title: Antitumor activity of Cetuximab in combination with Ixabepilone on triple negative breast cancer stem cells.
abstract: BACKGROUND
  Developing novel strategies against treatment-resistant triple negative breast cancer (TNBC) cells remains a significant challenge. The ErbB family, including epidermal growth factor receptor (EGFR), plays key roles in metastasis, tumorigenesis, cell proliferation, and drug resistance. Recently, these characteristics have been linked to a small subpopulation of cells classified as cancer stem cells (CSC) which are believed to be responsible for tumor initiation and maintenance. Ixabepilone is a new generation microtubule-stabilizing agent, which has been expected to be more efficacious than conventional taxanes. Here we aim to investigate whether the EGFR monoclonal antibody Cetuximab, in combination with Ixabepilone, is more effective in eliminating CSC populations compared to chemotherapy alone in TNBC.
  
  
  METHODS
  Representative TNBC cell lines (MDA-MB-231 and SUM159) were used to evaluate breast CSC populations. We used fluorescence-activated cell sorter analysis (CD44(+) and CD24(-/low), or Aldefluor(+)) and a self-renewal assay called mammosphere formation efficiency (MSFE) to measure CSC population size after treatment with Cetuximab, or Cetuximab plus Ixabepilone in vitro.
  
  
  RESULTS
  Although there was no significant decrease in cell viability, Cetuximab reduced MSFE and the CSC population in breast cancer cells in vitro and in vivo through inhibition of autophagy. Also, SUM159 and MDA-MB-231 orthotopic tumors demonstrated partial response to Centuximab or Ixabepilone monotherapy; however, the effect of the combination treatment was significant only in SUM159 tumors (p <0.0001), when compared to Ixabepilone alone.
  
  
  CONCLUSIONS
  Overall, our findings demonstrate that EGFR-targeted therapy by Cetuximab effectively reduces the CSC population in TNBC tumors. However, combination therapy with Ixabepilone may be effective only in a small subset of TNBCs, warranting further investigation of alternative approaches to target multiple pathways for TNBC treatment.
authors.affiliation: Methodist Cancer Center, Houston Methodist Hospital, 6445 Main Street, P21-34, Houston, TX, 77030, USA. taneitaneitanei@gmail.com.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Tanei
authors.affiliation: Methodist Cancer Center, Houston Methodist Hospital, 6445 Main Street, P21-34, Houston, TX, 77030, USA. dchoi@houstonmethodist.org.
authors.forename: Dong Soon
authors.initials: DS
authors.lastname: Choi
authors.affiliation: Methodist Cancer Center, Houston Methodist Hospital, 6445 Main Street, P21-34, Houston, TX, 77030, USA. AARodriguez@houstonmethodist.org.
authors.forename: Angel A
authors.initials: AA
authors.lastname: Rodriguez
authors.affiliation: Department of Surgery, Houston Methodist Hospital, Houston, TX, 77030, USA. jyhwang@houstonmethodist.org.
authors.forename: Diana Hwang
authors.initials: DH
authors.lastname: Liang
authors.affiliation: Methodist Cancer Center, Houston Methodist Hospital, 6445 Main Street, P21-34, Houston, TX, 77030, USA. dobrolec@bcm.edu.
authors.forename: Lacey
authors.initials: L
authors.lastname: Dobrolecki
authors.affiliation: Methodist Cancer Center, Houston Methodist Hospital, 6445 Main Street, P21-34, Houston, TX, 77030, USA. mghosh111@gmail.com.
authors.forename: Madhumita
authors.initials: M
authors.lastname: Ghosh
authors.affiliation: Methodist Cancer Center, Houston Methodist Hospital, 6445 Main Street, P21-34, Houston, TX, 77030, USA. melissa_landis@yahoo.com.
authors.forename: Melissa D
authors.initials: MD
authors.lastname: Landis
authors.affiliation: Methodist Cancer Center, Houston Methodist Hospital, 6445 Main Street, P21-34, Houston, TX, 77030, USA. jcchang@houstonmethodist.org.
authors.forename: Jenny C
authors.initials: JC
authors.lastname: Chang
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000068818:Cetuximab / Q000008:administration & dosage*; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D034261:Epothilones / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D014411:Neoplastic Stem Cells / Q000187:drug effects; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D034261:Epothilones; C430592:ixabepilone; D000068818:Cetuximab