IGFBP-2 expression in MCF-7 cells is regulated by the PI3K/AKT/mTOR pathway through Sp1-induced increase in transcription.
Insulin-like growth factor binding protein 2 (IGFBP-2) has been implicated in the pathophysiology of neoplasia. The PI3K/AKT/mTOR pathway has recently been shown to be a predominant regulator of IGFBP-2 at the protein level in MCF-7 breast cancer cells. However, there are gaps in knowledge with respect to the molecular mechanisms that underlie this regulation. Here, we show that the PI3K/AKT/mTOR pathway regulates IGFBP-2 protein levels by modulating IGFBP-2 mRNA abundance in MCF-7 cells. This change is achieved by regulating transcription through a critical region present in the first 200&#x00A0;bp upstream of the transcription initiation site where Sp1 transcription factor binds and drives transcription. IGF-1 treatment leads to increased nuclear abundance of Sp1 and increased IGFBP-2 mRNA and protein levels. Rapamycin and LY294002 induce a decline in Sp1 nuclear abundance and IGFBP-2 mRNA and protein levels. This work provides a mechanistic explanation for the observed effects of the PI3K/AKT/mTOR pathway on IGFBP-2 levels in MCF-7 cells.
Mireuta
Matei
M
Departments of Medicine and Oncology, Lady Davis Institute for Medical Research, Montreal SMBD Jewish General Hospital, and McGill University, Montreal, Quebec, CanadaH3T 1E2.
Darnel
Andrew
A
Pollak
Michael
M
D015153:Blotting, Western; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009369:Neoplasms / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D013002:Somatomedins; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014158:Transcription, Genetic
D002867:Chromones; D018971:Insulin-Like Growth Factor Binding Protein 2; D047908:Intracellular Signaling Peptides and Proteins; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D020123:Sirolimus; D013002:Somatomedins; D016329:Sp1 Transcription Factor; D058570:TOR Serine-Threonine Kinases; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C546842:MTOR protein, human