Malignant Transformation of Human Skin Fibroblasts by Two Alternative Pathways

Abstract

We developed a telomerase-positive, infinite life span human fibroblast cell strain (MSU-1.0) by transfection of a v-MYC oncogene and spontaneous over-expression of transcription factors SP1/SP3. Loss of expression of p14(ALT) and enhanced expression of SPRY2 gave rise to the MSU-1.1 cell strain. Unlike MSU-1.0 cells, the MSU-1.1 cells can be malignantly transformed by expression of N-RAS(LYS61) or H-Ras(v12) oncoproteins (driven by their original promoters) and expression of a SRC-family protein, v-FES. MSU-1.1 cells can also be malignantly transformed by high expression of these RAS oncogenes or the v-K-RAS oncogene. PDGF-B transformed MSU-1.1 cells give rise to benign tumors (fibromas) in athymic mice. A second route to malignant transformation of the MSU-1.1 cells involves loss of functional TP53 protein by carcinogen treatment and loss of expression of wild type p16(INK). These studies indicate 6-8 "hits" are required to activate the oncogenes and inactivate the suppressor genes we identified.

Specificity Protein Transcription Factors and Cancer: Opportunities for Drug Development

“…Differences in the expression and functions of Sp1 in human fibroblasts and patient-derived fibrosarcoma cell lines were investigated by knockdown studies. For exam-ple, carcinogen-or oncogene-induced transformation of human fibroblasts resulted in an 8-to 18-fold increase in expression of Sp1 protein, whereas knockdown of Sp1 in fibrosarcoma cell lines decreased their ability to form tumors in athymic mice (34), and the role of Sp1 and Sp3 in malignant transformation of human skin fibroblasts has been reviewed (35). EGF-mediated transformation of bladder epithelial cells is due to RING-domain-dependent induction of Sp1 and Sp-regulated miR-4295 (36), and Kras-induced transformation of MCF10a mammary cells is also due to Sp1-dependent repression of miR-200 family miRNAs (37).…”

Illuminating Radiogenomic Characteristics of Glioblastoma Multiforme through Integration of MR Imaging, Messenger RNA Expression, and DNA Copy Number Variation

“…The use of imaging features derived from cross-sectional imaging will likely play an increasingly important role in the diagnosis and monitoring of cancer progression; however, there is a need to further understand the molecular programs underlying these features. There is increasing recognition that there is no one mechanism for the development and progression of cancer and that one malignant neoplastic phenotype can result from multiple alternative pathways (8)(9)(10)(11)(12)(13). Gene dose is one mechanism that can lead to such transformations.…”

Specificity Proteins (Sp) and Cancer

“…These observations suggest that the process that drives the transformation of a normal cell to a tumor cell may also involve Sp transcription factors. This was investigated in a classical study that examined the effects of carcinogen or oncogene-induced transformation of human fibroblasts into fibrosarcoma cells in which the fibrosarcoma, but not the fibroblasts, had the ability to form tumors in athymic nude mice [ 43 , 44 ]. This dramatic change in the phenotype of fibrosarcoma cells compared to the fibroblasts was accompanied by an 8- to 18-fold increased expression of Sp1 protein, which is enhanced during fibroblast cell transformation.…”