MicroRNA-10a is reduced in breast cancer and regulated in part through retinoic acid.
BACKGROUND
MicroRNAs (miRNAs) are short non-coding RNA molecules that play a critical role in mRNA cleavage and translational repression, and are known to be altered in many diseases including breast cancer. MicroRNA-10a (miR-10a) has been shown to be deregulated in various cancer types. The aim of this study was to investigate miR-10a expression in breast cancer and to further delineate the role of retinoids and thyroxine in regulation of miR-10a.


METHODS
Following informed patient consent and ethical approval, tissue samples were obtained during surgery. miR-10a was quantified in malignant (n = 103), normal (n = 30) and fibroadenoma (n = 35) tissues by RQ-PCR. Gene expression of Retinoic Acid Receptor beta (RARβ) and Thyroid Hormone receptor alpha (THRα) was also quantified in the same patient samples (n = 168). The in vitro effects of all-trans Retinoic acid (ATRA) and L-Thyroxine (T4) both individually and in combination, on miR-10a expression was investigated in breast cancer cell lines, T47D and SK-BR-3.


RESULTS
The level of miR-10a expression was significantly decreased in tissues harvested from breast cancer patients (Mean (SEM) 2.1(0.07)) Log10 Relative Quantity (RQ)) compared to both normal (3.0(0.16) Log10 RQ, p < 0.001) and benign tissues (2.6(0.17) Log10 RQ, p < 0.05). The levels of both RARβ and THRα gene expression were also found to be decreased in breast cancer patients compared to controls (p < 0.001). A significant positive correlation was determined between miR-10a and RARβ (r = 0.31, p < 0.001) and also with THRα (r = 0.32, p < 0.001). In vitro stimulation assays revealed miR-10a expression was increased in both T47D and SK-BR-3 cells following addition of ATRA (2 fold (0.7)). While T4 alone did not stimulate miR-10a expression, the combination of T4 and ATRA was found to have a positive synergistic effect.


CONCLUSIONS
The data presented supports a potential tumour suppressor role for miR-10a in breast cancer, and highlights retinoic acid as a positive regulator of the microRNA.
Discipline of Surgery, School of Medicine, Clinical Science Institute, National University of Ireland, Galway, Galway, Ireland. sonja.khan@nuigalway.ie.
Sonja
S
Khan
Clinical Research Facility and School of Mathematics, Statistics and Applied Mathematics, National University of Ireland, Galway, Galway, Ireland. deirdrewall1@gmail.com.
Deirdre
D
Wall
Discipline of Surgery, School of Medicine, Clinical Science Institute, National University of Ireland, Galway, Galway, Ireland. catherine.curran@nuigalway.ie.
Catherine
C
Curran
Clinical Research Facility and School of Mathematics, Statistics and Applied Mathematics, National University of Ireland, Galway, Galway, Ireland. john.newell@nuigalway.ie.
John
J
Newell
Discipline of Surgery, School of Medicine, Clinical Science Institute, National University of Ireland, Galway, Galway, Ireland. michael.kerin@nuigalway.ie.
Michael J
MJ
Kerin
Discipline of Surgery, School of Medicine, Clinical Science Institute, National University of Ireland, Galway, Galway, Ireland. roisin.dwyer@nuigalway.ie.
Roisin M
RM
Dwyer
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism*; D018270:Carcinoma, Ductal, Breast / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D018226:Fibroadenoma / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism; D037021:Thyroid Hormone Receptors alpha / Q000235:genetics / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D055815:Young Adult
D014408:Biomarkers, Tumor; C547183:MIRN10 microRNA, human; D035683:MicroRNAs; D018168:Receptors, Retinoic Acid; D037021:Thyroid Hormone Receptors alpha; C082925:retinoic acid receptor beta; D014212:Tretinoin