The Intrinsic and Extrinsic Implications of RANKL/RANK Signaling in Osteosarcoma: From Tumor Initiation to Lung Metastases.

Benjamin Navet,Franck Verrecchia,Jorge Vargas-Franco,Clotilde Dumars,Dominique Heymann,Christopher Mueller,Kanji Mori,Frédéric Lézot,Marie-Françoise Heymann,Jérome Amiaud,Kosei Ando,Hideo Yagita,Régis Brion

doi:10.3390/cancers10110398

Abstract

Background: Osteosarcoma is the most frequent form of malignant pediatric bone tumor. Despite the current therapeutic arsenal, patient life-expectancy remains low if metastases are detected at the time of diagnosis, justifying research into better knowledge at all stages of osteosarcoma ontogenesis and identification of new therapeutic targets. Receptor Activator of Nuclear factor κB (RANK)expression has been reported in osteosarcoma cells, raising the question of Receptor Activator of Nuclear factor κB Ligand (RANKL)/RANK signaling implications in these tumor cells (intrinsic), in addition to previously reported implications through osteoclast activation in the tumor microenvironment (extrinsic). Methods: Based on in vitro and in vivo experimentations using human and mouse osteosarcoma cell lines, the consequences on the main cellular processes of RANK expression in osteosarcoma cells were analyzed. Results: The results revealed that RANK expression had no impact on cell proliferation and tumor growth, but stimulated cellular differentiation and, in an immune-compromised environment, increased the number of lung metastases. The analysis of RANKL, RANK and osteoprotegerin (OPG) expressions in biopsies of a cohort of patients revealed that while RANK expression in osteosarcoma cells was not significantly different between patients with or without metastases at the time of diagnosis, the OPG/RANK ratio decreased significantly. Conclusion: Altogether, these results are in favor of RANKL-RANK signaling inhibition as an adjuvant for the treatment of osteosarcoma.

Highlights

Osteosarcoma is the most common malignant pediatric primary bone tumor
Over-expressing human KHOS (HOS) cells, confirmed that RANK expression at the membrane surface had no Immuno-histologic assessment of RANK and Ki67 expressions in tumors developed from injections incidence in vivo on the proliferation of tumor cells, as evidenced by Ki67 immunostaining
Western Blot Analysis, Zymography Assay and Flow Cytometry. These are presented in the Supplementary Materials and Methods as Corresponding to the RANKL has previously been implicated in the initiation of osteosarcoma

Summary

Introduction

Osteosarcoma is the most common malignant pediatric primary bone tumor. It usually occurs in the metaphysis of the long bones in the second decade of life [1]. Despite the current therapeutic arsenal, patient life-expectancy remains low if metastases are detected at the time of diagnosis, justifying research into better knowledge at all stages of osteosarcoma ontogenesis and identification of new therapeutic targets. Receptor Activator of Nuclear factor κB (RANK)expression has been reported in osteosarcoma cells, raising the question of Receptor. Activator of Nuclear factor κB Ligand (RANKL)/RANK signaling implications in these tumor cells (intrinsic), in addition to previously reported implications through osteoclast activation in the tumor microenvironment (extrinsic). The analysis of RANKL, RANK and osteoprotegerin (OPG) expressions in biopsies of a cohort of patients revealed that while RANK expression in osteosarcoma cells was not significantly different between patients with or without metastases at the time of diagnosis, the OPG/RANK ratio decreased significantly

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