Symmetric Stem Cell Division Research Articles

W021006 病理標本の3次元再構築によるがんの特性の研究([W02100]バイオエンジニアリング部門,流体工学部門企画,腫瘍医工学)

We developed a program to align serial pathological tissue sections using projective transformation method for the conpensation of nonlinear deformation in each pathological sections. Cell recognition method is also improved for better cell number counting in the high cell density area. Using these improved programs, the cell proliferation kinetics of normal and cancer tissues are analyzed. The results indicate that the presence of intermittently proliferating cells in the proliferative zones of colorectal crypts and these intermittently proliferating cells are extensively increased in β-catenin accumuated cryps of Apc^<Min/+> mice colorectal mucosa; i.e. the early lesions of colorectal cancer. Intermittent proliferation is a characteristics of tissue stem cells. The number of these cells increases eigher by intermittent symmetric devision of stem cells or by reverse differentiation of serially proliferating cancer cells to intermittently proliferating cancer stem cells. Therefore, these results are thought to indicate that the symmetric intermittent division of stem cells and the reverse differentiation of cancer cells to stem cells are the hallmark of cancer cell proliferation.

Symmetric vs. Asymmetric Stem Cell Divisions: An Adaptation against Cancer?

Traditionally, it has been held that a central characteristic of stem cells is their ability to divide asymmetrically. Recent advances in inducible genetic labeling provided ample evidence that symmetric stem cell divisions play an important role in adult mammalian homeostasis. It is well understood that the two types of cell divisions differ in terms of the stem cells' flexibility to expand when needed. On the contrary, the implications of symmetric and asymmetric divisions for mutation accumulation are still poorly understood. In this paper we study a stochastic model of a renewing tissue, and address the optimization problem of tissue architecture in the context of mutant production. Specifically, we study the process of tumor suppressor gene inactivation which usually takes place as a consequence of two “hits”, and which is one of the most common patterns in carcinogenesis. We compare and contrast symmetric and asymmetric (and mixed) stem cell divisions, and focus on the rate at which double-hit mutants are generated. It turns out that symmetrically-dividing cells generate such mutants at a rate which is significantly lower than that of asymmetrically-dividing cells. This result holds whether single-hit (intermediate) mutants are disadvantageous, neutral, or advantageous. It is also independent on whether the carcinogenic double-hit mutants are produced only among the stem cells or also among more specialized cells. We argue that symmetric stem cell divisions in mammals could be an adaptation which helps delay the onset of cancers. We further investigate the question of the optimal fraction of stem cells in the tissue, and quantify the contribution of non-stem cells in mutant production. Our work provides a hypothesis to explain the observation that in mammalian cells, symmetric patterns of stem cell division seem to be very common.

Lineage Tracing Quantification Reveals Symmetric Stem Cell Division in Drosophila Male Germline Stem Cells

In the homeostatic state, adult stem cells divide either symmetrically to increase the stem cell number to compensate stem cell loss, or asymmetrically to maintain the population while producing differentiated cells. We have investigated the mode of stem cell division in the testes of Drosophila melanogaster by lineage tracing and confirm the presence of symmetric stem cell division in this system. We found that the rate of symmetric division is limited to 1-2% of total germline stem cell (GSC) divisions, but it increases with expression of a cell adhesion molecule, E-cadherin, or a regulator of the actin cytoskeleton, Moesin, which may modulate adhesiveness of germ cells to the stem cell niche. Our results indicate that the decision regarding asymmetric vs. symmetric division is a dynamically regulated process that contributes to tissue homeostasis, responding to the needs of the tissue.

Progastrin Stimulates Colonic Cell Proliferation via CCK2R- and β-Arrestin–Dependent Suppression of BMP2

Progastrin stimulates colonic mucosal proliferation and carcinogenesis through the cholecystokinin 2 receptor (CCK2R)-partly by increasing the number of colonic progenitor cells. However, little is known about the mechanisms by which progastrin stimulates colonic cell proliferation. We investigated the role of bone morphogenetic proteins (BMPs) in progastrin induction of colonic cell proliferation via CCK2R. We performed microarray analysis to compare changes in gene expression in the colonic mucosa of mice that express a human progastrin transgene, gastrin knockout mice, and C57BL/6 mice (controls); the effects of progastrin were also determined on in vitro colonic crypt cultures from cholecystokinin 2 receptor knockout and wild-type mice. Human colorectal and gastric cancer cells that expressed CCK2R were incubated with progastrin or Bmp2; levels of β-arrestin 1 and 2 were knocked down using small interfering RNAs. Cells were analyzed for progastrin binding, proliferation, changes in gene expression, and symmetric cell division. The BMP pathway was down-regulated in the colons of human progastrin mice compared with controls. Progastrin suppressed transcription of Bmp2 through a pathway that required CCK2R and was mediated by β-arrestin 1 and 2. In mouse colonic epithelial cells, down-regulation of Bmp2 led to decreased phosphorylation of Smads1/5/8 and suppression of inhibitor of DNA binding 4. In human gastric and colorectal cancer cell lines, CCK2R was necessary and sufficient for progastrin binding and induction of proliferation; these effects were blocked when cells were incubated with recombinant Bmp2. Incubation with progastrin increased the number of CD44(+), bromodeoxyuridine+, and NUMB(+) cells, indicating an increase in symmetric divisions of putative cancer stem cells. Progastrin stimulates proliferation in colons of mice and cultured human cells via CCK2R- and β-arrestin 1 and 2-dependent suppression of Bmp2 signaling. This process promotes symmetric cell division.

281 Mutant K-RAS in the Epithelial Stem Cell Compartment Promotes Symmetric Stem Cell Division and Crypt Fission but Not Tumorigenesis in the Mouse Intestine and Colon

cell sorting and 3) significantly expand organoids as either enriched for stem cells or as differentiated cells that retain a site-specific program of differentiation and are free from mesenchymal contamination. Here we present an improved isolation and culture method that addresses these needs. METHOD: Human gastrointestinal epithelial cells were cultured using an adaptation of our published mouse epithelium culturing system. This system utilizes conditioned media collected from an L cell line (L-WRN) engineered to secrete the factors required for epithelial stem cell growth (Wnt3a, R-spondin3 and Noggin). Importantly, cultures were established from biopsy tissue (2-3 biopsies with area of 6-24 mm2) collected during routine endoscopy. Cell sorting enrichment was not required. Epithelial cells were maintained as 3-dimensional organoids in basement membrane matrix (Matrigel) with 50% conditioned media (1:1 dilution with fresh crypt culture media). Analysis of cellular markers of proliferative and differentiated cells was performed using qRT-PCR, immunofluorescence and flow assisted cell sorting. RESULTS: Human epithelial cultures were established from multiple regions of the gastrointestinal tract, including small intestine (n=9), colon (n=23), stomach (n=2) and Barrett's esophagus (n=2). Biopsy donors included healthy and IBD patients. Mesenchymal cells carried over from the isolation process were eliminated during initial passages. Subsequent studies focused on intestinal organoids, which were maintained for.40 passages (.120 days) and were able to be stored as frozen stocks. In 50% conditioned media, the majority of cells were proliferative and expressed high levels of the stem cell markers, LGR5 and OLFM4. Accordingly, organoids expanded at a rapid rate and were split 1:3 every 3 days. An intestine-specific program of differentiation was achieved using lower percentage conditioned media plus additional factors, including the Notch inhibitor DAPT. CONCLUSIONS:We have generated a culture system that will allow for large-scale, functional experiments of human intestinal epithelial cells. This system will enable us to create a biobank of human epithelial cell lines. Moreover, because cultures can be established from endoscopic biopsies, tissue donors could potentially be pre-selected based on genotype to facilitate studies of the interactions between genotype and environmental factors.

Age-Dependent Transition from Cell-Level to Population-Level Control in Murine Intestinal Homeostasis Revealed by Coalescence Analysis

In multi-cellular organisms, tissue homeostasis is maintained by an exquisite balance between stem cell proliferation and differentiation. This equilibrium can be achieved either at the single cell level (a.k.a. cell asymmetry), where stem cells follow strict asymmetric divisions, or the population level (a.k.a. population asymmetry), where gains and losses in individual stem cell lineages are randomly distributed, but the net effect is homeostasis. In the mature mouse intestinal crypt, previous evidence has revealed a pattern of population asymmetry through predominantly symmetric divisions of stem cells. In this work, using population genetic theory together with previously published crypt single-cell data obtained at different mouse life stages, we reveal a strikingly dynamic pattern of stem cell homeostatic control. We find that single-cell asymmetric divisions are gradually replaced by stochastic population-level asymmetry as the mouse matures to adulthood. This lifelong process has important developmental and evolutionary implications in understanding how adult tissues maintain their homeostasis integrating the trade-off between intrinsic and extrinsic regulations.

Optimality in the Development of Intestinal Crypts

Intestinal crypts in mammals are comprised of long-lived stem cells and shorter-lived progenies. These two populations are maintained in specific proportions during adult life. Here, we investigate the design principles governing the dynamics of these proportions during crypt morphogenesis. Using optimal control theory, we show that a proliferation strategy known as a "bang-bang" control minimizes the time to obtain a mature crypt. This strategy consists of a surge of symmetric stem cell divisions, establishing the entire stem cell pool first, followed by a sharp transition to strictly asymmetric stem cell divisions, producing nonstem cells with a delay. We validate these predictions using lineage tracing and single-molecule fluorescence insitu hybridization of intestinal crypts in infant mice, uncovering small crypts that are entirely composed of Lgr5-labeled stem cells, which become a minority as crypts continue to grow. Our approach can be used to uncover similar design principles in other developmental systems.

Having the guts to grow

Symmetric intestinal stem cell division drives adaptive midgut growth.

Robust Spindle Alignment in Drosophila Neuroblasts by Ultrasensitive Activation of Pins

Cellular signaling pathways exhibit complex response profiles with features such as thresholds and steep activation (i.e., ultrasensitivity). In a reconstituted mitotic spindle orientation pathway, activation of Drosophila Pins (LGN in mammals) by Gαi is ultrasensitive (apparent Hill coefficient of 3.1), such that Pins recruitment of the microtubule binding protein Mud (NuMA) occurs over a very narrow Gαi concentration range. Ultrasensitivity is required for Pins function in neuroblasts as a nonultrasensitive Pins mutant fails to robustly couple spindle position to cell polarity. Pins contains three Gαi binding GoLoco domains (GLs); Gαi binding to GL3 activates Pins, whereas GLs 1 and 2 shape the response profile. Although cooperative binding is one mechanism for generating ultrasensitivity, we find GLs 1 and 2 act as "decoys" that compete against activation at GL3. Many signaling proteins contain multiple protein interaction domains, and the decoy mechanism may be a common method for generating ultrasensitivity in regulatory pathways.

Atypical protein kinase C (aPKCζ and aPKCλ) is dispensable for mammalian hematopoietic stem cell activity and blood formation

The stem-cell pool is considered to be maintained by a balance between symmetric and asymmetric division of stem cells. The cell polarity model proposes that the facultative use of symmetric and asymmetric cell division is orchestrated by a polarity complex consisting of partitioning-defective proteins Par3 and Par6, and atypical protein kinase C (aPKCζ and aPKCλ), which regulates planar symmetry of dividing stem cells with respect to the signaling microenvironment. However, the role of the polarity complex is unexplored in mammalian adult stem-cell functions. Here we report that, in contrast to accepted paradigms, polarization and activity of adult hematopoietic stem cell (HSC) do not depend on either aPKCζ or aPKCλ or both in vivo. Mice, having constitutive and hematopoietic-specific (Vav1-Cre) deletion of aPKCζ and aPKCλ, respectively, have normal hematopoiesis, including normal HSC self-renewal, engraftment, differentiation, and interaction with the bone marrow microenvironment. Furthermore, inducible complete deletion of aPKCλ (Mx1-Cre) in aPKCζ(-/-) HSC does not affect HSC polarization, self-renewal, engraftment, or lineage repopulation. In addition, aPKCζ- and aPKCλ-deficient HSCs elicited a normal pattern of hematopoietic recovery secondary to myeloablative stress. Taken together, the expression of aPKCζ, aPKCλ, or both are dispensable for primitive and adult HSC fate determination in steady-state and stress hematopoiesis, contrary to the hypothesis of a unique, evolutionary conserved aPKCζ/λ-directed cell polarity signaling mechanism in mammalian HSC fate determination.

Abstract 4931: Cancer stem cells in solid tumors: Symmetric division, niche size, and invasive tumor morphology

Abstract In recent years cancer stem cells have been identified as a minor subpopulation in numerous solid tumors that drives tumor initiation, development and metastasis. Although cancer stem cells have yet to be reliably isolated, populations enriched for tumor-initiating cells give an indication of the order of magnitude of the stem cells niche within primary tumors. Here we develop and discuss the predictions of a simple theoretical model of cancer stem cells and tumor growth dynamics. We evaluate the impact of cancer stem cell symmetric/asymmetric division and progeny cancer cell proliferation capacity on tumor progression and morphology. The model predicts that the frequency of symmetric cancer stem cell division determines the resulting stem cell pool size, and that the symmetric division frequency and the stem cell fraction are both typically small, consistent with the cancer stem cell hypothesis. At the same time, we show that intrinsic competition for space and environmental confinement can lead to an increasing stem cell fraction over time despite a fixed, low symmetric division probability. These findings offer a novel explanation for the apparent differences in reported stem cell numbers for different tumors as well as tumors of the same organ, and thus challenging the hypothesis of a fixed stem cell ratio for different tumors. The pivotal role of stem cell division strategies and stem cell ratio on spatio-temporal morphology evolution and self-organizing tumor patterning is discussed. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4931. doi:10.1158/1538-7445.AM2011-4931

P53 spreads out further: suppression of EMT and stemness by activating miR-200c expression

p53 spreads out further: suppression of EMT and stemness by activating miR-200c expression

Wnt Signaling Regulates Symmetry of Division of Neural Stem Cells in the Adult Brain and in Response to Injury

Neural stem cells comprise a small population of subependymal cells in the adult brain that divide asymmetrically under baseline conditions to maintain the stem cell pool and divide symmetrically in response to injury to increase their numbers. Using in vivo and in vitro models, we demonstrate that Wnt signaling plays a role in regulating the symmetric divisions of adult neural stem cells with no change in the proliferation kinetics of the progenitor population. Using BAT-gal transgenic reporter mice to identify cells with active Wnt signaling, we demonstrate that Wnt signaling is absent in stem cells in conditions where they are dividing asymmetrically and that it is upregulated when stem cells are dividing symmetrically, such as (a) during subependymal regeneration in vivo, (b) in response to stroke, and (c) during colony formation in vitro. Moreover, we demonstrate that blocking Wnt signaling in conditions where neural stem cells are dividing symmetrically inhibits neural stem cell expansion both in vivo and in vitro. Together, these findings reveal that the mechanism by which Wnt signaling modulates the size of the stem cell pool is by regulating the symmetry of stem cell division.

Stem Cell Fate in Proliferating Tissues: Equal Odds in a Game of Chance

Quantitative lineage tracing reveals stem cell fate invivo. A new study in a recent issue of Cell shows intestinal crypt stem cells are functionally equivalent, with equal odds of differentiation. Differentiating stem cells are replaced by the symmetric division of adjacent stem cells.

Role of symmetric and asymmetric division of stem cells in developing drug resistance

Often, resistance to drugs is an obstacle to a successful treatment of cancer. In spite of the importance of the problem, the actual mechanisms that control the evolution of drug resistance are not fully understood. Many attempts to study drug resistance have been made in the mathematical modeling literature. Clearly, in order to understand drug resistance, it is imperative to have a good model of the underlying dynamics of cancer cells. One of the main ingredients that has been recently introduced into the rapidly growing pool of mathematical cancer models is stem cells. Surprisingly, this all-so-important subset of cells has not been fully integrated into existing mathematical models of drug resistance. In this work we incorporate the various possible ways in which a stem cell may divide into the study of drug resistance. We derive a previously undescribed estimate of the probability of developing drug resistance by the time a tumor is detected and calculate the expected number of resistant cancer stem cells at the time of tumor detection. To demonstrate the significance of this approach, we combine our previously undescribed mathematical estimates with clinical data that are taken from a recent six-year follow-up of patients receiving imatinib for the first-line treatment of chronic myelogenous leukemia. Based on our analysis we conclude that leukemia stem cells must tend to renew symmetrically as opposed to their healthy counterparts that predominantly divide asymmetrically.

Notch regulates the switch from symmetric to asymmetric neural stem cell division in the Drosophila optic lobe

The proper balance between symmetric and asymmetric stem cell division is crucial both to maintain a population of stem cells and to prevent tumorous overgrowth. Neural stem cells in the Drosophila optic lobe originate within a polarised neuroepithelium, where they divide symmetrically. Neuroepithelial cells are transformed into asymmetrically dividing neuroblasts in a precisely regulated fashion. This cell fate transition is highly reminiscent of the switch from neuroepithelial cells to radial glial cells in the developing mammalian cerebral cortex. To identify the molecules that mediate the transition, we microdissected neuroepithelial cells and compared their transcriptional profile with similarly obtained optic lobe neuroblasts. We find genes encoding members of the Notch pathway expressed in neuroepithelial cells. We show that Notch mutant clones are extruded from the neuroepithelium and undergo premature neurogenesis. A wave of proneural gene expression is thought to regulate the timing of the transition from neuroepithelium to neuroblast. We show that the proneural wave transiently suppresses Notch activity in neuroepithelial cells, and that inhibition of Notch triggers the switch from symmetric, proliferative division, to asymmetric, differentiative division.

Higher percentage of CD133+ cells is associated with poor prognosis in colon carcinoma patients with stage IIIB

BackgroundCancer stem cell model suggested that tumor progression is driven by the overpopulation of cancer stem cells and eradicating or inhibiting the symmetric division of cancer stem cells would become the most important therapeutic strategy. However, clinical evidence for this hypothesis is still scarce. To evaluate the overpopulation hypothesis of cancer stem cells the association of percentage of CD133+ tumor cells with clinicopathological parameters in colon cancer was investigated since CD133 is a putative cancer stem cell marker shared by multiple solid tumors.Patients and methodsTumor tissues matched with adjacent normal tissues were collected from 104 stage IIIB colon cancer patients who were subject to radical resection between January, 1999 to July, 2003 in this center. The CD133 expression was examined with immunohistochemical staining. The correlation of the percentage of CD133+ cell with clinicopathological parameters and patients' 5-year survival was analyzed.ResultsThe CD133+ cells were infrequent and heterogeneous distribution in the cancer tissue. Staining of CD133 was localized not only on the glandular-luminal surface of cancer cells but also on the invasive budding and the poorly differentiated tumors with ductal structures. Both univariate and multivariate survival analysis revealed that the percentage of CD133+ cancer cells and the invasive depth of tumor were independently prognostic. The patients with a lower percentage of CD133+ cancer cells (less than 5%) were strongly associated with a higher 5-year survival rate than those with a higher percentage of CD133+ cancer cells (greater than or equal to 55%). Additionally, no correlation was obtained between the percentage of CD133+ cancer cells and the other clinicopathological parameters including gender, age, site of primary mass, pathologic types, grades, and invasive depth.ConclusionThe fact that a higher percentage CD133+ cells were strongly associated with a poorer prognosis in patients with locally advanced colon cancer implicated that CD133+ cancer cells contribute to the tumor progression, and the overpopulation hypothesis of cancer stem cell seems reasonable.

Regulation of Self-renewal and Differentiation in the Drosophila Nervous System

Stem cells can divide symmetrically to generate two similar daughter cells and expand the stem cell pool or asymmetrically to self-renew and generate differentiating daughter cells. The proper balance between symmetric and asymmetric division is critical for the generation and subsequent repair of tissues. Furthermore, unregulated stem cell division has been shown to result in tumorous overgrowth. The Drosophila nervous system has proved to be a fruitful model system for studying the biology of neural stem cell division and uncovering the molecular mechanisms that, when disrupted, can lead to tumor formation. We are using the Drosophila embryonic and larval nervous systems as models to study the regulation of symmetric and asymmetric stem cell division.

Imaging Hematopoietic Precursor Division in Real Time

Stem cells are thought to balance self-renewal and differentiation through asymmetric and symmetric divisions, but whether such divisions occur during hematopoietic development remains unknown. Using a Notch reporter mouse, in which GFP acts as a sensor for differentiation, we image hematopoietic precursors and show that they undergo both symmetric and asymmetric divisions. In addition we show that the balance between these divisions is not hardwired but responsive to extrinsic and intrinsic cues. Precursors in a prodifferentiation environment preferentially divide asymmetrically, whereas those in a prorenewal environment primarily divide symmetrically. Oncoproteins can also influence division pattern: although BCR-ABL predominantly alters the rate of division and death, NUP98-HOXA9 promotes symmetric division, suggesting that distinct oncogenes subvert different aspects of cellular function. These studies establish a system for tracking division of hematopoietic precursors and show that the balance of symmetric and asymmetric division can be influenced by the microenvironment and subverted by oncogenes.

Symmetric Division of Cancer Stem Cells – a Key Mechanism in Tumor Growth that should be Targeted in Future Therapeutic Approaches

As cancer stem cells (SCs) drive tumor growth, it is only through the elimination of those cancer SCs that a pharmacologic cure can be attained. To study ways to develop drugs that target cancer SC, we investigated changes in cellular mechanisms and kinetics that occur in SC populations during colorectal cancer (CRC) development. We used computer modeling to determine which changes could give rise to exponential increases in both SC and non-SC populations in CRC. Our results show that the only mechanism that can explain how these subpopulations increase exponentially in CRC development involves an increase in symmetric SC cell division. This finding suggests that any systemic therapies designed to effectively treat CRC and other cancers must act to control or eliminate symmetrical cancer SC division in tumors, while minimally affecting normal SC division in non-tumor tissues.