Characterization of a novel primary mammary tumor cell line reveals that cyclin D1 is regulated by the type I insulin-like growth factor receptor.
The importance of type I insulin-like growth factor receptor (IGF-IR) overexpression in mammary tumorigenesis was recently shown in two separate transgenic models. One of these models, the MTB-IGFIR transgenics, was generated in our lab to overexpress IGF-IR in mammary epithelial cells in a doxycycline (Dox)-inducible manner. To complement this transgenic model, primary cells that retained Dox-inducible expression of IGF-IR were isolated from a transgenic mammary tumor. This cell line, RM11A, expressed high levels of IGF-IR, phosphorylated Akt, and phosphorylated extracellular signal-regulated kinase 1/2 in the presence of Dox. IGF-IR overexpression provided the primary tumor cells with a survival advantage in serum-free media and seemed to induce ligand-independent activation of the IGF-IR because RM11A cells cultured in the presence of Dox were largely nonresponsive to exogenous IGFs. IGF-IR overexpression also augmented the growth of RM11A cells in vivo because injection of these cells into mammary glands of wild-type mice produced palpable tumors in 15.8 +/- 3.4 days when the mice were administered Dox, compared with 57.8 +/- 6.3 days in the absence of Dox. DNA microarray analysis revealed a number of genes regulated by IGF-IR, one of which was cyclin D1. Suppression of IGF-IR expression in vitro or in vivo was associated with a decrease in cyclin D1 protein, suggesting that at least some of the proliferative actions of IGF-IR are mediated through cyclin D1. Therefore, this article characterizes the first primary murine mammary tumor cell line with inducible IGF-IR expression. These cells provide a powerful in vitro/in vivo model to examine the function of IGF-IR in mammary tumorigenesis.
Jones
Robert A
RA
Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G2W1.
Campbell
Craig I
CI
Petrik
James J
JJ
Moorehead
Roger A
RA
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D019938:Cyclin D1 / Q000096:biosynthesis*; D015972:Gene Expression Regulation, Neoplastic; D008024:Ligands; D015674:Mammary Neoplasms, Animal / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D013997:Time Factors
D008024:Ligands; D012333:RNA, Messenger; D019938:Cyclin D1; D017526:Receptor, IGF Type 1