Heather A. Hartmann

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are toxicants of emerging concern due to their abundance in the environment and potential adverse health effects. PFAS are used in waterproof clothing, makeup, carpets, upholstery, cookware, and fast-food containers. Due to their universal use, they are found globally in the water supply. In fact, these organic pollutants have been found in the blood of 98% of Americans and have been linked to disruption in thyroid hormone biosynthesis and availability. Moreover, several studies have shown that cancer patients may have an increase in PFAS levels and that PFAS exposure increases thyroid cancer risk. Demonstration of concrete PFAS-mediated alterations in thyroid histology and function could have far-reaching implications. To understand the effects of PFAS on thyroid histology, we used a PFAS feeding model with a combination of 3 PFAS compounds (PFOS, PFOA, and GenX) vs control. Mice receiving PFAS treatment showed altered thyroid architecture and cell structure following PFAS exposure. RNA-sequencing data revealed several alterations in gene expression and multiple signaling pathways were dysregulated. Understanding the role of PFAS-mediated toxicity in the thyroid is critically important for the prevention of thyroid disease in the general population.

Tenascin-C (TNC) is a secreted extracellular matrix protein that is highly expressed during embryonic development and re-expressed during wound healing, inflammation, and neoplasia. Studies in developmental models suggest that TNC may regulate the Wnt signaling pathway. Our laboratory has shown high levels of Wnt signaling and TNC expression in anaplastic thyroid cancer (ATC), a highly lethal cancer with an abysmal approximately 3- to 5-month median survival. Here, we investigated the role of TNC in facilitating ligand-dependent Wnt signaling in thyroid cancer. We used bulk RNA-sequencing from 3 independent multi-institutional thyroid cancer patient cohorts. TNC expression was spatially localized in patient tumors with RNA in situ hybridization. The role of TNC was investigated in vitro using Wnt reporter assays and in vivo with a NOD.PrkdcscidIl2rg–/− mouse ATC xenograft tumor model. TNC expression was associated with aggressive thyroid cancer behavior, including anaplastic histology, extrathyroidal extension, and metastasis. Spatial localization of TNC in patient tissue demonstrated a dramatic increase in expression within cancer cells along the invasive edge, adjacent to Wnt ligand–producing fibroblasts. TNC expression was also increased in areas of intravascular invasion. In vitro, TNC bound Wnt ligands and potentiated Wnt signaling. Finally, in an ATC mouse model, TNC increased Wnt signaling, tumor burden, invasion, and metastasis. Altogether, TNC potentiated ligand-driven Wnt signaling and promotes cancer cell invasion and metastasis in a mouse model of thyroid cancer. Understanding the role of TNC and its interaction with Wnt ligands could lead to the development of novel biomarkers and targeted therapeutics for thyroid cancer.

Thyroid cancer progression from curable well-differentiated thyroid carcinoma to highly lethal anaplastic thyroid carcinoma is distinguished by tumor cell de-differentiation and recruitment of a robust stromal infiltrate. Combining an integrated thyroid cancer single-cell sequencing atlas with spatial transcriptomics and bulk RNA-sequencing, we define stromal cell subpopulations and tumor-stromal cross-talk occurring across the histologic and mutational spectrum of thyroid cancer. We identify distinct inflammatory and myofibroblastic cancer-associated fibroblast (iCAF and myCAF) populations and perivascular-like populations. The myCAF population is only found in malignant samples and is associated with tumor cell invasion, BRAF ^V600E mutation, lymph node metastasis, and disease progression. Tumor-adjacent myCAFs abut invasive tumor cells with a partial epithelial-to-mesenchymal phenotype. Tumor-distant iCAFs infiltrate inflammatory autoimmune thyroid lesions and anaplastic tumors. In summary, our study provides an integrated atlas of thyroid cancer fibroblast subtypes and spatial characterization at sites of tumor invasion and de-differentiation, defining the stromal reorganization central to disease progression.

Signaling through the Wnt/β‐catenin pathway is relayed through three multiprotein complexes: (1) the membrane‐associated signalosome, which includes the activated Wnt receptors, (2) the cytoplasmic destruction complex that regulates turnover of the transcriptional coactivator β‐catenin, and (3) the nuclear enhanceosome that mediates pathway‐specific transcription. Recent discoveries have revealed that Wnt receptor activities are tightly regulated to maintain proper tissue homeostasis and that aberrant receptor upregulation enhances Wnt signaling to drive tumorigenesis, highlighting the importance of signalosome control. These studies have focused on the detailed process by which Wnt ligands engage their coreceptors, LRP5/6 and Frizzled. However, the components that constitute the signalosome and the regulation of their assembly remain undefined. In this review, we discuss Wnt/β‐catenin signalosome composition and the mechanisms that regulate signalosome assembly, including the role of biomolecular condensates and ubiquitylation. We also summarize the evidence for the presence of Wnt ligand‐independent signalosome formation.

Tenascin-C (TNC) is a secreted extracellular matrix protein that is highly expressed during embryonic development and re-expressed during wound healing, inflammation, and neoplasia. Studies in developmental models suggest that TNC may regulate the Wnt signaling pathway. Our lab has shown high levels of Wnt signaling and TNC expression in anaplastic thyroid cancer (ATC), a highly lethal cancer with an abysmal ∼3-5 month median survival. Here, we investigated the role of TNC in facilitating ligand-dependent Wnt signaling in thyroid cancer. We utilized bulk RNA-sequencing from three independent multi-institutional thyroid cancer patient cohorts. TNC expression was spatially localized in patient tumors with RNA in situ hybridization. The role of TNC was investigated in vitro using Wnt reporter assays and in vivo with a NOD.PrkdcscidIl2rg-/- mouse ATC xenograft tumor model. TNC expression was associated with aggressive thyroid cancer behavior, including anaplastic histology, extrathyroidal extension, and metastasis. Spatial localization of TNC in patient tissue demonstrated a dramatic increase in expression within cancer cells along the invasive edge, adjacent to Wnt ligand-producing fibroblasts. TNC expression was also increased in areas of intravascular invasion. In vitro, TNC bound Wnt ligands and potentiated Wnt signaling. Finally, in an ATC mouse model, TNC increased Wnt signaling, tumor burden, invasion, and metastasis. Altogether, TNC potentiated ligand driven Wnt signaling and promotes cancer cell invasion and metastasis in a mouse model of thyroid cancer. Understanding the role of TNC and its interaction with Wnt ligands could lead to the development of novel biomarkers and targeted therapeutics for thyroid cancer.

A passive sampler for per- and polyfluoroalkyl substances (PFAS) in water has been developed which uses a porous organosilica adsorbent. Some performance characteristics, which remained incompletely answered after prior lab- and field-based testing, were assessed. The integrated response mode of the sampler was verified in bench-scale experiments where the aqueous phase concentration was varied 50-fold in the flow across passive samplers. It was found that the passive samplers were able to accumulate analytes and provide an accurate time-averaged concentration in situations where the PFAS concentration changed significantly over time. The integrated response is facilitated by an average 40-fold slower back diffusion rate compared to PFAS adsorption rates, attributed to in-particle diffusion. The maximum deployment time was assessed using a multi-month laboratory-based sampling event. It was found that the integrated response was maintained over 90 days except for perfluorobutanoic acid (PFBA) and perfluorodecanoic acid (PFDA) where adsorption reached equilibrium after 45 and 60 days of total sampling time, respectively. The mechanism of PFAS adsorption was explored using a column breakthrough curve in combination with previously reported adsorption isotherm data. The use of isotopic dilution for PFAS measurement was studied by measuring the adsorption, recovery, and stability of mass labeled surrogates in laboratory analysis. Surrogates were quantitatively bound and determined to be stable for at least 4 weeks in the adsorbed state. Sampling rates for EPA Method 1633 compounds N-methyl perfluorooctanesulfonamidoacetic acid and N-methyl perfluorooctanesulfonamide were also measured, expanding the existing sampling rate database to a total of 21 PFAS species.

A passive sampler designed to measure per‐ and polyfluoroalkyl substances (PFAS) was evaluated to determine chemical uptake rates under a variety of conditions. The sampler design is simple and robust, using organosilica modified with cross‐linked amine polymer in an high density polyethylene housing retained with polypropylene mesh. The addition of amine groups as a weak ion‐exchange resin in combination with Cu²⁺ was designed to promote binding of short‐chain PFAS. A five‐fold improvement in perfluorobutanoic acid adsorption was measured when Cu²⁺ was added to the polyethylenimine polymer. The samplers showed an integrated response to all analytes tested except for short‐chain PFAS. Sampling rates of PFAS analytes from simulated groundwater were on average 10 mL/day at flow rates of 0.038–1.9 cm/min. Relatively low variability in sampling rate was observed over the range of laboratory tested conditions (representing common conditions in environmental waters) including elevated ionic strength, sulfate concentration, and humic acid content.Article Impact Statement: Measuring per‐ and polyfluoroalkyl substances in environmental samples is important for monitoring. Passive samplers can offer practical advantages for making measurements.