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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

ICAM-1 expression induced by LPS in MDA-MB-231 breast cancer cells promotes their adhesion to THP-1 monocytes. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. THP-1 cells that had adhered to MDA-MB-231 cells were visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (B) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, after which the mRNA levels of ICAM-1, BLT2, MyD88 and GAPDH were measured by semi-quantitative RT-PCR. The protein levels of ICAM-1 and α-tubulin were measured by Western blot assay. (C) LPS-pretreated MDA-MB-231 cells (1 μg/ml, 24 h) were treated with anti-human ICAM-1 or anti-mouse IgG isotype control antibodies for 2 h, and the cells were 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) THP-1 cells were treated with anti-human Mac-1 or anti-mouse IgG isotype control antibodies for 2 h, and the THP-1 cells with calcein-AM-label were then co-cultured with LPS-pretreated MDA-MB-231 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.
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f1-molce-38-9-821: ICAM-1 expression induced by LPS in MDA-MB-231 breast cancer cells promotes their adhesion to THP-1 monocytes. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. THP-1 cells that had adhered to MDA-MB-231 cells were visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (B) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, after which the mRNA levels of ICAM-1, BLT2, MyD88 and GAPDH were measured by semi-quantitative RT-PCR. The protein levels of ICAM-1 and α-tubulin were measured by Western blot assay. (C) LPS-pretreated MDA-MB-231 cells (1 μg/ml, 24 h) were treated with anti-human ICAM-1 or anti-mouse IgG isotype control antibodies for 2 h, and the cells were 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) THP-1 cells were treated with anti-human Mac-1 or anti-mouse IgG isotype control antibodies for 2 h, and the THP-1 cells with calcein-AM-label were then co-cultured with LPS-pretreated MDA-MB-231 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.

Mentions: We assessed whether LPS enhanced the adhesion of MDA-MB-231 cells to THP-1 monocytes and found that adhesion was significantly increased by LPS treatment (Fig. 1A). To understand the mechanism by which LPS enhances the adhesion of MDA-MB-231 cells to monocytes, we examined whether LPS treatment up-regulates ICAM-1 expression in MDA-MB-231 cells. Semi-quantitative RT-PCR and western blot analyses revealed that the levels of ICAM-1 mRNA and protein, respectively, were markedly increased by LPS (Fig. 1B). ICAM-1 has been reported to directly interact with Mac-1 on the surface of monocytes (Usami et al., 2013). Therefore, to examine whether the adhesion of MDA-MB-231 cells to monocytes is mediated through interactions between ICAM-1 on the MDA-MB-231 cells and Mac-1 on the THP-1 monocytes, the cells were pre-treated with anti-human ICAM-1 antibody (for MDA-MB-231 cells) or anti-human Mac-1 antibody (for THP-1 cells). The adhesion of THP-1 monocytes to LPS-pretreated MDA-MB-231 cells was significantly inhibited by either anti-ICAM-1 or anti-Mac-1 antibody pretreatment (Figs. 1C and 1D). Together, these results suggest that LPS-induced ICAM-1 expressed on MDA-MB-231 cells interacts with Mac-1 on monocytes.


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)

ICAM-1 expression induced by LPS in MDA-MB-231 breast cancer cells promotes their adhesion to THP-1 monocytes. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. THP-1 cells that had adhered to MDA-MB-231 cells were visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (B) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, after which the mRNA levels of ICAM-1, BLT2, MyD88 and GAPDH were measured by semi-quantitative RT-PCR. The protein levels of ICAM-1 and α-tubulin were measured by Western blot assay. (C) LPS-pretreated MDA-MB-231 cells (1 μg/ml, 24 h) were treated with anti-human ICAM-1 or anti-mouse IgG isotype control antibodies for 2 h, and the cells were 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) THP-1 cells were treated with anti-human Mac-1 or anti-mouse IgG isotype control antibodies for 2 h, and the THP-1 cells with calcein-AM-label were then co-cultured with LPS-pretreated MDA-MB-231 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.
© Copyright Policy
Related In: Results  -  Collection

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

f1-molce-38-9-821: ICAM-1 expression induced by LPS in MDA-MB-231 breast cancer cells promotes their adhesion to THP-1 monocytes. (A) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h and then co-cultured with calcein-AM-labeled THP-1 cells for 1 h. THP-1 cells that had adhered to MDA-MB-231 cells were visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (B) MDA-MB-231 cells were treated with LPS (0, 1, and 5 μg/ml) for 24 h, after which the mRNA levels of ICAM-1, BLT2, MyD88 and GAPDH were measured by semi-quantitative RT-PCR. The protein levels of ICAM-1 and α-tubulin were measured by Western blot assay. (C) LPS-pretreated MDA-MB-231 cells (1 μg/ml, 24 h) were treated with anti-human ICAM-1 or anti-mouse IgG isotype control antibodies for 2 h, and the cells were 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) THP-1 cells were treated with anti-human Mac-1 or anti-mouse IgG isotype control antibodies for 2 h, and the THP-1 cells with calcein-AM-label were then co-cultured with LPS-pretreated MDA-MB-231 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.
Mentions: We assessed whether LPS enhanced the adhesion of MDA-MB-231 cells to THP-1 monocytes and found that adhesion was significantly increased by LPS treatment (Fig. 1A). To understand the mechanism by which LPS enhances the adhesion of MDA-MB-231 cells to monocytes, we examined whether LPS treatment up-regulates ICAM-1 expression in MDA-MB-231 cells. Semi-quantitative RT-PCR and western blot analyses revealed that the levels of ICAM-1 mRNA and protein, respectively, were markedly increased by LPS (Fig. 1B). ICAM-1 has been reported to directly interact with Mac-1 on the surface of monocytes (Usami et al., 2013). Therefore, to examine whether the adhesion of MDA-MB-231 cells to monocytes is mediated through interactions between ICAM-1 on the MDA-MB-231 cells and Mac-1 on the THP-1 monocytes, the cells were pre-treated with anti-human ICAM-1 antibody (for MDA-MB-231 cells) or anti-human Mac-1 antibody (for THP-1 cells). The adhesion of THP-1 monocytes to LPS-pretreated MDA-MB-231 cells was significantly inhibited by either anti-ICAM-1 or anti-Mac-1 antibody pretreatment (Figs. 1C and 1D). Together, these results suggest that LPS-induced ICAM-1 expressed on MDA-MB-231 cells interacts with Mac-1 on monocytes.

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