Zohreh Rezaei - Department Of Biology, University Of Sistan And Baluchestan, Zahedan, Iran
Kazem Dastjerdi - Department Of Molecular Medicine, Birjand University Of Medical Science, Birjand, Iran
Dor Mohammad Kordi Tamandani - Department Of Biology, University Of Sistan And Baluchestan, Zahedan, Iran

The humanized anti-HER2 antibody, trastuzumab (Herceptin), has been widely used for the treatment of early stage and metastatic types of Her2 positive breast cancers. However, the majority of patientsthat primarily respond to trastuzumab will progress again within 1 year. regardless of the high resistance rate, Characterization of the molecular mechanisms underlying this disease are still not well known.miRNAs are promising as important regulators of drug resistance. Altered microRNA expression levels in cancer cells have been associated with prognosis and response to chemotherapy. miR-23b is a critical regulatory factor in the progression of several cancer cell types that targets the relevant genes but its role in BT-474 cells are largely unclear. Trastuzumab-resistant BT-474 cells were generated by long-term in vitro culture of BT-474 cells in the presence of trastuzumab. The expression of miR-23b was then evaluated by Real-Time PCR. The MTT assay showed that BT-474 breast cancer cells wereresistant to this drug under long-term culturing with trastuzumab. miR-23b expression was downregulated in trastuzumab resistant cells in comparison with the parent cells but its downregulation is not significant. in conclusion, there was no correlations between mir-23b expression and resistance to Trastuzumab. To utilize miRNA as a diagnostic tool in clinical practice, further research is needed toidentify miRNA mechanisms and recognize its targets

Breast Cancer, Gene and Cancer, Cell and Cancer, Cancer Genetics, Drugs and Cancer