Publications by authors named "Steven X Hou"

42 Publications

An MST4-pβ-Catenin Signaling Axis Controls Intestinal Stem Cell and Tumorigenesis.

Adv Sci (Weinh) 2021 09 8;8(17):e2004850. Epub 2021 Jul 8.

State Key Laboratory of Genetic Engineering, Department of Cell and Developmental Biology, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China.

Elevated Wnt/β-catenin signaling has been commonly associated with tumorigenesis especially colorectal cancer (CRC). Here, an MST4-pβ-catenin signaling axis essential for intestinal stem cell (ISC) homeostasis and CRC development is uncovered. In response to Wnt3a stimulation, the kinase MST4 directly phosphorylates β-catenin at Thr40 to block its Ser33 phosphorylation by GSK3β. Thus, MST4 mediates an active process that prevents β-catenin from binding to and being degraded by β-TrCP, leading to accumulation and full activation of β-catenin. Depletion of MST4 causes loss of ISCs and inhibits CRC growth. Mice bearing either MST4 mutation with constitutive kinase activity or β-catenin mutation mimicking MST4-mediated phosphorylation show overly increased ISCs/CSCs and exacerbates CRC. Furthermore, the MST4-pβ-catenin axis is upregulated and correlated with poor prognosis of human CRC. Collectively, this work establishes a previously undefined machinery for β-catenin activation, and further reveals its function in stem cell and tumor biology, opening new opportunities for targeted therapy of CRC.
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http://dx.doi.org/10.1002/advs.202004850DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8425901PMC
September 2021

Arf1-mediated lipid metabolism sustains cancer cells and its ablation induces anti-tumor immune responses in mice.

Nat Commun 2020 01 10;11(1):220. Epub 2020 Jan 10.

The Basic Research Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD, 21702, USA.

Cancer stem cells (CSCs) may be responsible for treatment resistance, tumor metastasis, and disease recurrence. Here we demonstrate that the Arf1-mediated lipid metabolism sustains cells enriched with CSCs and its ablation induces anti-tumor immune responses in mice. Notably, Arf1 ablation in cancer cells induces mitochondrial defects, endoplasmic-reticulum stress, and the release of damage-associated molecular patterns (DAMPs), which recruit and activate dendritic cells (DCs) at tumor sites. The activated immune system finally elicits antitumor immune surveillance by stimulating T-cell infiltration and activation. Furthermore, TCGA data analysis shows an inverse correlation between Arf1 expression and T-cell infiltration and activation along with patient survival in various human cancers. Our results reveal that Arf1-pathway knockdown not only kills CSCs but also elicits a tumor-specific immune response that converts dying CSCs into a therapeutic vaccine, leading to durable benefits.
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http://dx.doi.org/10.1038/s41467-019-14046-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6954189PMC
January 2020

Cancer Stem Cells and Stem Cell Tumors in Drosophila.

Adv Exp Med Biol 2019 ;1167:175-190

The Basic Research Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD, USA.

Accumulative studies suggest that a fraction of cells within a tumor, known as cancer stem cells (CSCs) that initiate tumors, show resistance to most of the therapies, and causes tumor recurrence and metastasis. CSCs could be either transformed normal stem cells or reprogrammed differentiated cells. The eventual goal of CSC research is to identify pathways that selectively regulate CSCs and then target these pathways to eradicate CSCs. CSCs and normal stem cells share some common features, such as self-renewal, the production of differentiated progeny, and the expression of stem-cell markers, however, CSCs vary from normal stem cells in forming tumors. Specifically, CSCs are normally resistant to standard therapies. In addition, CSCs and non-CSCs can be mutually convertible in response to different signals or microenvironments. Even though CSCs are involved in human cancers, the biology of CSCs, is still not well understood, there are urgent needs to study CSCs in model organisms. In the last several years, discoveries in Drosophila have greatly contributed to our understanding of human cancer. Stem-cell tumors in Drosophila share various properties with human CSCs and maybe used to understand the biology of CSCs. In this chapter, we first briefly review CSCs in mammalian systems, then discuss stem-cell tumors in the Drosophila posterior midgut and Malpighian tubules (kidney) and their unique properties as revealed by studying oncogenic Ras protein (Ras)-transformed stem-cell tumors in the Drosophila kidney and dominant-negative Notch (N)-transformed stem-cell tumors in the Drosophila intestine. At the end, we will discuss potential approaches to eliminate CSCs and achieve tumor regression. In future, by screening adult Drosophila neoplastic stem-cell tumor models, we hope to identify novel and efficacious compounds for the treatment of human cancers.
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http://dx.doi.org/10.1007/978-3-030-23629-8_10DOI Listing
September 2019

Corrigendum to "The PDZ-GEF Gef26 regulates synapse development and function via FasII and Rap 1 at the Drosophila neuromuscular junction" [Exp. Cell Res. 374 (2019) 342-352].

Exp Cell Res 2019 Aug 10;381(1):164. Epub 2019 May 10.

The Key Laboratory of Development Genes and Human Diseases, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing, 210096, China. Electronic address:

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http://dx.doi.org/10.1016/j.yexcr.2019.04.024DOI Listing
August 2019

The PDZ-GEF Gef26 regulates synapse development and function via FasII and Rap1 at the Drosophila neuromuscular junction.

Exp Cell Res 2019 01 13;374(2):342-352. Epub 2018 Dec 13.

The Key Laboratory of Development Genes and Human Diseases, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China. Electronic address:

Guanine nucleotide exchange factors (GEFs) are essential for small G proteins to activate their downstream signaling pathways, which are involved in morphogenesis, cell adhesion, and migration. Mutants of Gef26, a PDZ-GEF (PDZ domain-containing guanine nucleotide exchange factor) in Drosophila, exhibit strong defects in wings, eyes, and the reproductive and nervous systems. However, the precise roles of Gef26 in development remain unclear. In the present study, we analyzed the role of Gef26 in synaptic development and function. We identified significant decreases in bouton number and branch length at larval neuromuscular junctions (NMJs) in Gef26 mutants, and these defects were fully rescued by restoring Gef26 expression, indicating that Gef26 plays an important role in NMJ morphogenesis. In addition to the observed defects in NMJ morphology, electrophysiological analyses revealed functional defects at NMJs, and locomotor deficiency appeared in Gef26 mutant larvae. Furthermore, Gef26 regulated NMJ morphogenesis by regulating the level of synaptic Fasciclin II (FasII), a well-studied cell adhesion molecule that functions in NMJ development and remodeling. Finally, our data demonstrate that Gef26-specific small G protein Rap1 worked downstream of Gef26 to regulate the level of FasII at NMJs, possibly through a βPS integrin-mediated signaling pathway. Taken together, our findings define a novel role of Gef26 in regulating NMJ development and function.
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http://dx.doi.org/10.1016/j.yexcr.2018.12.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8189168PMC
January 2019

Glycolytic reprogramming through PCK2 regulates tumor initiation of prostate cancer cells.

Oncotarget 2017 Oct 28;8(48):83602-83618. Epub 2017 Jun 28.

The Basic Research Laboratory, National Cancer Institute, National Institutes of Health Frederick, Frederick, MD 21702, USA.

Tumor-initiating cells (TICs) play important roles in tumor progression and metastasis. Identifying the factors regulating TICs may open new avenues in cancer therapy. Here, we show that TIC-enriched prostate cancer cell clones use more glucose and secrete more lactate than TIC-low clones. We determined that elevated levels of phosphoenolpyruvate carboxykinase isoform 2 (PCK2) are critical for the metabolic switch and the maintenance of TICs in prostate cancer. Information from prostate cancer patient databases revealed that higher PCK2 levels correlated with more aggressive tumors and lower survival rates. PCK2 knockdown resulted in low TIC numbers, increased cytosolic acetyl-CoA and cellular protein acetylation. Our data suggest PCK2 promotes tumor initiation by lowering acetyl-CoA level through reducing the mitochondrial tricarboxylic acid (TCA) cycle. Thus, PCK2 is a potential therapeutic target for aggressive prostate tumors.
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http://dx.doi.org/10.18632/oncotarget.18787DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5663539PMC
October 2017

The cell polarity protein Scrib functions as a tumor suppressor in liver cancer.

Oncotarget 2017 Apr;8(16):26515-26531

Department of Biochemistry and Molecular Biology, Molecular Oncology & Biomarkers Program, Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA.

Scrib is a membrane protein that is involved in the maintenance of apical-basal cell polarity of the epithelial tissues. However, Scrib has also been shown to be mislocalized to the cytoplasm in breast and prostate cancer. Here, for the first time, we report that Scrib not only translocates to the cytoplasm but also to the nucleus in hepatocellular carcinoma (HCC) cells, and in mouse and human liver tumor samples. We demonstrate that Scrib overexpression suppresses the growth of HCC cells in vitro, and Scrib deficiency enhances liver tumor growth in vivo. At the molecular level, we have identified the existence of a positive feed-back loop between Yap1 and c-Myc in HCC cells, which Scrib disrupts by simultaneously regulating the MAPK/ERK and Hippo signaling pathways. Overall, Scrib inhibits liver cancer cell proliferation by suppressing the expression of three oncogenes, Yap1, c-Myc and cyclin D1, thereby functioning as a tumor suppressor in liver cancer.
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http://dx.doi.org/10.18632/oncotarget.15713DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5432276PMC
April 2017

The SWI/SNF Complex Protein Snr1 Is a Tumor Suppressor in Imaginal Tissues.

Cancer Res 2017 02 6;77(4):862-873. Epub 2016 Dec 6.

Department of Biological Science, Florida State University, Tallahassee, Florida.

Components of the SWI/SNF chromatin-remodeling complex are among the most frequently mutated genes in various human cancers, yet only SMARCB1/hSNF5, a core member of the SWI/SNF complex, is mutated in malignant rhabdoid tumors (MRT). How SMARCB1/hSNF5 functions differently from other members of the SWI/SNF complex remains unclear. Here, we use imaginal epithelial tissues to demonstrate that Snr1, the conserved homolog of human SMARCB1/hSNF5, prevents tumorigenesis by maintaining normal endosomal trafficking-mediated signaling cascades. Removal of Snr1 resulted in neoplastic tumorigenic overgrowth in imaginal epithelial tissues, whereas depletion of any other members of the SWI/SNF complex did not induce similar phenotypes. Unlike other components of the SWI/SNF complex that were detected only in the nucleus, Snr1 was observed in both the nucleus and the cytoplasm. Aberrant regulation of multiple signaling pathways, including Notch, JNK, and JAK/STAT, was responsible for tumor progression upon -depletion. Our results suggest that the cytoplasmic Snr1 may play a tumor suppressive role in imaginal tissues, offering a foundation for understanding the pivotal role of SMARCB1/hSNF5 in suppressing MRT during early childhood. .
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http://dx.doi.org/10.1158/0008-5472.CAN-16-0963DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7885033PMC
February 2017

The lipolysis pathway sustains normal and transformed stem cells in adult Drosophila.

Nature 2016 Oct 28;538(7623):109-113. Epub 2016 Sep 28.

The Basic Research Laboratory, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.

Cancer stem cells (CSCs) may be responsible for tumour dormancy, relapse and the eventual death of most cancer patients. In addition, these cells are usually resistant to cytotoxic conditions. However, very little is known about the biology behind this resistance to therapeutics. Here we investigated stem-cell death in the digestive system of adult Drosophila melanogaster. We found that knockdown of the coat protein complex I (COPI)-Arf79F (also known as Arf1) complex selectively killed normal and transformed stem cells through necrosis, by attenuating the lipolysis pathway, but spared differentiated cells. The dying stem cells were engulfed by neighbouring differentiated cells through a draper-myoblast city-Rac1-basket (also known as JNK)-dependent autophagy pathway. Furthermore, Arf1 inhibitors reduced CSCs in human cancer cell lines. Thus, normal or cancer stem cells may rely primarily on lipid reserves for energy, in such a way that blocking lipolysis starves them to death. This finding may lead to new therapies that could help to eliminate CSCs in human cancers.
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http://dx.doi.org/10.1038/nature19788DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7798135PMC
October 2016

Whole-animal genome-wide RNAi screen identifies networks regulating male germline stem cells in Drosophila.

Nat Commun 2016 08 3;7:12149. Epub 2016 Aug 3.

Basic Research Laboratory, National Cancer Institute at Frederick, National Institutes of Health, 1050 Boyles Street, Building 560, Room 12-70, Frederick, Maryland 21702, USA.

Stem cells are regulated both intrinsically and externally, including by signals from the local environment and distant organs. To identify genes and pathways that regulate stem-cell fates in the whole organism, we perform a genome-wide transgenic RNAi screen through ubiquitous gene knockdowns, focusing on regulators of adult Drosophila testis germline stem cells (GSCs). Here we identify 530 genes that regulate GSC maintenance and differentiation. Of these, we further knock down 113 selected genes using cell-type-specific Gal4s and find that more than half were external regulators, that is, from the local microenvironment or more distal sources. Some genes, for example, versatile (vers), encoding a heterochromatin protein, regulates GSC fates differentially in different cell types and through multiple pathways. We also find that mitosis/cytokinesis proteins are especially important for male GSC maintenance. Our findings provide valuable insights and resources for studying stem cell regulation at the organismal level.
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http://dx.doi.org/10.1038/ncomms12149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4976209PMC
August 2016

The novel tumour suppressor Madm regulates stem cell competition in the Drosophila testis.

Nat Commun 2016 Jan 21;7:10473. Epub 2016 Jan 21.

The Basic Research Laboratory, National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702, USA.

Stem cell competition has emerged as a mechanism for selecting fit stem cells/progenitors and controlling tumourigenesis. However, little is known about the underlying molecular mechanism. Here we identify Mlf1-adaptor molecule (Madm), a novel tumour suppressor that regulates the competition between germline stem cells (GSCs) and somatic cyst stem cells (CySCs) for niche occupancy. Madm knockdown results in overexpression of the EGF receptor ligand vein (vn), which further activates EGF receptor signalling and integrin expression non-cell autonomously in CySCs to promote their overproliferation and ability to outcompete GSCs for niche occupancy. Conversely, expressing a constitutively activated form of the Drosophila JAK kinase (hop(Tum-l)) promotes Madm nuclear translocation, and suppresses vn and integrin expression in CySCs that allows GSCs to outcompete CySCs for niche occupancy and promotes GSC tumour formation. Tumour suppressor-mediated stem cell competition presented here could be a mechanism of tumour initiation in mammals.
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http://dx.doi.org/10.1038/ncomms10473DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4736159PMC
January 2016

The Nuclear Matrix Protein Megator Regulates Stem Cell Asymmetric Division through the Mitotic Checkpoint Complex in Drosophila Testes.

PLoS Genet 2015 Dec 29;11(12):e1005750. Epub 2015 Dec 29.

The Basic Research Laboratory, National Cancer Institute, National Institutes of Health, Frederick, Maryland, United States of America.

In adult Drosophila testis, asymmetric division of germline stem cells (GSCs) is specified by an oriented spindle and cortically localized adenomatous coli tumor suppressor homolog 2 (Apc2). However, the molecular mechanism underlying these events remains unclear. Here we identified Megator (Mtor), a nuclear matrix protein, which regulates GSC maintenance and asymmetric division through the spindle assembly checkpoint (SAC) complex. Loss of Mtor function results in Apc2 mis-localization, incorrect centrosome orientation, defective mitotic spindle formation, and abnormal chromosome segregation that lead to the eventual GSC loss. Expression of mitotic arrest-deficient-2 (Mad2) and monopolar spindle 1 (Mps1) of the SAC complex effectively rescued the GSC loss phenotype associated with loss of Mtor function. Collectively our results define a new role of the nuclear matrix-SAC axis in regulating stem cell maintenance and asymmetric division.
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http://dx.doi.org/10.1371/journal.pgen.1005750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703072PMC
December 2015

Genome-wide RNAi screen identifies networks involved in intestinal stem cell regulation in Drosophila.

Cell Rep 2015 Feb 19;10(7):1226-38. Epub 2015 Feb 19.

Basic Research Laboratory, National Cancer Institute at Frederick, NIH, Frederick, MD 21702, USA. Electronic address:

The intestinal epithelium is the most rapidly self-renewing tissue in adult animals and maintained by intestinal stem cells (ISCs) in both Drosophila and mammals. To comprehensively identify genes and pathways that regulate ISC fates, we performed a genome-wide transgenic RNAi screen in adult Drosophila intestine and identified 405 genes that regulate ISC maintenance and lineage-specific differentiation. By integrating these genes into publicly available interaction databases, we further developed functional networks that regulate ISC self-renewal, ISC proliferation, ISC maintenance of diploid status, ISC survival, ISC-to-enterocyte (EC) lineage differentiation, and ISC-to-enteroendocrine (EE) lineage differentiation. By comparing regulators among ISCs, female germline stem cells, and neural stem cells, we found that factors related to basic stem cell cellular processes are commonly required in all stem cells, and stem-cell-specific, niche-related signals are required only in the unique stem cell type. Our findings provide valuable insights into stem cell maintenance and lineage-specific differentiation.
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http://dx.doi.org/10.1016/j.celrep.2015.01.051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420031PMC
February 2015

Enteroendocrine cells are generated from stem cells through a distinct progenitor in the adult Drosophila posterior midgut.

Development 2015 Feb;142(4):644-53

Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21701, USA

Functional mature cells are continually replenished by stem cells to maintain tissue homoeostasis. In the adult Drosophila posterior midgut, both terminally differentiated enterocyte (EC) and enteroendocrine (EE) cells are generated from an intestinal stem cell (ISC). However, it is not clear how the two differentiated cells are generated from the ISC. In this study, we found that only ECs are generated through the Su(H)GBE(+) immature progenitor enteroblasts (EBs), whereas EEs are generated from ISCs through a distinct progenitor pre-EE by a novel lineage-tracing system. EEs can be generated from ISCs in three ways: an ISC becoming an EE, an ISC becoming a new ISC and an EE through asymmetric division, or an ISC becoming two EEs through symmetric division. We further identified that the transcriptional factor Prospero (Pros) regulates ISC commitment to EEs. Our data provide direct evidence that different differentiated cells are generated by different modes of stem cell lineage specification within the same tissues.
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http://dx.doi.org/10.1242/dev.113357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4325374PMC
February 2015

The Osa-containing SWI/SNF chromatin-remodeling complex regulates stem cell commitment in the adult Drosophila intestine.

Development 2013 Sep;140(17):3532-40

Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.

The proportion of stem cells versus differentiated progeny is well balanced to maintain tissue homeostasis, which in turn depends on the balance of the different signaling pathways involved in stem cell self-renewal versus lineage-specific differentiation. In a screen for genes that regulate cell lineage determination in the posterior midgut, we identified that the Osa-containing SWI/SNF (Brahma) chromatin-remodeling complex regulates Drosophila midgut homeostasis. Mutations in subunits of the Osa-containing complex result in intestinal stem cell (ISC) expansion as well as enteroendocrine (EE) cell reduction. We further demonstrated that Osa regulates ISC self-renewal and differentiation into enterocytes by elaborating Notch signaling, and ISC commitment to differentiation into EE cells by regulating the expression of Asense, an EE cell fate determinant. Our data uncover a unique mechanism whereby the commitment of stem cells to discrete lineages is coordinately regulated by chromatin-remodeling factors.
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http://dx.doi.org/10.1242/dev.096891DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3742141PMC
September 2013

Stem cells in the Drosophila digestive system.

Adv Exp Med Biol 2013 ;786:63-78

The Mouse Cancer Genetics Program, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702, USA.

Adult stem cells maintain tissue homeostasis by continuously replenishing damaged, aged and dead cells in any organism. Five types of region and organ-specific multipotent adult stem cells have been identified in the Drosophila digestive system: intestinal stem cells (ISCs) in the posterior midgut; hindgut intestinal stem cells (HISCs) at the midgut/hindgut junction; renal and nephric stem cells (RNSCs) in the Malpighian Tubules; type I gastric stem cells (GaSCs) at foregut/midgut junction; and type II gastric stem cells (GSSCs) at the middle of the midgut. Despite the fact that each type of stem cell is unique to a particular organ, they share common molecular markers and some regulatory signaling pathways. Due to the simpler tissue structure, ease of performing genetic analysis, and availability of abundant mutants, Drosophila serves as an elegant and powerful model system to study complex stem cell biology. The recent discoveries, particularly in the Drosophila ISC system, have greatly advanced our understanding of stem cell self-renewal, differentiation, and the role of stem cells play in tissue homeostasis/regeneration and adaptive tissue growth.
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http://dx.doi.org/10.1007/978-94-007-6621-1_5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7571253PMC
September 2013

Broad relays hormone signals to regulate stem cell differentiation in Drosophila midgut during metamorphosis.

Development 2012 Nov;139(21):3917-25

The Mouse Cancer Genetics Program, Frederick National Laboratory for Cancer Research, National Institutes of Health, Frederick, MD 21702, USA.

Like the mammalian intestine, the Drosophila adult midgut is constantly replenished by multipotent intestinal stem cells (ISCs). Although it is well known that adult ISCs arise from adult midgut progenitors (AMPs), relatively little is known about the mechanisms that regulate AMP specification. Here, we demonstrate that Broad (Br)-mediated hormone signaling regulates AMP specification. Br is highly expressed in AMPs temporally during the larva-pupa transition stage, and br loss of function blocks AMP differentiation. Furthermore, Br is required for AMPs to develop into functional ISCs. Conversely, br overexpression drives AMPs toward premature differentiation. In addition, we found that Br and Notch (N) signaling function in parallel pathways to regulate AMP differentiation. Our results reveal a molecular mechanism whereby Br-mediated hormone signaling directly regulates stem cells to generate adult cells during metamorphosis.
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http://dx.doi.org/10.1242/dev.083030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3472594PMC
November 2012

Generation and staining of intestinal stem cell lineage in adult midgut.

Methods Mol Biol 2012 ;879:47-69

Mouse Cancer Genetics Program, National Cancer Institute, Frederick, MD, USA.

Stem cell-mediated tissue repair is a promising approach in regenerative medicine. Intestinal epithelium is the most rapidly self-renewing tissue in adult mammals. Recently, using lineage tracing and molecular marker labeling, intestinal stem cells (ISCs) have been identified in Drosophila adult midgut. ISCs reside at the basement membrane and are multipotent as they produce both enterocytes and enteroendocrine cells. The adult Drosophila midgut provides an excellent in vivo model organ to study ISC behavior during aging, stress, regeneration, and infection. It has been demonstrated that Notch, Janus kinase/signal transducer and activator of transcription, epidermal growth factor receptor/mitogen-activated protein kinase, Hippo, and wingless signaling pathways regulate ISCs proliferation and differentiation. There are plenty of genetic tools and markers developed in recent years in Drosophila stem cell studies. These tools and markers are essential in the precise identification of stem cells as well as manipulation of genes in stem cell regulation. Here, we describe the details of genetic tools, markers, and immunolabeling techniques used in identification and characterization of adult midgut stem cells in Drosophila.
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http://dx.doi.org/10.1007/978-1-61779-815-3_4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7461621PMC
September 2012

The adult Drosophila gastric and stomach organs are maintained by a multipotent stem cell pool at the foregut/midgut junction in the cardia (proventriculus).

Cell Cycle 2011 Apr 1;10(7):1109-20. Epub 2011 Apr 1.

National Institutes of Health, Frederick, MD USA.

Stomach cancer is the second most frequent cause of cancer-related death worldwide. Thus, it is important to elucidate the properties of gastric stem cells, including their regulation and transformation. To date, such stem cells have not been identified in Drosophila. Here, using clonal analysis and molecular marker labeling, we identify a multipotent stem-cell pool at the foregut/midgut junction in the cardia (proventriculus). We found that daughter cells migrate upward either to anterior midgut or downward to esophagus and crop. The cardia functions as a gastric valve and the anterior midgut and crop together function as a stomach in Drosophila; therefore, we named the foregut/midgut stem cells as gastric stem cells (GaSC). We further found that JAK-STAT signaling regulates GaSCs' proliferation, Wingless signaling regulates GaSCs' self-renewal, and hedgehog signaling regulates GaSCs' differentiation. The differentiation pattern and genetic control of the Drosophila GaSCs suggest the possible similarity to mouse gastric stem cells. The identification of the multipotent stem cell pool in the gastric gland in Drosophila will facilitate studies of gastric stem cell regulation and transformation in mammal.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3100886PMC
http://dx.doi.org/10.4161/cc.10.7.14830DOI Listing
April 2011

Kidney stem cells found in adult zebrafish.

Cell Stem Cell 2011 Mar;8(3):247-9

The Mouse Cancer Genetics Program, National Cancer Institute at Frederick, National Institutes of Health, Frederick, MD 21702, USA.

Recently in Nature, Davidson and coworkers (Diep et al., 2011) identified nephron progenitors/stem cells located at the point of fusion with the pronephric tubules in adult zebrafish. Clumps of progenitors give rise to functional nephrons after serial transplantation, demonstrating the ability of tissue stem cells to regenerate damaged kidney structures.
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http://dx.doi.org/10.1016/j.stem.2011.02.008DOI Listing
March 2011

Spermatogonial stem cells, infertility and testicular cancer.

J Cell Mol Med 2011 Mar;15(3):468-83

Mouse Cancer Genetics Program, National Institutes of Health, National Cancer Institute at Frederick, Frederick, MD 21702, USA.

The spermatogonial stem cells (SSCs) are responsible for the transmission of genetic information from an individual to the next generation. SSCs play critical roles in understanding the basic reproductive biology of gametes and treatments of human infertility. SSCs not only maintain normal spermatogenesis, but also sustain fertility by critically balancing both SSC self-renewal and differentiation. This self-renewal and differentiation in turn is tightly regulated by a combination of intrinsic gene expression within the SSC as well as the extrinsic gene signals from the niche. Increased SSCs self-renewal at the expense of differentiation result in germ cell tumours, on the other hand, higher differentiation at the expense of self-renewal can result in male sterility. Testicular germ cell cancers are the most frequent cancers among young men in industrialized countries. However, understanding the pathogenesis of testis cancer has been difficult because it is formed during foetal development. Recent studies suggest that SSCs can be reprogrammed to become embryonic stem (ES)-like cells to acquire pluripotency. In the present review, we summarize the recent developments in SSCs biology and role of SSC in testicular cancer. We believe that studying the biology of SSCs will not only provide better understanding of stem cell regulation in the testis, but eventually will also be a novel target for male infertility and testicular cancers.
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http://dx.doi.org/10.1111/j.1582-4934.2010.01242.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3064728PMC
March 2011

Characterization of midgut stem cell- and enteroblast-specific Gal4 lines in drosophila.

Genesis 2010 Oct;48(10):607-11

Mouse Cancer Genetics Program, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland, USA.

The homeostasis of Drosophila midgut is maintained by multipotent intestinal stem cells (ISCs), each of which gives rise to a new ISC and an immature daughter cell, enteroblast (EB), after one asymmetric cell division. In Drosophila, the Gal4-UAS system is widely used to manipulate gene expression in a tissue- or cell-specific manner, but in Drosophila midgut, there are no ISC- or EB-specific Gal4 lines available. Here we report the generation and characterization of Dl-Gal4 and Su(H)GBE-Gal4 lines, which are expressed specifically in the ISCs and EBs separately. Additionally, we demonstrate that Dl-Gal4 and Su(H)GBE-Gal4 are expressed in adult midgut progenitors (AMPs) and niche peripheral cells (PCs) separately in larval midgut. These two Gal4 lines will serve as invaluable tools for navigating ISC behaviors.
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http://dx.doi.org/10.1002/dvg.20661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2958251PMC
October 2010

RapGEF2 is essential for embryonic hematopoiesis but dispensable for adult hematopoiesis.

Blood 2010 Oct 1;116(16):2921-31. Epub 2010 Jul 1.

Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA.

RapGEF2 is one of many guanine nucleotide exchange factors (GEFs) that specifically activate Rap1. Here, we generated RapGEF2 conditional knockout mice and studied its role in embryogenesis and fetal as well as adult hematopoietic stem cell (HSC) regulation. RapGEF2 deficiency led to embryonic lethality at ~ E11.5 due to severe yolk sac vascular defects. However, a similar number of Flk1(+) cells were present in RapGEF2(+/+) and RapGEF2(-/-) yolk sacs indicating that the bipotential early progenitors were in fact generated in the absence of RapGEF2. Further analysis of yolk sacs and embryos revealed a significant reduction of CD41 expressing cells in RapGEF2(-/-) genotype, suggesting a defect in the maintenance of definitive hematopoiesis. RapGEF2(-/-) cells displayed defects in proliferation and migration, and the in vitro colony formation ability of hematopoietic progenitors was also impaired. At the molecular level, Rap1 activation was impaired in RapGEF2(-/-) cells that in turn lead to defective B-raf/ERK signaling. Scl/Gata transcription factor expression was significantly reduced, indicating that the defects observed in RapGEF2(-/-) cells could be mediated through Scl/Gata deregulation. Inducible deletion of RapGEF2 during late embryogenesis in RapGEF2(cko/cko)ER(cre) mice leads to defective fetal liver erythropoiesis. Conversely, inducible deletion in the adult bone marrow, or specific deletion in B cells, T cells, HSCs, and endothelial cells has no impact on hematopoiesis.
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http://dx.doi.org/10.1182/blood-2010-01-262964DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2974602PMC
October 2010

Intestinal stem cell asymmetric division in the Drosophila posterior midgut.

Authors:
Steven X Hou

J Cell Physiol 2010 Sep;224(3):581-4

National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.

Over the past 2 years, our understanding of intestinal stem cells in the Drosophila posterior midgut has advanced greatly. In this review, I will focus on the establishment of these stem cells in their niche during development and the molecular mechanisms that regulate their asymmetric division in adults.
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http://dx.doi.org/10.1002/jcp.22194DOI Listing
September 2010

Tumor suppressors Sav/Scrib and oncogene Ras regulate stem-cell transformation in adult Drosophila malpighian tubules.

J Cell Physiol 2010 Sep;224(3):766-74

Mouse Cancer Genetics Program, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.

An increasing body of evidence suggests that tumors might originate from a few transformed cells that share many properties with normal stem cells. However, it remains unclear how normal stem cells are transformed into cancer stem cells (CSCs). Here, we demonstrated that mutations causing the loss of tumor suppressor Salvador (Sav) or Scribble (Scrib) or activation of the oncogene Ras transform normal stem cells into CSCs through a multistep process in the adult Drosophila Malpighian Tubules (MTs). In wild-type MTs, each stem cell generates one self-renewing and one differentiating daughter cell. However, in flies with loss-of-function sav or scrib or gain-of-function Ras mutations, both daughter cells grew and behaved like stem cells, leading to the formation of tumors in MTs. Ras functioned downstream of Sav and Scrib in regulating the stem-cell transformation. The Ras-transformed stem cells exhibited many of the hallmarks of cancer, such as increased proliferation, reduced cell death, and failure to differentiate. We further demonstrated that several signal transduction pathways (including MEK/MAPK, RhoA, PKA, and TOR) mediate Ras' function in the stem-cell transformation. Therefore, we have identified a molecular mechanism that regulates stem-cell transformation, and this finding may lead to strategies for preventing tumor formation in certain organs.
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http://dx.doi.org/10.1002/jcp.22179DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3391499PMC
September 2010

Competitiveness for the niche and mutual dependence of the germline and somatic stem cells in the Drosophila testis are regulated by the JAK/STAT signaling.

J Cell Physiol 2010 May;223(2):500-10

Mouse Cancer Genetics Program, National Institutes of Health, National Cancer Institute at Frederick, Frederick, Maryland 21702, USA.

In many tissues, two or more types of stem cells share a niche, and how the stem cells coordinate their self-renewal and differentiation is poorly understood. In the Drosophila testis, germ line stem cells (GSCs) and somatic cyst progenitor cells (CPCs) contact each other and share a niche (the hub). The hub expresses a growth factor unpaired (Upd) that activates the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway in GSCs to regulate the stem cell self-renewal. Here, we demonstrate that the JAK/STAT signaling also regulates CPCs self-renewal. We also show that a negative regulator, the suppressor of cytokine signaling 36E (SOCS36E), suppresses JAK/STAT signaling in somatic cells, preventing them from out-competing the GSCs. Furthermore, through selectively manipulating the JAK/STAT signaling level in either CPCs or GSCs, we demonstrate that the somatic JAK/STAT signaling is essential for self-renewal and maintenance of both CPCs and GSCs. These data suggest that a single JAK/STAT signal from the niche orchestrate the competitive and dependent co-existence of GSCs and CPCs in the Drosophila testis niche.
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http://dx.doi.org/10.1002/jcp.22073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2894562PMC
May 2010

JAK-STAT is restrained by Notch to control cell proliferation of the Drosophila intestinal stem cells.

J Cell Biochem 2010 Apr;109(5):992-9

The Mouse Cancer Genetics Program, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.

The Drosophila midgut epithelium undergoes continuous regeneration that is sustained by multipotent intestinal stem cells (ISCs) underneath. Notch signaling has dual functions to control ISC behavior: it slows down the ISC proliferation and drives the activated ISCs into different differentiation pathways at a dose-dependent manner. Here we identified a molecular mechanism to unite these two contradictory functions. We found JAK-STAT signaling controls ISC proliferation and this ability is negatively regulated by Notch at least through a transcriptional control of the JAK-STAT signaling ligand, unpaired (upd). This study provides insight into how stem cells, under steady conditions, balance the processes of proliferation and differentiation to maintain the stable cellular composition of a healthy tissue.
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http://dx.doi.org/10.1002/jcb.22482DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2893559PMC
April 2010

Regulation of intestinal stem cells in mammals and Drosophila.

J Cell Physiol 2010 Jan;222(1):33-7

The Mouse Cancer Genetics Program, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.

The digestive systems in mammals and Drosophila are quite different in terms of their complexity and organization, but their biological functions are similar. The Drosophila midgut is a functional equivalent of the mouse small intestine. Adult intestinal stem cells (ISCs) have been identified in both the mouse small intestine and Drosophila midgut. The anatomy and cell renewal in the Drosophila midgut are similar to those in the mouse small intestine: the intestinal epithelium in both systems is a tube composed of epithelial cells with absorptive and secretory functions; the Notch signaling controls absorptive versus secretory fate decisions in the intestinal epithelium; cell renewal in both systems starts from stem cells in the basal cell layer, and the differentiated cells then move toward the lumen. However, it is clear that the stem cells in the two systems are regulated in different ways. In this review, we will compare cell renewal and stem cell regulation in the two systems.
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http://dx.doi.org/10.1002/jcp.21928DOI Listing
January 2010

Multipotent stem cells in the Malpighian tubules of adult Drosophila melanogaster.

J Exp Biol 2009 Feb;212(Pt 3):413-23

Mouse Cancer Genetics Program, National Institutes of Health, National Cancer Institute, MD 21702, USA.

Excretion is an essential process of an organism's removal of the waste products of metabolism to maintain a constant chemical composition of the body fluids despite changes in the external environment. Excretion is performed by the kidneys in vertebrates and by Malpighian tubules (MTs) in Drosophila. The kidney serves as an excellent model organ to investigate the cellular and molecular mechanisms underlying organogenesis. Mammals and Drosophila share common principles of renal development. Tissue homeostasis, which is accomplished through self-renewal or differentiation of stem cells, is critical for the maintenance of adult tissues throughout the lifetime of an animal. Growing evidence suggests that stem cell self-renewal and differentiation is controlled by both intrinsic and extrinsic factors. Deregulation of stem cell behavior results in cancer formation, tissue degeneration, and premature aging. The mammalian kidney has a low rate of cellular turnover but has a great capacity for tissue regeneration following an ischemic injury. However, there is an ongoing controversy about the source of regenerating cells in the adult kidney that repopulate injured renal tissues. Recently, we identified multipotent stem cells in the MTs of adult Drosophila and found that these stem cells are able to proliferate and differentiate in several types of cells in MTs. Furthermore, we demonstrated that an autocrine JAK-STAT (Janus kinase-signal transducers and activators of transcription) signaling regulates stem cell self-renewal or differentiation of renal stem cells. The Drosophila MTs provide an excellent in vivo system for studying the renal stem cells at cellular and molecular levels. Understanding the molecular mechanisms governing stem cell self-renewal or differentiation in vivo is not only crucial to using stem cells for future regenerative medicine and gene therapy, but it also will increase our understanding of the mechanisms underlying cancer formation, aging and degenerative diseases. Identifying and understanding the cellular processes underlying the development and repair of the mammalian kidney may enable more effective, targeted therapies for acute and chronic kidney diseases in humans.
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http://dx.doi.org/10.1242/jeb.024216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699409PMC
February 2009

Germline stem cells. Preface.

Methods Mol Biol 2008 ;450

Mouse Cancer Genetics Program, National Institutes of Health, National Cancer Institute at Frederick, Frederick, MD, USA.

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http://dx.doi.org/10.1007/978-1-60327-214-8DOI Listing
May 2008
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