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At least 397 records · Page 22Linked to original sources
PubMed1987

Maturation signals for human B cells. Use of the MTT assay and EBV-transformed cell lines to define signals which promote cell growth or immunoglobulin secretion.

There are now several relatively well-defined signals that promote B-cell growth and maturation, usually termed 'growth' and 'differentiation' factors (e.g., IL-1, IL-2, BCGF, BSF-1 (IL-4) and BSF-2). In addition, much work has been carried out using continuous cell lines to examine the effects of these two classes of material. Using two different assays to enumerate cell growth and the ELISA to quantify Ig secretion, we would like to emphasize the importance of determining the final cell number when investigating so-called 'differentiation factors', particularly when continuous cell lines are the targets. The results presented here show that materials which promote DNA synthesis in B-cell lines (e.g., IL-1, BCGF) will also cause an increase in Ig secreted, suggesting that they can also promote Ig synthesis. However, when we used the MTT assay to quantitate cell numbers at the end of the assay and then calculated the Ig secreted per cell, only BSF-2 caused an increase in Ig secreted per cell. These results illustrate the importance of determining the final cell number when using continuous cell lines to investigate the actions of materials which modulate human B cell function and suggest that the MTT assay is a simple way of doing this.

Antibody-Producing Cells↗
PubMed1991

Antiproliferative activity of retinoids, interferon alpha and their combination in five human transformed cell lines.

Tretinoin, isotretinoin and acitretin were examined for their capacity to modulate the proliferation of the cell lines: HL-60 (acute promyelocytic leukemia), MCF7 (mammary carcinoma), SCC4, SCC15 and A431 (squamous cell carcinomas). Retinoids inhibited proliferation to a varying extent in all 5 cell lines. The cytokine IFN alpha had a significant antiproliferative effect only on HL-60, SCC4 and SCC15. The combination of retinoids with IFN alpha led in all 5 cell lines to a more profound reduction in proliferation than either retinoids or IFN alpha alone.

Acitretin↗
PubMed1991

Antibiotic magainins exert cytolytic activity against transformed cell lines through channel formation.

Magainins are an ionophoric class of vertebrate peptides with antibiotic activity against various microorganisms. Here we show that magainin 2 and synthetic analogues can rapidly and irreversibly lyse hematopoietic tumor and solid tumor target cells with a relative cytotoxic potency that parallels their antibacterial efficacy and at concentrations that are relatively nontoxic to well-differentiated cells. The cytotoxicity is prevented by cell depolarization. Magainins represent a natural cytolytic agent in vertebrates and may provide another therapeutic strategy for certain tumors.

Anti-Bacterial Agents↗
PubMed1987

A reiterated leader sequence is present in polyomavirus late transcripts produced by a transformed rat cell line.

In cells transformed by polyomavirus, the viral genome is integrated into the host DNA, and in the absence of excision, viral gene expression is limited to the early region. We report here that the ability of a unique transformed rat cell line, designated SS1A, to produce readily detectable levels of late mRNAs is due to rearrangements of the integrated viral sequences. The structure of the SS1A insertion, resulting from amplification and deletion events, allows for the formation of a primary late transcript that can subsequently be spliced to generate a reiterated leader attached to the body of the late mRNA coding sequences. The presence of transcripts containing such a leader was confirmed by sequencing the 5' end of cDNA copies of late mRNAs isolated from a library constructed with SS1A mRNA. These results suggest that a reiterated leader sequence is necessary to stabilize late mRNA.

Animals↗
PubMed1987

UDP-N-acetylglucosamine: lysosomal enzyme precursor N-acetylglucosamine-1-phosphate transferase activities in human ovarian tumor tissue and some transformed cell lines.

Uridine diphosphate-N-acetylglucosamine: lysosomal enzyme precursor N-acetyl-glucosamine-1-phosphate transferase, is a key enzyme involved in the intracellular targeting of lysosomal enzymes. This enzyme is elevated fourfold in primary ovarian tumor microsomes with respect to normal ovarian microsomes. This elevation is associated with significant increases in the specific activity of multiple lysosomal hydrolases, including beta-D-hexasaminidase, alpha-L-fucosidase, and beta-D-galactosidase. The activity of the phosphotransferase was also documented in several cell lines derived from human tumors. The possible role of this enzyme in tumor-associated phosphorylation is discussed.

Female↗
PubMed1972

Differentiation of blood group H in a human transformed cell line.

HeLa cells were separated into two populations by agglutination with anti-H ulex reagent which was defined according to its reactivity against L-fucose, the immunodeterminant sugar for blood group H. Chromosome studies of individual cells from each population indicated that they were karyotypically similar and that they possessed a single modal chromosome number of 69. Studies of tissue culture supernates and of cellular fractions and their supernates showed that HeLa cell group H was membrane associated and not soluble in nature. Cloning studies of single H(-) cells separated from H(-) cells agglutinated by anti-H demonstrated progeny comprised of mixed H(-)/H(-) cells, a finding which was supported by results of population studies on typed cells grown in monolayer culture. It is believed that the H- population represents germinal cells that are capable of dividing to form mixed H(-)/H(-) cellular progeny, the former representing a more fully differentiated cell form, which eventually exfoliates and becomes nonfunctional.

Agglutination Tests↗
PubMed1987

Continuing rearrangement of immunoglobulin and T-cell receptor genes in a Ha-ras-transformed lymphoid progenitor cell line.

The arrangement of immunoglobulin genes has been examined in a series of lymphoid cell lines transformed with the Harvey murine sarcoma virus. One cell line, HAFTL-1, expresses antigenic markers characteristic of B-lymphoid cells and undergoes frequent rearrangement at the JH locus (where J = joining and H = heavy chain) during propagation in culture. By molecular cloning and nucleotide sequence determination, these rearrangements were found to represent the earliest postulated step in heavy chain gene assembly: the joining of a diversity (D) segment to a JH segment. The HAFTL-1 cell line also undergoes infrequent D beta-to-J beta joining at the T-cell receptor beta locus in culture. The observations presented here suggest that the HAFTL-1 cell line represents the early stage of B-cell differentiation at which immunoglobulin gene rearrangement is initiated.

Animals↗
PubMed1980

Coexpression of a mutant beta-actin and the two normal beta- and gamma-cytoplasmic actins in a stably transformed human cell line.

HUT 14 is a cloned transformed cell line derived from normal diploid human KD fibroblasts. HUT 14 cells have an altered actin phenotype. In addition to the two nonmuscle actins beta and gamma, also present in the parent KD cells, they show the stable expression of a novel actin species (Ax-actin). Amino acid sequence analysis has been used to identify the three actins of HUT 14 cells. beta- and gamma-actins are identified as normal mammalian nonmuscle actins whereas Ax-actin is characterized as a beta-actin mutant revealing a single amino acid substitution at position 244. The results obtained are compatible with a simple mutational event involving a point mutation in one of the two beta-nonmuscle actin genes assumed to be present in proliferating human diploid fibroblasts. Certain emerging principles of nonmuscle actin gene expression in higher vertebrates are discussed.

Actins↗
PubMedDate not supplied

Karyological analysis of N-methyl-N'-nitro-N-nitrosoguanidine-transformed Syrian hamster cell lines using high resolution G-banding technique.

The karyotypes of two Syrian hamster cell lines transformed by N-methyl-N'-nitro-N-nitrosoguanidine have been analyzed using high resolution G-banding technique. The change of gene dosage appears to be the main feature of the chromosome aberrations. One of the cell lines (BHLB4) has been passaged in vitro for 68 times and has a pseudodiploid chromosome number of 44. The most common feature of aberrations of this cell line is monosomy of chromosome 15 and in addition trisomy of chromosome 8. The other cell line (HEC5) was newly transformed, having a modal chromosome number of 50. In spite of the occurrence of trisomy of some autosomes, monosomy of chromosome 15 was still evident. No obvious structural changes were found even in G-banded prophase chromosomes. Our observations support the previous report on the monosomy of chromosome 15, as the most common feature of virally- and chemically-transformed Syrian hamster cell lines.

Animals↗
PubMed1996

Development and characterization of v-myc/v-raf-transformed murine fetal thymocyte cell lines.

Transformed murine fetal thymocyte cell lines were derived by incubating fetal thymic organ cultures with a v-myc/v-raf-containing retroviral construct in order to model developmental stages within the early triple negative (CD3-CD4-CD8-) thymocyte population. The resulting 10 cell lines had a lymphoid morphology, were all CD44+, CD90+, and were triple negative by surface antigen analysis. The cell lines, however, were distinguishable by differences in the expression of T cell-associated and T cell-specific genes. The CD3 genes were observed to be discoordinately expressed, in that CD3 gamma chain gene expression was detected in 2 cell lines in the absence of CD3 delta and epsilon expression. Expression of the CD3 gamma chain gene was observed in cell lines without the expression of other T cell-specific genes or T cell receptor rearrangement and may be one of the earliest T cell-specific genes to be expressed. The transcription factor Ikaros was expressed in all 10 cell lines, whereas the transcription factor TCF1 alpha was expressed only in the 2 most differentiated lines. In 8 cell lines, expression of partial TCR beta and/or TCR alpha transcripts was observed by Northern blot. In several lines, expression of rearranged TCR alpha transcripts in the absence of TCR beta transcripts was demonstrated; however, TCR beta DJ rearrangements were observed by Southern blot in all but 1 of these cell lines. Thus, these cell lines, ordered based on the general pattern of additive gene expression observed, may reflect various stages of triple-negative thymocyte differentiation and provide an in vitro mechanism to elucidate some of the molecular events involved in early thymocyte development.

Animals↗
PubMed1993

The use of transformed T cell lines for clonal expansion of human B cells from peripheral blood, spleen, and tumor-infiltrating lymphocytes.

Human transformed T cell lines were able to induce polyclonal B cell activation and immunoglobulin (Ig) secretion from peripheral blood mononuclear cells, spleen cells and tumor-infiltrating lymphocytes (TIL). Cells from one of the lines tested, MOT, did not require any exogenous stimuli to induce maximal responses and under similar conditions induced higher levels of response than peripheral blood T cells or other T cell lines. MOT-induced B cell activation and Ig secretion required cell contact and factors present in the MOT culture supernatant. MOT cells induced B cell responses from TIL in the three tumors tested (melanoma, ovarian and colon cancer) and HIV-specific immunoglobulin secretion by spleen cells from an HIV+ patient.

Antibody Formation↗
PubMed1986

Establishment of two rabbit mammary epithelial cell lines with distinct oncogenic potential and differentiated phenotype after microinjection of transforming genes.

The goal of this work was to establish an assay for transformation of epithelial cells. Two epithelial cell lines were obtained after microinjecting transforming genes into primary rabbit mammary secretory cells. The cell lines were analyzed for their oncogenic potential and for the maintenance of a differentiated phenotype. A fully transformed cell line, which retained epithelial cell organization, was obtained by coinjecting simian virus 40 DNA and the activated human c-Ha-ras gene. The proliferation rate of these cells was high, with a doubling time of 16 h. Their growth was anchorage independent, and they had lost contact inhibition. The cells were tumorigenic in nude mice, but had no metastatic potential. Both microinjected DNAs were efficiently transcribed and translated, in contrast to the casein genes, which were expressed in primary cells but not in the transformed cell line. An immortalized cell line established after injection with simian virus 40 DNA alone was characterized by a moderate rate of proliferation with a doubling time of approximately 30 h. The growth of these cells was contact inhibited and anchorage dependent. The cells were not tumorigenic in nude mice. The viral DNA was expressed during early passages, as shown by the presence of the large T antigen in cell nuclei, but not at later passages. A high number of lactogenic hormone receptors were found associated with the cell surface. Despite the presence of these receptors, no induction of genes coding for milk proteins was observed after addition of prolactin. These data demonstrate that this assay system can be used to assess the immortalizing and transforming potential of candidate oncogenes in epithelial cells.

Animals↗