Data from Twist1-Induced Epithelial Dissemination Requires Prkd1 Signaling

Abstract

<div>Abstract<p>Dissemination is an essential early step in metastasis but its molecular basis remains incompletely understood. To define the essential targetable effectors of this process, we developed a 3D mammary epithelial culture model, in which dissemination is induced by overexpression of the transcription factor Twist1. Transcriptomic analysis and ChIP-PCR together demonstrated that protein kinase D1 (Prkd1) is a direct transcriptional target of Twist1 and is not expressed in the normal mammary epithelium. Pharmacologic and genetic inhibition of Prkd1 in the Twist1-induced dissemination model demonstrated that Prkd1 was required for cells to initiate extracellular matrix (ECM)–directed protrusions, release from the epithelium, and migrate through the ECM. Antibody-based protein profiling revealed that Prkd1 induced broad phosphorylation changes, including an inactivating phosphorylation of β-catenin and two microtubule depolymerizing phosphorylations of Tau, potentially explaining the release of cell–cell contacts and persistent activation of Prkd1. In patients with breast cancer, <i>TWIST1</i> and <i>PRKD1</i> expression correlated with metastatic recurrence, particularly in basal breast cancer. Prkd1 knockdown was sufficient to block dissemination of both murine and human mammary tumor organoids. Finally, <i>Prkd1</i> knockdown <i>in vivo</i> blocked primary tumor invasion and distant metastasis in a mouse model of basal breast cancer. Collectively, these data identify Prkd1 as a novel and targetable signaling node downstream of Twist1 that is required for epithelial invasion and dissemination.</p>Significance:<p>Twist1 is a known regulator of metastatic cell behaviors but not directly targetable. This study provides a molecular explanation for how Twist1-induced dissemination works and demonstrates that it can be targeted.</p></div>