Primary Cultures Of Human Fibroblasts Research Articles

INHIBITION OF PKC AND PKA BY CHEMOPREVENTIVE ORGANOSELENIUM COMPOUNDS

Numerous efficacy studies in rodents revealed that 1,4-phenylenebis(methylene)-selenocyanat (p-XSC) is a more effective chemopreventive organoselenium compound and less toxic than benzyl selenocyanate (BSC) or the inorganic compound Na2SeO3. To explore mechanisms which mediate chemopreventive activities of p-XSC we have tested its effect on protein kinase A and C using in vitro and cell culture systems. While p-XSC did completely inhibit PKC and PKA activity, BSC was less active and Na2SeO3 had no effect. Comparative EC,, revealed values of 0.1, 1 and > 10 mu M for p-XSC, BSC and Na2SeO3, respectively. p-XSC was also capable of inhibiting protein phosphorylation in cultures of primary human fibroblasts and altered morphology of rat fibroblast (R6) cells. When combined, sub-optimal doses of p-XSC and staurosporine yielded an additive effect on cell morphology. The ability of p-XSC and BSC to inhibit protein kinase A and C activities may in part account for the mechanism(s) by which these agents mediate their chemopreventive effects.

Adeno-associated virus vectors preferentially transduce cells in S phase.

Vectors based on adeno-associated virus can stably transfer genes by chromosomal integration in recipient cells. In this study we have infected stationary and dividing primary human fibroblast cultures with adeno-associated virus vectors encoding alkaline phosphatase and neomycin phosphotransferase. We find that the transduction frequency of S phase cells is about 200 times that of non-S phase cells. However, neither S phase nor mitosis is essential for transduction. Single-stranded vector genomes survive in stationary cultures and can be recruited for transduction by stimulating these cultures to divide. Stable transductants contain randomly integrated vector sequences. These findings have important implications for the use of adeno-associated virus vectors in gene therapy.

Na+-dependent high affinity uptake of l-glutamate in primary cultures of human fibroblasts isolated from three different types of tissue

Cultured human fibroblasts isolated from embryonic muscle, skin and peripheral nerve tissues were found to accumulate [3H]L-glutamate by a Na+-dependent uptake process strongly inhibited by several glutamate/aspartate analogues including d- and l-aspartate, d- and l-thero-3-hydroxyaspartate and l-trans-pyrrolidine-2,4-dicarboxylate but not d-glutamate. It was also reduced by elevated concentrations of K+, Rb+ and Cs+. The values of Km's were 5–20 μM, well within the ‘high affinity’ region. Variations in the capacity (Vmax) of [3H]l-glutamate uptake did not correlate with the origin (muscle, skin or nerve tissue) of the fibroblasts. The uptake characteristics suggest that it is mediated by a transport system similar to that commonly observed only in brain tissue.

Demonstration of a positive feedback loop of paracrine growth stimulation in a new co-culture model of breast cancer

A serum-free co-culture model of breast cancer was established using primary cultures of human fibroblasts and the breast cancer lines MCF-7, T47D and MDA-MB-231. The model was used to test the hypothesis that there is a positive feedback loop of paracrine growth stimulation between stromal fibroblasts and cancer cells. Cancer cell growth was dependent on co-culture with fibroblasts and fibroblast growth, in turn, was dependent on co-culture with cancer cells. Platelet derived growth factor (PDGF) was mitogenic for fibroblasts in mono-culture but not mitogenic for cancer cells. However, addition of PDGF to a co-culture of cancer cells with fibroblasts resulted in increased growth of the cancer cells, as predicted by the paracrine loop hypothesis. This model demonstrates one way in which benign stromal cells may be actively recruited into the malignant process.

Formation of large deletions by illegitimate recombination in the HPRT gene of primary human fibroblasts.

HPRT gene mutants were isolated from untreated and x-irradiated cultures of primary human fibroblasts, and mutants carrying large deletions were identified. The breakpoints of the deletions were mapped by methods based on the polymerase chain reaction, and the deletion junctions of four different mutants were sequenced. Alu repeats were associated with one end of three of these junctions, but in each case repeat sequences were not found at the other end. Sequence features found at the deletion breakpoints included in particular short direct and inverted repeats, which may mispair to promote illegitimate recombination. One mutant had additional bases inserted at the deletion junction; these bases formed a direct repeat with a sequence immediately adjacent to the junction, suggesting a mechanism of templated repair of broken DNA in deletion formation.

Differences between the regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and low density lipoprotein receptor in human hepatoma cells and fibroblasts reside primarily at the translational and post-translational levels.

We have carried out parallel analyses of the regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGr) and low density lipoprotein receptor (LDLr) in two highly differentiated human hepatoma cell lines, HepG2 and Hep3B, and primary cultures of human fibroblasts. Analyses of the levels of HMGr and LDLr mRNAs under a variety of culture conditions that perturb intracellular sterol metabolism, or which differ in the levels of extracellular sterols, indicated that the hepatoma cells and fibroblasts responded similarly in terms of the repression or induction ratios of both mRNAs. However, the absolute levels of the mRNAs were severalfold higher in the hepatoma cells. The major difference between the responses of the hepatoma cells and fibroblasts involved the increase in expression of LDLr which occurred upon shifting the cells from complete to lipoprotein-depleted serum. Under these conditions, the 3-fold increase in rate of synthesis of LDLr in the hepatomas was closely matched by increases in the level of its mRNA. In the case of fibroblasts, a 10-fold increase in translational efficiency was required to explain the 30-fold change in rate of synthesis of LDLr. Polysome profiles from both hepatoma cells and fibroblasts suggest that the rate of elongation or termination on LDLr mRNA is relatively low in the presence of reconstituted complete serum, and that it increases in fibroblasts upon lipoprotein depletion, but not in the hepatoma cells. These data indicate that hepatic expression of LDLr may be relatively refractory to induction by decreased circulating levels of lipoprotein when compared with peripheral tissues.

Structures of human genes coding for cytokine LD78 and their expression.

LD78 is a member of a newly identified superfamily of small inducible proteins involved in inflammatory responses, wound healing, and tumorigenesis. Southern blot analysis of the EcoRI-digested human genomic DNAs, using previously isolated LD78 cDNA as a probe, showed that in each individual there are 4.2- and 4.8-kilobase-pair (kb) fragments and that some have an additional 6.5-kb fragment. The 4.2-kb fragment contained genomic DNA sequences corresponding to the LD78 cDNA and was named the LD78 alpha gene. The 4.8-kb fragment contained similar sequences, showing 94% homology to the LD78 alpha gene, and was named the LD78 beta gene. The LD78 alpha gene was present in a single or a few copies per haploid genome, whereas the copy number of the LD78 beta gene and of the 6.5-kb fragment hybridizable to LD78 cDNA varied among the samples tested. Treatment of human myeloid cell lines HL-60 and U937 with phorbol 12-myristate 13-acetate (PMA) increased within 2 h cellular levels of the RNA hybridizable to LD78 cDNA. The human glioma cell line U105MG and primary culture of human fibroblasts also expressed the hybridizable RNA in response to PMA. Addition of cycloheximide had no apparent effect on this response in U937 cells and inhibited the response in fibroblasts, whereas it stimulated the response in HL-60 and U105MG cells. mRNA phenotyping experiments revealed that the LD78 alpha and LD78 beta genes were both transcribed in PMA-stimulated U937 cells.

Structures of Human Genes Coding for Cytokine LD78 and Their Expression

LD78 is a member of a newly identified superfamily of small inducible proteins involved in inflammatory responses, wound healing, and tumorigenesis. Southern blot analysis of the EcoRI-digested human genomic DNAs, using previously isolated LD78 cDNA as a probe, showed that in each individual there are 4.2- and 4.8-kilobase-pair (kb) fragments and that some have an additional 6.5-kb fragment. The 4.2-kb fragment contained genomic DNA sequences corresponding to the LD78 cDNA and was named the LD78 alpha gene. The 4.8-kb fragment contained similar sequences, showing 94% homology to the LD78 alpha gene, and was named the LD78 beta gene. The LD78 alpha gene was present in a single or a few copies per haploid genome, whereas the copy number of the LD78 beta gene and of the 6.5-kb fragment hybridizable to LD78 cDNA varied among the samples tested. Treatment of human myeloid cell lines HL-60 and U937 with phorbol 12-myristate 13-acetate (PMA) increased within 2 h cellular levels of the RNA hybridizable to LD78 cDNA. The human glioma cell line U105MG and primary culture of human fibroblasts also expressed the hybridizable RNA in response to PMA. Addition of cycloheximide had no apparent effect on this response in U937 cells and inhibited the response in fibroblasts, whereas it stimulated the response in HL-60 and U105MG cells. mRNA phenotyping experiments revealed that the LD78 alpha and LD78 beta genes were both transcribed in PMA-stimulated U937 cells.

Differential staining of chromosomes and spindle cannot be used as an assay to determine the effect of cancer promoters on primary cultures of human fibroblasts

The differential staining technique allows simultaneous visualization of chromosomes and spindle fibers. The relative sensitivity of this test for chemicals with high tumor-promoting activity (TPA and iodoacetic acid) or for low tumor-promoting chemicals (4β-PDD and α-phorbol) was analyzed. Moreover, to ensure a complementary reference system, metals with possible mutagenic (As > Hg > Cd) and carcinogenic (As > Cd = Hg) properties were tested in parallel. As and Hg, which are known as spindle poisons, do induce, as expected, a disaggregation of the spindle fibers; with Cd, no clear-cut disappearance of the spindle is observed. As far as the cancer promoters are concerned, there is no evidence that their ability to induce mitotic aneuploidy in yeast would be confirmed by the induction of spindle disappearance and/or abnormal chromosome segregation in primary cultures of human fibroblasts.

Purification and in vitro labeling of interferon from a human fibroblastoid cell line.

Interferon was produced from a clonal human fibroblastoid line. This cell line was derived from an established fibroblastoid culture treated with ethylmethane sulfonate and is capable of producing higher amounts human interferon than primary human fibroblast cultures. The interferon produced from this cell line was purified by concanavalin A and phenyl-Sepharose column chromatography followed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified interferon was then labeled with [125I]-iodine, with [3H]5-dimethylaminonaphthalene-1-sulfonyl-chloride and with sodium [3H]borohydride after periodate oxidation. An appreciable amount of biological activity was retained after both tritium labelings but not after iodination. When subjected to electrophoresis in the presence of sodium dodecyl sulfate all three radioactive interferon preparations comigrated with the purified interferon preparation as a single protein component with a molecular weight of 19,000. Both purified and radioactive preparations were also shown to migrate with the antiviral activity in polyacrylamide gels in the absence of sodium dodecyl sulfate. The specific activity of purified interferon preparations ranged from 2 X 10(8) to 10 X 10(8) units/mg of protein.

Human Tissues as Source of Colony‐Stimulating Factor in Human Bone Marrow Cultures

Human bone marrow cells were cultured by the agar method using feeder layers containing human tissue fragments of various origin. Colony stimulating factor (CSF) was shown to be released from all tissues tested (adipose tissue, skeletal muscle, peritoneum and vascular wall), and primary cultures of human fibroblasts could also stimulate colony growth. Colony growth of murine bone marrow cells was also stimulated by all feeder layers. Thus, the study demonstrates that monocytes and macrophages might not be the only source of CSF of possible importance for human granulopoiesis in vivo.