Comparison of the Anticancer Effects of a Complementary Peptide for Dickkopf WNT Signaling Pathway Inhibitor 3 (DKK3) With Conventional Anticancer Drugs in the Treatment of Oral Squamous Cell Carcinoma: A Pilot Study

Introduction Oral squamous cell carcinoma (OSCC), which is the most common cancer type in head and neck cancers, remains a serious health problem because of its high mortality. Treatment of OSCC is mainly performed with a combination of surgery and anticancer agents. However, despite the recent development of anticancer agents, the clinical outcome of OSCC has yet to be improved. Therefore, it is required to develop a new anticancer agent that targets a specific molecular target in OSCC. In this context, we identified DKK3 (Dickkopf WNT signaling pathway inhibitor 3) as a candidate for such targets. Our previous studies have demonstrated that DKK3 expression is observed in certain cancers, such as OSCC and esophageal squamous cell carcinoma, and DKK3 increases tumor malignancy through Akt activation in such cancers, while its expression is lost in many kinds of malignancies. Recently, we developed a complementary peptide targeting DKK3 (DKK3-CP) as a new anticancer substance and reported that DKK3-CP could significantly suppress cancer cell growth, migration, and invasion in OSCC-derived cells. In the present research, we compared the anticancer effects of the peptide with conventional anticancer agents as a pilot study. Methods OSCC-derived cell lines (HSC-3 and SAS) were treated with cisplatin (CDDP), cetuximab (Cmab), or DKK3-CP at various concentrations. As a control, saline was added to the cells, reproducing the no-treatment condition. The effects on cellular viability, cellular migration, and invasion were investigated. The differences within the groups were compared, and the differences between the groups at certain concentrations were compared by one-way ANOVA with Tukey's multiple comparisons. An orthotopic xenograft model was used for the evaluation of systemic administration of the agents. HSC-3 cells were orthotopically transplanted into the tongue of the mice, and after confirming tumor formation, anticancer agents were administered intraperitoneally. Saline was used for control to reproduce the no-treatment condition. Then, the animals were sacrificed and evaluated histologically. The Ki-67 index was also calculated. Results DKK3-CP showed significant suppressive effects for cell viability at 10 µM in both cell lines. In HSC-3 cells, there was no significant difference in the suppressive effect on cell viability among the anticancer agents, while the suppressive effects of DKK3-CP were significantly higher than that of CDDP in SAS cells. Migration and invasion assays revealed that DKK3-CP showed significant suppression of migration and invasion at 500 nM in both cell lines, and the effect was significantly higher than that of CDDP and Cmab. Systemic administration of DKK3-CP did not show weight loss in the mice. Histological evaluation revealed that all anticancer agents significantly decreased the Ki-67 index, although no significant difference was observed between those groups. Conclusion DKK3-CP showed tumor suppression effects comparable or superior to those of CDDP and Cmab. Although this is a pilot study and ideal concentration and administration methods of the agents, combination use of DKK3-CP with conventional agents, appropriate evaluation of side effects, and assessment of the long-term effects of administration should be resolved by further investigations, we showed the possibility of clinical use of DKK3-CP for the first time.