Epithelial-to-mesenchymal transition (EMT) confers primary resistance to trastuzumab (Herceptin)

Cell Cycle. 2012 Nov 1;11(21):4020-32. doi: 10.4161/cc.22225. Epub 2012 Sep 19.


The rate of inherent resistance to single-agent trastuzumab in HER2-overexpressing metastatic breast carcinomas is impressive at above 70%. Unfortunately, little is known regarding the distinctive genetic signatures that could predict trastuzumab refractoriness ab initio. The epithelial-to-mesenchymal transition (EMT) molecular features, HER2 expression status and primary responses to trastuzumab were explored in the public Lawrence Berkeley Laboratory (LBL) Breast Cancer Collection. Lentivirus-delivered small hairpin RNAs were employed to reduce specifically and stably the expression of EMT transcription factors in trastuzumab-refractory basal/HER2+ cells. Cell proliferation assays and pre-clinical nude mice xenograft-based studies were performed to assess the contribution of specific EMT transcription factors to inherent trastuzumab resistance. Primary sensitivity to trastuzumab was restricted to the SLUG/SNAIL2-negative subset of luminal/HER2+ cell lines, whereas all of the SLUG/SNAIL2-positive basal/HER2+ cell lines exhibited an inherent resistance to trastuzumab. The specific knockdown of SLUG/SNAIL2 suppressed the stem-related CD44+CD24(-/low) mesenchymal immunophenotype by transcriptionally upregulating the luminal epithelial marker CD24 in basal/HER2+ cells. Basal/HER2+ cells gained sensitivity to the growth-inhibitory effects of trastuzumab following SLUG/SNAIL2 gene depletion, which induced the expression of the mesenchymal-to-epithelial transition (MET) genes involved in promoting an epithelial phenotype. The isolation of CD44+CD24(-/low) mesenchymal cells by magnetic-activated cell sorting (MACS) confirmed their intrinsic unresponsiveness to trastuzumab. A reduction in tumor growth and dramatic gain in sensitivity to trastuzumab in vivo were confirmed when the SLUG/SNAIL2 knockdown basal/HER2+ cells were injected into nude mice. HER2 overexpression in a basal, rather than in a luminal molecular background, results in a basal/HER2+ breast cancer subtype that is intrinsically resistant to trastuzumab. EMT transcription factors might induce an enhanced phenotypic plasticity that would allow basal/HER2+ breast cancer cells to "enter" into and "exit" dynamically from trastuzumab-responsive stem cell-like states. The systematic determination of SLUG/SNAIL2 as a stem/CD44+CD24(-/low) cell-associated protein may improve the therapeutic management of HER2+ breast carcinomas.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal, Humanized / toxicity*
  • Antineoplastic Agents / toxicity*
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • CD24 Antigen / metabolism
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm / drug effects*
  • Epithelial-Mesenchymal Transition
  • Female
  • Humans
  • Hyaluronan Receptors / metabolism
  • Immunophenotyping
  • Mice
  • Mice, Nude
  • Receptor, ErbB-2 / metabolism
  • Snail Family Transcription Factors
  • Transcription Factors / antagonists & inhibitors
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transplantation, Heterologous
  • Trastuzumab


  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents
  • CD24 Antigen
  • Hyaluronan Receptors
  • SNAI1 protein, human
  • Snai1 protein, mouse
  • Snai2 protein, mouse
  • Snail Family Transcription Factors
  • Transcription Factors
  • Receptor, ErbB-2
  • Trastuzumab