SUMMARY Squamous cell carcinoma in the head and neck (HNSCC) is a common yet poorly understood cancer, with adverse clinical outcomes due to treatment resistance, recurrence, and metastasis. Putative cancer stem cells (CSCs) have been identified in HNSCC and BMI1 expression has been linked to these phenotypes, but optimal treatment strategies to overcome chemotherapeutic resistance and eliminate metastases have not yet been identified. Here, we show through lineage tracing and genetic ablation that BMI1+ CSCs mediate invasive growth and cervical lymph node metastasis in a mouse model of HNSCC. This model and primary human HNSCC samples contain highly tumorigenic, quiescent, and cisplatin-resistant BMI1+ CSCs, which exhibit increased AP-1 activity that drives invasive growth and metastasis of HNSCC. Inhibiting AP-1 or BMI1 sensitized tumors to cisplatin-based chemotherapy and eliminated lymph node metastases by targeting CSCs and the tumor bulk, suggesting potential regimens to overcome resistance to treatments and eradicate HNSCC metastasis.

Aberrant lineage specification of skeletal stem cells (SSCs) contributes to reduced bone mass and increased marrow adipose tissue (MAT) in osteoporosis and skeletal aging. Although master regulators of osteoblastic and adipogenic lineages have been identified, little is known about factors that are associated with MAT accumulation and osteoporotic bone loss. Here, we identify peroxisome-proliferator-activated receptor γ coactivator 1-α (PGC-1α) as a critical switch of cell fate decisions whose expression decreases with aging in human and mouse SSCs. Loss of PGC-1α promoted adipogenic differentiation of murine SSCs at the expense of osteoblastic differentiation. Deletion of PGC-1α in SSCs impaired bone formation and indirectly promoted bone resorption while enhancing MAT accumulation. Conversely, induction of PGC-1α attenuated osteoporotic bone loss and MAT accumulation. Mechanistically, PGC-1α maintains bone and fat balance by inducing TAZ. Our results suggest that PGC-1α is a potentially important therapeutic target in the treatment of osteoporosis and skeletal aging.

Background: Given the paucity of information on dose intensity, the objective of this study is to describe the use of adjuvant chemotherapy for stage III colon cancer, focusing on relative dose intensity (RDI), overall survival (OS) and disease-free survival (DFS).

We report a method for conformal nanopatterning of extracellular matrix proteins onto engineered surfaces independent of underlying microtopography. This enables fibronectin, laminin, and other proteins to be applied to biomaterial surfaces in complex geometries inaccessible using traditional soft lithography techniques. Engineering combinatorial surfaces that integrate topographical and biochemical micropatterns enhances control of the biotic-abiotic interface, used here to understand cardiomyocyte response to competing physical and chemical cues in the microenvironment.

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SummaryMesoderm derived from human embryonic stem cells (hESCs) is a major source of the mesenchymal stem/stromal cells (MSCs) that can differentiate into osteoblasts and chondrocytes for tissue regeneration. While significant progress has been made in understanding of molecular mechanisms of hESC differentiation into mesodermal cells, little is known about epigenetic factors controlling hESC fate toward mesoderm and MSCs. Identifying potential epigenetic factors that control hESC differentiation will undoubtedly lead to advancements in regenerative medicine. Here, we conducted an epigenome-wide analysis of hESCs and MSCs and uncovered that EZH2 was enriched in hESCs and was downregulated significantly in MSCs. The specific EZH2 inhibitor GSK126 directed hESC differentiation toward mesoderm and generated more MSCs by reducing H3K27me3. Our results provide insights into epigenetic landscapes of hESCs and MSCs and suggest that inhibiting EZH2 promotes mesodermal differentiation of hESCs.

The extracellular matrix (ECM) in tissues is synthesized and assembled by cells to form a 3D fibrillar, protein network with tightly regulated fiber diameter, composition and organization. In addition to providing structural support, the physical and chemical properties of the ECM play an important role in multiple cellular processes including adhesion, differentiation, and apoptosis. In vivo, the ECM is assembled by exposing cryptic self-assembly (fibrillogenesis) sites within proteins. This process varies for different proteins, but fibronectin (FN) fibrillogenesis is well-characterized and serves as a model system for cell-mediated ECM assembly. Specifically, cells use integrin receptors on the cell membrane to bind FN dimers and actomyosin-generated contractile forces to unfold and expose binding sites for assembly into insoluble fibers. This receptor-mediated process enables cells to assemble and organize the ECM from the cellular to tissue scales. Here, we present a method termed surface-initiated assembly (SIA), which recapitulates cell-mediated matrix assembly using protein-surface interactions to unfold ECM proteins and assemble them into insoluble fibers. First, ECM proteins are adsorbed onto a hydrophobic polydimethylsiloxane (PDMS) surface where they partially denature (unfold) and expose cryptic binding domains. The unfolded proteins are then transferred in well-defined micro- and nanopatterns through microcontact printing onto a thermally responsive poly(N-isopropylacrylamide) (PIPAAm) surface. Thermally-triggered dissolution of the PIPAAm leads to final assembly and release of insoluble ECM protein nanofibers and nanostructures with well-defined geometries. Complex architectures are possible by engineering defined patterns on the PDMS stamps used for microcontact printing. In addition to FN, the SIA process can be used with laminin, fibrinogen and collagens type I and IV to create multi-component ECM nanostructures. Thus, SIA can be used to engineer ECM protein-based materials with precise control over the protein composition, fiber geometry and scaffold architecture in order to recapitulate the structure and composition of the ECM in vivo.

Cell-matrix interactions are important for the physical integration of cells into tissues and the function of insoluble, mechanosensitive signaling networks. Studying these interactions in vitro can be difficult because the extracellular matrix (ECM) proteins that adsorb to in vitro cell culture surfaces do not fully recapitulate the ECM-dense basement membranes to which cells such as cardiomyocytes and endothelial cells adhere to in vivo. Towards addressing this limitation, we have developed a surface-initiated assembly process to engineer ECM proteins into nanostructured, microscale sheets that can be shrink wrapped around single cells and small cell ensembles to provide a functional and instructive matrix niche. Unlike current cell encapsulation technology using alginate, fibrin or other hydrogels, our engineered ECM is similar in density and thickness to native basal lamina and can be tailored in structure and composition using the proteins fibronectin, laminin, fibrinogen, and/or collagen type IV. A range of cells including C2C12 myoblasts, bovine corneal endothelial cells and cardiomyocytes survive the shrink wrapping process with high viability. Further, we demonstrate that, compared to non-encapsulated controls, the engineered ECM modulates cytoskeletal structure, stability of cell-matrix adhesions and cell behavior in 2D and 3D microenvironments.