TY - JOUR
T1 - Tyr phosphatase-mediated P-ERK inhibition suppresses senescence in EIA + v-raf transformed cells, which, paradoxically, are apoptosis-protected in a MEK-dependent manner
AU - de Vitis, Stefania
AU - Treglia, Antonella Sonia
AU - Ulianich, Luca
AU - Turco, Stefano
AU - Terrazzano, Giuseppe
AU - Lombardi, Angela
AU - Miele, Claudia
AU - Garbi, Corrado
AU - Beguinot, Francesco
AU - di Jeso, Bruno
N1 - Funding Information:
Abbreviations: ERK, extracellular signal–regulated kinase; MEK, mitogen-activated protein kinase/ERK kinase; MST2, mammalian sterile–twenty-like 2; MTT, (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide; OA, okadaic acid; OIS, oncogene-induced senescence; OV, sodium orthovanadate; PC EIA, adenovirus EIA–transfected PC Cl3 cells; PC EIA + Py, adenovirus EIA–transfected, polyoma murine leukemia virus (carrying polyoma–middle T)–infected PC Cl3 cells; PC EIA + raf, adenovirus EIA–transfected, murine sarcoma virus 3611 (carrying v-raf )–infected PC Cl3 cells; SA-β-Gal, senescence-associated β-galactosidase Address all correspondence to: Dr. Bruno Di Jeso, Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali (DiSTeBA), Facoltà di Scienze Matematiche Fisiche e Naturali, Università degli Studi del Salento, Strada Provinciale Lecce-Monteroni, 73100 Lecce, Italy. E-mail: bruno.dijeso@unisalento.it 1This work was supported by MIUR (60% funds to B.D.J.). The authors declare no conflict of interest. 2This article refers to supplementary materials, which are designated by Figures W1 to W6 and are available online at www.neoplasia.com. 3These authors contributed equally to this work. Received 10 August 2010; Revised 12 November 2010; Accepted 18 November 2010 Copyright © 2011 Neoplasia Press, Inc. All rights reserved 1522-8002/11/$25.00 DOI 10.1593/neo.101152
PY - 2011/2
Y1 - 2011/2
N2 - Activation of the Ras-Raf-extracellular signal-regulated kinase (ERK) pathway causes not only proliferation and suppression of apoptosis but also the antioncogenic response of senescence. How these contrasting effects are reconciled to achieve cell transformation and cancer formation is poorly understood. In a systemof two-step carcinogenesis (dedifferentiated PC EIA, transformed PC EIA-polyoma-middle T [PC EIA + Py] and PC EIA-v-raf [PC EIA + raf] cells], v-raf cooperated with EIA by virtue of a strong prosurvival effect, not elicited by Py-middle T, evident toward serumdeprivation- and H2O9-induced apoptosis. Apoptosis was detected by DNA fragmentation and annexin V staining. The prosurvival function of v-raf was, in part,mitogen-activated protein kinase/ERK kinase (MEK)-dependent, as shown by pharmacological MEK inhibition. The MEK-dependent antiapoptotic effect of v-raf was exerted despite a lower level of P-ERK1/2 in EIA + raf cells with respect to EIA + Py/EIA cells, which was dependent on a high tyrosine phosphatase activity, as shown by orthovanadate blockade. An ERK1/2 tyrosine phosphatase was likely involved. The high tyrosine phosphatase activity was instrumental to the complete suppression of senescence, detected by β-galactosidase activity, because tyrosine phosphatase blockade induced senescence in EIA+raf but not in EIA+Py cells. High tyrosine phosphatase activity and evasion from senescence were confirmed in an anaplastic thyroid cancer cell line. Therefore, besides EIA, EIA + raf cells suppress senescence through a new mechanism, namely, phosphatase-mediated P-ERK1/2 inhibition, but, paradoxically, retain the oncogenic effects of the Raf-ERK pathway.We propose that the survival effect of Raf is not a function of absolute P-ERK1/2 levels at a given time but is rather dynamically dependent on greater variations after an apoptotic stimulus.
AB - Activation of the Ras-Raf-extracellular signal-regulated kinase (ERK) pathway causes not only proliferation and suppression of apoptosis but also the antioncogenic response of senescence. How these contrasting effects are reconciled to achieve cell transformation and cancer formation is poorly understood. In a systemof two-step carcinogenesis (dedifferentiated PC EIA, transformed PC EIA-polyoma-middle T [PC EIA + Py] and PC EIA-v-raf [PC EIA + raf] cells], v-raf cooperated with EIA by virtue of a strong prosurvival effect, not elicited by Py-middle T, evident toward serumdeprivation- and H2O9-induced apoptosis. Apoptosis was detected by DNA fragmentation and annexin V staining. The prosurvival function of v-raf was, in part,mitogen-activated protein kinase/ERK kinase (MEK)-dependent, as shown by pharmacological MEK inhibition. The MEK-dependent antiapoptotic effect of v-raf was exerted despite a lower level of P-ERK1/2 in EIA + raf cells with respect to EIA + Py/EIA cells, which was dependent on a high tyrosine phosphatase activity, as shown by orthovanadate blockade. An ERK1/2 tyrosine phosphatase was likely involved. The high tyrosine phosphatase activity was instrumental to the complete suppression of senescence, detected by β-galactosidase activity, because tyrosine phosphatase blockade induced senescence in EIA+raf but not in EIA+Py cells. High tyrosine phosphatase activity and evasion from senescence were confirmed in an anaplastic thyroid cancer cell line. Therefore, besides EIA, EIA + raf cells suppress senescence through a new mechanism, namely, phosphatase-mediated P-ERK1/2 inhibition, but, paradoxically, retain the oncogenic effects of the Raf-ERK pathway.We propose that the survival effect of Raf is not a function of absolute P-ERK1/2 levels at a given time but is rather dynamically dependent on greater variations after an apoptotic stimulus.
UR - http://www.scopus.com/inward/record.url?scp=79951486303&partnerID=8YFLogxK
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U2 - 10.1593/neo.101152
DO - 10.1593/neo.101152
M3 - Article
C2 - 21403838
AN - SCOPUS:79951486303
SN - 1522-8002
VL - 13
SP - 120
EP - 130
JO - Neoplasia
JF - Neoplasia
IS - 2
ER -
