Overexpression of c-myc induces epithelial mesenchymal transition in mammary epithelial cells.
The c-myc gene is frequently overexpressed in human breast cancer and its target genes are involved in tumorigenesis. Epithelial mesenchymal transitions (EMT), where cells undergo a developmental switch from a polarized epithelial phenotype to a highly motile mesenchymal phenotype, are associated with invasion and motility of cancer cells. Basal E-cadherin expression was down-regulated in c-myc overexpressing MCF10A (c-myc-MCF10A) cells compared to GFP-overexpressing MCF10A (GFP-MCF10A) cells, while N-cadherin was distinctly increased in c-myc-MCF10A cells. Given that glycogen synthase kinase-3beta (GSK-3beta) and the snail axis have key roles in E-cadherin deregulation during EMT, we investigated the role of GSK-3beta/snail signaling pathways in the induction of EMT by c-myc overexpression. In contrast to GFP-MCF10A cells, both the transcriptional activity and the ubiquitination-dependent protein stability of snail were enhanced in c-myc-MCF10A cells, and this was reversed by GSK-3beta overexpression. We also found that c-myc overexpression inhibits GSK-3beta activity through activation of extracellular signal-regulated kinase (ERK). Inhibition of ERK by dominant negative mutant transfection or chemical inhibitor significantly suppressed snail gene transcription. These results suggest that c-myc overexpression during transformation of mammary epithelial cells (MEC) is involved in EMTs via ERK-dependent GSK-3beta inactivation and subsequent snail activation.
BK21 Project Team, College of Pharmacy, Chosun University, Seosuk-dong, Dong-gu, Gwangju 501-759, Republic of Korea.
Kyoung Bin
KB
Cho
Min Kyong
MK
Cho
Won Young
WY
Lee
Keon Wook
KW
Kang
D001943:Breast Neoplasms / Q000473:pathology*; D002460:Cell Line; D002465:Cell Movement; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D004847:Epithelial Cells; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D016259:Genes, myc; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology*; D008648:Mesoderm / Q000166:cytology*; D015854:Up-Regulation
C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3