Abstract 125: Exogenous MiR-125b inhibits head and neck squamous cell carcinoma growth by suppressing Bcl-2 expression

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL PURPOSE: Head and neck squamous cell cancer (HNSCC) is one of top ten cancers in the United States. The overall 5-year survival rate of HNSCC has not improved in the past two decades. B-cell lymphoma 2 (Bcl-2), an oncogene, is a key regulator of the apoptosis to promote cell proliferation and apoptosis arrest. Therefore, targeting Bcl-2 is an attractive strategy for restoring a normal apoptotic process and inhibiting cancer cell growth in HNSCC. MicroRNAs (miRNAs) are a class of ∼22-nucleotide-long, endogenously expressed, highly conserved of noncoding RNAs with important regulatory functions in proliferation, apoptosis and metastasis. In this study, we screened eight cancer-associated miRNAs levels (mir-21, -124, -125b, -147, -200a, -200b, -200c and -429) in twenty five human tissue specimens and four cell lines, including twenty HNSCC specimens and five normal controls, and three HNSCC cell lines (JHU-13, -22 and -29) and one transformed oral keratinocytes cell line (OKF-6). Based on the screening data, we further investigated the mechanism of miRNA-125b (miR-125b) regulated Bcl-2 expression and the therapeutic potential of exogenous miR-125b in a miR-125b stable transfected HNSCC cell line. Design Methods: The miRNA expression level was determined by quantitative RT-PCR. A stable expressed exogenous miR-125b HNSCC cell line (JHU-22miR125b) was generated by using lentivirus transfection. Colony formation and MTT assayed cell growth and cell viability and Western blot was used to analyze protein expression. Results: The expression levels of mir-124 and mir-125b were significant lower in both tumor tissue and tumor cell lines than control, and mir-21 was significant higher in tumors. Thus, mir-125b was selected as a candidate for further study. The level of miR-125b in the transfected cell lines (JHU-22miR125b) was increased more than five times compared with the control cells (Transfected with vector only, JHU-22vector). The levels of Bcl-2 protein and cell viability were significantly lower in JHU-22miR125b than JHU-22 vector. CONCLUSION: Bcl-2 is a direct target in miR-125b regulated Bcl-2 expression. Exogenous miR-125b suppresses the proliferation and growth of cultured HNSCC cells. The effect of exogenous miR-125b on inhibition of HNSCC growth via suppressing Bcl-2 expression will be further validated in tumor xanografts. This work was supported in part by grants P20 CA118770 from National Cancer Institute. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 125. doi:10.1158/1538-7445.AM2011-125