Abstract 1147: CDCA5 is a novel therapeutic target molecule in oral squamous cell carcinoma

Molecularly targeted drugs are used in the treatment of a variety of malignant tumors, but this approach to developing novel therapies for oral squamous cell carcinoma (OSCC) has lagged behind the progress seen for other cancers. We attempted to find appropriate molecular targets for OSCC, and identified cell division cycle associated 5 (CDCA5) as a cancer-related gene which was overexpressed in 9 human OSCC cells tested by microarray analysis. CDCA5 was initially identified as a substrate of anaphase-promoting complex and as a regulator of sister chromatid cohesion in HeLa cells. In addition, CDCA5 has been reported to be overexpressed in the majority of human lung cancers and urothelial cancers and to play a critical role in carcinogenesis. However, function of CDCA5 in OSCC remains still unknown. In this study, we investigated the expression and function of CDCA5 in OSCC. First, we confirmed the expression level of CDCA5 in 4 human OSCC cell lines and an immortalized non-neoplastic human keratinocyte cell line, HaCaT, by quantitative RT-PCR (qRT-PCR) and Western blotting. The expression levels of CDCA5 mRNA and protein were markedly elevated in all human OSCC cell lines compared to HaCaT cells. Next, we tested the effect of synthetic small interfering RNAs specific for CDCA5 (siCDCA5) on the growth of human OSCC cells. The RNA interference effect of siCDCA5 was confirmed by Western blotting. Transfection of siCDCA5 suppressed the expression of its target protein in all types of cells. The growth inhibitory effect of siCDCA5 in OSCC cells was evaluated by WST-8 assay. The Knockdown of CDCA5 significantly inhibited the growth of OSCC cells in vitro. Subsequently, we assessed the effect of siCDCA5 on the in vivo growth of human OSCC cells, green fluorescent protein (GFP)-SAS. We administered siCDCA5/atelocollagen complexes into the subcutaneous spaces around the xenograft tumors every 3 days. We found that these complexes significantly reduced the size of subcutaneously xenografted GFP-SAS tumors, compared to the control group treated with synthetic siRNA specific for GFP (siGFP)/atelocollagen complexes. Next, we analyzed the influence of siCDCA5 on the cell cycle of OSCC cells by flow cytometry. Suppression of CDCA5 resulted in the decrease in percentage of cells in G0/G1 phase and the increase in G2 phase. This indicated that the anti-proliferative effect of siCDCA5 was due to G2 arrest. Finally, we investigated the clinical significance of CDCA5 expression in OSCC. We examined the expression of CDCA5 in OSCC tissues by immunohistochemistry, and then found a significant association between CDCA5 expression levels and overall survival. These results suggest that CDCA5 functions as a critical gene supporting OSCC progression and that targeting CDCA5 may be a useful therapeutic strategy for OSCC. Citation Format: Norihiko Tokuzen, Koh-ichi Nakashiro, Hiroshi Tanaka, Kazuki Iwamoto, Hitoshi Akiyama, Hiroyuki Hamakawa. CDCA5 is a novel therapeutic target molecule in oral squamous cell carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1147.