Biomedical subjects

A F Chambers

Publications and source records attributed to A F Chambers.

131 records · Page 8Linked to original sources

PubMedDate not supplied

Comparison of metastatic properties of a variety of mouse, rat, and human cells in assays in nude mice and chick embryos.

We have previously developed an assay to measure experimental metastatic ability of cells following intravenous injection into chorioallantoic membrane (CAM) veins of naturally immune deficient chick embryos. Here we compare metastatic properties of different cell types (ras-transformed and control NIH 3T3, LTA, and 10T1/2; melanoma; and glioma) from several species (mouse, rat, human), using chick embryos and the more commonly-used immune deficient host, nude mice. We found a good correlation between the two assays. Both hosts have advantages and disadvantages in assessing metastatic properties. We conclude that the chick embryo assay is a useful alternative host for experimental metastasis studies. This assay correlates well with and is less costly than assays using nude mice.

Animals↗

PubMedDate not supplied

Resistance of murine LTA cells to oncogene--mediated progression from tumorigenic to metastatic phenotype.

We have previously shown that expression of the H-ras oncogene alone does not induce progression of a tumorigenic but non-metastatic murine fibroblast cell line (LTA) to a metastatic phenotype. Because myc genes, alone or with ras, have been implicated at different stages of progression in other systems, we examined the ability of v-myc, alone and in combination with H-ras, to induce malignant conversion of LTA. We found no increase in either "spontaneous" (assessed after s.c. injection into nude mice) or "experimental" (assessed after i.v. injection into chick embryos) metastatic ability in spite of high levels of v-myc RNA in LTA cells transfected with v-myc alone. Serial in vivo passaging did not consistently select for either myc expression or metastatic ability. Myc transfected cells expressing high levels of myc RNA were subsequently transfected with H-ras. LTA cells expressing both oncogenes at high levels remained non-metastatic. LTA cells thus are resistant to the effects of myc and ras oncogenes (alone and in combination) on a specific stage of tumor progression, that of malignant conversion, and may offer a good model for studying mechanisms of resistance to these oncogenes.

Animals↗

PubMedDate not supplied

Oncogene transformation and the metastatic phenotype.

In this review, we first discuss some of the experimental parameters that need to be considered in assessing the contribution of various oncogenes to tumor metastasis. We discuss the requirement for a number of in vivo assays to measure different aspects of metastatic ability and we describe a novel metastasis assay, which we have developed, in the naturally immune-deficient chick embryo. Other factors capable of influencing the effects of oncogenes in experimental studies of metastasis, including oncogene activation and the differentiated status of the recipient cell, are also examined. We present some of our experimental results analyzing the ability of two oncogenes, src and ras, to convert cells to a metastatic phenotype. We speculate that a major mechanism by which some oncogenes promote metastatic ability is by subverting a signal transduction process, resulting in activation of a set of genes, some of which appear to promote metastatic ability. Finally, we discuss the need for additional information on the contributions of oncogenes to tumor progression and metastasis in both experimental systems as well as in clinical tumors.

Animals↗

PubMedDate not supplied

Metastatic NIH 3T3 x LTA cell hybrids express 72 kDa type IV collagenase.

We previously reported that the murine fibroblast cell line LTA is tumorigenic but non-metastatic, and is non-responsive to a transfected H-ras oncogene. In contrast, NIH 3T3 cells are non-tumorigenic but are ras-responsive and become metastatic when transfected with ras. Somatic cell hybrids between LTA and NIH 3T3 cells are tumorigenic, metastatic and ras-responsive. Here we examined expression of type IV collagenases in parental LTA and NIH 3T3 cells (with and without ras) and four metastatic LTA x NIH 3T3 hybrids (also with and without ras). Parental NIH 3T3-derived cells had both 72 kDa and 92 kDa gelatinase activities, and LTA-derived cells had either aberrantly sized approximately 90 kDa activity alone or neither enzyme activity. All four metastatic hybrids expressed 60-72 kDa gelatinase activity, while three of them also had 92 kDa activity and one had only minimal 92 kDa activity. Thus the metastatic phenotype of the hybrids was associated with expression of 72 kDa gelatinase. Levels of RNA for tissue inhibitors of metalloproteinases (TIMP-1, TIMP-2) were relatively constant, suggesting independent regulation of type IV collagenases and their inhibitors. Southern blotting and probing with PCR-synthesized cDNA fragments of the mouse 72 kDa type IV collagenase gene showed that this gene was present in all cells although the structure of this gene in one of the three LTA cell lines differed from that of the other cells. Our results suggest that a key change in the metastatic hybrids, relative to non-metastatic parental LTA cells, is induction of expression of 72 kDa type IV collagenase.

3T3 Cells↗

PubMedDate not supplied

MMP-2 expression is associated with, but not sufficient for, malignant conversion of murine LTA cells.

We previously showed that tumorigenic, non-metastatic LTA cells can be converted to a metastatic phenotype either by cell fusion with non-malignant NIH 3T3 cells, or by transfection with genomic DNA from metastatic murine B16F1 or human 1GR37 melanoma cells. In order to identify a gene present in NIH 3T3 cells that is responsible for this conversion, we transferred DNA from an NIH 3T3 genomic library into LTA cells and tested for changes in metastatic properties, assessed in the chick embryo. We found that 3 of 4 pools of transfectant clones showed significantly increased metastatic ability over the vector-only control transfectants. All three metastatic transfectant pools showed significantly increased RNA levels of the 72 kDa type IV gelatinase (MMP-2). To test whether increased expression of MMP-2 was sufficient to convert LTA cells to metastatic ability, we transfected full length MMP-2 cDNA, in a CMV-promoter expression construct, into LTA cells. Stable transfectants with elevated MMP-2 RNA and enzymatic activity were obtained. The highest MMP-2 expressing clone was assayed for experimental metastatic ability in the chick embryo, and found to be no more metastatic than LTA parental cells. We conclude that increased MMP-2 expression accompanies the malignant conversion of LTA cells, but MMP-2 expression alone is not sufficient to bring about this change. The inability of LTA cells to metastasize thus appears to be due to a more complex defect than insufficient MMP-2. This study supports the idea that malignant conversion may require the concerted activation of multiple genes, which are in turn controlled by regulatory genes, whose identification will be important in understanding and controlling metastasis.

3T3 Cells↗