Abstract IA009: Dact1 biomolecular condensates mediate TGFβ-Wnt crosstalk in bone metastasis

Abstract

TGF-β signaling is a well established pathway driving different steps of bone metastasis progression. Wnt signaling plays a dichotomous role in bone metastasis, with recent studies showing that inhibition of Wnt signaling by DKK1 is critical for avoidance of immune clearance of dormant bone micrometastasis and activation of osteoclast activity during osteolytic outgrowth. On the other hand, engagement of bone vascular E-selectin by disseminated tumor cells (DTCs) promotes metastatic colonization in bone by activating Wnt signaling to enhance tumor initiating activity of DTCs. These findings imply a complex interplay between TGF-b and Wnt signaling in different stages of bone metastasis development that allows efficient colonization, dormancy and outgrowth of secondary tumors in bone. What mediates the dynamic transition of TGF-β and Wnt signaling states during metastasis is currently unknown. Here we present data describing a novel phase-separated organelle organized by bone metastasis promoting protein Dact1 which mediates the crosstalk of TGF-β and Wnt signaling. We found that Dact1 is induced by TGF-β signaling and forms dynamically regulated biomolecular condensates that suppress Wnt signaling. A high level of Dact1 expression is associated with an elevated risk of bone metastasis in breast cancer patients and Dact1 is necessary for bone metastasis in mouse models of breast and prostate cancers. Citation Format: Yibin Kang. Dact1 biomolecular condensates mediate TGFβ-Wnt crosstalk in bone metastasis [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr IA009.