Down-regulation of Skp2 expression inhibits invasion and lung metastasis in osteosarcoma

Yidan Zhang,David S Geller,Edmond F O’Donnell,Xiuquan Du,Rui Yang,Tingting Ren,Deyou Zheng,Sajida Piperdi,Jonathan Gill,Yang Liu,Jichuan Wang,Wendong Zhang,Michael Roth,Xiaolin Zi,Yoav S Zvi ,Richard Görlick ,B Batko ,Kenji Satô ,Pratistha Koirala,Jinghang Zhang,Nikolas Zaphiros,Bang H Hoang

doi:10.1038/s41598-018-32428-9

Abstract

Osteosarcoma (OS), the most common primary cancer of bone, exhibits a high propensity for local invasion and distant metastasis. This study sought to elucidate the role of S phase kinase-associated protein (Skp2) in osteosarcoma invasion and metastasis and to explore flavokawain A (FKA), a natural chalcone from kava extract, as a potential Skp2 targeting agent for preventing osteosarcoma progression. Skp2 was found to be overexpressed in multiple osteosarcoma cell lines, including 5 standard and 8 primary patient-derived cell lines. Patients whose tumors expressed high levels of Skp2 sustained a significantly worse metastasis-free (p = 0.0095) and overall survival (p = 0.0013) than those with low Skp2. Skp2 knockdown markedly reduced in vitro cellular invasion and in vivo lung metastasis in an orthotopic mouse model of osteosarcoma. Similar to Skp2 knockdown, treatment with FKA also reduced Skp2 expression in osteosarcoma cell lines and blocked the invasion of osteosarcoma cells in vitro and lung metastasis in vivo. Together, our findings suggest that Skp2 is a promising therapeutic target in osteosarcoma, and that FKA may be an effective Skp2-targeted therapy to reduce osteosarcoma metastasis.

Highlights

Osteosarcoma is the most common primary malignant bone tumor that often occurs in children and young adults[1,2,3]
Since p27 has been reported as a substrate for Skp2-mediated ubiquitination, we examined the expression of p27 in osteosarcoma cell lines[28]
Western blot analysis demonstrated that flavokawain A (FKA) suppresses Skp[2] at 6 hours, while no significant apoptosis by PARP cleavage was observed until 12 to 24 hours (Supplementary Fig. 6). These findings suggested that FKA-mediated suppression of Skp[2] is more likely to be the cause than the consequence of apoptosis

Summary

Introduction

Osteosarcoma is the most common primary malignant bone tumor that often occurs in children and young adults[1,2,3]. Gastric, and esophageal cancers, higher levels of Skp[2] are associated with tumor metastasis and poorer survival, while down-regulation of Skp[2] leads to inhibition of tumor growth and metastasis[12,14,16]. Given our recent findings that FKA inhibits prostate cancer by degrading Skp[2], we aimed to evaluate whether FKA has a therapeutic role in osteosarcoma by suppressing Skp[2]. We aimed to explore the potential role for FKA as a Skp2-targeted agent in preventing osteosarcoma progression. We found that depletion of Skp[2] by short hairpin RNA (shRNA) or by FKA results in down-regulation of Skp[2] and several of its targets, leading to inhibition of invasion and metastasis in osteosarcoma

Objectives

Methods

Results

Conclusion