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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

BLT2 inhibition attenuates LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were transfected with BLT2 (siBLT2) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA levels in these treated MDA-MB-231 cells were assayed by semi-quantitative RT-PCR (upper), and the ICAM-1 protein levels were determined by Western blot assay (lower). (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 then visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (C) MDA-MB-231 cells were transfected with an expression plasmid for human BLT2 (pcDNA-BLT2) or the empty plasmid (pcDNA), and then incubated for 24 h. Then, the cells were assayed for ICAM-1 mRNA levels by semiquantitative RT-PCR (upper) and protein levels by Western blot assay (lower). 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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f2-molce-38-9-821: BLT2 inhibition attenuates LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were transfected with BLT2 (siBLT2) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA levels in these treated MDA-MB-231 cells were assayed by semi-quantitative RT-PCR (upper), and the ICAM-1 protein levels were determined by Western blot assay (lower). (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 then visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (C) MDA-MB-231 cells were transfected with an expression plasmid for human BLT2 (pcDNA-BLT2) or the empty plasmid (pcDNA), and then incubated for 24 h. Then, the cells were assayed for ICAM-1 mRNA levels by semiquantitative RT-PCR (upper) and protein levels by Western blot assay (lower). 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: Interestingly, we found that the level of BLT2 expression was also significantly elevated in MDA-MB-231 cells following LPS treatment (Fig. 1B). Therefore, we next investigated whether the up-regulated BLT2 plays a role in the expression of ICAM-1 in MDA-MB-231 cells, thereby mediating their adhesion to THP-1 monocytes. To test this hypothesis, we examined the effects of BLT2 depletion and found that LPS-induced ICAM-1 expression was clearly suppressed by the siRNA-mediated knockdown of BLT2 in MDA-MB-231 cells (Fig. 2A). In addition, BLT2 knockdown clearly abolished the adhesion of MDA-MB-231 cells to THP-1 monocytes (Fig. 2B). Furthermore, we found that the overexpression of BLT2 alone results in the upregulation of ICAM-1 at both the transcript and protein levels (Fig. 2C). Together, these results suggest that the up-regulated BLT2 plays a role in the expression of ICAM-1 in MDA-MB-231 cells, thereby mediating their adhesion to THP-1 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)

BLT2 inhibition attenuates LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were transfected with BLT2 (siBLT2) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA levels in these treated MDA-MB-231 cells were assayed by semi-quantitative RT-PCR (upper), and the ICAM-1 protein levels were determined by Western blot assay (lower). (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 then visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (C) MDA-MB-231 cells were transfected with an expression plasmid for human BLT2 (pcDNA-BLT2) or the empty plasmid (pcDNA), and then incubated for 24 h. Then, the cells were assayed for ICAM-1 mRNA levels by semiquantitative RT-PCR (upper) and protein levels by Western blot assay (lower). 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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Related In: Results  -  Collection

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f2-molce-38-9-821: BLT2 inhibition attenuates LPS-induced ICAM-1 expression in MDA-MB-231 cells. (A) MDA-MB-231 cells were transfected with BLT2 (siBLT2) or control (siCont) siRNA for 24 h and then treated with LPS (1 μg/ml) for 24 h. The ICAM-1 mRNA levels in these treated MDA-MB-231 cells were assayed by semi-quantitative RT-PCR (upper), and the ICAM-1 protein levels were determined by Western blot assay (lower). (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 then visualized, and the number of adherent monocytes was determined using fluorescence microscopy. (C) MDA-MB-231 cells were transfected with an expression plasmid for human BLT2 (pcDNA-BLT2) or the empty plasmid (pcDNA), and then incubated for 24 h. Then, the cells were assayed for ICAM-1 mRNA levels by semiquantitative RT-PCR (upper) and protein levels by Western blot assay (lower). 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: Interestingly, we found that the level of BLT2 expression was also significantly elevated in MDA-MB-231 cells following LPS treatment (Fig. 1B). Therefore, we next investigated whether the up-regulated BLT2 plays a role in the expression of ICAM-1 in MDA-MB-231 cells, thereby mediating their adhesion to THP-1 monocytes. To test this hypothesis, we examined the effects of BLT2 depletion and found that LPS-induced ICAM-1 expression was clearly suppressed by the siRNA-mediated knockdown of BLT2 in MDA-MB-231 cells (Fig. 2A). In addition, BLT2 knockdown clearly abolished the adhesion of MDA-MB-231 cells to THP-1 monocytes (Fig. 2B). Furthermore, we found that the overexpression of BLT2 alone results in the upregulation of ICAM-1 at both the transcript and protein levels (Fig. 2C). Together, these results suggest that the up-regulated BLT2 plays a role in the expression of ICAM-1 in MDA-MB-231 cells, thereby mediating their adhesion to THP-1 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