The EGF receptor-sox2-EGF receptor feedback loop positively regulates the self-renewal of neural precursor cells

Platelet-derived growth factor receptors differentially inform intertumoral and intratumoral heterogeneity

Growth factor-mediated proliferation and self-renewal maintain tissue-specific stem cells and are frequently dysregulated in cancers. Platelet-derived growth factor (PDGF) ligands and receptors (PDGFRs) are commonly overexpressed in gliomas and initiate tumors, as proven in genetically engineered models. While PDGFRα alterations inform intertumoral heterogeneity toward a proneural glioblastoma (GBM) subtype, we interrogated the role of PDGFRs in intratumoral GBM heterogeneity. We found that PDGFRα is expressed only in a subset of GBMs, while PDGFRβ is more commonly expressed in tumors but is preferentially expressed by self-renewing tumorigenic GBM stem cells (GSCs). Genetic or pharmacological targeting of PDGFRβ (but not PDGFRα) attenuated GSC self-renewal, survival, tumor growth, and invasion. PDGFRβ inhibition decreased activation of the cancer stem cell signaling node STAT3, while constitutively active STAT3 rescued the loss of GSC self-renewal caused by PDGFRβ targeting. In silico survival analysis demonstrated that PDGFRB informed poor prognosis, while PDGFRA was a positive prognostic factor. Our results may explain mixed clinical responses of anti-PDGFR-based approaches and suggest the need for integration of models of cancer as an organ system into development of cancer therapies.

Sox2 targets cyclinE, p27 and survivin to regulate androgen-independent human prostate cancer cell proliferation and apoptosis

OBJECTIVES

Sox2 is a major transcription factor and the transforming growth factor-α (TGF-α)/EGFR autocrine loop is a hallmark of prostate cancer progression. In this study, we have evaluated the effects and potential mechanisms of Sox2 on cell proliferation and apoptosis, and investigated effects of TGF-α on expression of Sox2 on androgen-independent human prostate cancer cells.

MATERIALS AND METHODS

Expression of Sox2 has been determined by RT-PCR, western blot analysis and immunocytochemistry, using RNAi and over-expression strategy to study functions of Sox2 in DU145 and PC-3 cells. Changes in level of proliferation, cell cycle and apoptosis profiles were measured by MTT, colony-forming, bromodeoxyuridine incorporation assays, cell cycle and annexin V analysis.

RESULTS

Sox2 was expressed in six human prostate cancer cell lines, and its inhibition reduced cell proliferation and induced apoptosis in DU145 cells. We have shown that knock-down of Sox2 inhibited G(1) to S phase transition concomitantly with down-regulation of cyclin E and up-regulation of p27 proteins. Conversely, over-expression of Sox2 led to the opposite effect in PC-3 cells but its inhibition induced apoptosis by down-regulation of survivin in DU145 cells. We also found that TGF-α up-regulated Sox2 and survivin protein expression via the EGFR/PI3K/AKT pathway.

CONCLUSIONS

Sox2 expression is necessary for cell proliferation and evasion of apoptosis in prostate cancer cells and TGF-α could regulate Sox2 and survivin expression by activating the EGFR/PI3K/AKT pathway.

Cancer stem cells: distinct entities or dynamically regulated phenotypes?

The origins of tumor-propagating neoplastic stem-like cells [cancer stem cells (CSC)] and their relationship to the bulk population of tumor cells that lack stem-like tumor-propagating features (i.e., transit-amplifying cancer progenitor cells) remain unclear. Recent findings from multiple laboratories show that cancer progenitor cells have the capacity to dedifferentiate and acquire a stem-like phenotype in response to either genetic manipulation or environmental cues. These findings suggest that CSCs and relatively differentiated progenitors coexist in dynamic equilibrium and are subject to bidirectional conversion. In this review, we discuss emerging concepts regarding the stem-like phenotype, its acquisition by cancer progenitor cells, and the molecular mechanisms involved. Understanding the dynamic equilibrium between CSCs and cancer progenitor cells is critical for the development of therapeutic strategies to deplete tumors of their tumor-propagating and treatment-resistant cell subpopulations.

SRY-box-containing gene 2 regulation of nuclear receptor tailless (Tlx) transcription in adult neural stem cells

Adult neurogenesis is maintained by self-renewable neural stem cells (NSCs). Their activity is regulated by multiple signaling pathways and key transcription factors. However, it has been unclear whether these factors interplay with each other at the molecular level. Here we show that SRY-box-containing gene 2 (Sox2) and nuclear receptor tailless (TLX) form a molecular network in adult NSCs. We observed that both Sox2 and TLX proteins bind to the upstream region of Tlx gene. Sox2 positively regulates Tlx expression, whereas the binding of TLX to its own promoter suppresses its transcriptional activity in luciferase reporter assays. Such TLX-mediated suppression can be antagonized by overexpressing wild-type Sox2 but not a mutant lacking the transcriptional activation domain. Furthermore, through regions involved in DNA-binding activity, Sox2 and TLX physically interact to form a complex on DNAs that contain a consensus binding site for TLX. Finally, depletion of Sox2 revealed the potential negative feedback loop of TLX expression that is antagonized by Sox2 in adult NSCs. These data suggest that Sox2 plays an important role in Tlx transcription in cultured adult NSCs.

Interactions of human embryonic stem cell-derived neural progenitors with an electrospun nanofibrillar surface in vitro

Stem cell technology combined with nano-scaffold surfaces provides a new tool for better induction involved in cell lineage differentiations and therefore for central nervous system repair. This study was undertaken to investigate appropriate neural cell-substrate interactions. Neural progenitors (NPs) were established from human embryonic stem cells (hESCs), as a first step, using an adherent system and a defined medium supplemented with a combination of factors. Next, the behavior of hESC-derived NPs (hESC-NPs) was evaluated on a synthetic, randomly oriented, three-dimensional nanofibrillar matrix composed of electrospun polyamide nanofibers (Ultra-Web™) using a variety of experimental approaches. We have demonstrated that homogenous, expandable, and self-renewable NPs can be easily generated from hESCs; they can express related markers Nestin, Sox1, and Pax6; and they can undergo multipotency differentiation to neurons and glials. Functionally, NPs cultured on nanofibers demonstrated an increase in the rate of migration, proliferation, morphology, and neurite length when compared with NPs cultured on two-dimensional culture surfaces. The results suggest that topographical features of the extracellular matrix of the cell environment have paved the way for a better understanding of human neuronal development, thus allowing for future clinical applications.

Enhanced neural progenitor/stem cells self-renewal via the interaction of stress-inducible protein 1 with the prion protein

Prion protein (PrP(C) ), when associated with the secreted form of the stress-inducible protein 1 (STI1), plays an important role in neural survival, neuritogenesis, and memory formation. However, the role of the PrP(C) -STI1 complex in the physiology of neural progenitor/stem cells is unknown. In this article, we observed that neurospheres cultured from fetal forebrain of wild-type (Prnp(+/+) ) and PrP(C) -null (Prnp(0/0) ) mice were maintained for several passages without the loss of self-renewal or multipotentiality, as assessed by their continued capacity to generate neurons, astrocytes, and oligodendrocytes. The homogeneous expression and colocalization of STI1 and PrP(C) suggest that they may associate and function as a complex in neurosphere-derived stem cells. The formation of neurospheres from Prnp(0/0) mice was reduced significantly when compared with their wild-type counterparts. In addition, blockade of secreted STI1, and its cell surface ligand, PrP(C) , with specific antibodies, impaired Prnp(+/+) neurosphere formation without further impairing the formation of Prnp(0/0) neurospheres. Alternatively, neurosphere formation was enhanced by recombinant STI1 application in cells expressing PrP(C) but not in cells from Prnp(0/0) mice. The STI1-PrP(C) interaction was able to stimulate cell proliferation in the neurosphere-forming assay, while no effect on cell survival or the expression of neural markers was observed. These data suggest that the STI1-PrP(C) complex may play a critical role in neural progenitor/stem cells self-renewal via the modulation of cell proliferation, leading to the control of the stemness capacity of these cells during nervous system development.

Concise review: Quiescent and active states of endogenous adult neural stem cells: identification and characterization

The adult mammalian central nervous system (CNS) lacks the capacity for regeneration, making it a highly sought-after topic for researchers. The identification of neural stem cells (NSCs) in the adult CNS wiped out a long-held dogma that the adult brain contains a set number of neurons and is incapable of replacing them. The discovery of adult NSCs (aNSCs) stoked the fire for researchers who dream of brain self-repair. Unfortunately, the quiescent nature and limited plasticity of aNSCs diminish their regenerative potential. Recent studies evaluating aNSC plasticity under pathological conditions indicate that a switch from quiescent to active aNSCs in neurogenic regions plays an important role in both repairing the damaged tissue and preserving progenitor pools. Here, we summarize the most recent findings and present questions about characterizing the active and quiescent aNSCs in major neurogenic regions, and factors for maintaining their active and quiescent states, hoping to outline an emerging view for promoting the endogenous aNSC-based regeneration.

Epigenetic choreographers of neurogenesis in the adult mammalian brain

Epigenetic mechanisms regulate cell differentiation during embryonic development and also serve as important interfaces between genes and the environment in adulthood. Neurogenesis in adults, which generates functional neural cell types from adult neural stem cells, is dynamically regulated by both intrinsic state-specific cell differentiation cues and extrinsic neural niche signals. Epigenetic regulation by DNA and histone modifiers, non-coding RNAs and other self-sustained mechanisms can lead to relatively long-lasting biological effects and maintain functional neurogenesis throughout life in discrete regions of the mammalian brain. Here, we review recent evidence that epigenetic mechanisms carry out diverse roles in regulating specific aspects of adult neurogenesis and highlight the implications of such epigenetic regulation for neural plasticity and disorders.

SOX2 in gastric carcinoma, but not Hath1, is related to patients' clinicopathological features and prognosis

BACKGROUND

SOX2 and Hath1 are transcription factors that are critical for the control of terminal cell differentiation in the gastrointestinal mucosa. This study investigated the correlations between SOX2 and Hath1 expression in gastric carcinoma and patients' clinicopathological features and prognosis.

METHODS

Hath1 and SOX2 were detected by immunohistochemistry in gastric carcinoma (n = 50). Probability of survival of patients after surgery was estimated by the Kaplan-Meier method and compared using Log-rank test.

RESULTS

Hath1 and SOX2 were inversely expressed in gastric carcinoma. Patients with strong SOX2 expression (++ to +++) showed lower incidences of lymph node metastasis (p = 0.007), deeper invasion (p = 0.010), and III-IV clinical stages (p = 0.011) compared to patients with low SOX2 expression (- to +). There was no significant difference in SOX2 and Hath1 expression in the cancerous tissues of the patients with and without Helicobacter pylori infection (p > 0.05). The patients with strong expression of SOX2 in their cancerous tissues (++ to +++) had a better prognosis than those with low expression of SOX2 (- to +; p = 0.005). There was no correlation between Hath1 expression level and prognosis (p = 0.676).

CONCLUSIONS

SOX2 and Hath1 are inversely expressed in gastric carcinoma. SOX2 provides a survival advantage to patients of gastric carcinoma and appears to be associated with metastasis and clinical stages.