Abstract 4352: Tumor suppressive microRNAs (miR-29s/miR-218) regulate laminin-integrin signaling in head and neck squamous cell carcinoma
Authors: Kinoshita Takashi , Nohata Nijiro , Hanazawa Toyoyuki , Kikkawa Naoko , Yamamoto Noriko , Yoshino Hirofumi , Itesako Toshihiko , Enokida Hideki , Nakagawa Masayuki , Okamoto Yoshitaka , Seki Naohiko 
Published: May 2015

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy worldwide. In spite of advances in the therapy, the overall five-year survival rate for patients with HNSCC is around 40%. Distant metastasis after conventional therapy appears to be a major contributing factor for the restricted survival of HNSCC patients. Understanding the molecular pathways of HNSCC metastasis would help to improve diagnosis, approaches to therapy and prevention of the disease. Our recent study of microRNA (miRNA) expression signature of HNSCC has revealed that microRNA-29s (miR-29s) and microRNA-218 (miR-218) were significantly downregulated in cancer tissues, suggesting that these miRNAs are candidate of tumor suppressors. The aim of the study was to investigate the functional significance of miR-29s and miR-218 in HNSCC cells and to identify novel metastatic pathways regulated by these miRNAs.

METHODS: Cell proliferation, migration and invasion assays were performed to investigate the functional significance of miR-29s (miR-29a/b/c) and miR-218 and these target genes in HNSCC cell lines (FaDu and SAS). Cells were transfected with mature miRNAs or siRNAs by reverse transfection methods. Genome-wide gene expression data and in silico analysis were used to identify the molecular pathways and putative targets regulated by miR-29s or miR-218. The luciferase reporter assays were used to identify the actual binding sites of target genes regulated by these miRNAs.

RESULTS: Restoration of miR-29s or miR-218 in HNSCC cells revealed that these miRNAs significantly inhibited cancer cell migration and invasion. Genome-wide gene expression data and in silico analysis showed that focal adhesion pathway was a promising candidate of miR-29s and miR-218 target pathway. Interestingly, interaction between laminin-332 (LAMA3, LAMB3 and LAMC2) and α6β4 integrin (ITGA6 and ITGB4) triggers a number of signalling cascades, promoting both cell migration and cancer cell survival. Luciferase reporter assays showed that LAMC2 and ITGA6 were directly regulated by miR-29s. Also, LAMB3 was regulated by miR-218. Silencing of LAMB3, LAMC2 and ITGA6 genes significantly inhibited cell migration and invasion in cancer cells.

CONCLUSIONS: Downregulation of miR-29s and miR-218 were frequent events in HNSCC. These miRNAs acted as tumour suppressors and directly targeted laminin-integrin signalling. Recognition of tumour suppressive miRNA-mediated cancer pathways provides new insights into the potential mechanisms of HNSCC oncogenesis and metastasis and suggests novel therapeutic strategies for the disease.

Citation Format: Takashi Kinoshita, Nijiro Nohata, Toyoyuki Hanazawa, Naoko Kikkawa, Noriko Yamamoto, Hirofumi Yoshino, Toshihiko Itesako, Hideki Enokida, Masayuki Nakagawa, Yoshitaka Okamoto, Naohiko Seki. Tumor suppressive microRNAs (miR-29s/miR-218) regulate laminin-integrin signaling in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4352. doi:10.1158/1538-7445.AM2014-4352