title: Nuclear basic fibroblast growth factor regulates triple-negative breast cancer chemo-resistance.
abstract: BACKGROUND
  Chemotherapy remains the only available treatment for triple-negative (TN) breast cancer, and most patients exhibit an incomplete pathologic response. Half of patients exhibiting an incomplete pathologic response die within five years of treatment due to chemo-resistant, recurrent tumor growth. Defining molecules responsible for TN breast cancer chemo-resistance is crucial for developing effective combination therapies blocking tumor recurrence. Historically, chemo-resistance studies have relied on long-term chemotherapy selection models that drive genetic mutations conferring cell survival. Other models suggest that tumors are heterogeneous, being composed of both chemo-sensitive and chemo-resistant tumor cell populations. We previously described a short-term chemotherapy treatment model that enriches for chemo-residual TN tumor cells. In the current work, we use this enrichment strategy to identify a novel determinant of TN breast cancer chemotherapy resistance [a nuclear isoform of basic fibroblast growth factor (bFGF)].
  
  
  METHODS
  Studies are conducted using our in vitro model of chemotherapy resistance. Short-term chemotherapy treatment enriches for a chemo-residual TN subpopulation that over time resumes proliferation. By western blotting and real-time polymerase chain reaction, we show that this chemotherapy-enriched tumor cell subpopulation expresses nuclear bFGF. The importance of bFGF for survival of these chemo-residual cells is interrogated using short hairpin knockdown strategies. DNA repair capability is assessed by comet assay. Immunohistochemistry (IHC) is used to determine nuclear bFGF expression in TN breast cancer cases pre- and post- neoadjuvant chemotherapy.
  
  
  RESULTS
  TN tumor cells surviving short-term chemotherapy treatment express increased nuclear bFGF. bFGF knockdown reduces the number of chemo-residual TN tumor cells. Adding back a nuclear bFGF construct to bFGF knockdown cells restores their chemo-resistance. Nuclear bFGF-mediated chemo-resistance is associated with increased DNA-dependent protein kinase (DNA-PK) expression and accelerated DNA repair. In fifty-six percent of matched TN breast cancer cases, percent nuclear bFGF-positive tumor cells either increases or remains the same post- neoadjuvant chemotherapy treatment (compared to pre-treatment). These data indicate that in a subset of TN breast cancers, chemotherapy enriches for nuclear bFGF-expressing tumor cells.
  
  
  CONCLUSIONS
  These studies identify nuclear bFGF as a protein in a subset of TN breast cancers that likely contributes to drug resistance following standard chemotherapy treatment.
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. shenduo.li@duke.edu.
authors.forename: Shenduo
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. sturgis.payne@dm.duke.edu.
authors.forename: Sturgis
authors.initials: S
authors.lastname: Payne
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. fang.wang@dm.duke.edu.
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.affiliation: Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany. claus.peter@mh-hannover.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Claus
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. zuowei.su@dm.duke.edu.
authors.forename: Zuowei
authors.initials: Z
authors.lastname: Su
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. jeffrey.groth@dm.duke.edu.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Groth
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. joseph.geradts@astrazeneca.com.
authors.forename: Joseph
authors.initials: J
authors.lastname: Geradts
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. gustaaf.deridder@dm.duke.edu.
authors.forename: Gustaaf
authors.initials: G
authors.lastname: de Ridder
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. rebeca.alvarez@dm.duke.edu.
authors.forename: Rebeca
authors.initials: R
authors.lastname: Alvarez
authors.affiliation: Duke Cancer Institute, Durham, N.C., 27710, USA. kelly.marcom@dm.duke.edu.
authors.forename: Paul Kelly
authors.initials: PK
authors.lastname: Marcom
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. salvatore.pizzo@dm.duke.edu.
authors.forename: Salvatore V
authors.initials: SV
authors.lastname: Pizzo
authors.affiliation: Department of Pathology, Duke University Medical Center, P.O. Box 3712, Durham, N.C., 27710, USA. robin.bachelder@duke.edu.
authors.forename: Robin E
authors.initials: RE
authors.lastname: Bachelder
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D002470:Cell Survival / Q000235:genetics; D004249:DNA Damage; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D021381:Protein Transport; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D014410:Tumor Stem Cell Assay
chemical_list: D000970:Antineoplastic Agents; D016222:Fibroblast Growth Factor 2; D051747:DNA-Activated Protein Kinase