Ewing sarcoma (ES), an osteogenic malignancy that mainly affects children and young adults, is characterized by early metastasis to lung and bone. Microarray analysis revealed genes of the posterior HoxD locus to be clearly over-expressed in primary ES. Especially, genes such as HOXD10, HOXD11 and HOXD13 normally involved in bone formation and ossification pattern of bones are significantly over-expressed in ES. The expression of HOXD10, HOXD11 or HOXD13 seems not to be influenced via ES pathognomonic ews/ets translocations, since RNA interference of EWS-FLI1 or its over-expression in mesenchymal stem cells did not influence posterior HOXD expression. However, RNA knock down of the dickkopf 2 homolog DKK2, a canonical WNT/beta-catenin agonist and critical mediator of osteolytic tumor growth in ES (Hauer et al., 2013) resulted in a significant suppression of HOXD11 and HOXD13 expression. Subsequently, RNA interference of individual HoxD genes demonstrated posterior HOXD genes to suppress neuronal differentiation potential of ES. Furthermore, HOXD10, HOXD11 and HOXD13 were found to be critical for chondrogenic, however not for osteogenic differentiation, but promote the expression of bone-associated genes such as RUNX2. HOXD11 and HOXD13 further promote in vitro proliferation and contact independent growth of ES. Similarly, in vitro invasiveness of ES lines was dependent on HOXD10, HOXD11 as well as HOXD13 and seemed mediated via Matrix Metalloproteinase 1 (MMP1), since down-regulation of individual HoxD genes likewise resulted in a suppression of MMP1 expression. In line with these observations, knock down of HOXD11 or HOXD13 significantly suppressed metastasis in a xeno-transplant model in immune deficient Rag2-/-gammaC-/- mice. These data overall provide evidence that posterior HOXD genes are critical mediators of the differentiation phenotype of ES concurrently promoting their metastasis potential.

Reference:

Hauer K, Julia Calzada-Wack J, Steiger K, Grunewald TG, Baumhoer D, Plehm S, Buch T, Prazeres da Costa O, Esposito I, Burdach S, Richter GHS (2013). DKK2 mediates osteolysis, invasiveness and metastatic spread in Ewing sarcoma. Cancer Res. 73(2): 967-77.

Citation Format: Kristina von Heyking, Laura Roth, Miriam Ertl, Stefan Burdach, Günther H. Richter. The HoxD locus: Its contribution to the osteogenic phenotype and malignancy of Ewing sarcoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3106. doi:10.1158/1538-7445.AM2014-3106