INVESTIGADORES
PROIETTI ANASTASI Cecilia Jazmin
congresos y reuniones científicas
Título:
Tumor necrosis factor transactivates ErbB2 in breast cancer cells
Autor/es:
MARTÍN A. RIVAS, MERCEDES TKACH, CECILIA J. PROIETTI, CINTHIA ROSEMBLIT, WENDY BEGUELIN, VICTORIA SUNDBLAD, M. CELESTE DÍAZ FLAQUÉ, EDUARDO H. CHARREAU, PATRICIAV. ELIZALDE, ROXANA SCHILLACI
Lugar:
San Antonio, TX, USA
Reunión:
Simposio; CTRC-AACRSan Antonio Breast Cancer Symposium; 2008
Resumen:
Dear Applicant,
<!--
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0cm;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";
mso-ansi-language:EN-US;}
@page Section1
{size:612.0pt 792.0pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;
mso-header-margin:35.4pt;
mso-footer-margin:35.4pt;
mso-paper-source:0;}
div.Section1
{page:Section1;}
-->
We have previously shown that TNFα induces proliferation of the
murine mammary adenocarcinoma C4HD through activation of the PI-3K/Akt
signaling pathway that converges on the transcriptional activation of NF-κB.
Since C4HD tumor overexpresses ErbB-2 and given that this tyrosine kinase plays
a critical role in C4HD cell proliferation, we wondered whether interactions
between TNFα and ErbB-2 could be taking place. Our findings revealed that
treatment of C4HD cells with the ErbB2 inhibitor AG825 blocked TNFα-induced
proliferation. Similar results were obtained using the human ErbB2-overexpressing
cell line SK-BR-3. Then, we studied the effect of TNFα on ErbB2 phosphorylation
in C4HD and SK-BR-3 cells. We found that
TNFα increased total ErbB2 tyrosine phosphorylation in C4HD and SK-BR-3 cells, as
well as on the specific residues tyrosines 927 and 1172 in murine cells and on its
human homologues 877 and 1222. These effects where not caused by the release of
ErbBs ligands from the cell membrane by TNFα, since treatment with the
metalloprotease inhibitor GM6001 did not affect TNFα-induced ErbB2
phosphorylation. We then studied if c-Src was involved in the above effect
given that it is known to directly phosphorylate ErbB2 in the Tyr 877 residue.
We found that addition of PP2, a Src family inhibitor, completely inhibited phosphorylation
of Tyr 927/877 ErbB2, and that to a lesser degree it inhibited Tyr 1172/1222
ErbB2 in both cell types. We also performed an in vitro cold phosphorylation assay where we observed that c-Src
immunoprecipitated from C4HD cells treated with TNFa was able to phosphorylate ErbB2 on Tyr 927 residue. Taken together,
these results indicate that TNFa induces
phosphorylation of ErbB-2 at Tyr877/927 residue and that c-Src is the tyrosine
kinase involved in this effect. In addition, we observed that upon TNFα
stimulation, ErbB2 associated with ErbB3 leading to PI-3K/Akt pathway
activation. Treatment of cells with AG825 inhibited Akt and NF-κB activation by
TNFα, as evidenced by western blots of phospho proteins and reporter gene
studies, respectively. The above data for the first time identify TNFα as a
cytokine able to transactivate ErbB2, disclosing c-Src involvement in such
effect. Also we demonstrated that TNFa ability
to activate Akt and NF-kB transcriptional activation is dependent on ErbB2
phosphorylation in breast cancer cells that overexpress ErbB2. Interestingly,
TNFα appears as a new player in ErbB2-overexpressing breast tumors, and its eventual
worth as a prognostic factor in anti ErbB2 therapy is yet to be determined.