Polyclonal HER2-specific antibodies induced by vaccination mediate receptor internalization and degradation in tumor cells.
BACKGROUND
Sustained HER2 signaling at the cell surface is an oncogenic mechanism in a significant proportion of breast cancers. While clinically effective therapies targeting HER2 such as mAbs and tyrosine kinase inhibitors exist, tumors overexpressing HER2 eventually progress despite treatment. Thus, abrogation of persistent HER2 expression at the plasma membrane to synergize with current approaches may represent a novel therapeutic strategy.


METHODS
We generated polyclonal anti-HER2 antibodies (HER2-VIA) by vaccinating mice with an adenovirus expressing human HER2, and assessed their signaling effects in vitro and anti-tumor effects in a xenograft model. In addition, we studied the signaling effects of human HER2-specific antibodies induced by vaccinating breast cancer patients with a HER2 protein vaccine.


RESULTS
HER2-VIA bound HER2 at the plasma membrane, initially activating the downstream kinases extracellular signal-regulated protein kinase 1/2 and Akt, but subsequently inducing receptor internalization in clathrin-coated pits in a HER2 kinase-independent manner, followed by ubiquitination and degradation of HER2 into a 130 kDa fragment phosphorylated at tyrosine residues 1,221/1,222 and 1,248. Following vaccination of breast cancer patients with the HER2 protein vaccine, HER2-specific antibodies were detectable and these antibodies bound to cell surface-expressed HER2 and inhibited HER2 signaling through blocking tyrosine 877 phosphorylation of HER2. In contrast to the murine antibodies, human anti-HER2 antibodies induced by protein vaccination did not mediate receptor internalization and degradation.


CONCLUSIONS
These data provide new insight into HER2 trafficking at the plasma membrane and the changes induced by polyclonal HER2-specific antibodies. The reduction of HER2 membrane expression and HER2 signaling by polyclonal antibodies induced by adenoviral HER2 vaccines supports human clinical trials with this strategy for those breast cancer patients with HER2 therapy-resistant disease.
Department of Medicine, Duke University Medical Center, 595 Lasalle Street, Durham, NC 27710, USA.
Xiu-Rong
XR
Ren
Junping
J
Wei
Gangjun
G
Lei
Jiangbo
J
Wang
Jiuyi
J
Lu
Wenle
W
Xia
Neil
N
Spector
Larry S
LS
Barak
Timothy M
TM
Clay
Takuya
T
Osada
Erika
E
Hamilton
Kimberly
K
Blackwell
Amy C
AC
Hobeika
Michael A
MA
Morse
H Kim
HK
Lyerly
Wei
W
Chen
D000818:Animals; D000906:Antibodies / Q000276:immunology*; D001943:Breast Neoplasms / Q000276:immunology* / Q000628:therapy*; D019496:Cancer Vaccines / Q000276:immunology* / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D004705:Endocytosis / Q000276:immunology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology* / Q000378:metabolism; D014183:Transplantation, Heterologous; D054875:Ubiquitination; D014611:Vaccination
D000906:Antibodies; D019496:Cancer Vaccines; D048049:Extracellular Signal-Regulated MAP Kinases; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human