Osteosarcoma (OS) is a highly metastatic form of bone cancer in adolescents and young adults which is resistant to existing treatments. Development of an effective therapy has been hindered by very limited understanding of the mechanisms of osteosarcomagenesis. Here, we used genetically engineered mice to investigate the effects of deleting the tumor suppressor Wwox selectively in either osteoblast progenitors or mature osteoblasts. Mice with conditional deletion of Wwox in pre-osteoblasts (WwoxΔosx1) displayed a severe inhibition of osteogenesis accompanied by p53 upregulation, effects that were not observed in mice lacking Wwox in mature osteoblasts. Deletion of p53 in WwoxΔosx1 mice rescued the osteogenic defect. In addition, the Wwox;p53Δosx1 double knockout mice developed poorly differentiated osteosarcomas that resemble human OS in histology, location, metastatic behavior, and gene expression. Strikingly, the development of osteosarcomas in these mice was greatly accelerated compared to mice lacking p53 only. In contrast, combined WWOX and p53 inactivation in mature osteoblasts did not accelerate osteosarcomagenesis compared to p53 inactivation alone. These findings provide evidence that a WWOX-p53 network regulates normal bone formation and that disruption of this network in osteoprogenitors results in accelerated OS. The Wwox;p53Δosx1 double knockout establishes a new OS model with significant advancement over existing models.

Pancreatic cancer is one of the most lethal cancers, owing to its late diagnosis and resistance to chemotherapy. The tumor suppressor WW domain-containing oxidoreductase (WWOX), one of the most active fragile sites in the human genome (FRA16D), is commonly altered in pancreatic cancer. However, the direct contribution of WWOX loss to pancreatic cancer development and progression remains largely unknown. Here, we report that combined conditional deletion of Wwox and activation of KRasG12D in Ptf1a-CreER-expressing mice results in accelerated formation of precursor lesions and pancreatic carcinoma. At the molecular level, we found that WWOX physically interacts with SMAD3 and BMP2, which are known activators of the TGF-β signaling pathway. In the absence of WWOX, TGFβ/BMPs signaling was enhanced, leading to increased macrophage infiltration and enhanced cancer stemness. Finally, overexpression of WWOX in patient-derived xenografts led to diminished aggressiveness both in vitro and in vivo. Overall, our findings reveal an essential role of WWOX in pancreatic cancer development and progression and underscore its role as a bona fide tumor suppressor.

<div>Abstract<p>Osteosarcoma is a highly metastatic form of bone cancer in adolescents and young adults that is resistant to existing treatments. Development of an effective therapy has been hindered by very limited understanding of the mechanisms of osteosarcomagenesis. Here, we used genetically engineered mice to investigate the effects of deleting the tumor suppressor <i>Wwox</i> selectively in either osteoblast progenitors or mature osteoblasts. Mice with conditional deletion of <i>Wwox</i> in preosteoblasts (<i>Wwox^Δosx1</i>) displayed a severe inhibition of osteogenesis accompanied by p53 upregulation, effects that were not observed in mice lacking <i>Wwox</i> in mature osteoblasts. Deletion of <i>p53</i> in <i>Wwox^Δosx1</i> mice rescued the osteogenic defect. In addition, the <i>Wwox;p53^Δosx1</i> double knockout mice developed poorly differentiated osteosarcomas that resemble human osteosarcoma in histology, location, metastatic behavior, and gene expression. Strikingly, the development of osteosarcomas in these mice was greatly accelerated compared with mice lacking p53 only. In contrast, combined WWOX and p53 inactivation in mature osteoblasts did not accelerate osteosarcomagenesis compared with p53 inactivation alone. These findings provide evidence that a WWOX–p53 network regulates normal bone formation and that disruption of this network in osteoprogenitors results in accelerated osteosarcoma. The <i>Wwox;p53^Δosx1</i> double knockout establishes a new osteosarcoma model with significant advancement over existing models. <i>Cancer Res; 76(20); 6107–17. ©2016 AACR</i>.</p></div>

<p>Supplementary Methods, Figures and Tables</p>

<p>Supplementary Methods, Figures and Tables</p>