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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

A MyD88-BLT2 cascade mediates the induction of ICAM-1 expression in MDA-MB-231 cells by LPS. (A) MDA-MB-231 cells were transfected with MyD88 (siMyD88) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA and protein levels within the cells were assayed by semi-quantitative RT-PCR (upper) and Western blot assay (lower), respectively. (B) MDA-MB-231 cells were transfected and 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. (C) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid (Cont) and then incubated for 24 h. MDA-MB-231 cells were treated with the BLT2 inhibitor LY255823 for 24 h and then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and ICAM-1 protein levels by Western blot (lower). (D) MDA-MB-231 cells were transfected and treated as in (C) 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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f4-molce-38-9-821: A MyD88-BLT2 cascade mediates the induction of ICAM-1 expression in MDA-MB-231 cells by LPS. (A) MDA-MB-231 cells were transfected with MyD88 (siMyD88) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA and protein levels within the cells were assayed by semi-quantitative RT-PCR (upper) and Western blot assay (lower), respectively. (B) MDA-MB-231 cells were transfected and 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. (C) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid (Cont) and then incubated for 24 h. MDA-MB-231 cells were treated with the BLT2 inhibitor LY255823 for 24 h and then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and ICAM-1 protein levels by Western blot (lower). (D) MDA-MB-231 cells were transfected and treated as in (C) 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: Previously, we suggested that MyD88 acts downstream of LPS/TLR4 and upstream of BLT2 (Park and Kim, 2015). Therefore, we next tested whether MyD88 acts upstream of BLT2 in the LPS signaling pathway to stimulate ICAM-1 expression in MDA-MB-231 cells. The siRNA-mediated depletion of MyD88 in LPS-treated MDA-MB-231 cells resulted in a marked attenuation of ICAM-1 expression (Fig. 4A) and adhesion to THP-1 monocytes (Fig. 4B). Consistent with these results, we found that the overexpression of MyD88 alone results in the upregulation of ICAM-1 at both the transcript and protein levels whereas BLT2 inhibition by LY255283 abolishes the expression of ICAM-1 (Fig. 4C). In addition, the inhibition of BLT2 in MyD88-transfected MDA-MB-231 cells leads to a clear reduction in their adhesion to THP-1 monocytes (Fig. 4D). Together, these results suggest that LPS induces ICAM-1 expression in MDA-MB-231 cells through a MyD88-BLT2-linked cascade.


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)

A MyD88-BLT2 cascade mediates the induction of ICAM-1 expression in MDA-MB-231 cells by LPS. (A) MDA-MB-231 cells were transfected with MyD88 (siMyD88) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA and protein levels within the cells were assayed by semi-quantitative RT-PCR (upper) and Western blot assay (lower), respectively. (B) MDA-MB-231 cells were transfected and 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. (C) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid (Cont) and then incubated for 24 h. MDA-MB-231 cells were treated with the BLT2 inhibitor LY255823 for 24 h and then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and ICAM-1 protein levels by Western blot (lower). (D) MDA-MB-231 cells were transfected and treated as in (C) 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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Related In: Results  -  Collection

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

f4-molce-38-9-821: A MyD88-BLT2 cascade mediates the induction of ICAM-1 expression in MDA-MB-231 cells by LPS. (A) MDA-MB-231 cells were transfected with MyD88 (siMyD88) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA and protein levels within the cells were assayed by semi-quantitative RT-PCR (upper) and Western blot assay (lower), respectively. (B) MDA-MB-231 cells were transfected and 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. (C) MDA-MB-231 cells were transfected with an expression plasmid for MyD88 or an empty plasmid (Cont) and then incubated for 24 h. MDA-MB-231 cells were treated with the BLT2 inhibitor LY255823 for 24 h and then assayed for ICAM-1 mRNA levels by semi-quantitative RT-PCR (upper) and ICAM-1 protein levels by Western blot (lower). (D) MDA-MB-231 cells were transfected and treated as in (C) 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: Previously, we suggested that MyD88 acts downstream of LPS/TLR4 and upstream of BLT2 (Park and Kim, 2015). Therefore, we next tested whether MyD88 acts upstream of BLT2 in the LPS signaling pathway to stimulate ICAM-1 expression in MDA-MB-231 cells. The siRNA-mediated depletion of MyD88 in LPS-treated MDA-MB-231 cells resulted in a marked attenuation of ICAM-1 expression (Fig. 4A) and adhesion to THP-1 monocytes (Fig. 4B). Consistent with these results, we found that the overexpression of MyD88 alone results in the upregulation of ICAM-1 at both the transcript and protein levels whereas BLT2 inhibition by LY255283 abolishes the expression of ICAM-1 (Fig. 4C). In addition, the inhibition of BLT2 in MyD88-transfected MDA-MB-231 cells leads to a clear reduction in their adhesion to THP-1 monocytes (Fig. 4D). Together, these results suggest that LPS induces ICAM-1 expression in MDA-MB-231 cells through a MyD88-BLT2-linked cascade.

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