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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

ERK lies downstream of BLT2 in induction of ICAM-1 expression by LPS. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, and then the levels of p-ERK and ERK were measured by Western blotting. (B) MDA-MB-231 cells were incubated for 30 min with PD98059 (10 μM) and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and for ICAM-1 protein levels by Western blotting (lower). (C) MDA-MB-231 cells were treated as in (B) 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. (D) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid and then treated with LY255283 for 24 h. The cells were assayed for p-ERK and ERK protein levels by Western blot. (E) The scheme for the involvement of the MyD88-BLT2-ERK cascade in the induction of ICAM-1 expression in MDA-MB-231 cells by LPS and the subsequent adhesion of those cells to monocytes. 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 < 0.01, ***p < 0.005.
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f5-molce-38-9-821: ERK lies downstream of BLT2 in induction of ICAM-1 expression by LPS. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, and then the levels of p-ERK and ERK were measured by Western blotting. (B) MDA-MB-231 cells were incubated for 30 min with PD98059 (10 μM) and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and for ICAM-1 protein levels by Western blotting (lower). (C) MDA-MB-231 cells were treated as in (B) 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. (D) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid and then treated with LY255283 for 24 h. The cells were assayed for p-ERK and ERK protein levels by Western blot. (E) The scheme for the involvement of the MyD88-BLT2-ERK cascade in the induction of ICAM-1 expression in MDA-MB-231 cells by LPS and the subsequent adhesion of those cells to monocytes. 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 < 0.01, ***p < 0.005.

Mentions: To understand the signaling downstream of BLT2 that is involved in the LPS-induced expression of ICAM-1, we examined the role of ERK. ERK phosphorylation is increased following exposure to LPS (Fig. 5A). We also observed that the pre-treatment of MDA-MB-231 cells with PD98059, an ERK inhibitor, significantly suppressed both the LPS-mediated induction of ICAM-1 expression at the transcript and protein levels (Fig. 5B) and the subsequent adhesion to THP-1 monocytes (Fig. 5C). However, pretreatment with c-Jun N-terminal kinase inhibitor SP600125 or p38 kinase inhibitor SB203580 had no effect on LPS-enhanced ICAM-1 expression (data not shown). To investigate whether ERK activation lies downstream of the MyD88-BLT2 cascade, we examined the effect of BLT2 inhibition on the phosphorylation of ERK in MyD88-overexpressing MDA-MB-231 cells and found that MyD88-induced ERK phosphorylation was significantly suppressed by the inhibition of BLT2 by LY255283 (Fig. 5D). These data suggest that ERK lies downstream of the MyD88-BLT2 cascade involved in the LPS-mediated stimulation of ICAM-1 expression in MDA-MB-231 cells.


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)

ERK lies downstream of BLT2 in induction of ICAM-1 expression by LPS. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, and then the levels of p-ERK and ERK were measured by Western blotting. (B) MDA-MB-231 cells were incubated for 30 min with PD98059 (10 μM) and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and for ICAM-1 protein levels by Western blotting (lower). (C) MDA-MB-231 cells were treated as in (B) 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. (D) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid and then treated with LY255283 for 24 h. The cells were assayed for p-ERK and ERK protein levels by Western blot. (E) The scheme for the involvement of the MyD88-BLT2-ERK cascade in the induction of ICAM-1 expression in MDA-MB-231 cells by LPS and the subsequent adhesion of those cells to monocytes. 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 < 0.01, ***p < 0.005.
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f5-molce-38-9-821: ERK lies downstream of BLT2 in induction of ICAM-1 expression by LPS. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, and then the levels of p-ERK and ERK were measured by Western blotting. (B) MDA-MB-231 cells were incubated for 30 min with PD98059 (10 μM) and then incubated for 24 h in the presence or absence of LPS (1 μg/ml). The cells were assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and for ICAM-1 protein levels by Western blotting (lower). (C) MDA-MB-231 cells were treated as in (B) 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. (D) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid and then treated with LY255283 for 24 h. The cells were assayed for p-ERK and ERK protein levels by Western blot. (E) The scheme for the involvement of the MyD88-BLT2-ERK cascade in the induction of ICAM-1 expression in MDA-MB-231 cells by LPS and the subsequent adhesion of those cells to monocytes. 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 < 0.01, ***p < 0.005.
Mentions: To understand the signaling downstream of BLT2 that is involved in the LPS-induced expression of ICAM-1, we examined the role of ERK. ERK phosphorylation is increased following exposure to LPS (Fig. 5A). We also observed that the pre-treatment of MDA-MB-231 cells with PD98059, an ERK inhibitor, significantly suppressed both the LPS-mediated induction of ICAM-1 expression at the transcript and protein levels (Fig. 5B) and the subsequent adhesion to THP-1 monocytes (Fig. 5C). However, pretreatment with c-Jun N-terminal kinase inhibitor SP600125 or p38 kinase inhibitor SB203580 had no effect on LPS-enhanced ICAM-1 expression (data not shown). To investigate whether ERK activation lies downstream of the MyD88-BLT2 cascade, we examined the effect of BLT2 inhibition on the phosphorylation of ERK in MyD88-overexpressing MDA-MB-231 cells and found that MyD88-induced ERK phosphorylation was significantly suppressed by the inhibition of BLT2 by LY255283 (Fig. 5D). These data suggest that ERK lies downstream of the MyD88-BLT2 cascade involved in the LPS-mediated stimulation of ICAM-1 expression in MDA-MB-231 cells.

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