Anti-growth factor activities of benzothiophenes in human breast cancer cells.
We have tested the effects of two Eli-Lilly compounds, LY 117, 018 and raloxifene, on E2-regulated and IGF-I-induced proliferation or AP-1 activity in human breast cancer cells. We now demonstrate that both molecules have strong antiestrogenic and anti-growth factor inhibitory effects in MCF7 cells. They were as potent as ICI 182, 780 and more efficient than OH-Tam to prevent estradiol action whereas their inhibition on IGF-I stimulation was less than with ICI 182, 780 and equivalent to that of OH-Tam. Moreover, raloxifene was the most efficient molecule to prevent IGF-I-induced AP-1 activity, with a significant effect observed with a concentration as low as 5 x 10(-11)M in the presence of IGF-I alone. Similar dose-response curves were obtained with a combined treatment of IGF-I and E2 with a 2log shift. Their action on IGF-I-induced proliferation was completely abrogated in MCF7 transfectants in which the expression of an antiestrogen-regulated protein tyrosine phosphatase, PTPL1, was abolished by antisense RNA transfection. Accordingly, they were both able to dose-dependently regulate the expression of PTPL1 and to interfere with the PI3-K/Akt pathway by drastically decreasing Akt phosphorylation exclusively in wild-type PTPL1 expressing cells. Our data altogether demonstrate that raloxifene has a potent inhibitory effect on IGF-I action, with a drastic effect on AP-1 triggered responses as well as on Akt phosphorylation, suggesting that it might be a useful therapeutic agent in tumors in which these signalling pathways become constitutively active.
Freiss
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Inserm Unit 540 on Molecular and Cellular Endocrinology of Cancers, 60 rue de Navacelles, 34090 Montpellier, France.
Galtier
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F
Puech
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Aknin
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C
Maudelonde
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T
Chalbos
D
D
Vignon
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F
D001943:Breast Neoplasms / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D004965:Estrogen Antagonists / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011759:Pyrrolidines / Q000494:pharmacology*; D020849:Raloxifene Hydrochloride / Q000494:pharmacology*; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D013876:Thiophenes / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic
D004965:Estrogen Antagonists; D011518:Proto-Oncogene Proteins; D011759:Pyrrolidines; D020845:Selective Estrogen Receptor Modulators; D013876:Thiophenes; D018808:Transcription Factor AP-1; D020849:Raloxifene Hydrochloride; C025430:LY 117018; D007334:Insulin-Like Growth Factor I; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C516742:PTPN13 protein, human; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13; D017027:Protein Tyrosine Phosphatases