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Tumor associated macrophages protect colon cancer cells from TRAIL-induced apoptosis through IL-1beta-dependent stabilization of Snail in tumor cells.

Kaler P, Galea V, Augenlicht L, Klampfer L - PLoS ONE (2010)

Bottom Line: Macrophages and IL-1beta failed to inhibit TRAIL-induced apoptosis in HCT116 cells expressing dnIkappaB, dnAKT or dnTCF4, confirming that they oppose TRAIL-induced cell death through induction of Wnt signaling in tumor cells.Vitamin D(3) halts this amplifying loop by interfering with the release of IL-1beta from macrophages.Accordingly, vitamin D(3) sensitizes tumor cells to TRAIL-induced apoptosis, suggesting that the therapeutic efficacy of TRAIL could be augmented by this readily available chemopreventive agent.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, Albert Einstein Cancer Center, Montefiore Medical Center, New York, New York, United States of America.

ABSTRACT

Background: We recently reported that colon tumor cells stimulate macrophages to release IL-1beta, which in turn inactivates GSK3beta and enhances Wnt signaling in colon cancer cells, generating a self-amplifying loop that promotes the growth of tumor cells.

Principal findings: Here we describe that macrophages protect HCT116 and Hke-3 colon cancer cells from TRAIL-induced apoptosis. Inactivation of IL-1beta by neutralizing IL-1beta antibody, or silencing of IL-1beta in macrophages inhibited their ability to counter TRAIL-induced apoptosis. Accordingly, IL-1beta was sufficient to inhibit TRAIL-induced apoptosis. TRAIL-induced collapse of the mitochondrial membrane potential (Delta psi) and activation of caspases were prevented by macrophages or by recombinant IL-1beta. Pharmacological inhibition of IL-1beta release from macrophages by vitamin D(3), a potent chemopreventive agent for colorectal cancer, restored the ability of TRAIL to induce apoptosis of tumor cells cultured with macrophages. Macrophages and IL-1beta failed to inhibit TRAIL-induced apoptosis in HCT116 cells expressing dnIkappaB, dnAKT or dnTCF4, confirming that they oppose TRAIL-induced cell death through induction of Wnt signaling in tumor cells. We showed that macrophages and IL-1beta stabilized Snail in tumor cells in an NF-kappaB/Wnt dependent manner and that Snail deficient tumor cells were not protected from TRAIL-induced apoptosis by macrophages or by IL-1beta, demonstrating a crucial role of Snail in the resistance of tumor cells to TRAIL.

Significance: We have identified a positive feedback loop between tumor cells and macrophages that propagates the growth and promotes the survival of colon cancer cells: tumor cells stimulate macrophages to secrete IL-1beta, which in turn, promotes Wnt signaling and stabilizes Snail in tumor cells, conferring resistance to TRAIL. Vitamin D(3) halts this amplifying loop by interfering with the release of IL-1beta from macrophages. Accordingly, vitamin D(3) sensitizes tumor cells to TRAIL-induced apoptosis, suggesting that the therapeutic efficacy of TRAIL could be augmented by this readily available chemopreventive agent.

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Snail regulates Wnt signaling.A: HCT116 and Hke-3 cells were transfected with TOP-FLASH reporter together with an empty vector (neo), or the increasing concentrations of Snail expression vector. The experiment was performed in triplicate. B: Tumor cells were transfected with NSP or Snail specific siRNA and were treated with IL-1β as indicated. The levels of Snail were determined by immunoblotting. C: Tumor cells were transfected with TOP-FLASH reporter together with NSP or Snail specific siRNA. Data represent the average of two independent experiments each performed in duplicate.
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pone-0011700-g007: Snail regulates Wnt signaling.A: HCT116 and Hke-3 cells were transfected with TOP-FLASH reporter together with an empty vector (neo), or the increasing concentrations of Snail expression vector. The experiment was performed in triplicate. B: Tumor cells were transfected with NSP or Snail specific siRNA and were treated with IL-1β as indicated. The levels of Snail were determined by immunoblotting. C: Tumor cells were transfected with TOP-FLASH reporter together with NSP or Snail specific siRNA. Data represent the average of two independent experiments each performed in duplicate.

Mentions: Snail has been shown to interact with β-catenin and to promote the expression of Wnt target genes [38]. In accord with these data, we found that overexpression of Snail promotes TOP-FLASH-driven activity in both HCT116 and Hke-3 cells (Fig. 7A). In order to determine whether stabilization of Snail by macrophages/IL-1β contributes to their ability to drive Wnt signaling, we silenced Snail in tumor cells (Fig. 7B), and examined the ability of macrophages and IL-1β to induce Wnt signaling in Snail deficient HCT116 and Hke-3 cells. In contrast to HCT116 and Hke-3 cells transfected with NSP(nontargeting) RNAi, cells transfected with Snail specific RNAi failed to respond to macrophages and IL-1β with enhanced Wnt signaling (Fig. 7C). Snail deficiency did not impair IL-1β induced NF-κB activation in HCT116 cells (data not shown), demonstrating a specific requirement for Snail in macrophage mediated β-catenin driven transcription.


Tumor associated macrophages protect colon cancer cells from TRAIL-induced apoptosis through IL-1beta-dependent stabilization of Snail in tumor cells.

Kaler P, Galea V, Augenlicht L, Klampfer L - PLoS ONE (2010)

Snail regulates Wnt signaling.A: HCT116 and Hke-3 cells were transfected with TOP-FLASH reporter together with an empty vector (neo), or the increasing concentrations of Snail expression vector. The experiment was performed in triplicate. B: Tumor cells were transfected with NSP or Snail specific siRNA and were treated with IL-1β as indicated. The levels of Snail were determined by immunoblotting. C: Tumor cells were transfected with TOP-FLASH reporter together with NSP or Snail specific siRNA. Data represent the average of two independent experiments each performed in duplicate.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2908545&req=5

pone-0011700-g007: Snail regulates Wnt signaling.A: HCT116 and Hke-3 cells were transfected with TOP-FLASH reporter together with an empty vector (neo), or the increasing concentrations of Snail expression vector. The experiment was performed in triplicate. B: Tumor cells were transfected with NSP or Snail specific siRNA and were treated with IL-1β as indicated. The levels of Snail were determined by immunoblotting. C: Tumor cells were transfected with TOP-FLASH reporter together with NSP or Snail specific siRNA. Data represent the average of two independent experiments each performed in duplicate.
Mentions: Snail has been shown to interact with β-catenin and to promote the expression of Wnt target genes [38]. In accord with these data, we found that overexpression of Snail promotes TOP-FLASH-driven activity in both HCT116 and Hke-3 cells (Fig. 7A). In order to determine whether stabilization of Snail by macrophages/IL-1β contributes to their ability to drive Wnt signaling, we silenced Snail in tumor cells (Fig. 7B), and examined the ability of macrophages and IL-1β to induce Wnt signaling in Snail deficient HCT116 and Hke-3 cells. In contrast to HCT116 and Hke-3 cells transfected with NSP(nontargeting) RNAi, cells transfected with Snail specific RNAi failed to respond to macrophages and IL-1β with enhanced Wnt signaling (Fig. 7C). Snail deficiency did not impair IL-1β induced NF-κB activation in HCT116 cells (data not shown), demonstrating a specific requirement for Snail in macrophage mediated β-catenin driven transcription.

Bottom Line: Macrophages and IL-1beta failed to inhibit TRAIL-induced apoptosis in HCT116 cells expressing dnIkappaB, dnAKT or dnTCF4, confirming that they oppose TRAIL-induced cell death through induction of Wnt signaling in tumor cells.Vitamin D(3) halts this amplifying loop by interfering with the release of IL-1beta from macrophages.Accordingly, vitamin D(3) sensitizes tumor cells to TRAIL-induced apoptosis, suggesting that the therapeutic efficacy of TRAIL could be augmented by this readily available chemopreventive agent.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncology, Albert Einstein Cancer Center, Montefiore Medical Center, New York, New York, United States of America.

ABSTRACT

Background: We recently reported that colon tumor cells stimulate macrophages to release IL-1beta, which in turn inactivates GSK3beta and enhances Wnt signaling in colon cancer cells, generating a self-amplifying loop that promotes the growth of tumor cells.

Principal findings: Here we describe that macrophages protect HCT116 and Hke-3 colon cancer cells from TRAIL-induced apoptosis. Inactivation of IL-1beta by neutralizing IL-1beta antibody, or silencing of IL-1beta in macrophages inhibited their ability to counter TRAIL-induced apoptosis. Accordingly, IL-1beta was sufficient to inhibit TRAIL-induced apoptosis. TRAIL-induced collapse of the mitochondrial membrane potential (Delta psi) and activation of caspases were prevented by macrophages or by recombinant IL-1beta. Pharmacological inhibition of IL-1beta release from macrophages by vitamin D(3), a potent chemopreventive agent for colorectal cancer, restored the ability of TRAIL to induce apoptosis of tumor cells cultured with macrophages. Macrophages and IL-1beta failed to inhibit TRAIL-induced apoptosis in HCT116 cells expressing dnIkappaB, dnAKT or dnTCF4, confirming that they oppose TRAIL-induced cell death through induction of Wnt signaling in tumor cells. We showed that macrophages and IL-1beta stabilized Snail in tumor cells in an NF-kappaB/Wnt dependent manner and that Snail deficient tumor cells were not protected from TRAIL-induced apoptosis by macrophages or by IL-1beta, demonstrating a crucial role of Snail in the resistance of tumor cells to TRAIL.

Significance: We have identified a positive feedback loop between tumor cells and macrophages that propagates the growth and promotes the survival of colon cancer cells: tumor cells stimulate macrophages to secrete IL-1beta, which in turn, promotes Wnt signaling and stabilizes Snail in tumor cells, conferring resistance to TRAIL. Vitamin D(3) halts this amplifying loop by interfering with the release of IL-1beta from macrophages. Accordingly, vitamin D(3) sensitizes tumor cells to TRAIL-induced apoptosis, suggesting that the therapeutic efficacy of TRAIL could be augmented by this readily available chemopreventive agent.

Show MeSH
Related in: MedlinePlus