N-myc oncogene enhances mitogenic responsiveness of diploid human fibroblasts to growth factors but fails to immortalize.
Brondyk, W H, et al.
Oncogene, 6: 1269-76 (1991)
1991
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The N-myc gene is amplified in several types of human tumors. To assess the role of the N-myc gene in the transformation of normal human cells, we transfected an N-myc expression vector into diploid human fibroblasts. Transfected clones were isolated and found to express the N-myc gene at levels similar to those seen in a tumor cell line (neuroblastoma LA-N-1) which contains an amplified N-myc gene. The level of N-myc expression decreased as the N-myc clones senesced. Clones expressing N-myc had an increased saturation density and an altered morphology but did not have an extended lifespan. Under low serum conditions, neither the clones expressing N-myc nor the control cells showed anchorage-dependent growth. Clones expressing N-myc were compared to control cells to determine if different growth factors would affect the ability of cells to grow in soft agarose. Clones expressing N-myc and the control cells did not grow in soft agarose supplemented with epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha). However, compared to control cells, clones expressing N-myc grew in agarose 2.8- to 18-fold higher in response to basic fibroblast growth factor (bFGF) and 5.5- to 55-fold higher in response to platelet-derived growth factor B-chain homodimer (PDGF-BB). | 1861869
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Identification and characterization of the NMYC gene product in human neuroblastoma cells by monoclonal antibodies with defined specificities.
Ikegaki, N, et al.
Proc. Natl. Acad. Sci. U.S.A., 83: 5929-33 (1986)
1986
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Increased N-myc (now designated NMYC in human gene nomenclature) gene expression has been detected at the transcriptional level in certain types of neoplasms. As yet, the N-myc gene product has not been identified. To detect and characterize the N-myc gene product, we have developed monoclonal antibodies against the putative N-myc gene product made in Escherichia coli as a fusion protein. The antibodies that recognize the N-myc-specific regions were selected on the basis of their reactivities to different portions of the fusion protein. These monoclonal antibodies detect a pair of closely migrating polypeptides of 60 and 63 kDa in nuclear fractions of human neuroblastoma cells. The relative levels of the polypeptides are roughly proportional to the level of N-myc transcripts present in a panel of neuroblastoma lines. These two polypeptides have a half-life of approximately equal to 35 min, and they are indistinguishable from each other by their epitopic profiles. | 2426708
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