title: MiR-33a Decreases High-Density Lipoprotein-Induced Radiation Sensitivity in Breast Cancer.
abstract: We previously showed that high-density lipoprotein (HDL) radiosensitizes inflammatory breast cancer (IBC) cells in vitro and is associated with better local control after radiation therapy in IBC patients. The microRNA miR-33 family negatively regulates the adenosine triphosphate binding cassette transporter subfamily A member 1. We hypothesized that variations in miR-33a expression in IBC cancer cells versus non-IBC cells would correlate with radiation sensitivity following exposure to HDL in vitro.
  
  
  
  MiR-33a expression was analyzed by reverse transcriptase-polymerase chain reaction in 4 cell lines representing common clinical breast cancer subtypes. Overexpression and knockdown of miR-33a was demonstrated via transfection of an miR-33a mimic or an anti-miR-33a construct in high- and low-expressing miR-33a cell lines. Clonogenic survival in vitro in these cells was quantified at baseline and following HDL treatment. MiR-33a expression on distant relapse-free survival (DRFS) of 210 cases downloaded from the Oxford breast cancer dataset was determined.
  
  
  
  Expression levels of miR-33a were lower in IBC cell lines and IBC tumor samples than in non-IBC cell lines and normal breast tissue. Cholesterol concentrations in the cell membranes were higher in IBC cells than in non-IBC cells. Clonogenic survival following 24 hours of HDL treatment was decreased in response to irradiation in the low-miR-33a-expressing cell lines SUM149 and KPL4, but survival following HDL treatment decreased in the high-miR-33a-expressing cell lines MDA-MB-231 and SUM159. In the high-miR-33a-expressing cell lines, anti-miR-33a transfection decreased radiation resistance in clonogenic assays. Conversely, in the low-miR-33a-expressing cell lines, the miR-33a mimic reversed the HDL-induced radiation sensitization. Breast cancer patients in the top quartile based on miR-33a expression had markedly lower rates of DRFS than the bottom quartile (P=.0228, log-rank test). For breast cancer patients treated with radiation, high miR-33a expression predicted worse overall survival (P=.06).
  
  
  
  Our results reveal miR-33a negatively regulates HDL-induced radiation sensitivity in breast cancer.
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Adam R
authors.initials: AR
authors.lastname: Wolfe
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Arvind
authors.initials: A
authors.lastname: Bambhroliya
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Jay P
authors.initials: JP
authors.lastname: Reddy
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Bisrat G
authors.initials: BG
authors.lastname: Debeb
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Lei
authors.initials: L
authors.lastname: Huo
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Richard
authors.initials: R
authors.lastname: Larson
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.affiliation: Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Naoto T
authors.initials: NT
authors.lastname: Ueno
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: wwoodward@mdanderson.org.
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Woodward
mesh_terms: D064286:ATP Binding Cassette Transporter 1 / Q000032:analysis; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D058922:Inflammatory Breast Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D008075:Lipoproteins, HDL / Q000502:physiology*; D035683:MicroRNAs / Q000032:analysis / Q000502:physiology*; D011836:Radiation Tolerance
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D008075:Lipoproteins, HDL; C550416:MIRN33a microRNA, human; D035683:MicroRNAs