Inhibitors of HSP90 block p95-HER2 signaling in Trastuzumab-resistant tumors and suppress their growth.
The anti-HER2 antibody Trastuzumab (Herceptin) has been proven to be effective in the treatment of HER2-overexpressing breast cancer; resistance, however, invariably emerges in metastatic tumors. The expression of p95-HER2, a form of HER2 with a truncated extracellular domain that lacks the Trastuzumab binding epitope, has been implicated as a mechanism of resistance to the antibody. We utilized an in vivo tumor model that overexpresses p95-HER2 and showed it to be resistant to the signaling and antitumor effects of Trastuzumab. We find that both full-length and p95-HER2 interact with the HSP90 chaperone protein and are degraded in tumor cells exposed to HSP90 inhibitors in tissue culture and in vivo. Loss of expression of p95-HER2 is accompanied by downregulation of the phosphoinositide-3 kinase/AKT and extracellular signal-regulated kinase signaling pathways and inhibition of cell proliferation. Chronic administration of HSP90 inhibitors in vivo results in sustained loss of HER2 and p95-HER2 expression and inhibition of AKT activation, together with induction of apoptosis and complete inhibition of tumor growth in Trastuzumab-resistant, p95-HER2-overexpressing models. Thus, p95-HER2 is an HSP90 client protein, the expression and function of which can be effectively suppressed in vivo by HSP90 inhibitors. HSP90 inhibition is therefore a potentially effective therapeutic strategy for p95-HER2-mediated Trastuzumab-resistant breast cancer.
Department of Medicine, Memorial Sloan-Kettering Cancer Center (MSKCC), New York, NY 10065, USA.
S
S
Chandarlapaty
M
M
Scaltriti
P
P
Angelini
Q
Q
Ye
M
M
Guzman
C A
CA
Hudis
L
L
Norton
D B
DB
Solit
J
J
Arribas
J
J
Baselga
N
N
Rosen
D016475:3T3 Cells; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001665:Binding Sites / Q000235:genetics; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D005260:Female; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009154:Mutation; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D000068878:Trastuzumab; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D018841:HSP90 Heat-Shock Proteins; D006576:Heterocyclic Compounds, 4 or More Rings; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C534922:SNX 2112; C524056:Erbb2 protein, mouse