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Reduced expression of Toll-like receptor 4 inhibits human breast cancer cells proliferation and inflammatory cytokines secretion.

Yang H, Zhou H, Feng P, Zhou X, Wen H, Xie X, Shen H, Zhu X - J. Exp. Clin. Cancer Res. (2010)

Bottom Line: TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA were found to significantly inhibit TLR4 expression in MDA-MB-231 at both mRNA and protein levels as compared to vector control(vector transfected cells).TLR4AsiRNA mediated the strongest effect.The cytokines which were secreted by the TLR4 silenced cells, such as IL-6 and IL-8, also decreased significantly as compared with vector control.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Clinical Laboratory, The Second affiliated Hospital of Soochow University, Suzhou, Jiangsu, China.

ABSTRACT

Background: Tumor cell expression of Toll-like receptors (TLRs) can promote inflammation and cell survival in the tumor microenvironment. Toll-like receptor 4 (TLR4) signaling in tumor cells can mediate tumor cell immune escape and tumor progression, and it is regarded as one of the mechanisms for chronic inflammation in tumorigenesis and progression. The expression of TLR4 in human breast cancer cell line MDA-MB-231 and its biological function in the development and progression of breast cancer have not been investigated. We sought to characterize the expression of TLR1-TLR10 in the established human breast cancer cell line MDA-MB-231, and to investigate the biological roles of TLR4 in breast cancer cells growth, survival, and its potential as a target for breast cancer therapy.

Methods: TLRs mRNA and protein expressions were detected in human breast cancer cell line MDA-MB-231 by RT-PCR, real-time PCR and flow cytometry (FCM). RNA interference was used to knockdown the expression of TLR4 in MDA-MB-231. MDA-MB-231 transfected with the vector pGenesil-1 and the vector containing a scrambled siRNA were as controls. Recombinant plasmids named TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA specific to TLR4 were transfected into human breast cancer cell line MDA-MB-231 with Lipfectamine 2000 reagent. TLR4 mRNA and protein expressions were investigated by RT-PCR, real-time PCR, FCM and immunofluorescence after silence. MTT analysis was performed to detect cell proliferation and FCM was used to detect the secretion of inflammatory cytokines in supernatant of transfected cells.

Results: The human breast cancer cell line MDA-MB-231 was found to express TLR1-TLR10 at both the mRNA and protein levels. TLR4 was found to be the highest expressed TLR in MDA-MB-231. TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA were found to significantly inhibit TLR4 expression in MDA-MB-231 at both mRNA and protein levels as compared to vector control(vector transfected cells). TLR4AsiRNA mediated the strongest effect. Knockdown of TLR4 gene in MDA-MB-231 resulted in a dramatic reduction of breast cancer cell viability. The cytokines which were secreted by the TLR4 silenced cells, such as IL-6 and IL-8, also decreased significantly as compared with vector control. No significant difference was observed in siRNA control (Recombinant plasmid named ScrambledsiRNA transfected cells) compared to vector control.

Conclusions: These studies identified the expression levels of multiple TLRs in human breast cancer cell line MDA-MB-231 and demonstrated that knockdown of TLR4 could actively inhibit proliferation and survival of breast cancer cells. Taken together, our results suggest RNAi-directed targeting of TLR4 may be a beneficial strategy for breast cancer therapy.

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TLR4 expression and functional effect after TLR4 knockdown in human breast cancer cell line MDA-MB-231. A, immunofluorescence analysis of gene-specific siRNA on TLR4 protein expression in pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Nuclear staining was performed using DAPI (blue) (200×). B, MTT analysis of the proliferative rate of pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. C and D, IL-6 and IL-8 presence in the supernatant secreted by pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Cell supernatant was analyzed using flow cytometry. All results are representative of three separate experiments.
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Figure 3: TLR4 expression and functional effect after TLR4 knockdown in human breast cancer cell line MDA-MB-231. A, immunofluorescence analysis of gene-specific siRNA on TLR4 protein expression in pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Nuclear staining was performed using DAPI (blue) (200×). B, MTT analysis of the proliferative rate of pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. C and D, IL-6 and IL-8 presence in the supernatant secreted by pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Cell supernatant was analyzed using flow cytometry. All results are representative of three separate experiments.

Mentions: Real-time PCR had demonstrated a specific reduction at mRNA level for TLR4AsiRNA. We further analyzed the effects of TLR4AsiRNA on TLR4 protein expression in MDA-MB-231 using immunostaining with anti-TLR4 antibody. Red fluorescence of TLR4 staining under the fluorescence microscope was drastically reduced by TLR4AsiRNA in comparison to vector control. No obvious difference was seen in siRNA control (Figure 3A). To access the potential effects of TLR4AsiRNA-mediated TLR4 silencing on cell proliferation and survival, MTT analysis was performed on the cells cultured 0 h, 24 h, 48 h, and 72 h following 48 h of transfection. Targeting of TLR4AsiRNA against TLR4 effected the proliferative ability of MDA-MB-231 (Figure 3B). The proliferative rate was significantly decreased according to the time of culture after transfection with TLR4AsiRNA compared with vector control; no significant difference was observed in siRNA control (P > 0.05). The biological consequences caused by TLR4 silencing may be a result of changes in TLR4-mediated signaling and subsequent downstream functions. Because increased TLR4 activates TLR4/MyD88 signaling and subsequent downstream functions [17], we decided to examine the status of the TLR4-related inflammatory cytokines in MDA-MB-231 with TLR4 gene knockdown. Analysis of FCM revealed that IL-6 and IL-8 were markedly depressed in the supernatant of silenced cells. The inhibition ration of cytokine IL-6 and IL-8 was 47.8 ± 3.9% and 48.3 ± 4.1% respectively when compared with vector control (P < 0.05), no significant difference was seen in siRNA control (Figure 3C and Figure 3D). These results suggested that decreased TLR4 levels in tumor cells might endow cells with attenuated growth and survival capacity.


Reduced expression of Toll-like receptor 4 inhibits human breast cancer cells proliferation and inflammatory cytokines secretion.

Yang H, Zhou H, Feng P, Zhou X, Wen H, Xie X, Shen H, Zhu X - J. Exp. Clin. Cancer Res. (2010)

TLR4 expression and functional effect after TLR4 knockdown in human breast cancer cell line MDA-MB-231. A, immunofluorescence analysis of gene-specific siRNA on TLR4 protein expression in pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Nuclear staining was performed using DAPI (blue) (200×). B, MTT analysis of the proliferative rate of pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. C and D, IL-6 and IL-8 presence in the supernatant secreted by pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Cell supernatant was analyzed using flow cytometry. All results are representative of three separate experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2913950&req=5

Figure 3: TLR4 expression and functional effect after TLR4 knockdown in human breast cancer cell line MDA-MB-231. A, immunofluorescence analysis of gene-specific siRNA on TLR4 protein expression in pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Nuclear staining was performed using DAPI (blue) (200×). B, MTT analysis of the proliferative rate of pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. C and D, IL-6 and IL-8 presence in the supernatant secreted by pGenesil-1 vector, ScrambledsiRNA and TLR4AsiRNA transfected cells. Cell supernatant was analyzed using flow cytometry. All results are representative of three separate experiments.
Mentions: Real-time PCR had demonstrated a specific reduction at mRNA level for TLR4AsiRNA. We further analyzed the effects of TLR4AsiRNA on TLR4 protein expression in MDA-MB-231 using immunostaining with anti-TLR4 antibody. Red fluorescence of TLR4 staining under the fluorescence microscope was drastically reduced by TLR4AsiRNA in comparison to vector control. No obvious difference was seen in siRNA control (Figure 3A). To access the potential effects of TLR4AsiRNA-mediated TLR4 silencing on cell proliferation and survival, MTT analysis was performed on the cells cultured 0 h, 24 h, 48 h, and 72 h following 48 h of transfection. Targeting of TLR4AsiRNA against TLR4 effected the proliferative ability of MDA-MB-231 (Figure 3B). The proliferative rate was significantly decreased according to the time of culture after transfection with TLR4AsiRNA compared with vector control; no significant difference was observed in siRNA control (P > 0.05). The biological consequences caused by TLR4 silencing may be a result of changes in TLR4-mediated signaling and subsequent downstream functions. Because increased TLR4 activates TLR4/MyD88 signaling and subsequent downstream functions [17], we decided to examine the status of the TLR4-related inflammatory cytokines in MDA-MB-231 with TLR4 gene knockdown. Analysis of FCM revealed that IL-6 and IL-8 were markedly depressed in the supernatant of silenced cells. The inhibition ration of cytokine IL-6 and IL-8 was 47.8 ± 3.9% and 48.3 ± 4.1% respectively when compared with vector control (P < 0.05), no significant difference was seen in siRNA control (Figure 3C and Figure 3D). These results suggested that decreased TLR4 levels in tumor cells might endow cells with attenuated growth and survival capacity.

Bottom Line: TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA were found to significantly inhibit TLR4 expression in MDA-MB-231 at both mRNA and protein levels as compared to vector control(vector transfected cells).TLR4AsiRNA mediated the strongest effect.The cytokines which were secreted by the TLR4 silenced cells, such as IL-6 and IL-8, also decreased significantly as compared with vector control.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Clinical Laboratory, The Second affiliated Hospital of Soochow University, Suzhou, Jiangsu, China.

ABSTRACT

Background: Tumor cell expression of Toll-like receptors (TLRs) can promote inflammation and cell survival in the tumor microenvironment. Toll-like receptor 4 (TLR4) signaling in tumor cells can mediate tumor cell immune escape and tumor progression, and it is regarded as one of the mechanisms for chronic inflammation in tumorigenesis and progression. The expression of TLR4 in human breast cancer cell line MDA-MB-231 and its biological function in the development and progression of breast cancer have not been investigated. We sought to characterize the expression of TLR1-TLR10 in the established human breast cancer cell line MDA-MB-231, and to investigate the biological roles of TLR4 in breast cancer cells growth, survival, and its potential as a target for breast cancer therapy.

Methods: TLRs mRNA and protein expressions were detected in human breast cancer cell line MDA-MB-231 by RT-PCR, real-time PCR and flow cytometry (FCM). RNA interference was used to knockdown the expression of TLR4 in MDA-MB-231. MDA-MB-231 transfected with the vector pGenesil-1 and the vector containing a scrambled siRNA were as controls. Recombinant plasmids named TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA specific to TLR4 were transfected into human breast cancer cell line MDA-MB-231 with Lipfectamine 2000 reagent. TLR4 mRNA and protein expressions were investigated by RT-PCR, real-time PCR, FCM and immunofluorescence after silence. MTT analysis was performed to detect cell proliferation and FCM was used to detect the secretion of inflammatory cytokines in supernatant of transfected cells.

Results: The human breast cancer cell line MDA-MB-231 was found to express TLR1-TLR10 at both the mRNA and protein levels. TLR4 was found to be the highest expressed TLR in MDA-MB-231. TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA were found to significantly inhibit TLR4 expression in MDA-MB-231 at both mRNA and protein levels as compared to vector control(vector transfected cells). TLR4AsiRNA mediated the strongest effect. Knockdown of TLR4 gene in MDA-MB-231 resulted in a dramatic reduction of breast cancer cell viability. The cytokines which were secreted by the TLR4 silenced cells, such as IL-6 and IL-8, also decreased significantly as compared with vector control. No significant difference was observed in siRNA control (Recombinant plasmid named ScrambledsiRNA transfected cells) compared to vector control.

Conclusions: These studies identified the expression levels of multiple TLRs in human breast cancer cell line MDA-MB-231 and demonstrated that knockdown of TLR4 could actively inhibit proliferation and survival of breast cancer cells. Taken together, our results suggest RNAi-directed targeting of TLR4 may be a beneficial strategy for breast cancer therapy.

Show MeSH
Related in: MedlinePlus