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J Leavitt

Publications and source records attributed to J Leavitt.

66 records · Page 4Linked to original sources
PubMed1979

Two polypeptide changes associated with butyric acid resistance and the neoplastic state of Syrian hamster cells.

Seven differences in the polypeptide species of parental Syrian hamster embryo cells and cells of the highly tumorigenic derivative cell line BP6T were identified previously by employing the technique of two-dimensional polyacrylamide gel electrophoresis (Leavitt, J. and Moyzis, R. (1978) J. Biol. Chem. 253, 2497-2500). To determine which of these polypeptide changes are correlated with expression of the neoplastic state this work was extended to the comparative examination of nine established neoplastic cell lines which resulted from independent transformation events catalyzed by chemical carcinogen treatment, virus infection, or an unknown spontaneous event. Although no perfect correlation with a specific polypeptide change was found, two polypeptide changes, occurring independently or simultaneously, appear to be consistently associated with expression of neoplasticity. One polypeptide species, designated tau, having an isoelectric point of 4.6 and a molecular weight of 60 000 was lost or physically altered in all but one of these transformed cell lines; a second polypeptide species designated nu having an isoelectric point 5.5 and a molecular weight of 42 000 appeared in highly tumorigenic chemically transformed cell lines and in two virally transformed cell lines. A butyric acid supplement, used as a selective agent for butyric acid resistant cells, was employed to identify and isolate in a single step nascent neoplastic clonal lines transformed by ethylmethanesulfonate. These cell lines exhibited alterations either in tau or nu. The changes observed in tau are consistent with those expected to result from a somatic mutation event in the structural gene coding for tau; however, the alterations in tau could also be governed by a post-translational process. These findings suggest that alterations in expression of at least two major polypeptide species, tau and nu, are closely associated with primary steps in the neoplastic transformation process of Syrian hamster cells irrespective of the nature of the transforming agent.

Animals↗
PubMed1979

Hypoxanthine guanine phosphoribosyltransferase (HGPRT) in Gilles de la Tourette syndrome.

Hypoxanthine guanine phosphoribosyltransferase (HGPRT) and adenosine phosphoribosyltransferase (APRT) were examined from 11 individuals with Gilles de la Tourette syndrome, 10 of their first- or second-degree relatives, and 3 normal controls. It has been suggested that in some self-mutilating Tourette patients, HGPRT shows a time-related loss of activity at 4 degrees C, and an unusual isoelectrofocusing pattern. Although 3 patients experienced self-mutilation, no consistent abnormalities were found in the temperature-stability of their HGPRT at 4 degrees C and 70 degrees C, or in isoelectrofocusing of HGPRT purified by immunoprecipitation. An alteration of the purine metabolic pathway in Tourette syndrome has not been established.

Female↗
PubMed1978

Changes in gene expression accompanying neoplastic transformation of Syrian hamster cells.

Proteins solubilized from the chemically transformed, highly tumorigenic Syrian hamster cell line, BP6T, and the untransformed parental embryo cells, have been analyzed by two-dimensional gel electrophoresis. Differences in seven major polypeptides have been identified in cytoplasmic and nuclear cell fractions from these two related cell types. The tumorigenic cells have lost the ability to synthesize detectable amounts of five major polypeptides which are found in untransformed cells; in addition, the tumorigenic cells synthesize two new major polypeptide species not found in the untransformed cells. Butyric acid, an agent which suppresses in vitro cellular properties frequently associated with neoplasia, induces in a reversible fashion synthesis of two of these missing polypeptide species in the tumorigenic cells. The results indicate that a change in the synthesis of less than 1% of the major polypeptide species is associated with a chemical mediated induction of the high tumorigenic state of Syrian hamster cells.

Butyrates↗
PubMedDate not supplied

Discovery and characterization of two novel human cancer-related proteins using two-dimensional gel electrophoresis.

Comparative examination of protein synthesis in normal and neoplastic human fibroblasts led to the discovery of two novel microfilament proteins with roles in human neoplasia. One protein, a mutant beta-actin was found to convert nontumorigenic human fibroblasts to tumorigenicity. Recently, the oncogenic potential of this mutant beta-actin was verified independently and shown to alter the metastatic phenotype of human cells in conjunction with the myc and ras oncogenes. A second protein, leukocyte plastin, was discovered to be a marker of a majority of human cancer cells of nonhemopoietic origin. A survey of SV40-transformed human fibroblasts and human sarcoma and carcinoma cell types demonstrated that the L-plastin gene was activated at widely varying degrees in nearly all human cancer cells. Activation of the L-plastin gene was not detected in normal nonhemopoietic cells using sensitive reverse transcript-polymerase chain reaction, excepting those cells that expressed estrogen and progesterone receptors which mediate activation of L-plastin synthesis in reproductive tissues. Our most recent findings have revealed that activation of L-plastin synthesis in neoplastic cells that cannot phosphorylate L-plastin (e.g. those neoplastic cell types that express only trace amounts of L-plastin) results in the coinduction of two alternative inflammatory programs of gene expression which mediate cytolytic effects on surrounding cells. This inflammatory response appears to be mediated by "inappropriate" constitutive synthesis of L-plastin and failure of the induced cell to phosphorylate L-plastin. Our findings suggest explanations for the novel resistance of human cells to in vitro transformation and one role of oncogene activation in cancer. As a consequence of the interplay of two-dimensional (2-D) gel electrophoretic analyses with other sophisticated techniques of molecular biology, the formal characterization of two fundamentally important multigene families was completed with determination of many aspects of the structure and function of these proteins and their genes. The discovery and characterization of the mutant beta-actin and L-plastin and their relationship to the human neoplastic phenotype serve as useful models for the discovery of other important disease-related proteins/genes using 2-D gel electrophoresis.

Actins↗
PubMedDate not supplied

Smooth muscle alpha-action is a transformation-sensitive marker for mouse NIH 3T3 and Rat-2 cells.

Heteroploid mouse NIH 3T3 fibroblasts and several rat fibroblast strains (Rat-1, Rat-2 and REF-52) are cell lines of special interest in the field of carcinogenesis because of their extensive use as normal cells in transformation assays for putative cancer-causing genes. Exposure of these cells to carcinogenic chemicals or oncogenic DNA produces anchorage-independent cells with retracted cytoplasms that lack actin cables. All human fibroblast strains, normal and transformed, synthesize two electrophoretic forms of actin (beta- and gamma-actin). In contrast, we discovered that early-passage mouse and rat strains synthesize abundant amounts of each of the three electrophoretic forms of actin (alpha-, beta- and gamma-actin) but mouse and rat cancer cells express only beta- and gamma-actins. We now show that in NIH 3T3 and Rat-2 fibroblasts a third actin, the smooth muscle alpha isoform, is abundantly co-expressed with beta- and gamma-actin. In every instance tested following transformation to tumorigenicity, the accumulation of alpha-actin messenger RNA and alpha-actin synthesis was greatly inhibited. Shutdown of alpha-actin expression thus appears to be a reproducible transformation-sensitive marker in rodent fibroblasts.

Actins↗
PubMedDate not supplied

Use of L-plastin promoter to develop an adenoviral system that confers transgene expression in ovarian cancer cells but not in normal mesothelial cells.

The objective of this study was to develop an adenoviral vector system that would generate a pattern of expression of exogenous therapeutic genes appropriate for the treatment of ovarian cancer. For this purpose, we have generated a replication-deficient recombinant adenoviral vector, AdLPLacZ, which contains the human L-plastin (LP) promoter (LP-P) driving the Escherichia coli LacZ gene. LP is constitutively expressed at high levels in malignant epithelial cells but is not expressed in normal tissues, except at low levels in mature hematopoietic cells. Because adenoviral vectors infect early hematopoietic multilineage precursor cells only poorly or not at all, this vector would be of use in the peritoneal cavity and in vitro for marrow purging. We first analyzed the expression of the LacZ reporter gene in ovarian and breast cancer cell lines, normal fibroblasts, and leukemia cell lines using the adenoviral vector in which the LacZ gene is governed by the LP-P promoter (AdLPLacZ) or in which the LacZ gene is governed by the cytomegalovirus (CMV) promoter (AdCMVLacZ). We found equivalent and high levels of expression of beta-galactosidase (beta-gal) by AdLPLacZ and AdCMVLacZ vectors in the breast or ovarian cancer cell lines as well as in a fibrosarcoma cell line, indicating that the adenoviral vectors infected these cells and expressed their transgenes equally with the LP and CMV promoters. Expression of the LacZ gene with the CMV vector but not with the LP-P vector was observed in experiments with normal fibroblasts, indicating that the vectors infected the cells, but that the LP-P was not active within them. In hematopoietic cells such as U937 cells, no measurable beta-gal activity was detected in cells infected either by AdLPLacZ or by AdCMVLacZ, indicating that the adenoviral vectors were not infecting the cells. Although beta-gal activity was observed in fresh ascitic ovarian cancer cells after infection with adenoviral vectors containing CMV or the LP promoters, beta-gal activity was detected in a portion of a biopsy of normal peritoneum when the tissues were exposed to the AdCMVLacZ vector, but not when tissues were exposed to the AdLPLacZ vector. These results suggest that the transcription of therapeutic genes in cells infected by the AdLP vectors would be restricted to LP expression-positive ovarian carcinoma cells but would not be seen in the normal mesothelial cells of the peritoneal cavity. This possibility implies that adenoviral vectors carrying therapeutic genes driven by the LP-P would be of use for the intracavitary treatment ovarian cancer.

Adenoviridae↗