Importance of Ets1 Proto-Oncogene for Breast Cancer Progression

Abstract

Ets proteins are transcription factors, which share a unique DNA binding domain, the Ets domain. Some members of the Ets family are implicated in tumorigenesis. Ets1, the founder of the Ets family, is predominantly expressed in invasive tumors and able to activate certain genes encoding ECM-degrading proteases. We used RNA-interference in combination with DNA chip analysis to identify Ets1-regulated genes in MDA-MB-231 breast cancer cells. Of the Ets1-responsive proteases, matrix metalloproteases MMP1 and MMP9, but not MMP3 or uPA, showed reduced RNA levels when endogenous Ets1 expression was suppressed. These data suggest that Ets1 regulates only a certain subset of ECM-degrading proteases. How Ets1 is regulated in invasive breast cancer cells is unknown. The observations that protein kinase C inhibitors abrogated Ets1 expression and that protein kinase C was able to increase Ets1-dependent transcription imply that protein kinase C is a potential regulator of Ets1 activity in breast cancer cells.

Zusammenfassung

Ets-Proteine bilden eine Familie von Transkriptionsfaktoren, die sich durch eine spezifische DNA-Bindungsdomäne (Ets-Domäne) auszeichnen. Ets1, das erste Mitglied dieser Familie, ist präferenziell in invasiven Tumoren exprimiert und fähig, bestimmte Proteasengene zu aktivieren. RNA-Interferenz in Kombination mit DNA-Chip-Analyse wurde eingesetzt, um Ets1-regulierte Gene in MDA-MB-231-Brustkrebszellen zu identifizieren. Infolge der Unterdrückung der endogenen Ets1-Synthese wurde die Expression der Matrixmetalloproteasen MMP1 und MMP9, nicht aber die von MMP3 oder uPA, reduziert. Diese Daten zeigen, dass nur bestimmte Proteasen von Ets1 reguliert werden. Um die Regulation von Ets1 in Brustkrebszellen zu studieren, wurde eine Reihe von Inhibitoren eingesetzt. Mit Proteinkinase C-Hemmer ließ sich die Ets1-Expression komplett unterdrücken. Außerdem konnte die Ets1-abhängige Transkription durch Proteinkinase C verstärkt werden. Dies weist auf eine potentielle Bedeutung der Proteinkinase C als ein Regulator von Ets1 in invasiven Brustkrebszellen hin.

Key words

Ets proteins - PKC - proteases

Schlüsselwörter

Ets-Proteine - PKC - Proteasen

References

• 1 Sharrocks A D, Brown A L, Ling Y, Yates P R. The ETS-domain transcription factor family.  Int J Biochem Cell Biol. 1997;  29 1371-1387
• 2 Sementchenko V I, Watson D K. Ets target genes: past, present and future.  Oncogene. 2000;  19 6533-6548
• 3 Dittmer J, Nordheim A. Ets transcription factors and human disease.  Biochim Biophys Acta. 1998;  1377 F 1-F 11
• 4 Dittmer J. The Biology of the Ets1 Proto-Oncogene.  Mol Cancer. 2003;  2 29
• 5 Span P N, Manders P, Heuvel J J, Thomas C M, Bosch R R, Beex L V, Sweep C G. Expression of the transcription factor Ets-1 is an independent prognostic marker for relapse-free survival in breast cancer.  Oncogene. 2002;  21 8506-8509
• 6 Lelievre E, Lionneton F, Soncin F, Vandenbunder B. The Ets family contains transcriptional activators and repressors involved in angiogenesis.  Int J Biochem Cell Biol. 2001;  33 391-407
• 7 Fujimoto J, Aoki I, Toyoki H, Khatun S, Tamaya T. Clinical implications of expression of ETS-1 related to angiogenesis in uterine cervical cancers.  Ann Oncol. 2002;  13 1598-1604
• 8 Takai N, Miyazaki T, Fujisawa K, Nasu K, Miyakawa I. Expression of c-Ets1 is associated with malignant potential in endometrial carcinoma.  Cancer. 2000;  89 2059-2067
• 9 Majerus M A, Bibollet-Ruche F, Telliez J B, Wasylyk B, Bailleul B. Serum, AP-1 and Ets-1 stimulate the human ets-1 promoter.  Nucleic Acids Res. 1992;  20 2699-2703
• 10 Ron D, Kazanietz M G. New insights into the regulation of protein kinase C and novel phorbol ester receptors.  Faseb J. 1999;  13 1658-1676
• 11 Buchner K. The role of protein kinase C in the regulation of cell growth and in signalling to the cell nucleus.  J Cancer Res Clin Oncol. 2000;  126 1-11
• 12 Lindemann R K, Braig M, Ballschmieter P, Guise T A, Nordheim A, Dittmer J. Protein kinase Calpha regulates Ets1 transcriptional activity in invasive breast cancer cells.  Int J Oncol. 2003;  22 799-805
• 13 Platet N, Prevostel C, Derocq D, Joubert D, Rochefort H, Garcia M. Breast cancer cell invasiveness: correlation with protein kinase C activity and differential regulation by phorbol ester in estrogen receptor-positive and -negative cells.  Int J Cancer. 1998;  75 750-756
• 14 Lindemann R K, Ballschmieter P, Nordheim A, Dittmer J. Transforming growth factor beta regulates parathyroid hormone-related protein expression in MDA-MB-231 breast cancer cells through a novel Smad/Ets synergism.  J Biol Chem. 2001;  276 46661-46670
• 15 Soh J W, Lee E H, Prywes R, Weinstein I B. Novel roles of specific isoforms of protein kinase C in activation of the c-fos serum response element.  Mol Cell Biol. 1999;  19 1313-1324
• 16 Yang B S, Hauser C A, Henkel G, Colman M S, Van Beveren C, Stacey K J, Hume D A, Maki R A, Ostrowski M C. Ras-mediated phosphorylation of a conserved threonine residue enhances the transactivation activities of c-Ets1 and c-Ets2.  Mol Cell Biol. 1996;  16 538-547
• 17 Ballschmieter P, Braig M, Lindemann R K, Nordheim A, Dittmer J. Splicing variant DeltaVII-Ets1 is downregulated in invasive Ets1-expressing breast cancer cells.  Int J Oncol. 2003;  22 849-853
• 18 Orlandi L, Binda M, Folini M, Bearzatto A, Villa R, Daidone M G, Zaffaroni N. Ribozyme-mediated inhibition of PKCalpha sensitizes androgen-independent human prostate cancer cells to cisplatin-induced apoptosis.  Prostate. 2003;  54 133-143
• 19 Gill P K, Gescher A, Gant T W. Regulation of MDR1 promoter activity in human breast carcinoma cells by protein kinase C isozymes alpha and theta.  Eur J Biochem. 2001;  268 4151-4157
• 20 Roychowdhury D, Lahn M. Antisense therapy directed to protein kinase C-alpha (Affinitak, LY900003/ISIS 3521): potential role in breast cancer.  Semin Oncol. 2003;  30 30-33