Eduardo F Farias

Publications (30) View all

• Article: Mechanism of inhibition of MMTV-neu and MMTV-wnt1 induced mammary oncogenesis by RARalpha agonist AM580.

  Y Lu, S Bertran, T-A Samuels, R Mira-y-Lopez, E F Farias
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  ABSTRACT: We hypothesized that specific activation of a single retinoic acid receptor-alpha (RARalpha), without direct and concurrent activation of RARbeta and gamma, will inhibit mammary tumor oncogenesis in murine models relevant to human cancer. A total of 50 uniparous mouse mammary tumor virus (MMTV)-neu and 50 nuliparous MMTV-wnt1 transgenic mice were treated with RARalpha agonist (retinobenzoic acid, Am580) that was added to the diet for 40 (neu) and 35 weeks (wnt1), respectively. Among the shared antitumor effects was the inhibition of epithelial hyperplasia, a significant increase (P<0.05) in tumor-free survival and a reduction in tumor incidence and in the growth of established tumors. In both models, the mechanisms responsible for these effects involved inhibition of proliferation and survival pathways, and induction of apoptosis. The treatment was more effective in the MMTV-wnt1 model in which Am580 also induced differentiation, in both in vivo and three-dimensional (3D) cultures. In these tumors Am580 inhibited the wnt pathway, measured by loss of nuclear beta-catenin, suggesting partial oncogene dependence of therapy. Am580 treatment increased RARbeta and lowered the level of RARgamma, an isotype whose expression we linked with tumor proliferation. The anticancer effect of RARalpha, together with the newly discovered pro-proliferative role of RARgamma, suggests that specific activation of RARalpha and inhibition of RARgamma might be effective in breast cancer therapy.
  Oncogene 06/2010; 29(25):3665-76. · 6.37 Impact Factor
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  Available from: Eduardo F Farias

  Article: Inhibition of eIF2alpha dephosphorylation inhibits ErbB2-induced deregulation of mammary acinar morphogenesis.

  Sharon J Sequeira, Huei Chi Wen, Alvaro Avivar-Valderas, Eduardo F Farias, Julio A Aguirre-Ghiso
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  ABSTRACT: The ErbB2/Her2/Neu receptor tyrosine kinase is amplified in approximately 30% of human breast cancers. Phosphorylation of the translation initiation factor, eIF2alpha inhibits global protein synthesis and activates a stress signaling and growth suppressive program. We have shown that forced phosphorylation of eIF2alpha can suppress head and neck, colorectal carcinoma and multiple myeloma tumor growth and/or survival. Here we explore whether ErbB2 modulates eIF2alpha phosphorylation and whether forced phosphorylation of the latter can antagonize ErbB2 deregulation of mammary acinar morphogenesis. We tested whether ErbB2 signaling influenced eIF2alpha signaling and whether enhanced phosphorylation of the latter affected ErbB2-deregulated mammary acinar development. We obtained stable MCF10A cells overexpressing wild-type (Wt) Neu/ErbB2 or a constitutively active (CA) variant via retroviral delivery or mammary tumor cells from MMTV-Neu tumors. Western blotting, RT-PCR and confocal microscopy were used to analyze the effects of ErbB2 activation on eIF2alpha signaling and the effect of the GADD34-PP1C inhibitor salubrinal. Wt- and MMTV-Neu cells formed aberrant acini structures resembling DCIS, while CA-ErbB2 overexpression induced invasive lesions. In these structures we found that CA-ErbB2 but not the Wt variant significantly down-regulated the pro-apoptotic gene CHOP. This occurred without apparent modulation of basal phosphorylation of PERK and eIF2alpha or induction of its downstream target ATF4. However, inhibition of eIF2alpha dephosphorylation with salubrinal was sufficient to inhibit Wt- and CA-ErbB2- as well as MMTV-Neu-induced deregulation of acinar growth. This was linked to enhanced CHOP expression, inhibition of proliferation, induction of apoptosis and luminal clearing in Wt-ErbB2 and to inhibition of cyclin D1 levels and subsequent proliferation in CA-ErbB2 cells. Depending on the strength of ErbB2 signaling there is a differential regulation of CHOP and eIF2alpha phosphorylation. ErbB2 uncouples in basal conditions eIF2alpha phosphorylation from CHOP induction. However, this signal was restored by salubrinal treatment in Wt-ErbB2 expressing MCF10A cells as these DCIS-like structures underwent luminal clearing. In CA-ErbB2 structures apoptosis is not induced by salubrinal and instead a state of quiescence with reduced proliferation was achieved. Treatments that stabilize P-eIF2alpha levels may be effective in treating ErbB2 positive cancers without severely disrupting normal tissue function and structure.
  BMC Cell Biology 09/2009; 10:64. · 2.59 Impact Factor
• Article: Inhibition of eIF2α dephosphorylation inhibits ErbB2-induced deregulation of mammary acinar morphogenesis

  Sharon Sequeira, Huei Wen, Alvaro Avivar-Valderas, Eduardo Farias, Julio Aguirre-Ghiso
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  ABSTRACT: Abstract Background The ErbB2/Her2/Neu receptor tyrosine kinase is amplified in ~30% of human breast cancers. Phosphorylation of the translation initiation factor, eIF2α inhibits global protein synthesis and activates a stress signaling and growth suppressive program. We have shown that forced phosphorylation of eIF2α can suppress head and neck, colorectal carcinoma and multiple myeloma tumor growth and/or survival. Here we explore whether ErbB2 modulates eIF2α phosphorylation and whether forced phosphorylation of the latter can antagonize ErbB2 deregulation of mammary acinar morphogenesis. Results We tested whether ErbB2 signaling influenced eIF2α signaling and whether enhanced phosphorylation of the latter affected ErbB2-deregulated mammary acinar development. We obtained stable MCF10A cells overexpressing wild-type (Wt) Neu/ErbB2 or a constitutively active (CA) variant via retroviral delivery or mammary tumor cells from MMTV-Neu tumors. Western blotting, RT-PCR and confocal microscopy were used to analyze the effects of ErbB2 activation on eIF2α signaling and the effect of the GADD34-PP1C inhibitor salubrinal. Wt- and MMTV-Neu cells formed aberrant acini structures resembling DCIS, while CA-ErbB2 overexpression induced invasive lesions. In these structures we found that CA-ErbB2 but not the Wt variant significantly down-regulated the pro-apoptotic gene CHOP. This occurred without apparent modulation of basal phosphorylation of PERK and eIF2α or induction of its downstream target ATF4. However, inhibition of eIF2α dephosphorylation with salubrinal was sufficient to inhibit Wt- and CA-ErbB2- as well as MMTV-Neu-induced deregulation of acinar growth. This was linked to enhanced CHOP expression, inhibition of proliferation, induction of apoptosis and luminal clearing in Wt-ErbB2 and to inhibition of cyclin D1 levels and subsequent proliferation in CA-ErbB2 cells. Conclusion Depending on the strength of ErbB2 signaling there is a differential regulation of CHOP and eIF2α phosphorylation. ErbB2 uncouples in basal conditions eIF2α phosphorylation from CHOP induction. However, this signal was restored by salubrinal treatment in Wt-ErbB2 expressing MCF10A cells as these DCIS-like structures underwent luminal clearing. In CA-ErbB2 structures apoptosis is not induced by salubrinal and instead a state of quiescence with reduced proliferation was achieved. Treatments that stabilize P-eIF2α levels may be effective in treating ErbB2 positive cancers without severely disrupting normal tissue function and structure.
  BMC Cell Biology. 01/2009;
• Article: RalA requirement for v-Src- and v-Ras-induced tumorigenicity and overproduction of urokinase-type plasminogen activator: involvement of metalloproteases.

  J A Aguirre-Ghiso, P Frankel, E F Farias, Z Lu, H Jiang, A Olsen, L A Feig, E B de Kier Joffe, D A Foster
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  ABSTRACT: Overproduction of urokinase-type plasminogen activator (uPA) and metalloproteases (MMPs) is strongly correlated with tumorigenicity and with invasive and metastatic phenotypes of human and experimental tumors. We demonstrated previously that overproduction of uPA in tumor cells is mediated by a phospholipase D (PLD)- and protein kinase C-dependent mechanism. The oncogenic stimulus of v-Src and v-Ras results in the activation of PLD, which is dependent upon the monomeric GTPase RalA. We have therefore investigated whether RalA plays a role in uPA and MMP overproduction that is observed in response to oncogenic signals. We report here that NIH3T3 cells transformed by both v-Src and v-Ras, constitutively overproduce uPA and that expression of a dominant negative RalA mutant (S28N) blocks overproduction of uPA in both the v-Src-and v-Ras-transformed cells. v-Src and v-Ras also induced an upregulation of the activity of MMP-2 and MMP-9 as detected by zymograms, however only the v-Src induction correlated with MMP protein levels detected by Western blot analysis. The dominant negative RalA mutant blocked increased MMP-2 and 9 overproduction induced by v-Src, but not the increased activity of MMP-2 and 9 induced by v-Ras. And, consistent with a role for the RalA/PLD pathway in mitogenesis and tumor development, the dominant negative RalA mutant completely blocked tumor formation by v-Src- and v-Ras-transformed NIH3T3 cells injected subcutaneously in syngeneic mice. The data presented here implicate RalA and PLD as signaling mediators for tumor formation and protease production by transformed cells.
  Oncogene 09/1999; 18(33):4718-25. · 6.37 Impact Factor
• Article: Overproduction of urokinase-type plasminogen activator is regulated by phospholipase D- and protein kinase C-dependent pathways in murine mammary adenocarcinoma cells.

  J A Aguirre Ghiso, D F Alonso, E F Farías, E Bal de Kier Joffé
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  ABSTRACT: Urokinase-type plasminogen activator (uPA) initiates a proteolytic cascade with which invasive cells eliminate barriers to movement. The signaling pathways regulating uPA production in tumor cells remain unclear. We first studied the effects of n-butanol, a phospholipase D (PLD) and protein kinase C (PKC) inhibitor, on the production of uPA in murine mammary adenocarcinoma cells. Tumor cell monolayers treated during 24 h with 0.3% v/v n-butanol, secreted 45-50% less uPA to the culture medium than control monolayers (P < 0.001) as determined by radial caseinolysis, zymography and western blot. This inhibition occurred also with 5-h treatments and remained up to 5 h after the removal of the alcohol. Treatment with the phorbol ester PMA or with EGF, strongly increased uPA production (P < 0.001). Interestingly, a mild inhibition of uPA production was observed when PMA stimulation was assayed in cotreatments with n-butanol. In contrast EGF was unable to reverse the inhibition induced by n-butanol. H7 significantly inhibited uPA activity (P < 0.001) secreted to the culture media. Furthermore, phosphatidic acid significantly stimulated uPA production meanwhile propranolol, which blocks phosphatidic acid availability, reduced it, suggesting a main regulatory role for this intermediary metabolite. These results suggest for the first time that uPA production is regulated by PLD and PKC signal transduction pathways in murine mammary adenocarcinoma cells.
  Biochimica et Biophysica Acta 05/1997; 1356(2):171-84. · 4.66 Impact Factor