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Notch3 cooperates with the EGFR pathway to modulate apoptosis through the induction of bim.

Konishi J, Yi F, Chen X, Vo H, Carbone DP, Dang TP - Oncogene (2009)

Bottom Line: In vitro, these effects were enhanced when the epidermal growth factor receptor (EGFR) pathway was also inhibited, suggesting significant cross-talk between the two pathways.Using gamma-secretase inhibitor and erlotinib in a xenograft model, Bim induction and tumor inhibition were observed to be enhanced compared with either agent alone, consistent with our previous observation of significant synergism between Notch and EGFR-ras-MAPK signaling.Thus, our data support the hypothesis that Notch3 not only has a crucial role in lung cancer through regulating apoptosis, but also cooperates with the EGFR-MAPK pathway in modulating Bim.

View Article: PubMed Central - PubMed

Affiliation: Division of Hematology and Medical Oncology, Vanderbilt University Medical Center, Nashville, TN, USA.

ABSTRACT
Notch signaling is a highly conserved pathway important for normal embryonic development and cancer. We previously demonstrated a role for Notch3 in lung cancer pathogenesis. Notch3 inhibition resulted in tumor apoptosis and growth suppression. In vitro, these effects were enhanced when the epidermal growth factor receptor (EGFR) pathway was also inhibited, suggesting significant cross-talk between the two pathways. How Notch3 and epidermal growth factor receptor-mitogen-activated protein kinase (EGFR-MAPK) pathways cooperate in modulating apoptosis is not yet known. In this study, we provide evidence that Notch3 regulates Bim, a BH-3-only protein, via MAPK signaling. Furthermore, loss of Bim expression prevents tumor apoptosis induced by Notch3 inhibition. Using gamma-secretase inhibitor and erlotinib in a xenograft model, Bim induction and tumor inhibition were observed to be enhanced compared with either agent alone, consistent with our previous observation of significant synergism between Notch and EGFR-ras-MAPK signaling. Thus, our data support the hypothesis that Notch3 not only has a crucial role in lung cancer through regulating apoptosis, but also cooperates with the EGFR-MAPK pathway in modulating Bim.

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Notch3 and EGFR/ras/MAPK pathways cooperate in regulating Bim expression. (A) Bim is upregulated when HCC2429 was transfected with Notch3 siRNA as compared to control at 0 times, whereas inhibition of Notch3 signaling does not increase Bim expression over treatment with U0126 alone at both 6 and 24 hours, suggesting that Notch3 regulates Bim expression mainly through pERK. (B) AG1478 alone slightly diminishes Bim expression. However, treatment with both AG1478 and N3SiRNA resultes in the synergistic induction of Bim, compared to either treatment alone. Inhibition of pERK and EGFR with U0126 (C) and AG1478 (D), respectively, preventing Notch3-dependent suppression of Bim, supporting the hypothesis that modulation of Bim and apoptosis in lung cancer by Notch3 is dependent on intact EGFR/ras/MAPK signaling.
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Figure 4: Notch3 and EGFR/ras/MAPK pathways cooperate in regulating Bim expression. (A) Bim is upregulated when HCC2429 was transfected with Notch3 siRNA as compared to control at 0 times, whereas inhibition of Notch3 signaling does not increase Bim expression over treatment with U0126 alone at both 6 and 24 hours, suggesting that Notch3 regulates Bim expression mainly through pERK. (B) AG1478 alone slightly diminishes Bim expression. However, treatment with both AG1478 and N3SiRNA resultes in the synergistic induction of Bim, compared to either treatment alone. Inhibition of pERK and EGFR with U0126 (C) and AG1478 (D), respectively, preventing Notch3-dependent suppression of Bim, supporting the hypothesis that modulation of Bim and apoptosis in lung cancer by Notch3 is dependent on intact EGFR/ras/MAPK signaling.

Mentions: To better define the interaction between Notch3 and EGFR/ras/MAPK pathways in Bim modulation, we examined the effect of the MEK inhibitor U0126 and the EGFR inhibitor AG1478 on lung cancer cells treated with Notch3 siRNA. Interestingly, Bim expression is induced with the MEK inhibitor U0126, while the added loss of Notch3 signaling did not augment Bim expression (Figure 4A). One explanation for this observation is that the effect Notch3 has on Bim is dependent on intact MAPK signaling and that inhibiting Notch3 by siRNA is not of added benefit. On the other hand, when HCC2429 cells were treated with both Notch3 siRNA and AG1478 at 5 µM, Bim expression was induced significantly compared to Notch3 siRNA, U0126 or AG1478 alone (Figure 4B). The Akt-PI3K pathway regulates Bim through phosphorylation of the transcription factor Foxo3a (Urbich et al., 2005). Thus, inhibiting both Notch3 and EGFR synergistically affects Bim through both Foxo3a and MAPK signaling.


Notch3 cooperates with the EGFR pathway to modulate apoptosis through the induction of bim.

Konishi J, Yi F, Chen X, Vo H, Carbone DP, Dang TP - Oncogene (2009)

Notch3 and EGFR/ras/MAPK pathways cooperate in regulating Bim expression. (A) Bim is upregulated when HCC2429 was transfected with Notch3 siRNA as compared to control at 0 times, whereas inhibition of Notch3 signaling does not increase Bim expression over treatment with U0126 alone at both 6 and 24 hours, suggesting that Notch3 regulates Bim expression mainly through pERK. (B) AG1478 alone slightly diminishes Bim expression. However, treatment with both AG1478 and N3SiRNA resultes in the synergistic induction of Bim, compared to either treatment alone. Inhibition of pERK and EGFR with U0126 (C) and AG1478 (D), respectively, preventing Notch3-dependent suppression of Bim, supporting the hypothesis that modulation of Bim and apoptosis in lung cancer by Notch3 is dependent on intact EGFR/ras/MAPK signaling.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2813325&req=5

Figure 4: Notch3 and EGFR/ras/MAPK pathways cooperate in regulating Bim expression. (A) Bim is upregulated when HCC2429 was transfected with Notch3 siRNA as compared to control at 0 times, whereas inhibition of Notch3 signaling does not increase Bim expression over treatment with U0126 alone at both 6 and 24 hours, suggesting that Notch3 regulates Bim expression mainly through pERK. (B) AG1478 alone slightly diminishes Bim expression. However, treatment with both AG1478 and N3SiRNA resultes in the synergistic induction of Bim, compared to either treatment alone. Inhibition of pERK and EGFR with U0126 (C) and AG1478 (D), respectively, preventing Notch3-dependent suppression of Bim, supporting the hypothesis that modulation of Bim and apoptosis in lung cancer by Notch3 is dependent on intact EGFR/ras/MAPK signaling.
Mentions: To better define the interaction between Notch3 and EGFR/ras/MAPK pathways in Bim modulation, we examined the effect of the MEK inhibitor U0126 and the EGFR inhibitor AG1478 on lung cancer cells treated with Notch3 siRNA. Interestingly, Bim expression is induced with the MEK inhibitor U0126, while the added loss of Notch3 signaling did not augment Bim expression (Figure 4A). One explanation for this observation is that the effect Notch3 has on Bim is dependent on intact MAPK signaling and that inhibiting Notch3 by siRNA is not of added benefit. On the other hand, when HCC2429 cells were treated with both Notch3 siRNA and AG1478 at 5 µM, Bim expression was induced significantly compared to Notch3 siRNA, U0126 or AG1478 alone (Figure 4B). The Akt-PI3K pathway regulates Bim through phosphorylation of the transcription factor Foxo3a (Urbich et al., 2005). Thus, inhibiting both Notch3 and EGFR synergistically affects Bim through both Foxo3a and MAPK signaling.

Bottom Line: In vitro, these effects were enhanced when the epidermal growth factor receptor (EGFR) pathway was also inhibited, suggesting significant cross-talk between the two pathways.Using gamma-secretase inhibitor and erlotinib in a xenograft model, Bim induction and tumor inhibition were observed to be enhanced compared with either agent alone, consistent with our previous observation of significant synergism between Notch and EGFR-ras-MAPK signaling.Thus, our data support the hypothesis that Notch3 not only has a crucial role in lung cancer through regulating apoptosis, but also cooperates with the EGFR-MAPK pathway in modulating Bim.

View Article: PubMed Central - PubMed

Affiliation: Division of Hematology and Medical Oncology, Vanderbilt University Medical Center, Nashville, TN, USA.

ABSTRACT
Notch signaling is a highly conserved pathway important for normal embryonic development and cancer. We previously demonstrated a role for Notch3 in lung cancer pathogenesis. Notch3 inhibition resulted in tumor apoptosis and growth suppression. In vitro, these effects were enhanced when the epidermal growth factor receptor (EGFR) pathway was also inhibited, suggesting significant cross-talk between the two pathways. How Notch3 and epidermal growth factor receptor-mitogen-activated protein kinase (EGFR-MAPK) pathways cooperate in modulating apoptosis is not yet known. In this study, we provide evidence that Notch3 regulates Bim, a BH-3-only protein, via MAPK signaling. Furthermore, loss of Bim expression prevents tumor apoptosis induced by Notch3 inhibition. Using gamma-secretase inhibitor and erlotinib in a xenograft model, Bim induction and tumor inhibition were observed to be enhanced compared with either agent alone, consistent with our previous observation of significant synergism between Notch and EGFR-ras-MAPK signaling. Thus, our data support the hypothesis that Notch3 not only has a crucial role in lung cancer through regulating apoptosis, but also cooperates with the EGFR-MAPK pathway in modulating Bim.

Show MeSH
Related in: MedlinePlus