Expression profile of frizzled receptors in human medulloblastomas

Neurodegeneration-associated protein VAPB regulates proliferation in medulloblastoma

VAMP (Vesicle-associated membrane protein)-associated protein B and C (VAPB) has been widely studied in neurodegenerative diseases such as ALS, but little is known about its role in cancer. Medulloblastoma is a common brain malignancy in children and arises from undifferentiated cells during neuronal development. Therefore, medulloblastoma is an interesting model to investigate the possible relationship between VAPB and tumorigenesis. Here we demonstrate that high VAPB expression in medulloblastoma correlates with decreased overall patient survival. Consistent with this clinical correlation, we find that VAPB is required for normal proliferation rates of medulloblastoma cells in vitro and in vivo. Knockout of VAPB (VAPBKO) delayed cell cycle progression. Furthermore, transcript levels of WNT-related proteins were decreased in the VAPBKO. We conclude that VAPB is required for proliferation of medulloblastoma cells, thus revealing VAPB as a potential therapeutic target for medulloblastoma treatment.

Expression pattern, prognostic value and potential microRNA silencing of FZD8 in breast cancer

Breast cancer (BC) is one of the most widespread types of cancer affecting females, and therefore, early diagnosis is critical. BC is a complex heterogeneous disease affected by several key pathways. Among these, WNT proteins and their frizzled receptors (FZD) have been demonstrated to be crucial in regulating a number of cellular and molecular events in BC tumorigenesis. The role of the WNT receptor, FZD8, in BC has received minimal attention; for that reason, the present study examined the prognostic value of its protein expression pattern in a BC cohort. FZD8 cytoplasmic expression pattern analysis revealed that ~38% of the primary samples presented with a high expression profile, whereas ~63% of the samples had a low expression profile. Overall, ~46% of the malignant tissues in the lymph node-positive samples exhibited an increased FZD8 cytoplasmic expression, whereas 54% exhibited low expression levels. An increased expression of FZD8 was associated with several clinicopathological characteristics of the patients, including a low survival rate, tumor vascular invasion, tumor size and grade, and molecular subtypes. Affymetrix microarray triple-negative BC datasets were analyzed and compared with healthy breast tissues in order to predict the potential interfering microRNAs (miRNAs) in the WNT/FZD8 signaling pathway. A total of 29 miRNAs with the potential to interact with the WNT/FZD8 signaling pathway were identified, eight of which exhibited a significant prediction score. The target genes for each predicted miRNA were identified. On the whole, the findings of the present study suggest that FZD8 is a potential prognostic marker for BC, shedding some light onto the silencing mechanisms involved in the complex BC signaling.

The Molecular Landscape of Medulloblastoma in Teenagers and Young Adults

Medulloblastoma (MB) is a childhood malignant brain tumour but also occurs in teenagers and young adults (TYA). Considering that MB is heterogeneous, this study aimed to define the molecular landscape of MBs in TYAs. We collated more than 2000 MB samples that included 287 TYA patients (13-24 years). We performed computational analyses consisting of genome-wide methylation and transcriptomic profiles and developed a prognostics model for the TYAs with MB. We identified that TYAs predominantly comprised of Group 4 (40%) and Sonic Hedgehog (SHH)-activated (33%) tumours, with Wingless-type (WNT, 17%) and Group 3 (10%) being less common. TYAs with SHH tumours displayed significantly more gene expression alterations, whereas no gene was detected in the Group 4 tumours. Across MB subgroups, we identified unique and shared sets of TYA-specific differentially methylated probes and DNA-binding motifs. Finally, a 22-gene signature stratified TYA patients into high- and low-risk groups, and the prognostic significance of these risk groups persisted in multivariable regression models (P = 0.001). This study is an important step toward delineating the molecular landscape of TYAs with MB. The emergence of novel genes and pathways may provide a basis for improved clinical management of TYA with MB.

Cancer chemoprevention through Frizzled receptors and EMT

Frizzled (FZD) transmembrane receptors are well known for their role in β-catenin signaling and development and now understanding of their role in the context of cancer is growing. FZDs are often associated with the process of epithelial to mesenchymal transition (EMT) through β-catenin, but some also influence EMT through non-canonical pathways. With ten different FZDs, there is a wide range of activity from oncogenic to tumor suppressive depending on the tissue context. Alterations in FZD signaling can occur during development of premalignant lesions, supporting their potential as targets of chemoprevention agents. Agonizing or antagonizing FZD activity may affect EMT, which is a key process in lesion progression often targeted by chemoprevention agents. Recent studies identified a specific FZD as important for activity of an EMT inhibiting chemopreventive agent and other studies have highlighted the previously unrecognized potential for targeting small molecules to FZD receptors. This work demonstrates the value of investigating FZDs in chemoprevention and here we provide a review of FZDs in cancer EMT and their potential as chemoprevention targets.

DNA methylation and protein expression of Wnt pathway markers in progressive glioblastoma

BACKGROUND

Wnt signaling plays important roles in tumorigenesis, invasiveness and therapeutic resistance of glioblastoma (GBM).

METHODS

We simultaneously investigated six Wnt pathway markers (Wnt5a, Fzd-2, beta-catenin, Wnt3a, Wnt7b, Fzd-10) at epigenetic and protein levels in 21 sequential formalin-fixed paraffin-embedded GBM pairs and controls.

RESULTS

Expression levels of Wnt5a, beta-catenin and Wnt3a proteins either moderately or significantly increased, while those of Fzd-2, Wnt7b and Fzd-10 decreased in the primary (GBM-P) and recurrent (GBM-R) tumors compared to the controls. Methylation levels within promoters and genes showed corresponding decreases for Wnt5a, beta-catenin and Wnt3a in tumors vs. controls, while that of Fzd-10 was uniformly high. Comparing the GBM-P and GBM-R pairs, proteins of Fzd-2, beta-catenin and Wnt3a were either moderately or significantly up-, while that of Wnt7b was downregulated in GBM-R, but these patterns were not accompanied by inverse methylation patterns in the corresponding promoters and genes over time. No methylation differences were noted within promoters and genes of the same markers in 112 pairs of primary and recurrent GBMs in a database, suggesting that the observed changes in protein expression levels may not be explained by CpG methylation status alone. The promoter and gene methylation rate was the highest for Fzd-10 in the database cohort too, supporting the noted low Fzd-10 protein expression.

DISCUSSION

These analyses underscore the relevance of Wnt pathway molecules in the context of their methylation profiles in the development and evolution of GBM, and suggest that Wnt pathway regulation as a potential treatment target merits further studies.

Comprehensive Analysis Reveals a 4-Gene Signature in Predicting Response to Temozolomide in Low-Grade Glioma Patients

Low-grade gliomas (LGGs) are a highly heterogeneous group of slow-growing, lethal, diffusive brain tumors. Temozolomide (TMZ) is a frequently used primary chemotherapeutic agent for LGGs. Currently there is no consensus as to the optimal biomarkers to predict the efficacy of TMZ, which calls for decision-making for each patient while considering molecular profiles. Low-grade glioma data sets were retrieved from The Cancer Genome Atlas. Cox regression and survival analyses were applied to identify clinical features significantly associated with survival. Subsequently, Ordinal logistic regression, co-expression, and Cox regression analyses were applied to identify genes that correlate significantly with response rate, disease-free survival, and overall survival of patients receiving TMZ as primary therapy. Finally, gene expression and methylation analyses were exploited to explain the mechanism between these gene expression and TMZ efficacy in LGG patients. Overall survival was significantly correlated with age, Karnofsky Performance Status score, and histological grade, but not with IDH1 mutation status. Using 3 distinct efficacy end points, regression and co-expression analyses further identified a novel 4-gene signature of ASPM, CCNB1, EXO1, and KIF23 which negatively correlated with response to TMZ therapy. In addition, expression of the 4-gene signature was associated with those of genes involved in homologous recombination. Finally, expression and methylation profiling identified a largely unknown olfactory receptor OR51F2 as potential mediator of the roles of the 4-gene signature in reducing TMZ efficacy. Taken together, these findings propose the 4-gene signature as a novel panel of efficacy predictors of TMZ therapy, as well as potential downstream mechanisms, including homologous recombination, OR51F2, and DNA methylation independent of MGMT.

Overexpression of FZD1 and CAIX are Associated with Invasion, Metastasis, and Poor-Prognosis of the Pancreatic Ductal Adenocarcinoma

Approximately 80% of patients with pancreatic ductal adenocarcinoma (PDAC) have metastatic disease with poor prognosis, but clinically available biomarkers have not yet been identified. This study was to investigate the clinical significance of FZD1 and CAIX in PDACs. FZD1 and CAIX protein expression was measured using EnVision immunohistochemistry. Positive FZD1 or CAIX expression was significantly higher in PDAC than that in precursor lesions (p < 0.01). Positive FZD1 or CAIX expression was significantly lower in cases with well-differentiated adenocarcinoma, no-metastasis of the lymph node, no-invasion of regional tissues, and TNM I/II stage disease than in cases with poorly-differentiated adenocarcinoma, metastasis and invasion, and TNM stage III+ IV stage disease (p < 0.05 or p < 0.01). The expression of FZD1 positively correlated with CAIX in PDAC (P = 0.000). Univariate Kaplan-Meier analysis showed that FZD1 and/or CAIX expression (p < 0.001) was significantly associated with shorter overall survival (p < 0.05). Cox multivariate analysis showed that differentiation, tumor mass, lymph node metastasis, invasion, TNM stage, FZD1 and CAIX levels negatively correlated with overall survival. Positive FZD1 and CAIX expressions are poor prognostic factors in PDAC patients. FZD1 and CAIX might be important biological markers for the carcinogenesis, metastasis, invasion, and prognosis of PDAC.

Expression profile and clinical significance of Wnt signaling in human gliomas

Wnt signaling has been identified as a critical regulator of human tumor development in vitro. However, there remains a lack of studies systematically examining the expression pattern and clinical relevance of the core molecules of Wnt signaling in glioma tissues. In the present study, it was identified that the mRNA expression levels of Wnt3a and 5a, and their receptors frizzled 2, 6 and 7 increased, whereas Wnt7b was markedly decreased in glioma relative to non-tumor tissue. The mRNA levels of β-catenin, adenomatous polyposis coli gene product, glycogen synthase kinase 3β (GSK3β) and AXIN1 and its target genes cyclin D1 and AXIN2 did not differ. Similarly, the protein levels of Wnt2b, 3a and 5a were increased in gliomas, while β-catenin, GSK3β and cyclin D1 were not. Furthermore, based on data from the R2: Genomics Analysis and Visualization Platform, the expression of Wnt2b and 5a, and frizzled 2, 6 and 7 were highly associated with the prognosis of patients with glioma. Taken together, the results of the present study demonstrate that β-catenin is not upregulated in gliomas and that the Wnt signaling pathway may promote glioma development via noncanonical or alternative pathways.

ACE2 and FZD1 are prognosis markers in squamous cell/adenosquamous carcinoma and adenocarcinoma of gallbladder

The clinicopathological characteristics of squamous cell/adenosquamous carcinoma (SC/ASC) of the gallbladder have not been well documented, and no prognosis marker has been identified because of the rare occurrence of this gallbladder cancer subtype. In this study, we examined ACE2 and FZD1 expression in 46 SC/ASCs and 80 adenocarcinomas using immunohistochemistry and further analyzed their correlations with clinicopathological characteristics. We demonstrated that positive FZD1 and negative ACE2 expression were significantly associated with large tumor size, high TNM stage, lymph node metastasis and invasion of SC/ASC and AC. Univariate Kaplan-Meier analysis showed that positive FZD1 and negative ACE2 expression as well as differentiation, tumor size, TNM stage, lymph node metastasis, invasion, and surgical curability were closely associated with decreased overall survival in both SC/ASC (p < 0.001) and AC (p < 0.001) patients. The average survival time in SC/ASC and AC patients with FZD1(-)ACE2(+) expression was significantly longer than that in patients with FZD1(+)ACE2(-) or FZD1(+)ACE2(+) (p < 0.01). Multivariate Cox regression analysis showed that positive FZD1 and negative ACE2 expression are independent poor-prognostic factors for both SC/ASC and AC patients. In addition, FZD1 expression positively, but ACE2 expression negatively correlated with the expression of CA19-9 in SC/ASC and AC. Our study suggested that positive FZD1 and negative ACE2 expression are closely related to the expression of CA19-9; clinical, pathological, and biological behaviors; as well as poor-prognosis of gallbladder cancer.

Wnt pathway activity confers chemoresistance to cancer stem-like cells in a neuroblastoma cell line

Neuroblastoma is the most common solid tumor in infancy. We have shown that the neuroblastoma cell line SK-N-SH contains CD133+ cells that are more resistant than 133- cells to Doxorubicin (DOX), a common chemotherapeutic agent. We hypothesize that activation of wnt signaling pathway in CD133+ cells contributes to their chemoresistance. To test this hypothesis, CD133+ cells were positively selected using magnetic micro-beads. Subsequently, CD133+ and negatively selected CD133- cells were treated with 100 ng/ml of DOX for up to 72 h. Then, cells were either lysed for total RNA extraction or fixed for immunostaining. Wnt "SIGNATURE" PCR Array was used to determine if changes in wnt related gene expression levels occurred and to estimate a pathway activity score. Expression of wnt pathway proteins β-Catenin and p-GSK3β (S-9) was determined by immunocytochemistry. Two wnt pathway inhibitors were used to determine the changes in cell viability, using the MTT assay. Results showed that wnt related genes were differentially expressed in CD133+ cells as compared to CD133- cells, both with and without DOX treatment. Pathway activity scores showed that DOX treatment significantly suppressed the wnt pathway activity in CD133- cells. Expression of β-catenin and p-GSK3β (S-9) was significantly greater in DOX treated and untreated CD133+ cells. The presence of wnt inhibitors with DOX decreased the number of live cells in CD133+ group and the percentage of live cells in both groups were equal. These data suggest that higher wnt pathway activity could be responsible for the chemoresistance of CD133+ cells in neuroblastoma cell lines.

Medulloblastoma stem cells: modeling tumor heterogeneity

Brain tumors represent the leading cause of childhood cancer mortality, with medulloblastoma (MB) being the most frequent malignant tumor. In this review we discuss the morphological and molecular heterogeneity of this malignant childhood brain tumor and how this key feature has implicated the presence of a MB stem cell. We focus on evidence from cerebellar development, histopathological and molecular subtypes of MB, the recent identification of brain tumor-initiating cells (BTICs, also referred to as MB stem cells), and the current limitations in studying the interplay between MB stem cells and tumor heterogeneity.