title: The small molecule C-6 is selectively cytotoxic against breast cancer cells and its biological action is characterized by mitochondrial defects and endoplasmic reticulum stress.
abstract: BACKGROUND
  The establishment of drug resistance following treatment with chemotherapeutics is strongly associated with poor clinical outcome in patients, and drugs that target chemoresistant tumors have the potential to increase patient survival. In an effort to identify biological pathways of chemoresistant breast cancers that can be targeted therapeutically, a small molecule screen utilizing metastatic patient-derived breast cancer cells was conducted; from this previous report, the cytotoxic small molecule, C-6, was identified for its ability to selectively kill aggressive breast cancer cells in a caspase-independent manner. Here, we describe the cellular and molecular pathways induced following C-6 treatment in both normal and breast cancer cell lines.
  
  
  METHODS
  Transcriptome analyses and protein expression experiments were used to measure endoplasmic reticulum (ER) stress following C-6 treatment. Studies utilizing transmission electron microscopy and metabolomic profiling were conducted to characterize mitochondrial morphology and function in C-6-treated cells. Oxygen consumption rates and oxidative stress were also measured in breast cancer and normal mammary epithelial cells following treatment with the small molecule. Finally, structural modifications were made to the molecule and potency and cancer selectivity were evaluated.
  
  
  RESULTS
  Treatment with C-6 resulted in ER stress in both breast cancer cells and normal mammary epithelial cells. Gross morphological defects were observed in the mitochondria and these aberrations were associated with metabolic imbalances and a diminished capacity for respiration. Following treatment with C-6, oxidative stress was observed in three breast cancer cell lines but not in normal mammary epithelial cells. Finally, synthetic modifications made to the small molecule resulted in the identification of the structural components that contribute to C-6's cancer-selective phenotype.
  
  
  CONCLUSIONS
  The data reported here implicate mitochondrial and ER stress as a component of C-6's biological activity and provide insight into non-apoptotic cell death mechanisms; targeting biological pathways that induce mitochondrial dysfunction and ER stress may offer new strategies for the development of therapeutics that are effective against chemoresistant breast cancers.
authors.affiliation: Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah, 84112, USA. rachel.vaden@hci.utah.edu.
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Vaden
authors.affiliation: Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, 2000 Circle of Hope Drive, Salt Lake City, Utah, 84112, USA. keith.gligorich@hci.utah.edu.
authors.forename: Keith M
authors.initials: KM
authors.lastname: Gligorich
authors.affiliation: Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah, 84112, USA. janaegra@gmail.com.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Jana
authors.affiliation: Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah, 84112, USA. sigman@chem.utah.edu.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Sigman
authors.affiliation: Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, 825 Northeast 13th Street, Oklahoma City, OK, 73104, USA. bryan-welm@omrf.org.
authors.forename: Bryan E
authors.initials: BE
authors.lastname: Welm
mesh_terms: D000230:Adenocarcinoma; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001559:Benzhydryl Compounds / Q000494:pharmacology*; D001943:Breast Neoplasms; D002219:Carbamates / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D055442:Metabolome / Q000187:drug effects*; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000187:drug effects* / Q000648:ultrastructure; D018384:Oxidative Stress / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D059467:Transcriptome / Q000187:drug effects*
chemical_list: D000970:Antineoplastic Agents; D001559:Benzhydryl Compounds; D002219:Carbamates