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LPS Up-Regulates ICAM-1 Expression in Breast Cancer Cells by Stimulating a MyD88-BLT2-ERK-Linked Cascade, Which Promotes Adhesion to Monocytes.

Park GS, Kim JH - Mol. Cells (2015)

Bottom Line: Monocytes are the major inflammatory cells that infiltrate most solid tumors in humans.In this study, we found that LPS up-regulates ICAM-1 expression in MDA-MB-231 breast cancer cells, which facilitates their adhesion to THP-1 monocytes.Taken together, our results demonstrate for the first time that LPS up-regulates ICAM-1 expression in breast cancer cells via a MyD88-BLT2-ERK-linked signaling cascade, leading to the increased adhesion of breast cancer cells to monocytes.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.

ABSTRACT
Monocytes are the major inflammatory cells that infiltrate most solid tumors in humans. The interaction of tumor cells with infiltrating monocytes and their adhesion to these monocytes play a significant role in altering the tumor to become more aggressive. Recently, exposure to lipopolysaccharide (LPS) was suggested to promote cancer cell adhesion to monocytes; however, little is known about the details of the signaling mechanism involved in this process. In this study, we found that LPS up-regulates ICAM-1 expression in MDA-MB-231 breast cancer cells, which facilitates their adhesion to THP-1 monocytes. In addition, we analyzed the signaling mechanism underlying the up-regulation of ICAM-1 and found that the siRNA-mediated depletion of BLT2 markedly suppressed the LPS-induced expression of ICAM-1 in MDA-MB-231 cells and the subsequent adhesion of these cells to THP-1 monocytes. Moreover, we demonstrated that myeloid differentiation primary response gene 88 (MyD88) lies downstream of LPS/TLR4 and upstream of BLT2 and that this 'MyD88-BLT2' cascade mediates ERK activation and subsequent ICAM-1 expression, which is critical for the adhesion of MDA-MB-231 cells to THP-1 monocytes. Taken together, our results demonstrate for the first time that LPS up-regulates ICAM-1 expression in breast cancer cells via a MyD88-BLT2-ERK-linked signaling cascade, leading to the increased adhesion of breast cancer cells to monocytes.

No MeSH data available.


Related in: MedlinePlus

Inhibition of BLT2 ligands synthesis suppresses LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were incubated with MK886 (5 μM) and baicalein (20 μM) for 30 min and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and protein levels by Western blot assay (lower). (B) MDA-MB-231 cells were treated as in (A) and then the levels of LTB4 and 12(S)-HETE in cell supernatants were measured by ELISA. (C) MDA-MB-231 cells were treated as in (A) and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. The adherence of THP-1 cells to MDA-MB-231 cells was visualized, and the number of adherent monocytes was determined using fluorescence microscopy. The data are representative of three independent experiments with similar results. All quantitative data are represented as the mean ± SD from three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.005.
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f3-molce-38-9-821: Inhibition of BLT2 ligands synthesis suppresses LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were incubated with MK886 (5 μM) and baicalein (20 μM) for 30 min and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and protein levels by Western blot assay (lower). (B) MDA-MB-231 cells were treated as in (A) and then the levels of LTB4 and 12(S)-HETE in cell supernatants were measured by ELISA. (C) MDA-MB-231 cells were treated as in (A) and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. The adherence of THP-1 cells to MDA-MB-231 cells was visualized, and the number of adherent monocytes was determined using fluorescence microscopy. The data are representative of three independent experiments with similar results. All quantitative data are represented as the mean ± SD from three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.005.

Mentions: The biosynthesis of the BLT2 ligands, LTB4 and 12(S)-HETE, from arachidonic acid is catalyzed by 5-lipoxygenase (5-LO) and 12-lipoxygenase (12-LO), respectively (Powell et al., 1999). Previously, we reported that the levels of LTB4 and 12(S)-HETE were significantly increased in MDA-MB-231 cells by treatment with LPS (Park and Kim, 2015). To further demonstrate the role of BLT2 in the expression of ICAM-1, we pretreated the cells with the 5-LO activating protein (FLAP) inhibitor MK886 or 12-LO inhibitor baicalein and found that both ICAM-1 levels and adhesion to THP-1 cells were markedly suppressed in LPS-treated MDA-MB-231 cells (Figs. 3A and 3C). Under these experimental conditions, the LPS-induced increases in the levels of BLT2 ligands [LTB4 and 12(S)-HETE] were clearly suppressed by MK886 or baicalein, respectively (Fig. 3B). Together, these results suggest that BLT2 ligands [LTB4 and 12(S)-HETE] are necessary for the LPS-enhanced ICAM-1 expression.


LPS Up-Regulates ICAM-1 Expression in Breast Cancer Cells by Stimulating a MyD88-BLT2-ERK-Linked Cascade, Which Promotes Adhesion to Monocytes.

Park GS, Kim JH - Mol. Cells (2015)

Inhibition of BLT2 ligands synthesis suppresses LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were incubated with MK886 (5 μM) and baicalein (20 μM) for 30 min and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and protein levels by Western blot assay (lower). (B) MDA-MB-231 cells were treated as in (A) and then the levels of LTB4 and 12(S)-HETE in cell supernatants were measured by ELISA. (C) MDA-MB-231 cells were treated as in (A) and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. The adherence of THP-1 cells to MDA-MB-231 cells was visualized, and the number of adherent monocytes was determined using fluorescence microscopy. The data are representative of three independent experiments with similar results. All quantitative data are represented as the mean ± SD from three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.005.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4588726&req=5

f3-molce-38-9-821: Inhibition of BLT2 ligands synthesis suppresses LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were incubated with MK886 (5 μM) and baicalein (20 μM) for 30 min and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and protein levels by Western blot assay (lower). (B) MDA-MB-231 cells were treated as in (A) and then the levels of LTB4 and 12(S)-HETE in cell supernatants were measured by ELISA. (C) MDA-MB-231 cells were treated as in (A) and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. The adherence of THP-1 cells to MDA-MB-231 cells was visualized, and the number of adherent monocytes was determined using fluorescence microscopy. The data are representative of three independent experiments with similar results. All quantitative data are represented as the mean ± SD from three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.005.
Mentions: The biosynthesis of the BLT2 ligands, LTB4 and 12(S)-HETE, from arachidonic acid is catalyzed by 5-lipoxygenase (5-LO) and 12-lipoxygenase (12-LO), respectively (Powell et al., 1999). Previously, we reported that the levels of LTB4 and 12(S)-HETE were significantly increased in MDA-MB-231 cells by treatment with LPS (Park and Kim, 2015). To further demonstrate the role of BLT2 in the expression of ICAM-1, we pretreated the cells with the 5-LO activating protein (FLAP) inhibitor MK886 or 12-LO inhibitor baicalein and found that both ICAM-1 levels and adhesion to THP-1 cells were markedly suppressed in LPS-treated MDA-MB-231 cells (Figs. 3A and 3C). Under these experimental conditions, the LPS-induced increases in the levels of BLT2 ligands [LTB4 and 12(S)-HETE] were clearly suppressed by MK886 or baicalein, respectively (Fig. 3B). Together, these results suggest that BLT2 ligands [LTB4 and 12(S)-HETE] are necessary for the LPS-enhanced ICAM-1 expression.

Bottom Line: Monocytes are the major inflammatory cells that infiltrate most solid tumors in humans.In this study, we found that LPS up-regulates ICAM-1 expression in MDA-MB-231 breast cancer cells, which facilitates their adhesion to THP-1 monocytes.Taken together, our results demonstrate for the first time that LPS up-regulates ICAM-1 expression in breast cancer cells via a MyD88-BLT2-ERK-linked signaling cascade, leading to the increased adhesion of breast cancer cells to monocytes.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.

ABSTRACT
Monocytes are the major inflammatory cells that infiltrate most solid tumors in humans. The interaction of tumor cells with infiltrating monocytes and their adhesion to these monocytes play a significant role in altering the tumor to become more aggressive. Recently, exposure to lipopolysaccharide (LPS) was suggested to promote cancer cell adhesion to monocytes; however, little is known about the details of the signaling mechanism involved in this process. In this study, we found that LPS up-regulates ICAM-1 expression in MDA-MB-231 breast cancer cells, which facilitates their adhesion to THP-1 monocytes. In addition, we analyzed the signaling mechanism underlying the up-regulation of ICAM-1 and found that the siRNA-mediated depletion of BLT2 markedly suppressed the LPS-induced expression of ICAM-1 in MDA-MB-231 cells and the subsequent adhesion of these cells to THP-1 monocytes. Moreover, we demonstrated that myeloid differentiation primary response gene 88 (MyD88) lies downstream of LPS/TLR4 and upstream of BLT2 and that this 'MyD88-BLT2' cascade mediates ERK activation and subsequent ICAM-1 expression, which is critical for the adhesion of MDA-MB-231 cells to THP-1 monocytes. Taken together, our results demonstrate for the first time that LPS up-regulates ICAM-1 expression in breast cancer cells via a MyD88-BLT2-ERK-linked signaling cascade, leading to the increased adhesion of breast cancer cells to monocytes.

No MeSH data available.


Related in: MedlinePlus