Extracellular matrix proteins of the tenascin family resemble each other in their domain structure, and also share functions in modulating cell adhesion and cellular responses to growth factors. Despite these common features, the 4 vertebrate tenascins exhibit vastly different expression patterns. Tenascin-R is specific to the central nervous system. Tenascin-C is an “oncofetal” protein controlled by many stimuli (growth factors, cytokines, mechanical stress), but with restricted occurrence in space and time. In contrast, tenascin-X is a constituitive component of connective tissues, and its level is barely affected by external factors. Finally, the expression of tenascin-W is similar to that of tenascin-C but even more limited. In accordance with their highly regulated expression, the promoters of the tenascin-C and -W genes contain TATA boxes, whereas those of the other 2 tenascins do not. This article summarizes what is currently known about the complex transcriptional regulation of the 4 tenascin genes in development and disease.

Background: Extensive DNA sequencing has led to an unprecedented view of the diversity of individual genomes and their evolution among patients with clear cell renal cell carcinoma (ccRCC). Objective: To understand subclonal architecture and dynamics of patient-derived two-dimensional (2D) and three-dimensional (3D) ccRCC models in vitro, in order to determine whether they mirror ccRCC inter-and intratumor heterogeneity. Design, setting, and participants: We have established a comprehensive platform of living renal cancer cell models from ccRCC surgical specimens. Outcome measurements and statistical analysis: We confirmed the concordance of 2D and 3D patient-derived cell (PDC) models with the original tumor tissue in terms of histology, biomarker expression, cancer driver mutations, and copy number alterations. We addressed inter-and intrapatient heterogeneity by analyzing clonal dynamics during serial passaging. Results and limitations: In-depth genetic characterization verified the presence of heterogeneous cell populations, and revealed a high degree of similarity between subclonal compositions of monolayer and organoid cell cultures and the corresponding parental ccRCCs. Clonal dynamics were evident during serial passaging of cells in vitro, suggesting that PDC cultures can offer insights into evolutionary potential and treatment susceptibility of ccRCC subclones in vivo. Proof-of-concept drug profiling using selected ccRCC-targeted therapy agents highlighted patient-specific vulnerabilities in PDC models that could not be anticipated by interrogating commercially available cell lines. Conclusions: We demonstrate that PDC models mirror inter-and intratumor heterogeneity of ccRCC in vitro. Based on our findings, we envision that the use of these models will advance our understanding of the trajectories that cause genetic diversity and their consequences for treatment on an individual level. Patient summary: In this study, we developed two-and three-dimensional patient-derived models from clear cell renal cell carcinoma (ccRCC) as "mini-tumors in a dish." We show that these cell models retain important features of the human ccRCCs such as the profound tumor heterogeneity, thus highlighting their importance for cancer research and precision medicine.

Tenascin‐W is a matricellular protein with a dynamically changing expression pattern in development and disease. In adults, tenascin‐W is mostly restricted to stem cell niches, and is also expressed in the stroma of solid cancers. Here, we analyzed its expression in the bone microenvironment of breast cancer metastasis. Osteoblasts were isolated from tumor‐free or tumor‐bearing bones of mice injected with MDA‐MB231‐1833 breast cancer cells. We found a fourfold upregulation of tenascin‐W in the osteoblast population of tumor‐bearing mice compared to healthy mice, indicating that tenascin‐W is supplied by the bone metastatic niche. Transwell and co‐culture studies showed that human bone marrow stromal cells (BMSCs) express tenascin‐W protein after exposure to factors secreted by MDA‐MB231‐1833 breast cancer cells. To study tenascin‐W gene regulation, we identified and analyzed the tenascin‐W promoter as well as three evolutionary conserved regions in the first intron. 5′RACE analysis of mRNA from human breast cancer, glioblastoma and bone tissue showed a single tenascin‐W transcript with a transcription start site at a noncoding first exon followed by exon 2 containing the ATG translation start. Site‐directed mutagenesis of a SMAD4‐binding element in proximity of the TATA box strongly impaired promoter activity. TGFβ1 induced tenascin‐W expression in human BMSCs through activation of the TGFβ1 receptor ALK5, while glucocorticoids were inhibitory. Our experiments show that tenascin‐W acts as a niche component for breast cancer metastasis to bone by supporting cell migration and cell proliferation of the cancer cells.

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