Activation of the Notch1 Stem Cell Signaling Pathway during Routine Cell Line Subculture

De-differentiation in cultures of organoids from luminal-type breast cancer is restored by inhibition of NOTCH signaling

Estrogen receptor (ER) expression in breast cancer can change during progression and the treatment, but the mechanism has not been well studied. In this study, we successfully prepared organoids from samples obtained from 33 luminal-type breast cancer patients and studied their ER expression. The expression status was well maintained in primary organoids, whereas it decreased after passaging in most of the cases. In fact, the studied organoid lines were classified into those that retained a high level of ER expression (9%), those that completely lost it (9%), and those that repressed it to varying degrees (82%). In some cases, the ER expression was suddenly and drastically decreased after passaging. Marker protein immunohistochemistry revealed that after passaging, the differentiation status shifted from a luminal- to a basal-like status. Differentially expressed genes suggested the activation of NOTCH signaling in the passaged organoids, wherein a NOTCH inhibitor was able to substantially rescue the decreased ER expression and alter the differentiation status. Our findings suggest that the differentiation status of luminal-type cancer cells is quite flexible, and that by inhibiting the NOTCH signaling we can preserve the differentiation status of luminal-type breast cancer organoids.

Notch1 switches progenitor competence in inducing medulloblastoma

The identity of the cell of origin is a key determinant of cancer subtype, progression, and prognosis. Group 3 medulloblastoma (MB) is a malignant childhood brain cancer with poor prognosis and few candidates as putative cell of origin. We overexpressed the group 3 MB genetic drivers MYC and Gfi1 in different candidate cells of origin in the postnatal mouse cerebellum. We found that S100b⁺ cells are competent to initiate group 3 MB, and we observed that S100b⁺ cells have higher levels of Notch1 pathway activity compared to Math1⁺ cells. We found that additional activation of Notch1 in Math1⁺ and Sox2⁺ cells was sufficient to induce group 3 MB upon MYC/Gfi1 expression. Together, our data suggest that the Notch1 pathway plays a critical role in group 3 MB initiation.

Fragmentation of Small-Cell Lung Cancer Regulatory States in Heterotypic Microenvironments

Small-cell lung cancers derive from pulmonary neuroendocrine cells, which have stem-like properties to reprogram into other cell types upon lung injury. It is difficult to uncouple transcriptional plasticity of these transformed cells from genetic changes that evolve in primary tumors or secondary metastases. Profiling of single cells is also problematic if the required sample dissociation activates injury-like signaling and reprogramming. Here we defined cell-state heterogeneities in situ through laser capture microdissection-based 10-cell transcriptomics coupled with stochastic-profiling fluctuation analysis. In labeled cells from a small-cell lung cancer mouse model initiated by neuroendocrine deletion of Rb1-Trp53, variations in transcript abundance revealed cell-to-cell differences in regulatory state in vitro and in vivo. Fluctuating transcripts in spheroid culture were partly shared among Rb1-Trp53-null models, and heterogeneities increased considerably when cells were delivered intravenously to colonize the liver. Colonization of immunocompromised animals drove a fractional appearance of alveolar type II-like markers and poised cells for paracrine stimulation from immune cells and hepatocytes. Immunocompetency further exaggerated the fragmentation of tumor states in the liver, yielding mixed stromal signatures evident in bulk sequencing from autochthonous tumors and metastases. Dozens of transcript heterogeneities recurred irrespective of biological context; their mapped orthologs brought together observations of murine and human small-cell lung cancer. Candidate heterogeneities recurrent in the liver also stratified primary human tumors into discrete groups not readily explained by molecular subtype but with prognostic relevance. These data suggest that heterotypic interactions in the liver and lung are an accelerant for intratumor heterogeneity in small-cell lung cancer. SIGNIFICANCE: These findings demonstrate that the single-cell regulatory heterogeneity of small-cell lung cancer becomes increasingly elaborate in the liver, a common metastatic site for the disease.See related articles by Singh and colleagues, p. 1840 and Sutcliffe and colleagues, p. 1868.

A Three-Dimensional Culture Model of Reversibly Quiescent Myogenic Cells

Satellite cells (SC) are the stem cells of skeletal muscles. They are quiescent in adult animals but resume proliferation to allow muscle hypertrophy or regeneration after injury. The mechanisms balancing quiescence, self-renewal, and differentiation of SC are difficult to analyze in vivo owing to their complexity and in vitro because the staminal character of SC is lost when they are removed from the niche and is not adequately reproduced in the culture models currently available. To overcome these difficulties, we set up a culture model of the myogenic C2C12 cell line in suspension. When C2C12 cells are cultured in suspension, they enter a state of quiescence and form three-dimensional aggregates (myospheres) that produce the extracellular matrix and express markers of quiescent SC. In the initial phase of culture, a portion of the cells fuses in syncytia and abandons the myospheres. The remaining cells are mononucleated and quiescent but resume proliferation and differentiation when plated in a monolayer. The notch pathway controls the quiescent state of the cells as shown by the fact that its inhibition leads to the resumption of differentiation. Within this context, notch3 appears to play a central role in the activity of this pathway since the expression of notch1 declines soon after aggregation. In summary, the culture model of C2C12 in suspension may be used to study the cellular interactions of muscle stem cells and the pathways controlling SC quiescence entrance and maintenance.

Paneth Cell Multipotency Induced by Notch Activation following Injury

Paneth cells are post-mitotic intestinal epithelial cells supporting the stem cell niche and mucosal immunity. Paneth cell pathologies are observed in various gastrointestinal diseases, but their plasticity and response to genomic and environmental challenges remain unclear. Using a knockin allele engineered at the mouse Lyz1 locus, we performed detailed Paneth cell-lineage tracing. Irradiation induced a subset of Paneth cells to proliferate and differentiate into villus epithelial cells. RNA sequencing (RNA-seq) revealed that Paneth cells sorted from irradiated mice acquired a stem cell-like transcriptome; when cultured in vitro, these individual Paneth cells formed organoids. Irradiation activated Notch signaling, and forced expression of Notch intracellular domain (NICD) in Paneth cells, but not Wnt/β-catenin pathway activation, induced their dedifferentiation. This study documents Paneth cell plasticity, particularly their ability to participate in epithelial replenishment following stem cell loss, adding to a growing body of knowledge detailing the molecular pathways controlling injury-induced regeneration.

Novel TCR-Mediated Mechanisms of Notch Activation and Signaling

The Notch receptor is an evolutionarily highly conserved transmembrane protein that is essential to a wide spectrum of cellular systems. Notch signaling is especially important to T cell development, and its deregulation leads to leukemia. Although not well characterized, it continues to play an integral role in peripheral T cells, in which a unique mode of Notch activation can occur. In contrast to canonical Notch activation initiated by adjacent ligand-expressing cells, TCR stimulation is sufficient to induce Notch signaling. However, the interactions between these two pathways have not been defined. In this article, we show that Notch activation occurs in peripheral T cells within a few hours post-TCR stimulation and is required for optimal T cell activation. Using a panel of inhibitors against components of the TCR signaling cascade, we demonstrate that Notch activation is facilitated through initiation of protein kinase C-induced ADAM activity. Moreover, our data suggest that internalization of Notch via endocytosis plays a role in this process. Although ligand-mediated Notch stimulation relies on mechanical pulling forces that disrupt the autoinhibitory domain of Notch, we hypothesized that, in T cells in the absence of ligands, these conformational changes are induced through chemical adjustments in the endosome, causing alleviation of autoinhibition and receptor activation. Thus, T cells may have evolved a unique method of Notch receptor activation, which is described for the first time, to our knowledge, in this article.

Label-free isolation of prostate circulating tumor cells using Vortex microfluidic technology

There has been increased interest in utilizing non-invasive "liquid biopsies" to identify biomarkers for cancer prognosis and monitoring, and to isolate genetic material that can predict response to targeted therapies. Circulating tumor cells (CTCs) have emerged as such a biomarker providing both genetic and phenotypic information about tumor evolution, potentially from both primary and metastatic sites. Currently, available CTC isolation approaches, including immunoaffinity and size-based filtration, have focused on high capture efficiency but with lower purity and often long and manual sample preparation, which limits the use of captured CTCs for downstream analyses. Here, we describe the use of the microfluidic Vortex Chip for size-based isolation of CTCs from 22 patients with advanced prostate cancer and, from an enumeration study on 18 of these patients, find that we can capture CTCs with high purity (from 1.74 to 37.59%) and efficiency (from 1.88 to 93.75 CTCs/7.5 mL) in less than 1 h. Interestingly, more atypical large circulating cells were identified in five age-matched healthy donors (46-77 years old; 1.25-2.50 CTCs/7.5 mL) than in five healthy donors <30 years old (21-27 years old; 0.00 CTC/7.5 mL). Using a threshold calculated from the five age-matched healthy donors (3.37 CTCs/mL), we identified CTCs in 80% of the prostate cancer patients. We also found that a fraction of the cells collected (11.5%) did not express epithelial prostate markers (cytokeratin and/or prostate-specific antigen) and that some instead expressed markers of epithelial-mesenchymal transition, i.e., vimentin and N-cadherin. We also show that the purity and DNA yield of isolated cells is amenable to targeted amplification and next-generation sequencing, without whole genome amplification, identifying unique mutations in 10 of 15 samples and 0 of 4 healthy samples.

Stiffness-Controlled Thermoresponsive Hydrogels for Cell Harvesting with Sustained Mechanical Memory

Most mechanobiological investigations focused on in situ mechanical regulation of cells on stiffness-controlled substrates with few downstream applications, as it is still challenging to harvest and expand mechanically primed cells by enzymatic digestion (e.g., trypsin) without interrupting cellular mechanical memory between passages. This study develops thermoresponsive hydrogels with controllable stiffness to generate mechanically primed cells with intact mechanical memory for augmented wound healing. No significant cellular property alteration of the fibroblasts primed on thermoresponsive hydrogels with varied stiffness has been observed through thermoresponsive harvesting. When reseeding the harvested cells for further evaluation, softer hydrogels are proven to better sustain the mechanical priming effects compared to rigid tissue culture plate, which indicates that both the stiffness-controlled substrate and thermoresponsive harvesting are required to sustain cellular mechanical memory between passages. Moreover, epigenetics analysis reveals that thermoresponsive harvesting could reduce the rearrangement and loss of chromatin proteins compared to that of trypsinization. In vivo wound healing using mechanically primed fibroblasts shows featured epithelium and sebaceous glands, which indicates augmented skin recovery compared with trypsinized fibroblasts. Thus, the thermoresponsive hydrogel-based cell harvesting system offers a powerful tool to investigate mechanobiology between cell passages and produces abundant cells with tailored mechanical priming properties for cell-based applications.

The role of FSCN1 in migration and invasion of pituitary adenomas

The prediction of invasion or malignant behavior in PAs remains challenging. FSCN1, an actin-bundling protein, is associated with increased risk of mortality and metastasis in various cancer types. The objective of the study was to evaluate the expression of FSCN1 in 312 PAs cases, and to analyze its association with clinicopathologic features and invasion of PAs, thus serving as a promoter of cancer invasion. In non-function PAs (NFPA), FSCN1 nuclear-positive cases were 53/97 in the invasive group (IPA), and 21/115 in the noninvasive group (nIPA) (ⅹ(2) = 30.65, p = 0.004). FSCN1 cytoplasm-positive cases were 36/97 in IPA, and 8/107 in nIPA (ⅹ(2) = 29.09, p = 0.000). In growth hormone adenomas (GHomas), FSCN1 nuclear-positive were 10/13 in IPA, and 3/37 in nIPA (ⅹ(2) = 23.67, p = 0.000). FSCN1 cytoplasm-positive were 8/13 in IPA, and 2/37 in nIPA (Table 3 ⅹ(2) = 18.94, p = 0.000). Overall, a significant difference was found between FSCN1 expression and tumor size (ⅹ(2) = 46.21, p = 0.000), not age (ⅹ(2) = 2.09, p = 0.148). In the high FSCN1 expression group, 27/137 cases (19.7%) had tumor recurrence, and 10/175 cases (5.7%) in low FSCN1 level (ⅹ(2) = 14.40 p = 0.000). Reduction of FSCN1 suppressed the invasion level of GH3 cells through transwells test. In addition, reduction of FSCN1 can obviously down-regulate the level of Notch1 and DLL3. Our data may help in deciding whether FSCN1 can be a predictor for invasion and recurrence of PAs.