[MIR-520d expression analysis in breast cancer]

Breast cancer is the most common cancer in women. Non-coding RNAs especially miRNAs have important regulatory roles in cancer. MiRNAs are 21-24 nucleotides which have different levels of expression between tumors and normal tissues. In this study, we have analyzed expression level of miR-520d in three different groups of breast cancer. Fifty nine samples were divided into different groups according to their immunohistochemistry [IHC] classification: estrogen receptor [ER] positive and/or progesterone receptor [PR] positive group [as group I]; human epidermal growth factor receptor 2 [HER2] positive group [as group II]; and Triple negative group [as group III]. After small RNA extraction from tissues, cDNAs were synthesized and Real time RTPCR carried out using DNA binding dye. Expression levels were analyzed by LinRegPCR and REST software. MiR-520d under- expressed in all of three different groups. The expression ratio in groups I, II, and III were 0.193, 0.167, 0.21, respectively, but only the result from group II was significant [P=0.017]. According to the different clinicopathological status of breast cancer, miR-520d underexpressed significantly not only in patients with metastatic lymph node [P=0.019] but also in patients which have cancer at stage three [P=0.036]. In this study, we found that miR-520d possibly acts as a tumor suppressor. It may be useful for diagnosis of tumor from normal tissue. In addition, miR-520d significantly underexpressed in HER-2 positive group of breast cancers. Therefore, it may be useful as an additional diagnostic test in this group of breast tumors along with other biomarkers.