The posterior HOXD locus: Its contribution to phenotype and malignancy of Ewing sarcoma.

Kristina Von Heyking,Miriam Ertl,Julia Calzada-Wack,Frauke Neff,Günther H.S Richter,Oxana Schmidt,Stefan Burdach,Elizabeth R Lawlor,Laura Roth

doi:10.18632/oncotarget.9702

Abstract

Microarray analysis revealed genes of the posterior HOXD locus normally involved in bone formation to be over-expressed in primary Ewing sarcoma (ES). The expression of posterior HOXD genes was not influenced via ES pathognomonic EWS/ETS translocations. However, knock down of the dickkopf WNT signaling pathway inhibitor 2 (DKK2) resulted in a significant suppression of HOXD10, HOXD11 and HOXD13 while over-expression of DKK2 and stimulation with factors of the WNT signaling pathway such as WNT3a, WNT5a or WNT11 increased their expression. RNA interference demonstrated that individual HOXD genes promoted chondrogenic differentiation potential, and enhanced expression of the bone-associated gene RUNX2. Furthermore, HOXD genes increased the level of the osteoblast- and osteoclast-specific genes, osteocalcin (BGLAP) and platelet-derived growth factor beta polypeptide (PDGFB), and may further regulate endochondral bone development via induction of parathyroid hormone-like hormone (PTHLH). Additionally, HOXD11 and HOXD13 promoted contact independent growth of ES, while in vitro invasiveness of ES lines was enhanced by all 3 HOXD genes investigated and seemed mediated via matrix metallopeptidase 1 (MMP1). Consequently, knock down of HOXD11 or HOXD13 significantly suppressed lung metastasis in a xeno-transplant model in immune deficient mice, providing overall evidence that posterior HOXD genes promote clonogenicity and metastatic potential of ES.

Highlights

Ewing sarcomas (ES) are bone or soft tissue tumors with a prominent stemness phenotype, mostly occurring in children and adolescents
First we recognized a low level of expression of HOXD10, HOXD11 and HOXD13 in neural crest-derived mesenchymal stem cells (NCMSC) as well as in undifferentiated, freshly isolated neural crest stem cells (NCSC) or adult bone marrow derived MSC (BM-MSC)
We observed genes such as HOXD10, HOXD11 and HOXD13 normally involved in bone formation and ossification pattern of bones [22], to be www.impactjournals.com/oncotarget significantly over-expressed in ES

Summary

Introduction

Ewing sarcomas (ES) are bone or soft tissue tumors with a prominent stemness phenotype, mostly occurring in children and adolescents. We demonstrated the pro-metastatic gene dickkopf WNT signaling pathway inhibitor 2 (DKK2) to be critical for malignant growth of ES [5]. It can act as either an agonist or antagonist of WNT/β-catenin signaling, depending on the cellular context and the presence of the co-factor Kremen 2 [12,13,14]. DKK2 promotes bone infiltration and osteolysis in vivo and subsequent analyses defined DKK2 as a key factor in osteotropic malignancy [5]

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Conclusion