Establishment and characterization of a parietal endoderm-like cell line derived from Engelbreth–Holm–Swarm tumor (EHSPEL), a possible resource for an engineered basement membrane matrix

Targeting Tumor Microenvironment for Cancer Therapy

Cancer development is highly associated to the physiological state of the tumor microenvironment (TME). Despite the existing heterogeneity of tumors from the same or from different anatomical locations, common features can be found in the TME maturation of epithelial-derived tumors. Genetic alterations in tumor cells result in hyperplasia, uncontrolled growth, resistance to apoptosis, and metabolic shift towards anaerobic glycolysis (Warburg effect). These events create hypoxia, oxidative stress and acidosis within the TME triggering an adjustment of the extracellular matrix (ECM), a response from neighbor stromal cells (e.g., fibroblasts) and immune cells (lymphocytes and macrophages), inducing angiogenesis and, ultimately, resulting in metastasis. Exosomes secreted by TME cells are central players in all these events. The TME profile is preponderant on prognosis and impacts efficacy of anti-cancer therapies. Hence, a big effort has been made to develop new therapeutic strategies towards a more efficient targeting of TME. These efforts focus on: (i) therapeutic strategies targeting TME components, extending from conventional therapeutics, to combined therapies and nanomedicines; and (ii) the development of models that accurately resemble the TME for bench investigations, including tumor-tissue explants, “tumor on a chip” or multicellular tumor-spheroids.

Expression and chain assembly of human laminin-332 in an insect cell-free translation system

Laminins are a family of large heterotrimeric glycoproteins comprising alpha, beta, and gamma chains. To determine the molecular mechanisms underlying chain assembly in vitro, we expressed human laminin-332 subunits in an insect cell-free translation system. We successfully produced the beta3-gamma2 heterodimer and the alpha3-beta3-gamma2 heterotrimer of the laminin coiled-coil (LCC) domain following co-translation of each chain. The alpha3-beta3 and the alpha3-gamma2 heterodimer were not detected, suggesting that the alpha3 chain can assemble with only beta3-gamma2 heterodimer to form a heterotrimer via disulfide bonds. These results are consistent with those of a previous report indicating that laminin chain assembly proceeds through the beta-gamma heterodimer to the alpha-beta-gamma heterotrimer in vivo. We suggest that the cell-free translation system is a valid system with which to study the mechanisms underlying laminin chain assembly.

Regulation of mesodermal differentiation of mouse embryonic stem cells by basement membranes

Basement membranes (BMs) have been implicated in cell fate determination during development. Embryoid bodies (EBs) derived from mouse embryonic stem cells deficient in the laminin gamma1 chain are incapable of depositing a BM, resulting in failure of primitive ectoderm epithelialization. To elucidate the mechanisms involved in this phenomenon, we compared the gene expression profiles of EBs with or without a BM to identify the genes showing BM-dependent expression. We found that the expressions of marker genes for the epithelial-mesenchymal transition (EMT), including the transcription factor Snai2, were up-regulated in LAMC1(-/-) EBs, whereas restoration of a BM to LAMC1(-/-) EBs suppressed the up-regulation of these genes. Overexpression of Snai2 induced the EMT in control EBs by molecular and morphological criteria, suggesting that suppression of the EMT regulatory genes is involved in BM-dependent epithelialization of primitive ectoderm. Despite the failure of primitive ectoderm epithelialization in BM-deficient EBs, mesodermal differentiation was not compromised, but rather accelerated. Furthermore, at later stages of control EB differentiation, the BM was disrupted at the gastrulation site where mesodermal markers were strongly expressed only in cells that had lost contact with the BM. Taken together, these results indicate that the BM prevents the EMT and precocious differentiation of primitive ectoderm toward mesoderm in EBs, implying that BMs are important for the control of mammalian gastrulation.

Constitutive gene expression predisposes morphogen-mediated cell fate responses of NT2/D1 and 27X-1 human embryonal carcinoma cells

Human embryonal carcinoma (EC) cell lines exhibit considerable heterogeneity in their levels of pluripotency. Thus, NT2/D1 cells differentiate into neural lineages upon exposure to all-trans retinoic acid (ATRA) and non-neural epithelial lineages upon exposure to bone morphogenetic protein-2 (BMP-2). In contrast, 27X-1 cells differentiate into extra-embryonic endodermal (ExE) cells upon treatment with either morphogen. To understand the molecular basis for the differential responses of the two cell lines, we performed gene expression profiling at the undifferentiated EC cell line state to identify constitutive differences in gene expression. NT2/D1 cells preferentially expressed transcripts associated with neurectodermal development, whereas 27X-1 cells expressed high levels of transcripts associated with mesendodermal characteristics. We then determined temporal expression profiles of 27X-1 cells during ExE differentiation upon treatment with ATRA and BMP-2 and compared the data with changes in gene expression observed during BMP-2- and ATRA-induced differentiation of NT2/D1 cells. ATRA and BMP-2 induced distinct sets of transcription factors and phenotypic markers in the two EC cell lines, underlying distinct lineage choices. Although 27X-1 differentiation yielded comprehensive gene expression profiles of parietal endodermal lineages, we were able to use the combined analysis of 27X-1 data with data derived from yolk sac tumors for the identification of transcripts associated with visceral endoderm formation. Our results demonstrate constitutive differences in the levels of pluripotency between NT2/D1 and 27X-1 cells that correlate with lineage potential. This study also demonstrates that EC cells can serve as robust models to investigate early lineage choices during both embryonic and extra-embryonic human development.

A novel large-scale production system for modified basement membrane matrices using gene-swapped parietal endoderm cells

Parietal endoderm-like cells, including Engelbreth-Holm-Swarm tumor and differentiated F9 embryonal carcinoma cells, produce huge amounts of basement membrane components, including laminin-1 (alpha1beta1gamma1). We employed a double-lox system-based gene-swapping strategy in F9 cells to replace the laminin alpha1 gene with a laminin alpha5 minigene. The gene-swapped F9 cells secreted laminin-10 (alpha5beta1gamma1) consisting of the exogenous alpha5 subunit and endogenous beta1 and gamma1 subunits on differentiation. The laminin-10 concentration in the conditioned medium exceeded 10 mg/l, which is 10-fold higher than the concentrations achieved by conventional recombinant expression systems. The gene-swapped F9 cells deposited basement membrane-like matrices containing laminin-10 on culture dishes, offering a novel microenvironment for in vitro cell manipulation.

Sox7 plays crucial roles in parietal endoderm differentiation in F9 embryonal carcinoma cells through regulating Gata-4 and Gata-6 expression

During early rodent development, the parietal endoderm appears from an inner cell mass and produces large amounts of basement membrane components, such as laminin-1 and collagen IV. To elucidate the regulatory network for gene expression during these procedures, we constructed a series of short interfering RNA expression vectors targeted to various transcription factors, transfected them into F9 embryonal carcinoma cells, and evaluated the effects of the gene silencing on the induction of parietal endoderm differentiation and basement membrane component production by treating F9 cells with all trans-retinoic acid and dibutyryl cyclic AMP. Among the transcription factors tested, silencing of Sox7 or combined silencing of Gata-4 and Gata-6 resulted in suppression of cell shape changes and laminin-1 production, which are the hallmarks of parietal endoderm differentiation. In cells silenced for Sox7, induction of Gata-4 and Gata-6 by retinoic acid and cyclic AMP treatment was inhibited, while induction of Sox7 was not affected in cells silenced for Gata-4 and Gata-6, indicating that Sox7 is an upstream regulatory factor for these Gata factors. Nevertheless, silencing of Sox7 did not totally cancel the action of retinoic acid, since upregulation of coup-tf2, keratin 19, and retinoic acid receptor beta2 was not abolished in Sox7-silenced F9 cells. Although overexpression of Sox7 alone was insufficient to induce parietal endoderm differentiation, overexpression of Gata-4 or Gata-6 in Sox7-silenced F9 cells restored the differentiation into parietal endoderm. Sox7 is therefore required for the induction of Gata-4 and Gata-6, and the interplay among these transcription factors plays a crucial role in parietal endoderm differentiation.