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Int J Radiat Oncol Biol Phys. 2016 Jun 1;95(2):791-9. doi: 10.1016/j.ijrobp.2016.01.025. Epub 2016 Jan 22.

MiR-33a Decreases High-Density Lipoprotein-Induced Radiation Sensitivity in Breast Cancer.

Author information

1
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.
2
Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
3
Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
4
Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, The University of Texas MD Anderson Cancer Center, Houston, Texas.
5
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.

Abstract

PURPOSE:

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.

METHODS AND MATERIALS:

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.

RESULTS:

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).

CONCLUSIONS:

Our results reveal miR-33a negatively regulates HDL-induced radiation sensitivity in breast cancer.

PMID:
27055396
PMCID:
PMC4851902
DOI:
10.1016/j.ijrobp.2016.01.025
[Indexed for MEDLINE]
Free PMC Article

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