Gene expression signature of c-MYC-immortalized human fibroblasts reveals loss of growth inhibitory response to TGFb

ABSTRACT: Cancer cells exhibit the ability to proliferate indefinitely, but paradoxically, overexpression of cellular oncogenes in primary cells can result in a rapid and irreversible cell cycle arrest known as oncogene-induced senescence (OIS). However, we have shown that constitutive overexpression of the oncogene c-MYC in primary human foreskin fibroblasts results in a population of cells with unlimited lifespan; these immortalized cells are henceforth referred to as iMYC. Here, in order to further elucidate the mechanisms underlying the immortalization process, a gene expression signature of three independently established iMYC cell lines compared to matched early passage c-MYC overexpressing cells was derived. Network analysis of this "iMYC signature" indicated that a large fraction of the down-regulated genes were functionally connected and major nodes centered around the TGFb, IL-6 and IGF-1 signaling pathways. Here, we focused on the functional validation of the alteration of TGFb response during c-MYC-mediated immortalization. The results demonstrate loss of sensitivity of iMYC cells to activation of TGFb signaling upon ligand addition. Furthermore, we show that aberrant regulation of the p27 tumor suppressor protein in iMYC cells is a key event that contributes to loss of response to TGFb. These findings highlight the potential to reveal key pathways contributing to the self-renewal of cancer cells through functional mining of the unique gene expression signature of cells immortalized by c-MYC. Cell Cycle. 2011 Aug 1;10(15). Cell culture. Human foreskin fibroblast cell lines expressing empty vector pBABE or vector with gene sequence encoding c-MYC were previously described in PMID 17982115. Cells were cultured in Dulbecco’s modified eagle medium (DMEM) supplemented with 10% fetal bovine serum and penicillinstreptomycin. For cell growth assays, equal number of cells per cell line were plated and counted on the specified days after plating. Microarray analysis. Total RNA was purified using an RNeasy kit (Qiagen, Valencia, CA). Genome-scale expression analysis was performed using custom microarrays (Affymetrix, Santa Clara, CA) containing oligonucleotide probes corresponding to approximately 22,000 human genes. Microarray analysis was performed as described in PMID 12925520. Data were analyzed using Rosetta Resolver(TM) software. We determined a p-value cutoff of 0.01 for genes in all three samples.

ORGANISM(S): Homo sapiens

SUBMITTER: Julja Burchard 

PROVIDER: E-GEOD-31002 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress