Human Cancer Biology Upregulated JAG1 Enhances Cell Proliferation in Adrenocortical Carcinoma

Purpose: The purpose of this study was to examine the expression andmolecular significance of JAG1, a ligand for the Notch developmental signaling pathway, in adrenocortical carcinoma (ACC). Experimental Design:Humanmicroarray data were analyzed for genes expressing ligands for theNotch pathway and validated with quantitative real-time PCR (QPCR) and immunoblots of RNA and protein, respectively. ACC cells lines were assessed for Notch pathway member expression by immunoblot, QPCR, and immunofluorescence. Notch pathway activity was also determined using a reporter gene (luciferase) activation. Proliferation experiments using a Jag1 knockdown strategy (Jag1KD) and an inhibitor of Notchdependent transcription (DNMaml) used a coculture systemwith fluorescence-activated cell-sorting (FACS) analysis. Tumor stage and mitotic rate of human ACC samples were correlated to JAG1 expression. Results: The Notch ligand JAG1 mRNA and protein are upregulated in ACCs. JAG1 upregulation can be modeled in the Y1 mouse ACC cell line that expresses Jag1, Notch receptors, downstream signaling molecules, and exhibits density-dependent Notch activation. Jag1 enhances cell proliferation through activation of canonical Notch signaling as shown through Jag1KD and coculture experiments. Inhibition of Notch signaling at the level of postreceptor signaling (DNMaml), results in similar inhibition of cell proliferation. Analysis of clinical data indicates that Jag1 expression correlates with both grade and stage of ACCs, supporting a role of JAG1-dependent Notch activation in late-stage ACCs. Conclusions: JAG1 is theprimary upregulatedNotch ligand inACCs and enhancesACCcell proliferation and tumor aggressiveness in a non–cell-autonomous manner through activation of Notch signaling in adjacent cells. Clin Cancer Res; 18(9); 2452–64. 2012 AACR.