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


CONCLUSIONS
Our present study demonstrates that upregulated HSP27 in human breast cancer cells can reduce Herceptin susceptibility by increasing Her2 protein stability.
Kang
Se Hun
SH
Research Institute and Hospital, National Cancer Center, Republic of Korea. neology7@ncc.re.kr
Kang
Keon Wook
KW
Kim
Kyung-Hee
KH
Kwon
Bumi
B
Kim
Seok-Ki
SK
Lee
Ho-Young
HY
Kong
Sun-Young
SY
Lee
Eun Sook
ES
Jang
Sang-Geun
SG
Yoo
Byong Chul
BC
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D004795:Enzyme Stability; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D018832:Molecular Chaperones; D009362:Neoplasm Metastasis; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D000068878:Trastuzumab; D015854:Up-Regulation
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C057725:HSPB1 protein, human