S-adenosylmethionine blocks osteosarcoma cells proliferation and invasion in vitro and tumor metastasis in vivo: therapeutic and diagnostic clinical applications.

Surabhi Parashar,Moshe Szyf,Zahid Hussain,Haseeb Ahmed Khan,Shafaat A Rabbani,Ani Arakelian,David Cheishvili,Imrana Tanvir

doi:10.1002/cam4.386

Abstract

Osteosarcoma (OS) is an aggressive and highly metastatic form of primary bone cancer affecting young children and adults. Previous studies have shown that hypomethylation of critical genes is driving metastasis. Here, we examine whether hypermethylation treatment can block OS growth and pulmonary metastasis. Human OS cells LM-7 and MG-63 were treated with the ubiquitous methyl donor S-adenosylmethionine (SAM) or its inactive analog S-adenosylhomocystine (SAH) as control. Treatment with SAM resulted in a dose-dependent inhibition of tumor cell proliferation, invasion, cell migration, and cell cycle characteristics. Inoculation of cells treated with 150 μmol/L SAM for 6 days into tibia or via intravenous route into Fox Chase severe combined immune deficient (SCID) mice resulted in the development of significantly smaller skeletal lesions and a marked reduction in pulmonary metastasis as compared to control groups. Epigenome wide association studies (EWAS) showed differential methylation of several genes involved in OS progression and prominent signaling pathways implicated in bone formation, wound healing, and tumor progression in SAM-treated LM-7 cells. Real-time polymerase chain reaction (qPCR) analysis confirmed that SAM treatment blocked the expression of several prometastatic genes and additional genes identified by EWAS analysis. Immunohistochemical analysis of normal human bone and tissue array from OS patients showed significantly high levels of expression of one of the identified gene platelet-derived growth factor alpha (PDGFA). These studies provide a possible mechanism for the role of DNA demethylation in the development and metastasis of OS to provide a rationale for the use of hypermethylation therapy for OS patients and identify new targets for monitoring OS development and progression.

Highlights

Osteosarcoma (OS) is third most common childhood cancer affecting long bones accounting for 20% of all bone cancers [1, 2]
We have previously shown that SAM treatment causes hypermethylation of urokinase type plasminogen activator in breast cancer cells and the knock down of methyl DNA-binding protein 2 resulting in silencing of the uPA gene by reverting the hypomethylated state of this gene in breast and prostate cancer cells [24, 25]
In the majority of studies, to date focus has been on understanding the hypermethylation of tumor suppressor genes and targeting these processes therapeutically, whereas little attention was paid to the potential role of hypomethylation of prometastatic genes

Summary

Introduction

Osteosarcoma (OS) is third most common childhood cancer affecting long bones accounting for 20% of all bone cancers [1, 2]. While recent advances in neoadjuvant chemotherapy and surgery has improved the long-term survival rates of patients without metastatic disease, patients who exhibit metastasis continue to respond poorly to chemotherapy and have poor prognosis [5,6,7,8]. This poor response to therapy is associated with a high incidence of drug toxicity and efforts to change chemotherapeutic regimen has yielded limited success with no improvement in outcome [9]. It is crucial to understand the molecular mechanism of tumor metastasis for early diagnosis, predict prognosis, and identify new targets for the development of more effective therapeutic strategies

Methods

Results

Conclusion