Spontaneous epithelial-mesenchymal transition and resistance to HER-2-targeted therapies in HER-2-positive luminal breast cancer

• Published in: PloS one Vol. 8; no. 8; p. e71987
• Main Authors: Lesniak, David, Sabri, Siham, Xu, Yaoxian, Graham, Kathryn, Bhatnagar, Pravin, Suresh, Mavanur, Abdulkarim, Bassam
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 26.08.2013; Public Library of Science (PLoS)
• Subjects: Antibodies, Monoclonal, Humanized - pharmacology; Antineoplastic Agents - pharmacology; Biology; Biotechnology; Blocking antibodies; Blotting, Western; Breast cancer; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Cancer; Cancer therapies; CD24 Antigen - metabolism; CD44 antigen; Cell Line, Tumor; Cell Proliferation - drug effects; Clonal selection; Cloning; Clusters; Colonies; Drug Resistance, Neoplasm - drug effects; Drug Resistance, Neoplasm - genetics; Epithelial-Mesenchymal Transition - genetics; ErbB-2 protein; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic - drug effects; Genotype & phenotype; Glycosylation; Glycosylation - drug effects; HER protein; Humans; Hyaluronan Receptors - metabolism; Integrin beta1 - genetics; Integrin beta1 - metabolism; Medical prognosis; Medical research; Medicine; Mesenchyme; Metastasis; Molecular Targeted Therapy - methods; Monoclonal antibodies; Oncology; Pharmaceutical sciences; Pharmacy; Quinazolines - pharmacology; Receptor, ErbB-2 - antagonists & inhibitors; Receptor, ErbB-2 - genetics; Receptor, ErbB-2 - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Stem cells; Targeted cancer therapy; Trastuzumab; Tumors; Quebec Canada
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0071987

Resistance to trastuzumab, a rationally designed HER-2-targeting antibody, remains a major hurdle in the management of HER-2-positive breast cancer. Preclinical studies suggest the mechanisms of trastuzumab resistance are numerous. Unfortunately, the majority of these studies are based around HER-2-positive (HER-2+) luminal cell lines. The role of epithelial to mesenchymal transition (EMT), a genetic program that confers a basal phenotype, may represent a novel mechanism of escape for HER-2+ luminal cells from trastuzumab treatment. Here we investigated this possibility using a model of clonal selection in HER-2+ luminal breast cancer cells. Following a random isolation and expansion of "colony clusters" from SKBR-3 cell lines, several colony clusters underwent a spontaneous EMT in-vitro. In addition to expression of conventional EMT markers, all mesenchymal colony clusters displayed a predominant CD44+/CD24- phenotype with decreased HER-2 expression and elevated levels of a β1-integrin isoform with a high degree of N-glycosylation. Treatment with a β1-integrin function-blocking antibody, AIIB2, preferentially decreased the N-glycosylated form of β1-integrin, impaired mammosphere formation and restored epithelial phenotype in mesenchymal colony clusters. Using this model we provide the first clear evidence that resistance to trastuzumab (and lapatinib) can occur spontaneously as HER-2+ cells shift from a luminal to a basal/mesenchymal phenotype following EMT. While the major determinant of trastuzumab resistance in mesenchymal colony clusters is likely the down regulation of the HER-2 protein, our evidence suggests that multiple factors may contribute, including expression of N-glycosylated β1-integrin.