title: Inhibition of the MAP kinase activity suppresses estrogen-induced breast tumor growth both in vitro and in vivo.
abstract: Elevated expression of mitogen-activated protein kinase (Erk/MAPK) has been noted in a significant percentage of primary human breast cancers. To directly assess the importance of Erk/MAPK activation in estrogen (E2)-induced tumor progression, we blocked E2-signaling with MEK-inhibitor CI-1040 and/or tamoxifen (Tam). Our data show that both MEK-inhibitor CI-1040 and Tam blocked E2-induced MAPK phosphorylation and cell proliferation in MCF-7 breast cancer cells in vitro. However, in vivo studies show that anti-tumor efficacy of combining the CI-1040 and Tam was similar to single agent(s). Furthermore, sequential treatment with Tam followed by CI-1040 or CI-1040 followed by Tam did not significantly reduce E2-induced tumor growth. This suggests that the combination of CI-1040 and Tam may not be synergistic in inhibiting E2-induced tumor growth. However, these findings also indicate that MAPK plays a critical role in E2-induced tumor growth, and that this could be a potential therapeutic target to combat hormonally regulated growth in ER-positive tumors.
authors.affiliation: Department of Pathology, Wayne State University School of Medicine, Detroit, MI 48201, USA. kreddy@med.wayne.edu
authors.forename: Kaladhar B
authors.initials: KB
authors.lastname: Reddy
authors.forename: Selina
authors.initials: S
authors.lastname: Glaros
mesh_terms: D001549:Benzamides / Q000494:pharmacology; D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013629:Tamoxifen / Q000494:pharmacology
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D001549:Benzamides; D004965:Estrogen Antagonists; D004967:Estrogens; D013629:Tamoxifen; D004958:Estradiol; D020930:MAP Kinase Kinase Kinases