LAUSR

Osteosarcoma is a pediatric bone cancer that has no targeted therapy and has had no treatment advances for the last three decades. Osteosarcoma frequently metastasizes to the lungs, reducing patient survival with metastatic disease to 20% after 5 years. The goal of this study is to describe the function of WNT5B and its signaling pathway in osteosarcoma stem cells, metastasis and chemoresistance and its potential as a therapeutic target. Using RNA sequencing from publicly available datasets and immunohistochemistry on tumor microarrays, we reveal that WNT5B is the most expressed WNT in osteosarcoma patients and correlates with both metastasis and survival. Osteosarcoma is thought to result from a block in differentiation, and based on WNT5B’s role in inhibiting osteoblast differentiation of mesenchymal stem cells from normal bone, we hypothesized a role for WNT5B in osteosarcoma stem cells. In spheroids, we show that both protein and mRNA levels of WNT5B are enhanced in the stem cell population compared to adherent cells. We found that WNT5B upregulates the expression of the stemness gene SOX2 and directs stemness phenotypes, such as sphere forming efficiency, proliferation and migration. We show a reduction in sphere forming efficiency with 143B-WNT5B-knockdown cells compared to parental control cells which can be rescued with re-introduction of WNT5B. Additionally, we show that WNT5B drives proliferation and migration of osteosarcoma stem cells through increasing sphere size and capability to migrate on collagen matrix. Further, WNT5B enhances osteosarcoma chemoresistance to methotrexate. Through revealing a novel role for WNT5B in osteosarcoma cancer stem cells and therapy resistance, we present the WNT5B pathway as a candidate for therapeutically targeting osteosarcoma stem cells in patients. Citation Format: Rachel S. Perkins, Sarocha Suthon, Gustavo A. Miranda-Carboni, Susan A. Krum. WNT5B drives osteosarcoma stemness, metastasis and chemoresistance. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3527.