Ets2 and protein kinase C epsilon are important regulators of parathyroid hormone-related protein expression in MCF-7 breast cancer cells.
Parathyroid hormone-related protein (PTHrP) promotes the metastatic potential and proliferation of breast cancer cells, and acts anti-apoptotically. In invasive MDA-MB-231 breast cancer cells, transforming growth factor beta-regulated PTHrP synthesis is mediated by an Ets1/Smad3-dependent activation of the PTHrP P3 promoter. In the present study, we studied the regulation of PTHrP expression in non-invasive, Ets1-deficient and transforming growth factor beta-resistant MCF-7 cells. We found PMA to be a strong stimulator of P3-dependent PTHrP expression in MCF-7 cells. Mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK) kinase 1 (MEK-1)/ERK1/2 inhibitor PD98059 interfered with this activity. Promoter studies revealed that the PMA effect depended on the Ets and stimulating protein-1 (Sp1)-binding sites. Of several Ets factors tested, Ets2, but not Ese-1, Elf-1 or Ets1, supported the PMA-dependent increase in promoter activity. PD98059 and a threonine to alanine mutation of the ERK1/2-responsive Ets2 phosphorylation site at position 72 inhibited the Ets2/PMA effect. Activated protein kinase C (PKC) epsilon could mimic PMA by stimulating the P3 promoter alone or in co-operation with Ets2 in an MEK-1/ERK1/2-dependent manner. Activated PKC alpha, although capable of co-operating with Ets2, failed to induce transcription from the P3 promoter on its own. The Ets2/PKalpha synergistic effect was neither sensitive to PD98059 nor to Thr(72)/Ala(72) mutation. PMA neither increased the expression of Sp1 nor modulated the transcriptional activity of Sp1. However, it induced the displacement of a yet unknown factor from the Sp1-binding site, which may result in Sp1 recruitment to the promoter. Our results suggest an ERK1/2-dependent Ets2/PKC epsilon synergism to be involved in PTHrP expression in MCF-7 breast cancer cells.
Lindemann
Ralph K
RK
Institut für Zellbiologie, Abteilung Molekularbiologie, Universität Tübingen, Auf der Morgenstelle 15, Germany.
Braig
Melanie
M
Hauser
Craig A
CA
Nordheim
Alfred
A
Dittmer
Jürgen
J
D001483:Base Sequence; D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D002461:Cell Line, Transformed; D004268:DNA-Binding Proteins; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D044162:Parathyroid Hormone-Related Protein; D036361:Peptide Hormones / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C107465:ERF protein, human; C494069:ETS2 protein, human; D004791:Enzyme Inhibitors; D005419:Flavonoids; C470121:PTHLH protein, human; D044162:Parathyroid Hormone-Related Protein; D036361:Peptide Hormones; D050787:Proto-Oncogene Protein c-ets-2; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; C016658:phorbolol myristate acetate; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one