Wnt5a suppresses epithelial ovarian cancer by promoting cellular senescence

WNT5A and Its Receptors in the Bone-Cancer Dialogue

Wnt signaling is critical for tumorigenesis and skeletal remodeling. However, its contribution to the formation of metastatic bone lesions remains poorly defined. One major challenge of unraveling its role in cancer progression is the high complexity of Wnt signaling, which includes numerous ligands, receptors, and inhibitors, with intricate biological effects and specific signaling pathways depending on the cellular context. In this perspective, we summarize the role of the noncanonical Wnt ligand WNT5A in the development and metastatic process of osteotropic cancer entities. We focus on its tumor-suppressive function in breast cancer, tumor promoting effects in melanoma, and ambiguous role in prostate cancer, and discuss potential challenges and opportunities that may be associated with targeting Wnt signaling for cancer therapy and treatment of bone metastases. © 2016 American Society for Bone and Mineral Research.

WNT5A-ROR2 is induced by inflammatory mediators and is involved in the migration of human ovarian cancer cell line SKOV-3

Background

Wnt5A, which is a member of the non-transforming Wnt protein family, is implicated in inflammatory processes. It is also highly expressed by ovarian cancer cells. ROR2, which is a member of the Ror-family of receptor tyrosine kinases, acts as a receptor or co-receptor for Wnt5A. The Wnt5A–ROR2 signaling pathway plays essential roles in the migration and invasion of several types of tumor cell and influences their cell polarity. We investigated the modulation of Wnt5A–ROR2 by inflammatory mediators and its involvement in the migration of the human ovarian cancer cell line SKOV-3.

Methods

SKOV-3 cells were treated with LPS (lipopolysaccharide), LTA (lipoteichoic acid) and recombinant human IL-6 alone or in combination with STAT3 inhibitor (S1155S31-201) or NF-kB inhibitor (BAY11-7082) for 4, 8, 12, 24 and 48 h. The Wnt5A and ROR2 expression levels were determined at the gene and protein levels. Cells were transfected with specific siRNA against Wnt5A in the absence or presence of human anti-ROR2 antibody and cell migration was assessed using transwells.

Results

There was a strong downregulation of Wnt5A expression in the presence of STAT3 or NF-kB inhibitors. Cell stimulation with LTA or IL-6 for 8 h led to significantly increased levels of Wnt5A (5- and 3-fold higher, respectively). LPS, LTA or IL-6 treatment significantly increased ROR2 expression (2-fold after 48 h). LPS- or LTA-induced Wnt5A or ROR2 expression was abrogated in the presence of STAT3 inhibitor (p < 0.001). IL-6-induced Wnt5A expression was abrogated by both STAT3 and NF-kB inhibitors (p < 0.001). Although not significant, IL-6-induced ROR2 expression showed a modest decrease when STAT3 inhibitor was used. Moreover, cell migration was decreased by 80 % in siRNA Wnt5A-transfected cells in the presence of anti-human ROR2 antibody (p < 0.001).

Conclusions

This study revealed for the first time that inflammatory mediators modulate Wnt5A and ROR2 through NF-kB and STAT3 transcription factors and this may play a role in ovarian cancer cell migration. The results described here provide new insight into the role of the Wnt5A–ROR2 complex in ovarian cancer progression in relation to inflammation.

Dysregulation of WNT5A/ROR2 Signaling Characterizes the Progression of Barrett-Associated Esophageal Adenocarcinoma

The mechanism underlying the progression of normal esophageal mucosa to esophageal adenocarcinoma remains elusive. WNT5A is a noncanonical WNT, which mainly functions via the receptor tyrosine kinase-like orphan receptor 2 (ROR2), and has an unclear role in carcinogenesis. In this study, we aimed to determine the role of WNT5A/ROR2 signaling in esophageal adenocarcinoma. Analysis of WNT5A and ROR2 expression patterns in healthy controls, Barrett and esophageal adenocarcinoma patients' esophageal clinical specimens as well as in various esophageal cell lines demonstrated a ROR2 overexpression in esophageal adenocarcinoma tissues compared with Barrett and healthy mucosa, whereas WNT5A expression was found significantly downregulated toward esophageal adenocarcinoma formation. Treatment of esophageal adenocarcinoma OE33 cells with human recombinant WNT5A (rhWNT5A) significantly suppressed proliferation, survival, and migration in a dose-dependent fashion. rhWNT5A was found to inhibit TOPflash activity in ROR2 wild-type cells, whereas increased TOPflash activity in ROR2-knockdown OE33 cells. In addition, ROR2 knockdown alone abolished cell proliferation and weakened the migration properties of OE33 cells. These findings support an early dysregulation of the noncanonical WNT5A/ROR2 pathway in the pathogenesis of esophageal adenocarcinoma, with the loss of WNT5A expression together with the ROR2 overexpression to be consistent with tumor promotion.

IMPLICATIONS

The dysregulation of WNT5A/ROR2 noncanonical WNT signaling in Barrett-associated esophageal adenocarcinoma introduces possible prognostic markers and novel targets for tailored therapy of this malignancy. Mol Cancer Res; 14(7); 647-59. ©2016 AACR.

Wnt/β-catenin signaling in bone marrow niche

The bone marrow (BM) niche is a specific physiological environment for hematopoietic and non-hematopoietic stem cells (HSCs). Several signaling pathways (including Wnt/β-catenin) regulate various aspects of stem cell growth, function and death in the BM niche. In addition, the canonical Wnt pathway is crucial for directing self-renewal and differentiation as important mechanisms in many types of stem cells. We review the role of the Wnt/β-catenin pathway in the BM niche and its importance in stem cells. Relevant literature was identified by a PubMed search (1997-2014) of English-language literature by using the following keywords: BM niche, Wnt/β-catenin signaling, osteoblast, osteoclast and bone disease. The Wnt/β-catenin pathway regulates the stability of the β-catenin proto-oncogene. The stabilized β-catenin then translocates to the nucleus, forming a β-catenin-TCF/LEF complex regulating the transcription of specific target genes. Stem cells require β-catenin to mediate their response to Wnt signaling for maintenance and transition from the pluripotent state during embryogenesis. In adult stem cells, Wnt signaling functions at various hierarchical levels to contribute to the specification of the diverse tissues. Aberrant Wnt/β-catenin signaling and its downstream transcriptional regulators are observed in several malignant stem cells and human cancers. Because Wnt signaling can maintain stem cells and cancer cells, the ability to modulate the Wnt pathway either positively or negatively may be of therapeutic relevance. The controlled activation of Wnt signaling might allow us to enhance stem and progenitor cell activity when regeneration is needed.

Wnt signalling in gynaecological cancers: A future target for personalised medicine?

The three major gynaecological cancers, ovarian, uterine and cervical, contribute a significant burden to global cancer mortality, and affect women in both developed and developing countries. However, unlike other cancer types that have seen rapid advances and incorporation of targeted treatments in recent years, personalised medicine is not yet a reality in the treatment of gynaecological cancers. Advances in sequencing technology and international collaborations and initiatives such as The Cancer Genome Atlas are now revealing the molecular basis of these cancers, and highlighting key signalling pathways involved. One pathway which plays a role in all three cancer types, is the Wnt signalling pathway. This complex developmental pathway is altered in most human malignancies, and members of this pathway, particularly the recently linked ROR receptor tyrosine kinases may be attractive future therapeutic targets. This review provides an up-to-date summary of research into Wnt signalling and ovarian, uterine and cervical cancers, and discusses the potential of the Wnt pathway as a future target for personalised medicine in gynaecological cancers.

Effect of WNT5A on epithelial-mesenchymal transition and its correlation with tumor invasion and metastasis in nasopharyngeal carcinoma

OBJECTIVE

To investigate the correlation between nasopharyngeal carcinoma cell WNT5A and epithelial-mesenchymal transition (emt)/metastasis, and investigate its possible mechanisms.

METHODS

RT-PCR and gene transfection were used to detect the expression of nasopharyngeal carcinoma cell strains WNT5A and EMT related factor 5-8F. Transient transfection of NPC cell line 5-8F was determined by liposome of plasmid with WNT5A gene. The differential expressions of WNT5A and EMT-related factors in cells before and after transfection were detected by RT-PCR. Cell scratch assay and Transwell assay were used to detect the motility abilities of cells before and after 5-8F transfection.

RESULTS

The expressions of WNT5A and EMT related factors matrix metalloproteinase-2 of the WNT5A transferred group in the nasopharyngeal carcinoma cell line 5-8F were higher than the blank control group and the empty vector transferred group, and the transfer ability of the WNT5A transferred group was higher than that in the blank control group and the empty vector transferred group, while the expressions of EMT related factors E-cadherin were lower than that in the blank control group and the empty vector transferred group, and the transfer ability of the WNT5A transferred group was higher than that in the blank control group and the empty vector transferred group.

CONCLUSIONS

In nasopharyngeal carcinoma cells, WNT5A can regulate the epithelial-mesenchymal transition and affect the ability of tumor invasion and metastasis of nasopharyngeal carcinoma.

WIF1 re-expression in glioblastoma inhibits migration through attenuation of non-canonical WNT signaling by downregulating the lncRNA MALAT1

Glioblastoma is the most aggressive primary brain tumor in adults and due to the invasive nature cannot be completely removed. The WNT inhibitory factor 1 (WIF1), a secreted inhibitor of WNTs, is systematically downregulated in glioblastoma and acts as strong tumor suppressor. The aim of this study was the dissection of WIF1-associated tumor-suppressing effects mediated by canonical and non-canonical WNT signaling. We found that WIF1 besides inhibiting the canonical WNT pathway selectively downregulates the WNT/calcium pathway associated with significant reduction of p38-MAPK (p38-mitogen-activated protein kinase) phosphorylation. Knockdown of WNT5A, the only WNT ligand overexpressed in glioblastoma, phenocopied this inhibitory effect. WIF1 expression inhibited cell migration in vitro and in an orthotopic brain tumor model, in accordance with the known regulatory function of the WNT/Ca(2+) pathway on migration and invasion. In search of a mediator for this function differential gene expression profiles of WIF1-expressing cells were performed. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), a long non-coding RNA and key positive regulator of invasion, emerged as the top downregulated gene. Indeed, knockdown of MALAT1 reduced migration in glioblastoma cells, without effect on proliferation. Hence, loss of WIF1 enhances the migratory potential of glioblastoma through WNT5A that activates the WNT/Ca(2+) pathway and MALAT1. These data suggest the involvement of canonical and non-canonical WNT pathways in glioblastoma promoting key features associated with this deadly disease, proliferation on one hand and invasion on the other. Successful targeting will require a dual strategy affecting both canonical and non-canonical WNT pathways.

Paracrine WNT5A Signaling Inhibits Expansion of Tumor-Initiating Cells

It is not well understood how paracrine communication between basal and luminal cell populations in the mammary gland affects tumorigenesis. During ErbB2-induced mammary tumorigenesis, enriched mammary stem cells that represent a subpopulation of basal cells exhibit enhanced tumorigenic capacity compared with the corresponding luminal progenitors. Transcript profiling of tumors derived from basal and luminal tumor-initiating cells (TIC) revealed preferential loss of the noncanonical Wnt ligand WNT5A in basal TIC-derived tumors. Heterozygous loss of WNT5A was correlated with shorter survival of breast cancer patients. In a mouse model of ErbB2-induced breast cancer, Wnt5a heterozygosity promoted tumor multiplicity and pulmonary metastasis. As a TGFβ substrate, luminal cell-produced WNT5A induced a feed-forward loop to activate SMAD2 in a RYK and TGFβR1-dependent manner to limit the expansion of basal TIC in a paracrine fashion, a potential explanation for the suppressive effect of WNT5A in mammary tumorigenesis. Our results identify the WNT5A/RYK module as a spatial regulator of the TGFβ-SMAD signaling pathway in the context of mammary gland development and carcinogenesis, offering a new perspective on tumor suppression provided by basal-luminal cross-talk in normal mammary tissue.

Wnt7a is a novel inducer of β-catenin-independent tumor-suppressive cellular senescence in lung cancer

Cellular senescence is an initial barrier for carcinogenesis. However, the signaling mechanisms that trigger cellular senescence are incompletely understood, particularly in vivo. Here we identify Wnt7a as a novel upstream inducer of cellular senescence. In two different mouse strains (C57Bl/6J and FVB/NJ), we show that the loss of Wnt7a is a major contributing factor for increased lung tumorigenesis owing to reduced cellular senescence, and not reduced apoptosis, or autophagy. Wnt7a-null mice under de novo conditions and in both the strains display E-cadherin-to-N-cadherin switch, reduced expression of cellular senescence markers and reduced expression of senescence-associated secretory phenotype, indicating a genetic predisposition of these mice to increased carcinogen-induced lung tumorigenesis. Interestingly, Wnt7a induced an alternate senescence pathway, which was independent of β-catenin, and distinct from that of classical oncogene-induced senescence mediated by the well-known p16^INK4a and p19^ARF pathways. Mechanistically, Wnt7a induced cellular senescence via inactivation of S-phase kinase-associated protein 2, an important alternate regulator of cellular senescence. Additionally, we identified Iloprost, a prostacyclin analog, which initiates downstream signaling cascades similar to that of Wnt7a, as a novel inducer of cellular senescence, presenting potential future clinical translational strategies. Thus pro-senescence therapies using either Wnt7a or its mimic, Iloprost, might represent a new class of therapeutic treatments for lung cancer.

Synthetic lethality by targeting EZH2 methyltransferase activity in ARID1A-mutated cancers

ARID1A, a chromatin remodeler, shows one of the highest mutation rates across many cancer types. Notably, ARID1A is mutated in over 50% of ovarian clear cell carcinomas, which currently has no effective therapy. To date, clinically applicable targeted cancer therapy based on ARID1A mutational status has not been described. Here we show that inhibition of the EZH2 methyltransferase acts in a synthetic lethal manner in ARID1A mutated ovarian cancer cells. ARID1A mutational status correlates with response to the EZH2 inhibitor. We identified PIK3IP1 as a direct ARID1A/EZH2 target, which is upregulated by EZH2 inhibition and contributes to the observed synthetic lethality by inhibiting PI3K/AKT signaling. Significantly, EZH2 inhibition causes regression of ARID1A mutated ovarian tumors in vivo. Together, these data demonstrate for the first time a synthetic lethality between ARID1A mutation and EZH2 inhibition. They indicate that pharmacological inhibition of EZH2 represents a novel treatment strategy for ARID1A mutated cancers.

Using distance covariance for improved variable selection with application to learning genetic risk models

Variable selection is of increasing importance to address the difficulties of high dimensionality in many scientific areas. In this paper, we demonstrate a property for distance covariance, which is incorporated in a novel feature screening procedure together with the use of distance correlation. The approach makes no distributional assumptions for the variables and does not require the specification of a regression model and hence is especially attractive in variable selection given an enormous number of candidate attributes without much information about the true model with the response. The method is applied to two genetic risk problems, where issues including uncertainty of variable selection via cross validation, subgroup of hard-to-classify cases, and the application of a reject option are discussed.

BRAF mutation is associated with a specific cell type with features suggestive of senescence in ovarian serous borderline (atypical proliferative) tumors

Serous borderline tumor also known as atypical proliferative serous tumor (APST) is the precursor of ovarian low-grade serous carcinoma (LGSC). In this study, we correlated the morphologic and immunohistochemical phenotypes of 71 APSTs and 18 LGSCs with the mutational status of KRAS and BRAF, the most common molecular genetic changes in these neoplasms. A subset of cells characterized by abundant eosinophilic cytoplasm (EC), discrete cell borders, and bland nuclei was identified in all (100%) 25 BRAF-mutated APSTs but in only 5 (10%) of 46 APSTs without BRAF mutations (P<0.0001). Among the 18 LGSCs, EC cells were found in only 2, and both contained BRAF mutations. The EC cells were present admixed with cuboidal and columnar cells lining the papillae and appeared to be budding from the surface, resulting in individual cells and clusters of detached cells "floating" above the papillae. Immunohistochemistry showed that the EC cells always expressed p16, a senescence-associated marker, and had a significantly lower Ki-67 labeling index than adjacent cuboidal and columnar cells (P=0.02). In vitro studies supported the interpretation that these cells were undergoing senescence, as the same morphologic features could be reproduced in cultured epithelial cells by ectopic expression of BRAF(V600E). Senescence was further established by markers such as SA-β-gal staining, expression of p16 and p21, and reduction in DNA synthesis. In conclusion, this study sheds light on the pathogenesis of this unique group of ovarian tumors by showing that BRAF mutation is associated with cellular senescence and the presence of a specific cell type characterized by abundant EC. This "oncogene-induced senescence" phenotype may represent a mechanism that impedes progression of APSTs to LGSC.

Wnt5A promotes an adaptive, senescent-like stress response, while continuing to drive invasion in melanoma cells

We have previously shown that Wnt5A drives invasion in melanoma. We have also shown that Wnt5A promotes resistance to therapy designed to target the BRAF(V600E) mutation in melanoma. Here, we show that melanomas characterized by high levels of Wnt5A respond to therapeutic stress by increasing p21 and expressing classical markers of senescence, including positivity for senescence-associated β-galactosidase (SA-β-gal), senescence-associated heterochromatic foci (SAHF), H3K9Me chromatin marks, and PML bodies. We find that despite this, these cells retain their ability to migrate and invade. Further, despite the expression of classic markers of senescence such as SA-β-gal and SAHF, these Wnt5A-high cells are able to colonize the lungs in in vivo tail vein colony-forming assays. This clearly underscores the fact that these markers do not indicate true senescence in these cells, but instead an adaptive stress response that allows the cells to evade therapy and invade. Notably, silencing Wnt5A reduces expression of these markers and decreases invasiveness. The combined data point to Wnt5A as a master regulator of an adaptive stress response in melanoma, which may contribute to therapy resistance.

Role of the stem cell niche in the pathogenesis of epithelial ovarian cancers

Ovarian cancer is the fifth leading cause of cancer-related deaths among women in the United States. Recent extensive genomic analyses of epithelial ovarian cancer (EOC), particularly the most common and deadly form of high-grade serous ovarian carcinoma, have provided important insights into the repertoire of molecular aberrations that are characteristic for this malignancy. However, interpretation of the discovered aberrations is complicated because the origin and mechanisms of progression of EOC remain uncertain. Here, we summarize current views on the cell of origin of EOC and discuss recent findings of a cancer-prone stem cell niche for ovarian surface epithelium, one of the major likely sources of EOC. We also outline future directions and challenges in studying the role of stem cell niches in EOC pathogenesis.

An analysis of polymorphisms within the Wnt signaling pathway in relation to ovarian cancer risk in a Polish population

Background and Objective

The Wnt/β-catenin signaling pathway has been considered to be a factor in the development and progression of ovarian cancer.

Methods

All patients with ovarian cancer and controls were tested for BRCA1 mutations (5382incC, C61G, 4153delA) with HybProbe assays and for BRCA2 mutation (5946delT) using high-resolution melting curve analysis (HRM). Mutation carriers were excluded from the association analysis. We studied nine single nucleotide polymorphisms (SNPs) located in CTNNB1 (β-catenin) [rs4533622, rs2953], APC (rs11954856, rs351771, rs459552), and AXIN2 (rs4074947, rs7224837, rs3923087, rs2240308) in women with ovarian cancer without BRCA1/BRCA2 mutations (n = 228) and controls (n = 282). Genotyping of CTNNB1 rs4533622, rs2953, APC rs351771, AXIN2 rs4074947, rs3923087, and rs2240308 was performed by HRM, while that of APC rs11954856, rs459552 and AXIN2 rs7224837 was conducted by PCR followed by the appropriate restriction enzyme digestion [PCR–restriction fragment length polymorphism (PCR-RFLP)].

Results

The most common BRCA1/BRCA2 mutations were identified in 30 patients with ovarian cancer. These mutations were not found in controls. The lowest p values of the trend test (p_trend) were observed for the APC rs351771 and rs11954856 SNPs in patients with ovarian cancer (p_trend = 0.006 and p_trend = 0.007, respectively). Using a dominant inheritance model, we found that the APC rs11954856 SNP is associated with an increased risk of ovarian cancer development [odds ratio = 2.034 (95 % CI 1.302–3.178); p = 0.002]. We also observed significant allelic differences for the APC rs351771 SNP between patients and controls (p = 0.006).

Conclusion

Our study demonstrated significantly increased APC rs11954856 and rs351771 SNP frequencies in Polish women with ovarian cancer.

Electronic supplementary material

The online version of this article (doi:10.1007/s40291-013-0059-y) contains supplementary material, which is available to authorized users.

IL-1β mediates MCP-1 induction by Wnt5a in gastric cancer cells

BACKGROUND

Both Wnt5a overexpression and macrophage infiltration have been implicated in inflammation and cancer. The aim of this study is to reveal the involvement of Wnt5a in macrophage recruitment in gastric cancer.

METHODS

mRNA expression in gastric cancer tissues and cells was investigated by real-time PCR. Protein secretion by gastric cancer cells was determined by ELISA. PcDNA3.1-Wnt5a expression vector and Wnt5a siRNA vector were used to overexpress and silence Wnt5a expression in gastric cells, respectively. Macrophage migration was analyzed by transwell, and macrophage cytoskeleton was stained with FITC-phalloidin.

RESULTS

Wnt5a was overexpressed in gastric cancer tissues, and correlated with monocyte chemotactic protein 1 (MCP-1) and interleukin 1β (IL-1β), respectively. In gastric cancer cells, Wnt5a induced MCP-1 expression, which was mediated by IL-1β. Conditioned medium from gastric cancer cells transfected with Wnt5a stimulated macrophage chemotaxis and cytoskeletal changes via MCP-1, which were suppressed by recombinant IL-1 receptor antagonist (rIL-1Ra).

CONCLUSIONS

These results suggest that Wnt5a is involved in macrophage recruitment by upregulating MCP-1, and IL-1Ra may be used to inhibit macrophage recruitment in gastric cancer.

Expression profiling of primary and metastatic ovarian tumors reveals differences indicative of aggressive disease

The behavior and genetics of serous epithelial ovarian cancer (EOC) metastasis, the form of the disease lethal to patients, is poorly understood. The unique properties of metastases are critical to understand to improve treatments of the disease that remains in patients after debulking surgery. We sought to identify the genetic and phenotypic landscape of metastatic progression of EOC to understand how metastases compare to primary tumors. DNA copy number and mRNA expression differences between matched primary human tumors and omental metastases, collected at the same time during debulking surgery before chemotherapy, were measured using microarrays. qPCR and immunohistochemistry validated findings. Pathway analysis of mRNA expression revealed metastatic cancer cells are more proliferative and less apoptotic than primary tumors, perhaps explaining the aggressive nature of these lesions. Most cases had copy number aberrations (CNAs) that differed between primary and metastatic tumors, but we did not detect CNAs that are recurrent across cases. A six gene expression signature distinguishes primary from metastatic tumors and predicts overall survival in independent datasets. The genetic differences between primary and metastatic tumors, yet common expression changes, suggest that the major clone in metastases is not the same as in primary tumors, but the cancer cells adapt to the omentum similarly. Together, these data highlight how ovarian tumors develop into a distinct, more aggressive metastatic state that should be considered for therapy development.

Ovarian cancer stem cells: are they real and why are they important?

The cancer stem cell hypothesis has been put forward as a paradigm to describe varying levels of aggressiveness in heterogeneous tumors. Specifically, many subpopulations have been clearly demonstrated to possess increased tumorigenicity in mice, broad differentiating capacity, and resistance to therapy. However, the extent to which these experimental findings are potentially clinically significant is still not clear. This review will describe the principles of this emerging hypothesis, ways in which it may be appropriate in ovarian cancer based on the clinical course of the disease, and how we might exploit it to improve outcomes in ovarian cancer patients.

Identification of ribonucleotide reductase M2 as a potential target for pro-senescence therapy in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the leading cause of gynecological-related cancer deaths in the United States. There is, therefore, an urgent need to develop novel therapeutic strategies for this devastating disease. Cellular senescence is a state of stable cell growth arrest that acts as an important tumor suppression mechanism. Ribonucleotide reductase M2 (RRM2) plays a key role in regulating the senescence-associated cell growth arrest by controlling biogenesis of 2'-deoxyribonucleoside 5'-triphosphates (dNTPs). The role of RRM2 in EOC remains poorly understood. Here we show that RRM2 is expressed at higher levels in EOCs compared with either normal ovarian surface epithelium (P<0.001) or fallopian tube epithelium (P<0.001). RRM2 expression significantly correlates with the expression of Ki67, a marker of cell proliferation (P<0.001). Moreover, RRM2 expression positively correlates with tumor grade and stage, and high RRM2 expression independently predicts a shorter overall survival in EOC patients (P<0.001). To delineate the functional role of RRM2 in EOC, we knocked down RRM2 expression in a panel of EOC cell lines. Knockdown of RRM2 expression inhibits the growth of human EOC cells. Mechanistically, RRM2 knockdown triggers cellular senescence in these cells. Notably, this correlates with the induction of the DNA damage response, a known mediator of cellular senescence. These data suggest that targeting RRM2 in EOCs by suppressing its activity is a novel pro-senescence therapeutic strategy that has the potential to improve survival of EOC patients.

Regulation of prostate cancer cell migration toward bone marrow stromal cell-conditioned medium by Wnt5a signaling

Bone is a major site of metastasis for several types of malignant tumor. Specific interactions between tumor cells and the bone microenvironment contribute to the tendency of tumors to metastasize to bone. Furthermore, Wnt5a participates in the progression of several types of malignant tumor. This study investigates the role of Wnt5a in the migration of the prostate cancer (PCa) cell line PC3 toward bone marrow stromal cell (BMSC)‑conditioned medium (CM). The expression of 22 genes associated with bone metastasis was measured in three PCa cell lines (LNCaP, PC3 and DU145). Subsequently, the proliferation and migration capacities of PC3 cells treated either with small interfering RNA (siRNA) against Wnt5a or with recombinant mouse (rm) Wnt5a were analyzed with alamarBlue and transwell assays. BMSC‑CM was collected to evaluate its effect on PC3 cell migration. Also, the expression of Wnt5a in BMSCs was knocked down prior to collection of the CM to evaluate its effects on the migration of PC3 cells. Significantly higher levels of Wnt5a mRNA expression were identified in the PC3 cells, compared with those in LNCaP and DU145 cells. Silencing Wnt5a expression with siRNA reduced the migration capacity of PC3 cells by 50%. The addition of rmWnt5a improved the migration capacity of PC3 cells in a concentration‑dependent manner. PC3 cells preferred to migrate toward BMSC‑CM than toward the control. CM from Wnt5a siRNA‑treated BMSCs significantly reduced PC3 cell migration. Wnt5a promotes PC3 cell migration toward BMSC‑CM, indicating that Wnt5a is a potential therapeutic target for the treatment of advanced PCa.

Targeting ROR1 inhibits epithelial-mesenchymal transition and metastasis

Metastasis is responsible for 90% of cancer-related deaths. Strategies are needed that can inhibit the capacity of cancer cells to migrate across the anatomic barriers and colonize distant organs. Here, we show an association between metastasis and expression of a type I receptor tyrosine kinase-like orphan receptor, ROR1, which is expressed during embryogenesis and by various cancers, but not by normal postpartum tissues. We found that expression of ROR1 associates with the epithelial-mesenchymal transition (EMT), which occurs during embryogenesis and cancer metastasis. Breast adenocarcinomas expressing high levels of ROR1 were more likely to have gene expression signatures associated with EMT and had higher rates of relapse and metastasis than breast adenocarcinomas expressing low levels of ROR1. Suppressing expression of ROR1 in metastasis-prone breast cancer cell lines, MDA-MB-231, HS-578T, or BT549, attenuated expression of proteins associated with EMT (e.g., vimentin, SNAIL-1/2, and ZEB1), enhanced expression of E-cadherin, epithelial cytokeratins (e.g., CK-19), and tight junction proteins (e.g., ZO-1), and impaired their migration/invasion capacity in vitro and the metastatic potential of MDA-MB-231 cells in immunodeficient mice. Conversely, transfection of MCF-7 cells to express ROR1 reduced expression of E-cadherin and CK-19, but enhanced the expression of SNAIL-1/2 and vimentin. Treatment of MDA-MB-231 with a monoclonal antibody specific for ROR1 induced downmodulation of vimentin and inhibited cancer cell migration and invasion in vitro and tumor metastasis in vivo. Collectively, this study indicates that ROR1 may regulate EMT and metastasis and that antibodies targeting ROR1 can inhibit cancer progression and metastasis.

Multifaceted roles of GSK-3 and Wnt/β-catenin in hematopoiesis and leukemogenesis: opportunities for therapeutic intervention

Glycogen synthase kinase-3 (GSK-3) is well documented to participate in a complex array of critical cellular processes. It was initially identified in rat skeletal muscle as a serine/threonine kinase that phosphorylated and inactivated glycogen synthase. This versatile protein is involved in numerous signaling pathways that influence metabolism, embryogenesis, differentiation, migration, cell cycle progression and survival. Recently, GSK-3 has been implicated in leukemia stem cell pathophysiology and may be an appropriate target for its eradication. In this review, we will discuss the roles that GSK-3 plays in hematopoiesis and leukemogenesis as how this pivotal kinase can interact with multiple signaling pathways such as: Wnt/β-catenin, phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt/mammalian target of rapamycin (mTOR), Ras/Raf/MEK/extracellular signal-regulated kinase (ERK), Notch and others. Moreover, we will discuss how targeting GSK-3 and these other pathways can improve leukemia therapy and may overcome therapeutic resistance. In summary, GSK-3 is a crucial regulatory kinase interacting with multiple pathways to control various physiological processes, as well as leukemia stem cells, leukemia progression and therapeutic resistance. GSK-3 and Wnt are clearly intriguing therapeutic targets.

A high-content screening assay for small-molecule modulators of oncogene-induced senescence

Cellular senescence is a state of stable cell growth arrest. Activation of oncogenes such as RAS in mammalian cells typically triggers cellular senescence. Oncogene-induced senescence (OIS) is an important tumor suppression mechanism, and suppression of OIS contributes to cell transformation. Oncogenes trigger senescence through a multitude of incompletely understood downstream signaling events that frequently involve protein kinases. To identify target proteins required for RAS-induced senescence, we developed a small-molecule screen in primary human fibroblasts undergoing senescence induced by oncogenic RAS (H-Ras(G12V)). Using a high-content imaging system to monitor two hallmarks of senescence, senescence-associated β-galactosidase activity expression and inhibition of proliferation, we screened a library of known small-molecule kinase inhibitors for those that suppressed OIS. Identified compounds were subsequently validated and confirmed using a third marker of senescence, senescence-associated heterochromatin foci. In summary, we have established a novel high-content screening platform that may be useful for elucidating signaling pathways mediating OIS by targeting critical pathway components.

Suppression of nucleotide metabolism underlies the establishment and maintenance of oncogene-induced senescence

Oncogene-induced senescence is characterized by a stable cell growth arrest, thus providing a tumor suppression mechanism. However, the underlying mechanisms for this phenomenon remain unknown. Here, we show that a decrease in deoxyribonucleotide triphosphate (dNTP) levels underlies oncogene-induced stable senescence-associated cell growth arrest. The decrease in dNTP levels is caused by oncogene-induced repression of ribonucleotide reductase subunit M2 (RRM2), a rate-limiting protein in dNTP synthesis. This precedes the senescence-associated cell-cycle exit and coincides with the DNA damage response. Consistently, RRM2 downregulation is both necessary and sufficient for senescence. Strikingly, suppression of nucleotide metabolism by RRM2 repression is also necessary for maintenance of the stable senescence-associated cell growth arrest. Furthermore, RRM2 repression correlates with senescence status in benign nevi and melanoma, and its knockdown drives senescence of melanoma cells. These data reveal the molecular basis whereby the stable growth arrest of oncogene-induced senescence is established and maintained through suppression of nucleotide metabolism.

WNT signalling pathways as therapeutic targets in cancer

Since the initial discovery of the oncogenic activity of WNT1 in mouse mammary glands, our appreciation for the complex roles for WNT signalling pathways in cancer has increased dramatically. WNTs and their downstream effectors regulate various processes that are important for cancer progression, including tumour initiation, tumour growth, cell senescence, cell death, differentiation and metastasis. Although WNT signalling pathways have been difficult to target, improved drug-discovery platforms and new technologies have facilitated the discovery of agents that can alter WNT signalling in preclinical models, thus setting the stage for clinical trials in humans.

SUZ12 promotes human epithelial ovarian cancer by suppressing apoptosis via silencing HRK

Epithelial ovarian cancer (EOC) ranks first as the cause of death for gynecological cancers in the United States. SUZ12 is a component of the polycomb repressive complex 2 (PRC2) and is essential for PRC2-mediated gene silencing by generating trimethylation on lysine 27 residue of histone H3 (H3K27Me3). The role of SUZ12 in EOC has never been investigated. Here, we show that SUZ12 is expressed at significantly higher levels in human EOC (n = 117) compared with either normal human ovarian surface epithelium (n = 35, P < 0.001) or fallopian tube epithelium (n = 15, P < 0.001). There is a positive correlation between expression of SUZ12 and EZH2 in human EOC (P < 0.001). In addition, expression of SUZ12 positively correlates with Ki67, a marker of cell proliferation (P < 0.001), and predicts shorter overall survival (P = 0.0078). Notably, knockdown of SUZ12 suppresses the growth of human EOC cells in vitro and in vivo in both orthotopic and subcutaneous xenograft EOC models. In addition, SUZ12 knockdown decreases the levels of H3K27Me3 and triggers apoptosis of human EOC cells. Mechanistically, we identified Harakiri (HRK), a proapoptotic gene, as a novel SUZ12 target gene, and showed that HRK upregulation mediates apoptosis induced by SUZ12 knockdown in human EOC cells. In summary, we show that SUZ12 promotes the proliferation of human EOC cells by inhibiting apoptosis and HRK is a novel SUZ12 target gene whose upregulation contributes to apoptosis induced by SUZ12 knockdown.

WNT secretion and signalling in human disease

Wnt signalling, a key pathway involved in various aspects of embryonic development, also underlies many human diseases, in particular, cancer. Research focused on signal transduction within signal-receiving cells led to the discovery of many Wnt pathway components, but study of the secretion of Wnt ligands themselves was neglected until recently. Attention was drawn to this highly regulated process by the association of aberrant Wnt levels with an increasing number of diseases. Studying the biogenesis and processing of active Wnt ligands will open new avenues for generating therapeutics to specifically target aberrant Wnt signalling. Here we review the proteins required for Wnt secretion and signalling at the plasma membrane, ending with a discussion on potential therapeutic approaches to treat Wnt-induced diseases.

ALDH1A1 is a novel EZH2 target gene in epithelial ovarian cancer identified by genome-wide approaches

Epithelial ovarian cancer (EOC) remains the most lethal gynecologic malignancy in the United States. EZH2 silences gene expression through trimethylating lysine 27 on histone H3 (H3K27Me3). EZH2 is often overexpressed in EOC and has been suggested as a target for EOC intervention. However, EZH2 target genes in EOC remain poorly understood. Here, we mapped the genomic loci occupied by EZH2/H3K27Me3 using chromatin immunoprecipitation followed by next-generation sequencing (ChIP-seq) and globally profiled gene expression in EZH2-knockdown EOC cells. Cross-examination of gene expression and ChIP-seq revealed a list of 60 EZH2 direct target genes whose expression was upregulated more than 1.5-fold upon EZH2 knockdown. For three selected genes (ALDH1A1, SSTR1, and DACT3), we validated their upregulation upon EZH2 knockdown and confirmed the binding of EZH2/H3K27Me3 to their genomic loci. Furthermore, the presence of H3K27Me3 at the genomic loci of these EZH2 target genes was dependent upon EZH2. Interestingly, expression of ALDH1A1, a putative marker for EOC stem cells, was significantly downregulated in high-grade serous EOC (n = 53) compared with ovarian surface epithelial cells (n = 10, P < 0.001). Notably, expression of ALDH1A1 negatively correlated with expression of EZH2 (n = 63, Spearman r = -0.41, P < 0.001). Thus, we identified a list of 60 EZH2 target genes and established that ALDH1A1 is a novel EZH2 target gene in EOC cells. Our results suggest a role for EZH2 in regulating EOC stem cell equilibrium via regulation of ALDH1A1 expression.