Herceptin/trastuzumab is a monoclonal antibody that selectively targets the Her2 protein and remains the standard of care for Her2-positive breast cancer. Nevertheless, the biological processes altered by trastuzumab to impede cancer progression are presently unclear. Results from our preliminary studies show that trastuzumab causes cellular senescence in both cultured breast cancer cells and tumors derived from human patients who have undergone treatment in adjuvant therapy. This observed senescent phenotype is associated with several hallmarks of senescence including an inability to proliferate, induction of the cell cycle inhibitors p16 and p21, senescence-associated ?-galactosidase activity, and upregulation of the secreted proteins IGFBP3 and IGFBP5. Previous studies have indicated that high-level expression of the insulin-like growth factor 1 receptor (IGF1R) is associated with a lower response rate to trastuzumab. Consistent with this, elevated levels of IGF1R expression and phosphorylation were found in trastuzumab-resistant breast cancer cells following Her2 inhibition. Importantly, trastuzumab resistance can be overcome by combining trastuzumab with either a selective IGF1R inhibitor or recombinant IGFBPs, resulting in cellular senescence. Collectively, these results reveal the biological underpinnings of trastuzumab's clinical efficacy and suggest a practical approach for the treatment of Her2-positive, trastuzumab-resistant breast cancer. Capitalizing on these new findings, we propose the following two specific aims to explore the molecular basis that distinguish breast cancer patients who are sensitive to trastuzumab from those who are resistant.
Aim 1 will assess the potential contributions of several mechanisms that may control the expression level of IGF1R associated with sensitivity/resistance to trastuzumab.
Aim 2 will explore whether tyrosine kinase receptors, in addition to IGF1R, could be involved in the development of a trastuzumab-resistant phenotype. Together results from these exploratory experiments will lay the foundation a systemic analysis of molecular determinants at the mechanistic level for sensitivity and resistant to this standard therapy for Her2-positive breast cancer can be conducted in the future.

Public Health Relevance

The proposed research will uncover molecular basis for the development of resistance to Herceptin-based therapy for Her2-positive breast cancer patients, thus providing alternative therapeutic targets to combat the resistant phenotype and potentially huge benefits for the treatment of those patients.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21CA186800-01
Application #
8737478
Study Section
Special Emphasis Panel (ZCA1)
Program Officer
Forry, Suzanne L
Project Start
2014-07-01
Project End
2016-06-30
Budget Start
2014-07-01
Budget End
2015-06-30
Support Year
1
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Duke University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
City
Durham
State
NC
Country
United States
Zip Code
27705
Alexander, Peter B; Chen, Rui; Gong, Chang et al. (2017) Distinct Receptor Tyrosine Kinase Subsets Mediate Anti-HER2 Drug Resistance in Breast Cancer. J Biol Chem 292:748-759
Alexander, Peter B; Wang, Xiao-Fan (2015) Resistance to receptor tyrosine kinase inhibition in cancer: molecular mechanisms and therapeutic strategies. Front Med 9:134-8