Abstract 3118: Identification of tumor suppressive microRNA-451a in hypopharyngeal squamous cell carcinoma based on microRNA expression signature
Authors: Fukumoto Ichiro , Kinoshita Takashi , Hanazawa Toyoyuki , Kikkawa Naoko , Chiyomaru Takeshi , Enokida Hideki , Yamamoto Noriko , Goto Yusuke , Nishikawa Rika , Nakagawa Masayuki , Okamoto Yoshitaka , Seki Naohiko 
Published: August 2015

Abstract
Background: Hypopharyngeal squamous cell carcinoma (HSCC) has a very poor prognosis because of its high rates of regional and distant metastasis. In spite of considerable advances in multimodality therapy, including surgery, radiotherapy and chemotherapy, the overall survival rate for patients with HSCC is only 15% - 45%. Identification of differentially expressed miRNAs and their regulated molecular targets in tumor cells might enhance our understanding of the molecular mechanisms of metastasis in human cancers. Recent our microRNA signature revealed that miR-451a was downregulated in HSCC clinical specimens, suggesting that it might be tumor suppressive microRNA. The aim of study was to investigate the functional significance of miR-451a and to identify the molecular targets regulated by miR-451a in HSCC. Method: XTT, migration, invasion assay were performed after transfection with miR-451a in FaDu (derived from a primary HSCC) and SAS (derived from a primary tongue SCC). Genome-wide gene expression analysis were used to analyze the candidate genes regulated by miR-451a. The expression levels of miR-451a and ESDN/DCBLD2 were analyzed by qRT-PCR in HSCC clinical specimens and cell lines. The luciferase reporter assay was used to identify the actual binding site of miR-451a in target gene. We performed qRT-PCR and Western blotting in two cell lines to investigate whether restoration of miR-451a altered ESDN/DCBLD2 gene and protein expression. Result: The expression levels of miR-451a was significantly lower in clinical HSCC specimens and cell lines compared with non-cancerous specimens. Restoration of miR-451a inhibited cancer cell migration and invasion in two cell lines. Genome-wide gene expression analysis of miR-451a transfectant showed that five genes (SPC25, MIF, ESDN/DCBLD2,C4orf46 and AKR1B1) were downregulated. Among these candidate genes, we focused on ESDN/DCBLD2 because it was the most significantly upregulated in cancer tissues, and was shown a negative correlation between the expression of miR-451a in Spearman's rank test. Luciferase reporter assay showed that ESDN/DCBLD2 was directly regulated by miR-451a in SAS. The mRNA and protein expression levels of ESDN/DCBLD2 were significantly repressed in miR-451a transfectant. Silencing of ESDN/DCBLD2 inhibited cell migration and invasion significantly in two cell lines. Conclusion: These data showed that tumor suppressive miR-451a inhibits cancer cell migration and invasion through regulating ESDN/DCBLD2. The identification of novel target oncogenes regulated by miR-451a might lead to a better understanding of HSCC metastasis and the development of new therapeutic strategies to treat this disease.
Citation Format: Ichiro Fukumoto, Takashi Kinoshita, Toyoyuki Hanazawa, Naoko Kikkawa, Takeshi Chiyomaru, Hideki Enokida, Noriko Yamamoto, Yusuke Goto, Rika Nishikawa, Masayuki Nakagawa, Yoshitaka Okamoto, Naohiko Seki. Identification of tumor suppressive microRNA-451a in hypopharyngeal squamous cell carcinoma based on microRNA expression signature. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3118. doi:10.1158/1538-7445.AM2015-3118