Pancreatic cancer is characterized by an extensive desmoplastic stroma, the functional relevance of which is poorly understood. Activated fibroblasts are a prevalent component of the stroma, and traditionally, these cells have been considered as a homogenous population derived from pancreatic stellate cells. In this study, we highlight a previously unappreciated heterogeneity of the fibroblast population within the stroma. In particular, a subset of stromal fibroblasts has characteristics of mesenchymal stem cells (MSCs). MSCs are present in the normal pancreas as well as in the carcinomatous pancreas (CA-MSCs). Here, we determine that CA-MSCs have increased tumor-promoting function compared with MSCs in normal pancreas. This ability to promote tumor growth is associated with CA-MSCs' unique ability to promote alternative macrophage polarization. Thus, our study identifies a previously uncharacterized cell population within the stroma and sheds light on tumor-promoting interactions between different components of the stroma. Targeting the stroma is emerging as a new paradigm in pancreatic cancer; however, efforts to that effect are hampered by our limited understanding of the nature and function of stromal components. Here, we uncover previously unappreciated heterogeneity within the stroma and identify interactions among stromal components that promote tumor growth and could be targeted therapeutically.

Adrenocortical carcinoma (ACC) is a rare but highly aggressive cancer with limited treatment options and poor survival for patients with advanced disease. An improved understanding of the transcriptional programs engaged in ACC will help direct rational, targeted therapies. Whereas activating mutations in Wnt/β-catenin signaling are frequently observed, the β-catenin-dependent transcriptional targets that promote tumor progression are poorly understood. To address this question, we analyzed ACC transcriptome data and identified a novel Wnt/β-catenin-associated signature in ACC enriched for the extracellular matrix (ECM) and predictive of poor survival. This suggested an oncogenic role for Wnt/β-catenin in regulating the ACC microenvironment. We further investigated the minor fibrillar collagen, collagen XI alpha 1 (COL11A1), and found that COL11A1 expression originates specifically from cancer cells and is strongly correlated with both Wnt/β-catenin activation and poor patient survival. Inhibition of constitutively active Wnt/β-catenin signaling in the human ACC cell line, NCI-H295R, significantly reduced the expression of COL11A1 and other ECM components and decreased cancer cell viability. To investigate the preclinical potential of Wnt/β-catenin inhibition in the adrenal microenvironment, we developed a minimally invasive orthotopic xenograft model of ACC and demonstrated that treatment with the newly developed Wnt/β-catenin:TBL1 inhibitor Tegavivint significantly reduced tumor growth. Together, our data support that the inhibition of aberrantly active Wnt/β-catenin disrupts transcriptional reprogramming of the microenvironment and reduces ACC growth and survival. Furthermore, this β-catenin-dependent oncogenic program can be therapeutically targeted with a newly developed Wnt/β-catenin inhibitor. These results show promise for the further clinical development of Wnt/β-catenin inhibitors in ACC and unveil a novel Wnt/β-catenin-regulated transcriptome.

Adrenocortical carcinoma (ACC) is a rare, but highly aggressive cancer with limited treatment options and poor survival for patients with advanced disease. Improved understanding of transcriptional programs engaged in ACC will help direct rational, targeted therapies. While activating mutations in Wnt/β-catenin signaling are frequently observed, the β-catenin-dependent transcriptional targets that promote tumor progression are poorly understood. To address this question, we used independent component analysis and identified a novel Wnt/β-catenin-associated signature in ACC predictive of poor survival. This signature was enriched for the extracellular matrix (ECM), suggesting a potential role for Wnt/β-catenin in regulating the ACC microenvironment. We further investigated the minor fibrillar collagen, collagen XI alpha 1 ( COL11A1 ), and found that COL11A1 expression strongly correlated with both Wnt/β-catenin activation and poor patient survival. Inhibition of constitutively active Wnt/β-catenin signaling in the human ACC cell line, NCI-H295R, significantly reduced expression of COL11A1 and other ECM components, and decreased viability of cancer cells in vitro . To investigate the preclinical potential of Wnt/β-catenin inhibition in vivo , we developed and characterized a novel orthotopic xenograft model utilizing minimally invasive techniques. Treatment with the newly developed Wnt/β-catenin:TBL1 inhibitor Tegavivint significantly reduced tumor growth in this preclinical model. Together, our data supports that inhibition of aberrantly active Wnt/β-catenin disrupts transcriptional reprogramming of the microenvironment and reduces ACC growth and survival. Furthermore, this β-catenin-dependent oncogenic program can be therapeutically targeted with a newly developed Wnt/β-catenin inhibitor. These results show promise for further clinical development of Wnt/β-catenin inhibitors in ACC and unveil a novel Wnt/β-catenin-regulated transcriptome. Simple Summary: Adrenocortical carcinoma (ACC) is a rare, often deadly cancer arising from the adrenal gland. Mortality associated with ACC remains unchanged over the last several decades. The rarity of ACC, an incomplete understanding of its molecular basis, and limited availability of pre-clinical models have hampered the development of new effective therapies. The present work aims to address these gaps with a focus on the Wnt/β-catenin cell signaling pathway, which is aberrantly activated in ~40% of ACC tumors. We discover a novel ECM program activated in ACC that is associated with Wnt/β-catenin and poor survival. Wnt/β-catenin inhibition disrupts expression of ECM genes and induces loss of cancer cell viability. To extend these findings, we develop a rapid orthotopic mouse model of ACC and demonstrate that disruption of the Wnt/β-catenin axis with novel small molecule inhibitor Tegavivint is a potential effective therapeutic strategy to reduce ACC tumor burden in vivo .