Open Access

ARTICLE

DKK3 Overexpression Increases the Malignant Properties of Head and Neck Squamous Cell Carcinoma Cells

Naoki Katase^*†, Shin-Ichiro Nishimatsu^†‡, Akira Yamauchi^§, Masahiro Yamamura^¶, Kumiko Terada^†‡, Masumi Itadani^§, Naoko Okada^¶#, Nur Mohammad Monsur Hassan^**, Hitoshi Nagatsuka^††, Tohru Ikeda^*‡‡, Tsutomu Nohno^†, Shuichi Fujita^*

* Department of Oral Pathology and Bone Metabolism, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
† Department of Molecular and Developmental Biology, Kawasaki Medical School, Kurashiki, Okayama, Japan
‡ Department of Natural Sciences, Kawasaki Medical School, Kurashiki, Okayama, Japan
§ Department of Biochemistry, Kawasaki Medical School, Kurashiki, Okayama, Japan
¶ Department of Clinical Oncology, Kawasaki Medical School, Kurashiki, Okayama, Japan
# Department of Surgery, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
** School of Dentistry and Health Sciences, Charles Sturt University, Orange, New South Wales, Australia
†† Department of Oral Pathology and Medicine, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
‡‡ Department of Oral Pathology, Tokyo Medical and Dental University, Tokyo, Japan

Oncology Research 2018, 26(1), 45-58. https://doi.org/10.3727/096504017X14926874596386

Abstract

DKK3, a member of the dickkopf Wnt signaling pathway inhibitor family, is believed to be a tumor suppressor because of its reduced expression in cancer cells. However, our previous studies have revealed that DKK3 expression is predominantly observed in head and neck/oral squamous cell carcinoma (HNSCC/OSCC). Interestingly, HNSCC/OSCC patients with DKK3 expression showed a high rate of metastasis and poorer survival, and siRNA-mediated knockdown of DKK3 in HNSCC-derived cancer cell lines resulted in reduced cellular migration and invasion. From these data, it was hypothesized that DKK3 might exert an oncogenic function specific to HNSCC. In the present research, the DKK3 overexpression model was established, and its influences were investigated, together with molecular mechanism studies. The DKK3 expression profile in cancer cell lines was investigated, including HNSCC/OSCC, esophageal, gastric, colorectal, pancreatic, prostatic, and lung cancers. DKK3 overexpression was performed in HNSCC-derived cells by transfection of expression plasmid. The effects of DKK3 overexpression were assessed on cellular proliferation, migration, invasion, and in vivo tumor growth. The molecular mechanism of DKK3 overexpression was investigated by Western blotting and microarray analysis. DKK3 overexpression significantly elevated cellular proliferation, migration, and invasion, as well as increased mRNA expression of cyclin D1 and c-myc. However, reporter assays did not show TCF/LEF activation, suggesting that the increased malignant property of cancer cells was not driven by the Wnt/β-catenin pathway. For the investigation of the pathways/molecules in DKK3-mediated signals, the Western blot analyses revealed that phosphorylation of Akt (S473) and c-Jun (Ser63) was elevated. The application of a PI3K kinase inhibitor, LY294002, on HSC-3 DKK3 cells significantly decreased tumor cell proliferation, migration, and invasion. From these results, we demonstrated that DKK3 might contribute to cellular proliferation, invasion, migration, and tumor cell survival in HNSCC cells through a mechanism other than the canonical Wnt signaling pathway, which might be attributed to PI3K–Akt signaling.

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