Heat shock factors (HSFs) are the master regulators of transcription under protein-damaging conditions, acting in an environment where the overall transcription is silenced. We determined the genomewide transcriptional program that is rapidly provoked by HSF1 and HSF2 under acute stress in human cells. Our results revealed the molecular mechanisms that maintain cellular homeostasis, including HSF1-driven induction of polyubiquitin genes, as well as HSF1-and HSF2-mediated expression patterns of cochaperones, transcriptional regulators, and signaling molecules. We characterized the genomewide transcriptional response to stress also in mitotic cells where the chromatin is tightly compacted. We found a radically limited binding and transactivating capacity of HSF1, leaving mitotic cells highly susceptible to proteotoxicity. In contrast, HSF2 occupied hundreds of loci in the mitotic cells and localized to the condensed chromatin also in meiosis. These results highlight the importance of the cell cycle phase in transcriptional responses and identify the specific mechanisms for HSF1 and HSF2 in transcriptional orchestration. Moreover, we propose that HSF2 is an epigenetic regulator directing transcription throughout cell cycle progression.ChIP-seq | ENCODE | human genome | proteostasis C ells exposed to proteotoxic conditions provoke a rapid and transient response to maintain homeostasis. The stress response induces profound cellular adaptation as cytoskeleton and membranes are reorganized, cell cycle progression is stalled, and the global transcription and translation are silenced (1, 2). Despite the silenced chromatin environment, the stressed cell mounts a transcriptional program that involves induction of genes coding for heat shock proteins (HSPs). HSPs are molecular chaperones and proteases that assist in protein folding and maintain cellular structures and molecular functions (3).Heat shock factor 1 (HSF1) is an evolutionarily well-conserved transcription factor that is rapidly activated by stress and absolutely required for the stress-induced HSP expression (4). Aberrant HSF1 levels are associated with stress sensitivity, aging, neurodegenerative diseases, and cancer (5-9). Instead of a single HSF in yeasts and invertebrates, vertebrates contain a family of four members, HSF1-4. HSF2 and HSF4 are involved in corticogenesis, spermatogenesis, and formation of sensory epithelium, and they have primarily been considered as developmental factors (10-14). HSF1 and HSF2 share high sequence homology of the DNA-binding and oligomerization domains and are able to form heterotrimers at the chromatin (15, 16). Moreover, HSF2 participates in the regulation of stress-responsive genes and is required for proper protein clearance also at febrile temperatures (17,18). Although HSF1 and HSF2 have been shown to interplay on the heat shock elements (HSEs) of the target loci, their impacts on transcription of chaperone genes are remarkably different; HSF1 is a potent inducer of transcription, whereas HSF2 is a poor transactivator o...

Alongside cancer cells, tumours exhibit a complex stroma containing a repertoire of cells, matrix molecules and soluble factors that actively crosstalk between each other. Recognition of this multifaceted concept of the tumour microenvironment (TME) calls for authentic TME mimetics to study cancer in vitro. Traditionally, tumourigenesis has been investigated in non-human, three-dimensional rat type I collagen containing organotypic discs or by means of mouse sarcoma-derived gel, such as Matrigel®. However, the molecular compositions of these simplified assays do not properly simulate human TME. Here, we review the main properties and benefits of using human leiomyoma discs and their matrix Myogel for in vitro assays. Myoma discs are practical for investigating the invasion of cancer cells, as are cocultures of cancer and stromal cells in a stiff, hypoxic TME mimetic. Myoma discs contain soluble factors and matrix molecules commonly present in neoplastic stroma. In Transwell, IncuCyte, spheroid and sandwich assays, cancer cells move faster and form larger colonies in Myogel than in Matrigel®. Additionally, Myogel can replace Matrigel® in hanging-drop and tube-formation assays. Myogel also suits three-dimensional drug testing and extracellular vesicle interactions. To conclude, we describe the application of our myoma-derived matrices in 3D in vitro cancer assays.This article is part of the discussion meeting issue ‘Extracellular vesicles and the tumour microenvironment’.

Previous studies indicate that bilberry with high amounts of phenolic compounds can inhibit carcinogenic processes of colorectal cancer in vitro and in vivo. However, no studies have focused on the effects of bilberry on oral cancer. In this study, we aimed to examine the effects of bilberry powder on oral squamous cell carcinoma (OSCC) cells using both in vitro and in vivo assays. The effects of 0, 1, 10, and 25 mg/mL of whole bilberry powder on the viability, proliferation, migration, and invasion of OSCC (HSC-3) cells were examined and compared with 0.01 mg/mL of cetuximab. Two oral keratinocyte cell lines served as controls. Tumor area was analyzed in zebrafish microinjected with HSC-3 cells and treated with 2.5, 10, or 25 µg/mL of bilberry powder. Metastases in the head or tail areas were counted. Bilberry powder inhibited the viability, proliferation, migration, and invasion of HSC-3 cells (p < 0.05), which was more pronounced with higher concentrations. Cetuximab had no effect on HSC-3 cell migration or invasion. Compared to controls, the tumor area in zebrafish treated with bilberry powder (10 and 25 µg/mL) was reduced significantly (p = 0.038 and p = 0.021, respectively), but the number of fish with metastases did not differ between groups. Based on our in vitro and in vivo experiments, we conclude that whole bilberry powder has anti-tumor effects on OSCC cells.