A Novel Oncogenic Role of Inositol Phosphatase SHIP2 in ER-Negative Breast Cancer Stem Cells: Involvement of JNK/Vimentin Activation

Biomechanics of cancer stem cells

Cancer stem cells (CSCs) have been believed to be one driving force for tumor progression and drug resistance. Despite the significance of biochemical signaling in malignancy, highly malignant tumor cells or CSCs exhibit lower cellular stiffness than weakly malignant cells or non-CSCs, which are softer than their healthy counterparts, suggesting the inverse correlation between cell stiffness and malignancy. Recent years have witnessed the rapid accumulation of evidence illustrating the reciprocity between cell cytoskeleton/mechanics and CSC functions and the potential of cellular stiffness for specific targeting of CSCs. However, a systematic understanding of tumor cell mechanics and their role in CSCs and tumor progression is still lacking. The present review summarizes the recent progress in the alterations of tumor cell cytoskeleton and stiffness at different stages of tumor progression and recapitulates the relationship between cellular stiffness and CSC functions. The altered cell mechanics may mediate the mechanoadaptive responses that possibly empower CSCs to survive and thrive during metastasis. Furthermore, we highlight the possible impact of tumor cell mechanics on CSC malignancy, which may potentiate low cell stiffness as a mechanical marker for CSC targeting.

Toward Targeted Therapies in Oesophageal Cancers: An Overview

Oesophageal cancer is one of the leading causes of cancer-related death worldwide. Oesophageal cancer occurs as squamous cell carcinoma (ESCC) or adenocarcinoma (EAC). Prognosis for patients with either ESCC or EAC is poor, with less than 20% of patients surviving more than 5 years after diagnosis. A major progress has been made in the development of biomarker-driven targeted therapies against breast and lung cancers, as well as melanoma. However, precision oncology for patients with oesophageal cancer is still virtually non-existent. In this review, we outline the recent advances in oesophageal cancer profiling and clinical trials based on targeted therapies in this disease.

O-Acetyl-GD2 as a Therapeutic Target for Breast Cancer Stem Cells

Synopsis

A sugar-lipid molecule called OAcGD2 is a novel marker for breast cancer stem cells. Treatment with anti-OAcGD2 mAb8B6 may have superior anticancer efficacy by targeting cancer stem cells, thereby reducing metastasis and recurrence of cancer.

Background

Cancer stem cells (CSCs) that drive tumor progression and disease recurrence are rare subsets of tumor cells. CSCs are relatively resistant to conventional chemotherapy and radiotherapy. Eradication of CSCs is thus essential to achieve durable responses. GD2 was reported to be a CSC marker in human triple-negative breast cancer, and anti-GD2 immunotherapy showed reduced tumor growth in cell lines. Using a specific anti-OAcGD2 antibody, mAb8D6, we set out to determine whether OAcGD2⁺ cells exhibit stem cell properties and mAb8D6 can inhibit tumor growth by targeting OAcGD2⁺CSCs.

Method

OAcGD2 expression in patient-derived xenografts (PDXs) of breast cancer was determined by flow cytometric analyses using mAb8D6. The stemness of OAcGD2⁺ cells isolated by sorting and the effects of mAb8B6 were assessed by CSC growth and mammosphere formation in vitro and tumor growth in vivo using PDX models.

Result

We found that the OAcGD2 expression levels in six PDXs of various molecular subtypes of breast cancer highly correlated with their previously defined CSC markers in these PDXs. The sorted OAcGD2⁺ cells displayed a greater capacity for mammosphere formation in vitro and tumor initiation in vivo than OAcGD2⁻ cells. In addition, the majority of OAcGD2⁺ cells were aldehyde dehydrogenase (ALDH⁺) or CD44^hiCD24^lo, the known CSC markers in breast cancer. Treatment of PDXs-bearing mice with mAb8B6, but not doxorubicin, suppressed the tumor growth, along with reduced CSCs as assessed by CSC markers and in vivo tumorigenicity. In vitro, mAb8B6 suppressed proliferation and mammosphere formation and induced apoptosis of OAcGD2⁺ breast cancer cells harvested from PDXs, in a dose-dependent manner. Finally, administration of mAb8B6 in vivo dramatically suppressed tumor growth of OAcGD2⁺ breast CSCs (BCSCs) with complete tumor abrogation in 3/6 mice.

Conclusion

OAcGD2 is a novel marker for CSC in various subtypes of breast cancer. Anti-OAcGD2 mAb8B6 directly eradicated OAcGD2⁺ cells and reduced tumor growth in PDX model. Our data demonstrate the potential of mAb8B6 as a promising immunotherapeutic agent to target BCSCs.

Identification of significant genes and therapeutic agents for breast cancer by integrated genomics

Breast cancer is the most commonly diagnosed malignancy in women; thus, more cancer prevention research is urgently needed. The aim of this study was to predict potential therapeutic agents for breast cancer and determine their molecular mechanisms using integrated bioinformatics. Summary data from a large genome-wide association study of breast cancer was derived from the UK Biobank. The gene expression profile of breast cancer was from the Oncomine database. We performed a network-wide association study and gene set enrichment analysis to identify the significant genes in breast cancer. Then, we performed Gene Ontology analysis using the STRING database and conducted Kyoto Encyclopedia of Genes and Genomes pathway analysis using Cytoscape software. We verified our results using the Gene Expression Profile Interactive Analysis, PROgeneV2, and Human Protein Atlas databases. Connectivity map analysis was used to identify small-molecule compounds that are potential therapeutic agents for breast cancer. We identified 10 significant genes in breast cancer based on the gene expression profile and genome-wide association study. A total of 65 small-molecule compounds were found to be potential therapeutic agents for breast cancer.

Therapeutic Targeting of Nemo-like Kinase in Primary and Acquired Endocrine-resistant Breast Cancer

PURPOSE

Endocrine resistance remains a major clinical challenge in estrogen receptor (ER)-positive breast cancer. Despite the encouraging results from clinical trials for the drugs targeting known survival signaling, relapse is still inevitable. There is an unmet need to discover new drug targets in the unknown escape pathways. Here, we report Nemo-like kinase (NLK) as a new actionable kinase target that endows previously uncharacterized survival signaling in endocrine-resistant breast cancer.

EXPERIMENTAL DESIGN

The effects of NLK inhibition on the viability of endocrine-resistant breast cancer cell lines were examined by MTS assay. The effect of VX-702 on NLK activity was verified by kinase assay. The modulation of ER and its coactivator, SRC-3, by NLK was examined by immunoprecipitation, kinase assay, luciferase assay, and RNA sequencing. The therapeutic effects of VX-702 and everolimus were tested on cell line- and patient-derived xenograft (PDX) tumor models.

RESULTS

NLK overexpression endows reduced endocrine responsiveness and is associated with worse outcome of patients treated with tamoxifen. Mechanistically, NLK may function, at least in part, via enhancing the phosphorylation of ERα and its key coactivator, SRC-3, to modulate ERα transcriptional activity. Through interrogation of a kinase profiling database, we uncovered and verified a highly selective dual p38/NLK inhibitor, VX-702. Coadministration of VX-702 with the mTOR inhibitor, everolimus, demonstrated a significant therapeutic effect in cell line-derived xenograft and PDX tumor models of acquired or de novo endocrine resistance.

CONCLUSIONS

Together, this study reveals the potential of therapeutic modulation of NLK for the management of the endocrine-resistant breast cancers with active NLK signaling.

PTEN and Other PtdIns(3,4,5)P3 Lipid Phosphatases in Breast Cancer

The phosphoinositide 3-kinase (PI3K)/AKT signalling pathway is hyperactivated in ~70% of breast cancers. Class I PI3K generates PtdIns(3,4,5)P₃ at the plasma membrane in response to growth factor stimulation, leading to AKT activation to drive cell proliferation, survival and migration. PTEN negatively regulates PI3K/AKT signalling by dephosphorylating PtdIns(3,4,5)P₃ to form PtdIns(4,5)P₂. PtdIns(3,4,5)P₃ can also be hydrolysed by the inositol polyphosphate 5-phosphatases (5-phosphatases) to produce PtdIns(3,4)P₂. Interestingly, while PTEN is a bona fide tumour suppressor and is frequently mutated/lost in breast cancer, 5-phosphatases such as PIPP, SHIP2 and SYNJ2, have demonstrated more diverse roles in regulating mammary tumourigenesis. Reduced PIPP expression is associated with triple negative breast cancers and reduced relapse-free and overall survival. Although PIPP depletion enhances AKT phosphorylation and supports tumour growth, this also inhibits cell migration and metastasis in vivo, in a breast cancer oncogene-driven murine model. Paradoxically, SHIP2 and SYNJ2 are increased in primary breast tumours, which correlates with invasive disease and reduced survival. SHIP2 or SYNJ2 overexpression promotes breast tumourigenesis via AKT-dependent and independent mechanisms. This review will discuss how PTEN, PIPP, SHIP2 and SYNJ2 distinctly regulate multiple functional targets, and the mechanisms by which dysregulation of these distinct phosphoinositide phosphatases differentially affect breast cancer progression.

Genome-wide copy number variation analysis identified ANO1 as a novel oncogene and prognostic biomarker in esophageal squamous cell cancer

Copy number variations (CNVs) represent one of the most common genomic alterations. This study aimed to evaluate the roles of genes within highly aberrant genome regions in the prognosis of esophageal squamous cell cancer (ESCC). Exome sequencing data from 81 paired ESCC tissues were used to screen aberrant genomic regions. The associations between CNVs and gene expression were evaluated using gene expression data from the same individuals. Then, an RNA expression array profile from 119 ESCC samples was adopted for differential gene expression and prognostic analyses. Two independent ESCC cohorts with 315 subjects were further recruited to validate the prognostic value using immunohistochemistry tests. Finally, we explored the potential mechanism of our identified novel oncogene in ESCC. In total, 2003 genes with CNVs were observed, of which 76 genes showed recurrent CNVs in more than three samples. Among them, 32 genes were aberrantly expressed in ESCC tumor tissues and statistically correlated with CNVs. Strikingly, 4 (CTTN, SHANK2, INPPL1 and ANO1) of the 32 genes were significantly associated with the prognosis of ESCC patients. Patients with a positive expression of ANO1 had a poorer prognosis than ANO1 negative patients (overall survival rate: 42.91% versus 26.22% for ANO1-/+ samples, P < 0.001). Functionally, ANO1 promoted ESCC cell proliferation, migration and invasion by activating transforming growth factor-β pathway. Knockdown of ANO1 significantly inhibited tumor progression in vitro and in vivo. In conclusion, ANO1 is a novel oncogene in ESCC and may serve as a prognostic biomarker for ESCC.

GPER-induced signaling is essential for the survival of breast cancer stem cells

G protein-coupled estrogen receptor-1 (GPER), a member of the G protein-coupled receptor (GPCR) superfamily, mediates estrogen-induced proliferation of normal and malignant breast epithelial cells. However, its role in breast cancer stem cells (BCSCs) remains unclear. Here we showed greater expression of GPER in BCSCs than non-BCSCs of three patient-derived xenografts of ER- /PR+ breast cancers. GPER silencing reduced stemness features of BCSCs as reflected by reduced mammosphere forming capacity in vitro, and tumor growth in vivo with decreased BCSC populations. Comparative phosphoproteomics revealed greater GPER-mediated PKA/BAD signaling in BCSCs. Activation of GPER by its ligands, including tamoxifen (TMX), induced phosphorylation of PKA and BAD-Ser118 to sustain BCSC characteristics. Transfection with a dominant-negative mutant BAD (Ser118Ala) led to reduced cell survival. Taken together, GPER and its downstream signaling play a key role in maintaining the stemness of BCSCs, suggesting that GPER is a potential therapeutic target for eradicating BCSCs.

DNLC: differential network local consistency analysis

BACKGROUND

The biological network is highly dynamic. Functional relations between genes can be activated or deactivated depending on the biological conditions. On the genome-scale network, subnetworks that gain or lose local expression consistency may shed light on the regulatory mechanisms related to the changing biological conditions, such as disease status or tissue developmental stages.

RESULTS

In this study, we develop a new method to select genes and modules on the existing biological network, in which local expression consistency changes significantly between clinical conditions. The method is called DNLC: Differential Network Local Consistency. In simulations, our algorithm detected artificially created local consistency changes effectively. We applied the method on two publicly available datasets, and the method detected novel genes and network modules that were biologically plausible.

CONCLUSIONS

The new method is effective in finding modules in which the gene expression consistency change between clinical conditions. It is a useful tool that complements traditional differential expression analyses to make discoveries from gene expression data. The R package is available at https://cran.r-project.org/web/packages/DNLC.

Phosphoinositide 5-phosphatases SKIP and SHIP2 in ruffles, the endoplasmic reticulum and the nucleus: An update

Phosphoinositides (PIs) are phosphorylated derivatives of phosphatidylinositol. They act as signaling molecules linked to essential cellular mechanisms in eukaryotic cells, such as cytoskeleton organization, mitosis, polarity, migration or invasion. PIs are phosphorylated and dephosphorylated by a large number of PI kinases and PI phosphatases acting at the 5-, 4- and 3- position of the inositol ring. PI 5-phosphatases i.e. OCRL, INPP5B, SHIP1/2, Synaptojanin 1/2, INPP5E, INPP5J, SKIP (INPP5K) are enzymes that dephosphorylate the 5-phosphate position of PIs. Several human genetic diseases such as the Lowe syndrome, some congenital muscular dystrophy and opsismodysplasia are due to mutations in PI phosphatases, resulting in loss-of-function. The PI phosphatases are also up or down regulated in several human cancers such as glioblastoma or breast cancer. Their cellular localization, that is dynamic and varies in response to stimuli, is an important issue to understand function. This is the case for two members of the PI 5-phosphatase SKIP and SHIP2. Both enzymes are in ruffles, plasma membranes, the endoplasmic reticulum, a situation that is unique for SKIP, and the nucleus. Following localization, PI 5-phosphatases act on specific cellular pools of PIs, which in turn interact with target proteins. Nuclear PIs have emerged as regulators of genome functions in different area of cell signaling. They often localize to nuclear speckles, as do several PI metabolizing kinases and phosphatases. We asked whether SKIP and SHIP2 could have an impact on nuclear PI(4,5)P2. In two glioblastoma cell models, lowering SKIP expression had an impact on nuclear PI(4,5)P2. In a model of SHIP2 deletion in MCF-7 cells, no change in nuclear PI(4,5)P2 was observed. Finally, we present evidence of an anti-tumoral role of SKIP in vivo, in xenografts using as model U87shSKIP cells.

Upregulation of SHIP2 participates in the development of breast cancer via promoting Wnt/β-catenin signaling

Purpose

Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) gene is associated with arthrosclerosis, gastric cancer and diabetes. In this study, we revealed that overexpression of SHIP2 is closely implicated with the development of breast cancer (BC).

Methods

The BC tissue and adjacent cancerous tissue were obtained from BC patients who had underwent mastectomy. BC cells with either overexpression or knockdown of SHIP2 were analyzed to determine cell proliferation, migration, invasion and apoptosis using the CCK-8 assay, colony formation assay, scratch assay, transwell assay and flow cytometry, respectively. A rat BC xenograft model was constructed to explore the role of SHIP2 on tumor growth in vivo.

Results

The expression levels of SHIP2 in BC tissues and cells were significantly higher than those in adjacent tissues and normal breast cells, respectively. Silencing SHIP2 suppressed BC cells proliferation and promoted apoptosis. Overexpression of SHIP2 enhanced the cells migration/invasion in BC. Moreover, SHIP2 participated in the Wnt/β-catenin pathway by regulating GSK-3β and its downstream genes. β-Catenin activator LiCl could significantly eliminate the effect of si-SHIP2 on BC cells. Moreover, overexpression of SHIP2 increased tumor volume and weight in rat model, and Wnt/β-catenin pathway inhibitor ICG001 reversed the promoting effect of SHIP2 on tumorigenesis.

Conclusion

Upregulation of SHIP2 could increase the migration, invasion, proliferation, and decrease apoptosis in BC cells. Moreover, SHIP2 participated in the progression of BC via activating the Wnt/β-catenin pathway.

s-SHIP Promoter Expression Identifies Mouse Mammary Cancer Stem Cells

During normal mammary gland development, s-SHIP promoter expression marks a distinct type of mammary stem cells, at two different stages, puberty and early mid-pregnancy. To determine whether s-SHIP is a marker of mammary cancer stem cells (CSCs), we generated bitransgenic mice by crossing the C3(1)-SV40 T-antigen transgenic mouse model of breast cancer, and a transgenic mouse (11.5kb-GFP) expressing green fluorescent protein from the s-SHIP promoter. Here we show that in mammary tumors originating in these bitransgenic mice, s-SHIP promoter expression enriches a rare cell population with CSC activity as demonstrated by sphere-forming assays in vitro and limiting dilution transplantation in vivo. These s-SHIP-positive CSCs are characterized by lower expression of Delta-like non-canonical Notch ligand 1 (DLK1), a negative regulator of the Notch pathway. Inactivation of Dlk1 in s-SHIP-negative tumor cells increases their tumorigenic potential, suggesting a role for DLK1 in mammary cancer stemness.

Intermediate Filaments as Effectors of Cancer Development and Metastasis: A Focus on Keratins, Vimentin, and Nestin

Intermediate filament (IF) proteins make up the largest family of cytoskeletal proteins in metazoans, and are traditionally known for their roles in fostering structural integrity in cells and tissues. Remarkably, individual IF genes are tightly regulated in a fashion that reflects the type of tissue, its developmental and differentiation stages, and biological context. In cancer, IF proteins serve as diagnostic markers, as tumor cells partially retain their original signature expression of IF proteins. However, there are also characteristic alterations in IF gene expression and protein regulation. The use of high throughput analytics suggests that tumor-associated alterations in IF gene expression have prognostic value. Parallel research is also showing that IF proteins directly and significantly impact several key cellular properties, including proliferation, death, migration, and invasiveness, with a demonstrated impact on the development, progression, and characteristics of various tumors. In this review, we draw from recent studies focused on three IF proteins most associated with cancer (keratins, vimentin, and nestin) to highlight how several “hallmarks of cancer” described by Hanahan and Weinberg are impacted by IF proteins. The evidence already in hand establishes that IF proteins function beyond their classical roles as markers and serve as effectors of tumorigenesis.

Phosphoinositide phosphatases in cancer cell dynamics-Beyond PI3K and PTEN

Phosphoinositides are a group of lipids that regulate intracellular signaling and subcellular biological events. The signaling by phosphatidylinositol-3,4,5-trisphosphate and Akt mediates the action of growth factors that are essential for cell proliferation, gene transcription, cell migration, and polarity. The hyperactivation of this signaling has been identified in different cancer cells; and, it has been implicated in oncogenic transformation and cancer cell malignancy. Recent studies have argued the role of phosphoinositides in cancer cell dynamics, including actin cytoskeletal rearrangement at the plasma membrane and the organization of intracellular compartments. The focus of this review is to summarize the impact of the activities of phosphoinositide phosphatases on intracellular signaling related to cancer cell dynamics and to discuss how the abnormalities in the activities of the enzymes alter the levels of phosphoinositides in cancer cells.

Underexpression of INPPL1 is associated with aggressive clinicopathologic characteristics in papillary thyroid carcinoma

Purpose

To study the relationship between INPPL1 gene and clinicopathologic characteristics of papillary thyroid carcinoma (PTC).

Patients and methods

INPPL1 expression in PTCs was tested by quantitative real-time reverse transcription PCR. The Cancer Genome Atlas (TCGA) RNA-seq data and our mRNA data were used to analyze and reveal the relationship between INPPL1 and aggressive clinicopathologic characteristics of PTC.

Results

When compared to normal thyroid tissues, INPPL1 was significantly downregulated in PTC tissues, as revealed by our data and TCGA data. INPPL1 underexpression was remarkably related to aggressive clinicopathologic characteristics such as lymph node metastasis (LNM), histological type, tumor size, mulitifocality, and disease stage in TCGA data. Meanwhile, LNM was confirmed to be associated with underexpression of INPPL1 in our data. In addition, logistic analysis clearly showed that underexpression of INPPL1 was an independent factor for LNM in PTC.

Conclusion

INPPL1 may be a novel tumor suppressor gene in PTC, which was significantly correlated with aggressive clinicopathologic characteristics, especially LNM.

The impact of phosphoinositide 5-phosphatases on phosphoinositides in cell function and human disease

Phosphoinositides (PIs) are recognized as major signaling molecules in many different functions of eukaryotic cells. PIs can be dephosphorylated by multiple phosphatase activities at the 5-, 4-, and 3- positions. Human PI 5-phosphatases belong to a family of 10 members. Except for inositol polyphosphate 5-phosphatase A, they all catalyze the dephosphorylation of PI(4,5)P₂ and/or PI(3,4,5)P₃ at the 5- position. PI 5-phosphatases thus directly control the levels of PI(3,4,5)P₃ and participate in the fine-tuning regulatory mechanisms of PI(3,4)P₂ and PI(4,5)P₂ Second messenger functions have been demonstrated for PI(3,4)P₂ in invadopodium maturation and lamellipodia formation. PI 5-phosphatases can use several substrates on isolated enzymes, and it has been challenging to establish their real substrate in vivo. PI(4,5)P₂ has multiple functions in signaling, including interacting with scaffold proteins, ion channels, and cytoskeleton proteins. PI 5-phosphatase isoenzymes have been individually implicated in human diseases, such as the oculocerebrorenal syndrome of Lowe, through mechanisms that include lipid control. Oncogenic and tumor-suppressive functions of PI 5-phosphatases have also been reported in different cell contexts. The mechanisms responsible for genetic diseases and for oncogenic or tumor-suppressive functions are not fully understood. The regulation of PI 5-phosphatases is thus crucial in understanding cell functions.

Lipid phosphatase SHIP2 functions as oncogene in colorectal cancer by regulating PKB activation

Colorectal cancer (CRC) is the second most common cause of cancer-related death, encouraging the search for novel therapeutic targets affecting tumor cell proliferation and migration. These cellular processes are under tight control of two opposing groups of enzymes; kinases and phosphatases. Aberrant activity of kinases is observed in many forms of cancer and as phosphatases counteract such "oncogenic" kinases, it is generally assumed that phosphatases function as tumor suppressors. However, emerging evidence suggests that the lipid phosphatase SH2-domain-containing 5 inositol phosphatase (SHIP2), encoded by the INPPL1 gene, may act as an oncogene. Just like the well-known tumor suppressor gene Phosphatase and Tensin Homolog (PTEN) it hydrolyses phosphatidylinositol (3,4,5) triphosphate (PI(3,4,5)P3). However, unlike PTEN, the reaction product is PI(3,4)P2, which is required for full activation of the downstream protein kinase B (PKB/Akt), suggesting that SHIP2, in contrast to PTEN, could have a tumor initiating role through PKB activation. In this work, we investigated the role of SHIP2 in colorectal cancer. We found that SHIP2 and INPPL1 expression is increased in colorectal cancer tissue in comparison to adjacent normal tissue, and this is correlated with decreased patient survival. Moreover, SHIP2 is more active in colorectal cancer tissue, suggesting that SHIP2 can induce oncogenesis in colonic epithelial cells. Furthermore, in vitro experiments performed on colorectal cancer cell lines shows an oncogenic role for SHIP2, by enhancing chemoresistance, cell migration, and cell invasion. Together, these data indicate that SHIP2 expression contributes to the malignant potential of colorectal cancer, providing a possible target in the fight against this devastating disease.

Prognostic value of the expression of cancer stem cell-related markers CD133 and CD44 in hepatocellular carcinoma: From patients to patient-derived tumor xenograft models

High expression of cancer stem cell (CSC) markers is related to poor prognosis of patients with hepatocellular carcinoma (HCC). However, the expression of these markers in patient-derived xenograft (PDX) models and the relationship of the expression levels of these markers between HCC patients and their PDX models at subsequent low passages are unclear. To investigate the prognostic impact of putative CSC markers in patients with HCC and in related PDX models, the expression of CD133, CD90, CD44, ALDH1, CK7, CK19, OCT4, SOX2, vimentin, nestin, CD13 and EpCam were assessed by quantitative reverse transcription-PCR (qRT-PCR) and then were validated using immunohistochemistry in tumor or peritumoral tissues from patients and tumor tissues from PDX models. Cumulative survival analysis of the patients and animals was conducted using the Kaplan-Meier method and the log-rank test. Only the expression levels of CD133 and CD44 were higher in tumor tissues than in the peritumoral tissues of HCC patients by qRT-PCR. High consistency of the prognostic value of the expression of CD133/CD44 was observed in HCC patients and the PDX models. High expression levels of CD133 and CD44 were positively related to the poor prognosis of HCC patients and to that in the PDX models. PDX HCC models in the present study have been suggested to be predictive of disease outcome, which could shed light on personalized medicine and the mechanisms of CSC marker expression on prognosis.

s-SHIP expression identifies a subset of murine basal prostate cells as neonatal stem cells

Isolation of prostate stem cells (PSCs) is crucial for understanding their biology during normal development and tumorigenesis. In this aim, we used a transgenic mouse model expressing GFP from the stem cell-specific s-SHIP promoter to mark putative stem cells during postnatal prostate development. Here we show that cells identified by GFP expression are present transiently during early prostate development and localize to the basal cell layer of the epithelium. These prostate GFP+ cells are a subpopulation of the Lin- CD24+ Sca-1+ CD49f+ cells and are capable of self-renewal together with enhanced growth potential in sphere-forming assay in vitro, a phenotype consistent with that of a PSC population. Transplantation assays of prostate GFP+ cells demonstrate reconstitution of prostate ducts containing both basal and luminal cells in renal grafts. Altogether, these results demonstrate that s-SHIP promoter expression is a new marker for neonatal basal prostate cells exhibiting stem cell properties that enables PSCs in situ identification and isolation via a single consistent parameter. Transcriptional profiling of these GFP+ neonatal stem cells showed an increased expression of several components of the Wnt signaling pathway. It also identified stem cell regulators with potential applications for further analyses of normal and cancer stem cells.

Inhibition of SHIP2 activity inhibits cell migration and could prevent metastasis in breast cancer cells

Metastasis of breast cancer cells to distant organs is responsible for approximately 50 % in cancer related deaths in women worldwide. SHIP2 is a phosphoinositide 5-phosphatase for PI(3,4,5)P3 and PI(4,5)P2. Through depletion of SHIP2 in triple negative MDA-MB-231 cells and the use of SHIP2 inhibitors, it appeared that cell migration is positively controlled by SHIP2. The effect of SHIP2 on migration, observed in MDA-MB-231 cells, appears to be mediated by PI(3,4)P2. Adhesion on fibronectin is always increased in SHIP2 depleted cells. Apoptosis measured in MDA-MB-231 cells is also increased in SHIP2 depleted cells as compared to control cells. In xenograft mice, SHIP2 depleted MDA-MB-231 cells form significantly smaller tumors compared to control cells and less metastasis detected in lung sections. Our data reveal a general role of SHIP2 in the control of cell migration in breast cancer cells and a second messenger role for PI(3,4)P2 in the migration mechanism. In this model, SHIP2 function on apoptosis on cells incubated in vitro, or in mice tumor digested cells, could account for its role on tumor growth determined in vivo.

SHIP2 Regulates Lumen Generation, Cell Division, and Ciliogenesis through the Control of Basolateral to Apical Lumen Localization of Aurora A and HEF 1

Lumen formation during epithelial morphogenesis requires the creation of a luminal space at cell interfaces named apical membrane-initiation sites (AMISs). This is dependent upon integrated signaling from mechanical and biochemical cues, vesicle trafficking, cell division, and processes tightly coupled to ciliogenesis. Deciphering relationships between polarity determinants and lumen or cilia generation remains a fundamental issue. Here, we report that Src homology 2 domain-containing inositol 5-phosphatase 2 (SHIP2), a basolateral determinant of polarity, regulates RhoA-dependent actin contractility and cell division to form AMISs. SHIP2 regulates mitotic spindle alignment. SHIP2 is expressed in G1 phase, whereas Aurora A kinase is enriched in mitosis. SHIP2 binds Aurora A kinase and the scaffolding protein HEF1 and promotes their basolateral localization at the expense of their luminal expression connected with cilia resorption. Furthermore, SHIP2 expression increases cilia length. Thus, our findings offer new insight into the relationships among basolateral proteins, lumen generation, and ciliogenesis.

ZIC2 promotes viability and invasion of human osteosarcoma cells by suppressing SHIP2 expression and activating PI3K/AKT pathways

Osteosarcoma is a malignant tumor of the skeletal system. The zinc finger transcription factor ZIC2 has been reported to be highly expressed in human cancers. The present study evaluated the effects of ZIC2 and the possible underlying mechanisms in the human osteosarcoma cells. The expression levels of ZIC2 in human fetal osteoblastic cell line (hFOB1.19), osteosarcoma cell lines (U-2OS, SaoS2, and MG63), normal bone tissue, and osteosarcoma tumor were analyzed by Western blot, and real-time quantitative RT-PCR (qRT-PCR). Osteosarcoma cells with either overexpressed ZIC2 or suppressed ZIC2 were analyzed to determine cell viability, colony formation, and cell invasion. The expressions of SHIP2 and PI3K/AKT signal pathway-related proteins were analyzed by Western blot and qRT-PCR. We first showed that ZIC2 is highly expressed in osteosarcoma cells and tissues. Then we demonstrated that overexpression of ZIC2 promoted viability, migration, and invasion of osteosarcoma cells, whereas suppression of ZIC2 showed opposite effects. Furthermore, SHIP2 expression was negatively regulated by ZIC2. Importantly, ZIC2 overexpression activated the PI3K/AKT signal pathway; however, overexpressed SHIP2 inhibited these effects. Lastly, we showed that activation of the PI3K/AKT signal pathway is essential for the effects of ZIC2 on osteosarcoma cells, as the effects of ZIC2 on the osteosarcoma cells were reversed by a PI3K/AKT inhibitor. Overall, ZIC2 is highly expressed in osteosarcoma cells and tissues, and its overexpression promotes viability, invasion of osteosarcoma cells via SHIP2 suppression, and PI3K/AKT activation. Thus, ZIC2 can be considered as a novel drug target for osteosarcoma management.

5'-Inositol phosphatase SHIP2 recruits Mena to stabilize invadopodia for cancer cell invasion

Invadopodia are membrane protrusions used by cancer cells to remodel and invade the extracellular matrix. Here, Rajadurai et al. show that the lipid phosphatase SHIP2 recruits the Ena/VASP-family actin regulatory protein Mena to stabilize invadopodia membrane protrusions and promote cell invasion.

Invadopodia are specialized membrane protrusions that support degradation of extracellular matrix (ECM) by cancer cells, allowing invasion and metastatic spread. Although early stages of invadopodia assembly have been elucidated, little is known about maturation of invadopodia into structures competent for ECM proteolysis. The localized conversion of phosphatidylinositol(3,4,5)-triphosphate and accumulation of phosphatidylinositol(3,4)-bisphosphate at invadopodia is a key determinant for invadopodia maturation. Here we investigate the role of the 5′-inositol phosphatase, SHIP2, and reveal an unexpected scaffold function of SHIP2 as a prerequisite for invadopodia-mediated ECM degradation. Through biochemical and structure-function analyses, we identify specific interactions between SHIP2 and Mena, an Ena/VASP-family actin regulatory protein. We demonstrate that SHIP2 recruits Mena, but not VASP, to invadopodia and that disruption of SHIP2–Mena interaction in cancer cells leads to attenuated capacity for ECM degradation and invasion in vitro, as well as reduced metastasis in vivo. Together, these findings identify SHIP2 as a key modulator of carcinoma invasiveness and a target for metastatic disease.

Regulation of CD44 expression and focal adhesion by Golgi phosphatidylinositol 4-phosphate in breast cancer

CD44, a transmembrane receptor, is expressed in the standard or variant form and plays a critical role in tumor progression and metastasis. This protein regulates cell adhesion and migration in breast cancer cells. We previously reported that phosphatidylinositol-4-phosphate (PI(4)P) at the Golgi regulates cell migration and invasion in breast cancer cell lines. In this study, we showed that an increase in PI(4)P levels at the Golgi by knockdown of PI(4)P phosphatase SAC1 increased the expression of standard CD44, variant CD44, and ezrin/radixin phosphorylation and enhanced the formation of focal adhesions mediated by CD44 and ezrin/radixin in MCF7 and SK-BR-3 cells. In contrast, knockdown of PI 4-kinase IIIβ in highly invasive MDA-MB-231 cells decreased these factors. These results suggest that SAC1 expression and PI(4)P at the Golgi are important in tumor progression and metastasis and are potential prognostic markers of breast cancers.

Suppression of SHIP2 contributes to tumorigenesis and proliferation of gastric cancer cells via activation of Akt

BACKGROUND

The Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) is implicated in diabetes, arthrosclerosis, and cancer. However, the role of SHIP2 in human gastric cancer remains unclear.

METHODS

The expression levels of SHIP2 in gastric cancer tissues, a panel of gastric cancer cell lines, and normal gastric epithelial cells were analyzed by immunohistochemistry (IHC), Western blot, and real-time quantitative RT-PCR (qRT-PCR). Gastric cancer cells with either overexpressed SHIP2 or co-overexpressed SHIP2 and Akt were analyzed to determine cell proliferation, colony formation, apoptosis, cell migration, and invasion assays. Normal gastric epithelial cells with knockdown SHIP2 or co-knockdown SHIP2 and Akt were subjected by anchorage-independent growth assays. The effect of SHIP2 on tumor growth in vivo was detected by xenograft tumorigenesis assays.

RESULTS

SHIP2 was commonly downregulated in gastric cancer compared with normal gastric mucosa, and overexpression of SHIP2 inhibited cell proliferation, induced apoptosis, suppressed cell motility and invasion in gastric cancer cells in vitro, and retarded the growth of xenograft gastric tumors in vivo, while knockdown of SHIP2 in normal gastric epithelial cells promoted anchorage-independent growth. Moreover, overexpression of SHIP2 inactivated Akt, and upregulated p21, p27, and the pro-apoptotic protein Bim. Restoring Akt activation in gastric cancer cells largely blocked the inhibition of PI3K/Akt signaling by SHIP2 and reversed the inhibitory effect of SHIP2 on tumorigenesis and proliferation.

CONCLUSIONS

This study demonstrates, for the first time, that SHIP2 is frequently downregulated in gastric cancer, and reduced SHIP2 expression promotes tumorigenesis and proliferation of gastric cancer via activation of the PI3K/Akt signaling.

Tracking and Finding Slow-Proliferating/Quiescent Cancer Stem Cells with Fluorescent Nanodiamonds

Quiescent cancer stem cells (CSCs) have long been considered to be a source of tumor initiation. However, identification and isolation of these cells have been hampered by the fact that commonly used fluorescent markers are not sufficiently stable, both chemically and photophysically, to allow tracking over an extended period of time. Here, it is shown that fluorescent nanodiamonds (FNDs) are well suited for this application. Genotoxicity tests of FNDs with comet and micronucleus assays for human fibroblasts and breast cancer cells indicate that the nanoparticles neither cause DNA damage nor impair cell growth. Using AS-B145-1R breast cancer cells as the model cell line for CSC, it is found that the FND labeling outperforms 5-ethynyl-2'-deoxyuridine (EdU) and carboxyfluorescein diacetate succinimidyl ester (CFSE) in regards to its long-term tracking capability (>20 d). Moreover, through a quantification of their stem cell activity by measuring mammosphere-forming efficiencies (MFEs) and self-renewal rates, the FND-positive cells are identified to have an MFE twice as high as that of the FND-negative cells isolated from the same dissociated mammospheres. Thus, the nanoparticle-based labeling technique provides an effective new tool for tracking and finding slow-proliferating/quiescent CSCs in cancer research.

Upregulation of microRNA-492 induced by epigenetic drug treatment inhibits the malignant phenotype of clear cell renal cell carcinoma in vitro

Clear cell renal cell carcinoma (ccRCC) is the most common type of cancer of the renal parenchyma. MicroRNAs (miRNAs) are non-coding RNAs of ~22 nucleotides in length, which function as post‑transcriptional regulators. Recently, the downregulation of miRNA (miR)-492 was observed to be associated with ccRCC; however, the molecular mechanism by which miR492 inhibited ccRCC remained to be elucidated. In the present study, it was demonstrated that miR-492 was markedly downregulated in ccRCC tissues when compared with adjacent normal tissues, as determined by reverse transcription-quantitative poymerase chain reaction (PCR). This downregulation was predominantly due to the hypermethylation of the CpG island of the miR-492 promoter, which was detected by methylation specific PCR and bisulfite genomic sequencing PCR, and was shown to inhibit miR-492 transcription. Through the use of a DNA demethylation agent, 5-aza-2'-deoxycytidine or the histone deacetylase inhibitor 4-phenylbutyric acid, the expression level of miR-492 was significantly upregulated in ccRCC cells, which further inhibited cell proliferation and invasion, while promoting cell apoptosis and adhesion. In conclusion, the present study provided novel insights into the potential mechanisms involved in ccRCC and it is hypothesized that miR-492 may become a promising therapeutic agent in the treatment of ccRCC.

Enrichment of Human Stem-Like Prostate Cells with s-SHIP Promoter Activity Uncovers a Role in Stemness for the Long Noncoding RNA H19

Understanding normal and cancer stem cells should provide insights into the origin of prostate cancer and their mechanisms of resistance to current treatment strategies. In this study, we isolated and characterized stem-like cells present in the immortalized human prostate cell line, RWPE-1. We used a reporter system with green fluorescent protein (GFP) driven by the promoter of s-SHIP (for stem-SH2-domain-containing 5'-inositol phosphatase) whose stem cell-specific expression has been previously shown. We observed that s-SHIP-GFP-expressing RWPE-1 cells showed stem cell characteristics such as increased expression of stem cell surface markers (CD44, CD166, TROP2) and pluripotency transcription factors (Oct4, Sox2), and enhanced sphere-forming capacity and resistance to arsenite-induced cell death. Concomitant increased expression of the long noncoding RNA H19 was observed, which prompted us to investigate a putative role in stemness for this oncofetal gene. Targeted suppression of H19 with siRNA decreased Oct4 and Sox2 gene expression and colony-forming potential in RWPE-1 cells. Conversely, overexpression of H19 significantly increased gene expression of these two transcription factors and the sphere-forming capacity of RWPE-1 cells. Analysis of H19 expression in various prostate and mammary human cell lines revealed similarities with Sox2 expression, suggesting that a functional relationship may exist between H19 and Sox2. Collectively, we provide the first evidence that s-SHIP-GFP promoter reporter offers a unique marker for the enrichment of human stem-like cell populations and highlight a role in stemness for the long noncoding RNA H19.

Breast cancer stem cells, EMT and therapeutic targets

A small heterogeneous population of breast cancer cells acts as seeds to induce new tumor growth. These seeds or breast cancer stem cells (BCSCs) exhibit great phenotypical plasticity which allows them to undergo "epithelial to mesenchymal transition" (EMT) at the site of primary tumor and a future reverse transition. Apart from metastasis they are also responsible for maintaining the tumor and conferring it with drug and radiation resistance and a tendency for post-treatment relapse. Many of the signaling pathways involved in induction of EMT are involved in CSC generation and regulation. Here we are briefly reviewing the mechanism of TGF-β, Wnt, Notch, TNF-α, NF-κB, RTK signalling pathways which are involved in EMT as well as BCSCs maintenance. Therapeutic targeting or inhibition of the key/accessory players of these pathways could control growth of BCSCs and hence malignant cancer. Additionally several miRNAs are dysregulated in cancer stem cells indicating their roles as oncogenes or tumor suppressors. This review also lists the miRNA interactions identified in BCSCs and discusses on some newly identified targets in the BCSC regulatory pathways like SHIP2, nicastrin, Pin 1, IGF-1R, pro-inflammatory cytokines and syndecan which can be targeted for therapeutic achievements.