae. Spreading on CBF, HBF, or PF4 was paralleled by formation of close contacts. Spreading and to some extent attachment of cells on CBF was inhibited with a small peptide containing the Arg-Gly-Asp-Ser sequence; responses on HBF were unaffected by this peptide. When mixtures of CBF and PF4 were tested, cells still failed to form tight-focal contacts and stress fibers. These results demonstrate that the binding of CBF to its probable receptor under conditions routinely used to assay spreading activity results in an incomplete adhesive response compared with intact pFN. While this partial response may result from quantitative differences in the density of active cell-binding domains on the substratum, the pattern of microfilament reorganization produced by the binding of PF4 to cell surface heparan sulfate proteoglycans suggests that the ability of pFN to promote formation of tight-focal contacts and stress fibers may reside in the coordinate interaction of two or more binding activities in the intact molecule.

Actin Cytoskeleton↗

PubMedDate not supplied

Molecular mechanisms for organ-specific colon carcinoma metastasis.

The mechanistic basis of a metastatic cell's ability to proliferate in the parenchyma of certain organs and develop organ-specific metastases remains largely unknown. Signals from paracrine and/or autocrine pathways may regulate tumour cell proliferation, with the eventual outcome dependent on the net balance of stimulatory and inhibitory factors. Recent data demonstrate that organ microenvironments can modulate gene expression of tumour cells, including regulation of growth at the organ-specific metastatic site. Analyses of highly metastatic human colon carcinoma (hCC) cells selected in nude mice as well as in situ mRNA hybridisation analyses of archival colon carcinoma specimens correlated high levels of epidermal growth factor receptor with the malignant hCC cell's ability to grow in the liver parenchyma. These same metastatic cells can also respond to specific mitogens produced by tissue undergoing repair, demonstrating that physiological signals can be utilised by neoplastic cells. This article will address experimental evidence supporting the premise that organ-derived, paracrine growth factors regulate the growth of malignant cells that express the appropriate receptors.

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PubMedDate not supplied

Orthotopic models are necessary to predict therapy of transplantable tumors in mice.

Rapid evaluation of new cytotoxic agents and biological response modifiers for therapy of cancer and elucidation of their mechanisms of action require the use of relevant animal models. It is well established that the faithful reproduction of the tumor microenvironment that allows the emergence of subpopulations of tumor cells with the biological and metastatic properties observed in clinical cancer occurs with orthotopic tumor models (transplantable and transgenic). This review summarizes the evidence that phenotypic properties of metastatic cells are governed by the expression of genes that are regulated by interaction with the relevant organ environment. While ectopic models of cancer allow rapid screening of new compounds and transgenic models afford opportunities to study early cellular and molecular events in tumor progression and metastasis, orthotopic transplantation of tumor cells remains an affordable, reproducible and reliable methodology for the study of organ-specific determinants of the biology and therapy of cancer.

Animals↗

PubMedDate not supplied

Regulation of tumor cell growth at organ-specific metastases.

The hallmark of malignant neoplasms is their ability to spread beyond the site of origin and produce metastases in distant organs. This nonrandom process depends on the interaction of specific tumor cells with a compatible milieu provided by a particular organ microenvironment; the molecular basis of which is under intense investigation. Recent analysis of human colon carcinoma (HCC) cells obtained from surgical specimens and implanted into athymic nude mice suggested that whereas nonmetastatic and highly metastatic cells can grow at local sites, growth per se in the secondary organ-specific site was associated only with high-metastatic HCC cells. These cells also respond in a specific manner to physiological mitogenic signals produced by damaged normal tissues. This article addresses the biological and molecular evidence supporting the hypothesis that organ-derived, perhaps, organ-specific, paracrine growth factors stimulate the growth of receptive malignant cells that possess the appropriate receptors.

Animals↗

PubMedDate not supplied

Correlation of growth capacity of cells in hard agarose with successful transfection by the activated c-Ha-ras oncogene and in vivo proliferative capacity at metastatic sites.

The purpose of this study was to determine whether the degree of anchorage-independent growth of rodent or human cells in increasing concentrations of agarose correlated with successful transfection of the cells with an activated c-Ha-ras oncogene and tumorigenicity in nude mice. NIH 3T3 cells, C3H 10T1/2 fibroblasts, four clones of the murine K-1735 melanoma with different metastatic capacities and the TE85 human osteogenic sarcoma line were transfected with plasmids containing the 6.6-kilobase BamHI fragment of the mutant human c-Ha-ras gene and the neo gene, which confers resistance to neomycin (pSV2-neoEJ). Cells transfected with pSV2-neo, a plasmid containing the neo gene, served as controls. Cells from parental or transfected lines (selected by Geneticin) were plated into medium containing 0.3%, 0.6% 0.9%, or 1.2% agarose. These cells were also injected subcutaneously and intravenously into nude mice. The production of tumor cell colonies in dense agarose (greater than or equal to 0.6%) correlated with successful transfection with pSV2-neoEJ and production of experimental metastases in the lung of nude mice. We conclude that the degree of anchorage-independent growth of cells predicts successful transfection with activated c-Ha-ras oncogene and tumorigenic behavior in vivo. Thus this technique may be useful for the detection of cells transfected with transforming oncogenes.

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PubMedDate not supplied

Intertumoral heterogeneity of receptor-tyrosine kinases expression in human melanoma cell lines with different metastatic capabilities.

Human melanocytes respond to several growth factors whose receptors have tyrosine kinase activity. Abnormalities in the expression of tyrosine kinase receptors may play an important role in the initiation and progression of melanoma. We therefore determined the steady-state mRNA expression of five tyrosine kinase receptors, epidermal growth factor receptor (EGF-R), c-met, nerve growth factor receptor (NGF-R), colony-stimulating factor receptor (CSF-R) and c-kit, in eleven human melanoma cell lines with different metastatic potentials in nude mice. All cell lines except for one nonmetastatic line established from a primary melanoma lost expression of c-kit. Expression of the other four tyrosine kinase receptors varied among the lines. The expression level of individual tyrosine kinase receptor did not correlate with the metastatic potential of the cells. These results suggest that metastatic human melanoma cell lines are heterogeneous for expression of tyrosine kinase receptors, with each cell type manifesting a distinct repertoire of receptor tyrosine kinases. The different profile of tyrosine kinase activities in different metastatic melanomas complicates its use for prognosis.

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