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Upregulated HSP27 in human breast cancer cells reduces Herceptin susceptibility by increasing Her2 protein stability.

Kang SH, Kang KW, Kim KH, Kwon B, Kim SK, Lee HY, Kong SY, Lee ES, Jang SG, Yoo BC - BMC Cancer (2008)

Bottom Line: However, Her2 expression was reduced by a greater amount in SK-BR-3 parent cells than in SK-BR-3 HR cells.Interestingly, co-immunoprecipitation analysis showed that HSP27 can bind to Her2.In the absence of Herceptin, HSP27 expression is suppressed and Her2 expression is reduced, indicating that downregulation of Her2 by Herceptin can be obstructed by the formation of a Her2-HSP27 complex.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Institute and Hospital, National Cancer Center, Republic of Korea. neology7@ncc.re.kr

ABSTRACT

Background: Elucidating the molecular mechanisms by which tumors become resistant to Herceptin is critical for the treatment of Her2-overexpressed metastatic breast cancer.

Methods: To further understand Herceptin resistance mechanisms at the molecular level, we used comparative proteome approaches to analyze two human breast cancer cell lines; Her2-positive SK-BR-3 cells and its Herceptin-resistant SK-BR-3 (SK-BR-3 HR) cells.

Results: Heat-shock protein 27 (HSP27) expression was shown to be upregulated in SK-BR-3 HR cells. Suppression of HSP27 by specific siRNA transfection increased the susceptibility of SK-BR-3 HR cells to Herceptin. In the presence of Herceptin, Her2 was downregulated in both cell lines. However, Her2 expression was reduced by a greater amount in SK-BR-3 parent cells than in SK-BR-3 HR cells. Interestingly, co-immunoprecipitation analysis showed that HSP27 can bind to Her2. In the absence of Herceptin, HSP27 expression is suppressed and Her2 expression is reduced, indicating that downregulation of Her2 by Herceptin can be obstructed by the formation of a Her2-HSP27 complex.

Conclusion: Our present study demonstrates that upregulated HSP27 in human breast cancer cells can reduce Herceptin susceptibility by increasing Her2 protein stability.

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Related in: MedlinePlus

Interactions between HSP27 and Her2, and reduced Her2 levels after HSP27 suppression. (a) Western-blot analysis of immunoprecipitates of anti-Her2 and anti-HSP2 antibodies. (b) Reduced Her2 levels associated with HSP27 suppression. (c) Reduced levels of Her2 in control and HSP27-suppressed cells in the presence of Herceptin. Data (b, c) are means ± standard deviations of three independent experiments.
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Figure 4: Interactions between HSP27 and Her2, and reduced Her2 levels after HSP27 suppression. (a) Western-blot analysis of immunoprecipitates of anti-Her2 and anti-HSP2 antibodies. (b) Reduced Her2 levels associated with HSP27 suppression. (c) Reduced levels of Her2 in control and HSP27-suppressed cells in the presence of Herceptin. Data (b, c) are means ± standard deviations of three independent experiments.

Mentions: To test the interaction between HSP27 and Her2, immunoprecipitate of the anti-Her2 antibody was proved by the anti-HSP27 antibody, and vice versa (Fig. 4a). Immunoreactive signals of Her2 and HSP27 were clearly detected in the immunoprecipitates of anti-HSP27 and anti-Her2, respectively (Fig. 4a). Without treatment of Herceptin, the HSP27 in SK-BR-3 HR was suppressed, and the level of Her2 was compared to that of the controls transfected by either buffer only or NS siRNA (Fig. 4b). In the absence of Herceptin, the Her2 protein level was not affected by siRNA transfection conditions, but HSP27 suppression was accompanied by a decrease in the Her2 protein level (Fig. 4b). However, in the presence of Herceptin Her2 protein was decreased not only in cells transfected by HSP27 siRNA but also in the controls (Fig. 4c).


Upregulated HSP27 in human breast cancer cells reduces Herceptin susceptibility by increasing Her2 protein stability.

Kang SH, Kang KW, Kim KH, Kwon B, Kim SK, Lee HY, Kong SY, Lee ES, Jang SG, Yoo BC - BMC Cancer (2008)

Interactions between HSP27 and Her2, and reduced Her2 levels after HSP27 suppression. (a) Western-blot analysis of immunoprecipitates of anti-Her2 and anti-HSP2 antibodies. (b) Reduced Her2 levels associated with HSP27 suppression. (c) Reduced levels of Her2 in control and HSP27-suppressed cells in the presence of Herceptin. Data (b, c) are means ± standard deviations of three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2567332&req=5

Figure 4: Interactions between HSP27 and Her2, and reduced Her2 levels after HSP27 suppression. (a) Western-blot analysis of immunoprecipitates of anti-Her2 and anti-HSP2 antibodies. (b) Reduced Her2 levels associated with HSP27 suppression. (c) Reduced levels of Her2 in control and HSP27-suppressed cells in the presence of Herceptin. Data (b, c) are means ± standard deviations of three independent experiments.
Mentions: To test the interaction between HSP27 and Her2, immunoprecipitate of the anti-Her2 antibody was proved by the anti-HSP27 antibody, and vice versa (Fig. 4a). Immunoreactive signals of Her2 and HSP27 were clearly detected in the immunoprecipitates of anti-HSP27 and anti-Her2, respectively (Fig. 4a). Without treatment of Herceptin, the HSP27 in SK-BR-3 HR was suppressed, and the level of Her2 was compared to that of the controls transfected by either buffer only or NS siRNA (Fig. 4b). In the absence of Herceptin, the Her2 protein level was not affected by siRNA transfection conditions, but HSP27 suppression was accompanied by a decrease in the Her2 protein level (Fig. 4b). However, in the presence of Herceptin Her2 protein was decreased not only in cells transfected by HSP27 siRNA but also in the controls (Fig. 4c).

Bottom Line: However, Her2 expression was reduced by a greater amount in SK-BR-3 parent cells than in SK-BR-3 HR cells.Interestingly, co-immunoprecipitation analysis showed that HSP27 can bind to Her2.In the absence of Herceptin, HSP27 expression is suppressed and Her2 expression is reduced, indicating that downregulation of Her2 by Herceptin can be obstructed by the formation of a Her2-HSP27 complex.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Institute and Hospital, National Cancer Center, Republic of Korea. neology7@ncc.re.kr

ABSTRACT

Background: Elucidating the molecular mechanisms by which tumors become resistant to Herceptin is critical for the treatment of Her2-overexpressed metastatic breast cancer.

Methods: To further understand Herceptin resistance mechanisms at the molecular level, we used comparative proteome approaches to analyze two human breast cancer cell lines; Her2-positive SK-BR-3 cells and its Herceptin-resistant SK-BR-3 (SK-BR-3 HR) cells.

Results: Heat-shock protein 27 (HSP27) expression was shown to be upregulated in SK-BR-3 HR cells. Suppression of HSP27 by specific siRNA transfection increased the susceptibility of SK-BR-3 HR cells to Herceptin. In the presence of Herceptin, Her2 was downregulated in both cell lines. However, Her2 expression was reduced by a greater amount in SK-BR-3 parent cells than in SK-BR-3 HR cells. Interestingly, co-immunoprecipitation analysis showed that HSP27 can bind to Her2. In the absence of Herceptin, HSP27 expression is suppressed and Her2 expression is reduced, indicating that downregulation of Her2 by Herceptin can be obstructed by the formation of a Her2-HSP27 complex.

Conclusion: Our present study demonstrates that upregulated HSP27 in human breast cancer cells can reduce Herceptin susceptibility by increasing Her2 protein stability.

Show MeSH
Related in: MedlinePlus