Small-molecule inhibitors of phosphatidylinositol 3-kinase/Akt signaling inhibit Wnt/beta-catenin pathway cross-talk and suppress medulloblastoma growth

Chronic NaAsO2 exposure promotes migration and invasion of prostate cancer cells by Akt/GSK-3β/β-catenin/TCF4 axis-mediated epithelial-mesenchymal transition

Inorganic arsenic is a Class I human Carcinogen. However, the role of chronic inorganic arsenic exposure on prostate cancer metastasis still unclear. This study aimed to investigate the effects and mechanism of chronic NaAsO2 exposure on migration and invasion of prostate cancer cells. DU145 and PC-3 cells were exposed to NaAsO2 (2 μM) for 25 generations. Wound healing and Transwell assays showed that chronic NaAsO2 exposure promoted migration and invasion of DU145 and PC-3 cells. In addition, chronic NaAsO2 exposure induced epithelial-mesenchymal transition (EMT) of DU145 cells by promoting β-catenin/TCF4 transcriptional activity. Mechanically, NaAsO2 promoted GSK-3β inactivation in the "disruption complex" through Akt- mediated phosphorylation at serine 9, and then inhibited the phosphorylation and ubiquitination degradation of β-catenin, which led to its nuclear translocation. Ly294002, a selective phosphatidylinositol 3-kinase (PI3K)/Akt inhibitor, suppressed the β-catenin/TCF4 complex activation and EMT through blocking Akt-mediated GSK-3β inactivation in the "disruption complex" in chronic NaAsO2 exposed DU145 and PC-3 cells. Moreover, Ly294002 alleviated chronic NaAsO2-induced migration and invasion in DU145 and PC-3 cells. These findings provide evidence that chronic arsenic exposure promotes migration and invasion of prostate cancer cells via an EMT mechanism driven by the AKT/GSK-3β/β-catenin/TCF4 signaling axis. Akt is expected to be a potential therapeutic target for chronic arsenic exposure-mediated prostate cancer metastasis.

High-throughput neural stem cell-based drug screening identifies S6K1 inhibition as a selective vulnerability in sonic hedgehog-medulloblastoma

BACKGROUND

Medulloblastoma (MB) is one of the most common malignant brain tumors in children. Current treatments have increased overall survival but can lead to devastating side effects and late complications in survivors, emphasizing the need for new, improved targeted therapies that specifically eliminate tumor cells while sparing the normally developing brain.

METHODS

Here, we used a sonic hedgehog (SHH)-MB model based on a patient-derived neuroepithelial stem cell system for an unbiased high-throughput screen with a library of 172 compounds with known targets. Compounds were evaluated in both healthy neural stem cells (NSCs) and tumor cells derived from the same patient. Based on the difference of cell viability and drug sensitivity score between normal cells and tumor cells, hit compounds were selected and further validated in vitro and in vivo.

RESULTS

We identified PF4708671 (S6K1 inhibitor) as a potential agent that selectively targets SHH-driven MB tumor cells while sparing NSCs and differentiated neurons. Subsequent validation studies confirmed that PF4708671 inhibited the growth of SHH-MB tumor cells both in vitro and in vivo, and that knockdown of S6K1 resulted in reduced tumor formation.

CONCLUSIONS

Overall, our results suggest that inhibition of S6K1 specifically affects tumor growth, whereas it has less effect on non-tumor cells. Our data also show that the NES cell platform can be used to identify potentially effective new therapies and targets for SHH-MB.

ARF suppression by MYC but not MYCN confers increased malignancy of aggressive pediatric brain tumors

Medulloblastoma, the most common malignant pediatric brain tumor, often harbors MYC amplifications. Compared to high-grade gliomas, MYC-amplified medulloblastomas often show increased photoreceptor activity and arise in the presence of a functional ARF/p53 suppressor pathway. Here, we generate an immunocompetent transgenic mouse model with regulatable MYC that develop clonal tumors that molecularly resemble photoreceptor-positive Group 3 medulloblastoma. Compared to MYCN-expressing brain tumors driven from the same promoter, pronounced ARF silencing is present in our MYC-expressing model and in human medulloblastoma. While partial Arf suppression causes increased malignancy in MYCN-expressing tumors, complete Arf depletion promotes photoreceptor-negative high-grade glioma formation. Computational models and clinical data further identify drugs targeting MYC-driven tumors with a suppressed but functional ARF pathway. We show that the HSP90 inhibitor, Onalespib, significantly targets MYC-driven but not MYCN-driven tumors in an ARF-dependent manner. The treatment increases cell death in synergy with cisplatin and demonstrates potential for targeting MYC-driven medulloblastoma.

Pathological implications of metabolic reprogramming and its therapeutic potential in medulloblastoma

Tumor-specific alterations in metabolism have been recognized to sustain the production of ATP and macromolecules needed for cell growth, division and survival in many cancer types. However, metabolic heterogeneity poses a challenge for the establishment of effective anticancer therapies that exploit metabolic vulnerabilities. Medulloblastoma (MB) is one of the most heterogeneous malignant pediatric brain tumors, divided into four molecular subgroups (Wingless, Sonic Hedgehog, Group 3 and Group 4). Recent progresses in genomics, single-cell sequencing, and novel tumor models have updated the classification and stratification of MB, highlighting the complex intratumoral cellular diversity of this cancer. In this review, we emphasize the mechanisms through which MB cells rewire their metabolism and energy production networks to support and empower rapid growth, survival under stressful conditions, invasion, metastasis, and resistance to therapy. Additionally, we discuss the potential clinical benefits of currently available drugs that could target energy metabolism to suppress MB progression and increase the efficacy of the current MB therapies.

Medulloblastoma and the DNA Damage Response

Medulloblastoma (MB) is the most common malignant brain tumor in children with standard of care consisting of surgery, radiation, and chemotherapy. Recent molecular profiling led to the identification of four molecularly distinct MB subgroups – Wingless (WNT), Sonic Hedgehog (SHH), Group 3, and Group 4. Despite genomic MB characterization and subsequent tumor stratification, clinical treatment paradigms are still largely driven by histology, degree of surgical resection, and presence or absence of metastasis rather than molecular profile. Patients usually undergo resection of their tumor followed by craniospinal radiation (CSI) and a 6 month to one-year multi-agent chemotherapeutic regimen. While there is clearly a need for development of targeted agents specific to the molecular alterations of each patient, targeting proteins responsible for DNA damage repair could have a broader impact regardless of molecular subgrouping. DNA damage response (DDR) protein inhibitors have recently emerged as targeted agents with potent activity as monotherapy or in combination in different cancers. Here we discuss the molecular underpinnings of genomic instability in MB and potential avenues for exploitation through DNA damage response inhibition.

Crosstalk between PI3K/AKT/mTOR and WNT/β-Catenin signaling in GBM - Could combination therapy checkmate the collusion?

Glioblastoma multiforme is one of the calamitous primary glial brain tumors with extensive heterogeneity at cellular and molecular levels. While maximal surgical resection trailed by radio and chemotherapy employing temozolomide remains the gold-standard treatment for malignant glioma patients, the overall prognosis remains dismal and there exists an unmet need for effective therapeutic strategies. In this context, we hypothesize that proper understanding of signaling pathways responsible for glioblastoma multiforme proliferation would be the first trump card while searching for novel targeted therapies. Among the pathways aberrantly activated, PI3K/AKT/mTOR is the most significant pathway, that is clinically implicated in malignancies such as high-grade glioma. Further, the WNT/β-Catenin cascade is well-implicated in several malignancies, while its role in regulating glioma pathogenesis has only emerged recently. Nevertheless, oncogenic activation of both these pathways is a frequent event in malignant glioma that facilitates tumor proliferation, stemness and chemo-resistance. Recently, it has been reported that the cross-talk of PI3K/AKT/mTOR pathway with multiple signaling pathways could promote glioma progression and reduce the sensitivity of glioma cells to the standard therapy. However, very few studies had focused on the relationship between PI3K/AKT/mTOR and WNT/β-Catenin pathways in glioblastoma multiforme. Interestingly, in homeostatic and pathologic circumstances, both these pathways depict fine modulation and are connected at multiple levels by upstream and downstream effectors. Thus, gaining deep insights on the collusion between these pathways would help in discovering unique therapeutic targets for glioblastoma multiforme management. Hence, the current review aims to address, "the importance of inter-play between PI3K/AKT/mTOR and WNT/β-Catenin pathways", and put forward, "the possibility of combinatorially targeting them", for glioblastoma multiforme treatment enhancement.

Discovery and functional assessment of a novel adipocyte population driven by intracellular Wnt/β-catenin signaling in mammals

Wnt/β-catenin signaling has been well established as a potent inhibitor of adipogenesis. Here, we identified a population of adipocytes that exhibit persistent activity of Wnt/β-catenin signaling, as revealed by the Tcf/Lef-GFP reporter allele, in embryonic and adult mouse fat depots, named as Wnt⁺ adipocytes. We showed that this β-catenin-mediated signaling activation in these cells is Wnt ligand- and receptor-independent but relies on AKT/mTOR pathway and is essential for cell survival. Such adipocytes are distinct from classical ones in transcriptomic and genomic signatures and can be induced from various sources of mesenchymal stromal cells including human cells. Genetic lineage-tracing and targeted cell ablation studies revealed that these adipocytes convert into beige adipocytes directly and are also required for beige fat recruitment under thermal challenge, demonstrating both cell autonomous and non-cell autonomous roles in adaptive thermogenesis. Furthermore, mice bearing targeted ablation of these adipocytes exhibited glucose intolerance, while mice receiving exogenously supplied such cells manifested enhanced glucose utilization. Our studies uncover a unique adipocyte population in regulating beiging in adipose tissues and systemic glucose homeostasis.

Continuous wave irradiation at 0.1 terahertz facilitates transmembrane transport of small molecules

The bioeffects of terahertz (THz) radiation received growing attention because of its influence on the interactions between biomolecules. Our work aimed to investigate the effects of THz irradiation on cell membrane, especially cell membrane permeability. We found that 0.1 THz irradiation promoted the endocytosis of FM4-64-labeled cells and the inhibition of dynamin attenuated but did not fully abolish the THz promoted endocytosis. Moreover, 0.1 THz irradiation also promoted the transmembrane of the rhodamine, as well as the chemical compounds GDC0941 and H89, evidenced by the confocal microscope observation and the western blotting analysis, respectively. These findings demonstrated 0.1 THz irradiation facilitated the transmembrane transport of small molecules by promoting both the cellular endocytosis and the diffusion process. Our study provided direct evidence that THz could affect the cell membrane permeability, broadened the THz affected cellular physiological processes, and implied its potential application in regulating the cell membrane functions.

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THz irradiation enhances endocytic activity of neuronal cells

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THz irradiation increases the permeation of rhodamine derivatives into cells

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THz irradiation promotes the cellular uptake of small drugs GDC0941 and H89

Mutational pattern of PIK3CA exon 20 in circulating DNA in breast cancer

Breast cancer (BC) is one of the most common cancers with diverse mutations, etiology and causes. Mutational signature of the driver genes could allow for better understanding disease etiology and progression. This study aims to assess PIK3CA Exon 20 somatic mutational signature in relation to potential underlying etiology. Circulating DNA of 71 Egyptian BC patients was isolated, amplified for PIK3CA Exon 20, and sequenced. Mutational signature was determined according to COSMIC v2 signature. Public BC dataset was analysed to assess PIK3CA mutations effect on the transcriptomic profile. Somatic mutations of PIK3CA exon 20 were found in 66.2% of the study cohort. Nucleotide substitution patterns were similar to general nucleotide substitution patterns in BC. Signature 3 and 9 were the most common signatures in the studied BC patients. Signature of Aristolochic acid exposure was found in some cases. The most common nucleotide substitution was T > A transversion, but substitutions T > G and T > C were correlated to each other and to the total mutation number. PIK3CA mutations were found to disrupt several pathways including RAC1, PDGF, Wnt, and integrin signalling. PIK3CA exon 20 mutational signatures in Egyptian BC patients could suggest a disease etiology involving homologous recombination deficiency (HRD) and polymerase eta (Pol η). Nucleotide substitution patterns could indicate the role of exposure to oxidative stress and some carcinogens such as 4-aminobiphenyl and Aristolochic acid.

Subgroup-Specific Diagnostic, Prognostic, and Predictive Markers Influencing Pediatric Medulloblastoma Treatment

Medulloblastoma (MB) is the most common malignant central nervous system tumor in pediatric patients. Mainstay of therapy remains surgical resection followed by craniospinal radiation and chemotherapy, although limitations to this therapy are applied in the youngest patients. Clinically, tumors are divided into average and high-risk status on the basis of age, metastasis at diagnosis, and extent of surgical resection. However, technological advances in high-throughput screening have facilitated the analysis of large transcriptomic datasets that have been used to generate the current classification system, dividing patients into four primary subgroups, i.e., WNT (wingless), SHH (sonic hedgehog), and the non-SHH/WNT subgroups 3 and 4. Each subgroup can further be subdivided on the basis of a combination of cytogenetic and epigenetic events, some in distinct signaling pathways, that activate specific phenotypes impacting patient prognosis. Here, we delve deeper into the genetic basis for each subgroup by reviewing the extent of cytogenetic events in key genes that trigger neoplastic transformation or that exhibit oncogenic properties. Each of these discussions is further centered on how these genetic aberrations can be exploited to generate novel targeted therapeutics for each subgroup along with a discussion on challenges that are currently faced in generating said therapies. Our future hope is that through better understanding of subgroup-specific cytogenetic events, the field may improve diagnosis, prognosis, and treatment to improve overall quality of life for these patients.

Tumor Growth in the High Frequency Medulloblastoma Mouse Model Ptch1+/-/Tis21KO Has a Specific Activation Signature of the PI3K/AKT/mTOR Pathway and Is Counteracted by the PI3K Inhibitor MEN1611

We have previously generated a mouse model (Ptch1^+/−/Tis21^KO), which displays high frequency spontaneous medulloblastoma, a pediatric tumor of the cerebellum. Early postnatal cerebellar granule cell precursors (GCPs) of this model show, in consequence of the deletion of Tis21, a defect of the Cxcl3-dependent migration. We asked whether this migration defect, which forces GCPs to remain in the proliferative area at the cerebellar surface, would be the only inducer of their high frequency transformation. In this report we show, by further bioinformatic analysis of our microarray data of Ptch1^+/−/Tis21^KO GCPs, that, in addition to the migration defect, they show activation of the PI3K/AKT/mTOR pathway, as the mRNA levels of several activators of this pathway (e.g., Lars, Rraga, Dgkq, Pdgfd) are up-regulated, while some inhibitors (e.g. Smg1) are down-regulated. No such change is observed in the Ptch1^+/− or Tis21^KO background alone, indicating a peculiar synergy between these two genotypes. Thus we investigated, by mRNA and protein analysis, the role of PI3K/AKT/mTOR signaling in MBs and in nodules from primary Ptch1^+/−/Tis21^KO MB allografted in the flanks of immunosuppressed mice. Activation of the PI3K/AKT/mTOR pathway is seen in full-blown Ptch1^+/−/Tis21^KO MBs, relative to Ptch1^+/−/Tis21^WT MBs. In Ptch1^+/−/Tis21^KO MBs we observe that the proliferation of neoplastic GCPs increases while apoptosis decreases, in parallel with hyper-phosphorylation of the mTOR target S6, and, to a lower extent, of AKT. In nodules derived from primary Ptch1^+/−/Tis21^KO MBs, treatment with MEN1611, a novel PI3K inhibitor, causes a dramatic reduction of tumor growth, inhibiting proliferation and, conversely, increasing apoptosis, also of tumor CD15⁺ stem cells, responsible for long-term relapses. Additionally, the phosphorylation of AKT, S6 and 4EBP1 was significantly inhibited, indicating inactivation of the PI3K/AKT/mTOR pathway. Thus, PI3K/AKT/mTOR pathway activation contributes to Ptch1^+/−/Tis21^KO MB development and to high frequency tumorigenesis, observed when the Tis21 gene is down-regulated. MEN1611 could provide a promising therapy for MB, especially for patient with down-regulation of Btg2 (human ortholog of the murine Tis21 gene), which is frequently deregulated in Shh-type MBs.

INPP4B promotes PI3Kα-dependent late endosome formation and Wnt/β-catenin signaling in breast cancer

INPP4B suppresses PI3K/AKT signaling by converting PI(3,4)P₂ to PI(3)P and INPP4B inactivation is common in triple-negative breast cancer. Paradoxically, INPP4B is also a reported oncogene in other cancers. How these opposing INPP4B roles relate to PI3K regulation is unclear. We report PIK3CA-mutant ER⁺ breast cancers exhibit increased INPP4B mRNA and protein expression and INPP4B increased the proliferation and tumor growth of PIK3CA-mutant ER⁺ breast cancer cells, despite suppression of AKT signaling. We used integrated proteomics, transcriptomics and imaging to demonstrate INPP4B localized to late endosomes via interaction with Rab7, which increased endosomal PI3Kα-dependent PI(3,4)P₂ to PI(3)P conversion, late endosome/lysosome number and cargo trafficking, resulting in enhanced GSK3β lysosomal degradation and activation of Wnt/β-catenin signaling. Mechanistically, Wnt inhibition or depletion of the PI(3)P-effector, Hrs, reduced INPP4B-mediated cell proliferation and tumor growth. Therefore, INPP4B facilitates PI3Kα crosstalk with Wnt signaling in ER⁺ breast cancer via PI(3,4)P₂ to PI(3)P conversion on late endosomes, suggesting these tumors may be targeted with combined PI3K and Wnt/β-catenin therapies.

Mini-Review: PDPK1 (3-phosphoinositide dependent protein kinase-1), An Emerging Cancer Stem Cell Target

Cancer stem cells (CSCs) are subpopulations of tumor cells that possess abilities for self-renewal, differentiation, and tumor initiation. These rare but therapy-recalcitrant cells are assumed to repopulate tumors following administration of systemic chemotherapy driving therapy failure, tumor recurrence, and disease progression. In early clinical trials, anti-CSC therapies have found limited success to-date possibly due to the inherent heterogeneity and plasticity of CSCs and the incomplete characterization of essential CSC targets. Here, we review the role of 3-phosphoinositide dependent protein kinase-1 (PDPK1) as an emerging CSC target. While most previous studies have relied on CSC models which are based on lineage and tissue-specific marker profiles to define the relationships between putative target and CSC traits, this review discusses PDPK1 and its role in CSC biology with an emphasis on CSC systems which are based on proposed function like label-retaining cancer cells (LRCCs).

Targeting the crosstalk between canonical Wnt/β-catenin and inflammatory signaling cascades: A novel strategy for cancer prevention and therapy

Emerging scientific evidence indicates that inflammation is a critical component of tumor promotion and progression. Most cancers originate from sites of chronic irritation, infections and inflammation, underscoring that the tumor microenvironment is largely orchestrated by inflammatory cells and pro-inflammatory molecules. These inflammatory components are intimately involved in neoplastic processes which foster proliferation, survival, invasion, and migration, making inflammation the primary target for cancer prevention and treatment. The influence of inflammation and the immune system on the progression and development of cancer has recently gained immense interest. The Wnt/β-catenin signaling pathway, an evolutionarily conserved signaling strategy, has a critical role in regulating tissue development. It has been implicated as a major player in cancer development and progression with its regulatory role on inflammatory cascades. Many naturally-occurring and small synthetic molecules endowed with inherent anti-inflammatory properties inhibit this aberrant signaling pathway, making them a promising class of compounds in the fight against inflammatory cancers. This article analyzes available scientific evidence and suggests a crosslink between Wnt/β-catenin signaling and inflammatory pathways in inflammatory cancers, especially breast, gastrointestinal, endometrial, and ovarian cancer. We also highlight emerging experimental findings that numerous anti-inflammatory synthetic and natural compounds target the crosslink between Wnt/β-catenin pathway and inflammatory cascades to achieve cancer prevention and intervention. Current challenges, limitations, and future directions of research are also discussed.

hCINAP is potentially a direct target gene of HIF-1 and is required for hypoxia-induced EMT and apoptosis in cervical cancer cells

The early metastasis of cervical cancer is a multistep process requiring the cancer cells to adapt to the signal input from different tissue environments, including hypoxia. Hypoxia-induced epithelial-to-mesenchymal transition (EMT) plays a critical role in the ability to invade surrounding tissues. However, the molecular mechanisms underlying EMT in cervical cancer remain to be elucidated. Herein, we show that hypoxia-inducible factor-1alpha (HIF-1α) and aryl hydrocarbon receptor nuclear translocator (ARNT) are recruited to the human coilin-interacting nuclear ATPase protein (hCINAP) promoter and initiate hCINAP expression in hypoxia. Ablation of hCINAP decreased the migratory capacity and EMT of cervical cancer cells under hypoxic conditions. Furthermore, hCINAP regulated EMT through the Akt–mTOR signaling pathway, and inhibits hypoxia-induced p53-dependent apoptosis. Our data collectively show that hCINAP may have essential roles in the metastasis of cervical cancer and could be a potential target for curing cervical cancer.

Neutrophil Adhesion and the Release of the Free Amino Acid Hydroxylysine

During infection or certain metabolic disorders, neutrophils can escape from blood vessels, invade and attach to other tissues. The invasion and adhesion of neutrophils is accompanied and maintained by their own secretion. We have previously found that adhesion of neutrophils to fibronectin dramatically and selectively stimulates the release of the free amino acid hydroxylysine. The role of hydroxylysine and lysyl hydroxylase in neutrophil adhesion has not been studied, nor have the processes that control them. Using amino acid analysis, mass spectrometry and electron microscopy, we found that the lysyl hydroxylase inhibitor minoxidil, the matrix metalloproteinase inhibitor doxycycline, the PI3K/Akt pathway inhibitors wortmannin and the Akt1/2 inhibitor and drugs that affect the actin cytoskeleton significantly and selectively block the release of hydroxylysine and partially or completely suppress spreading of neutrophils. The actin cytoskeleton effectors and the Akt 1/2 inhibitor also increase the phenylalanine release. We hypothesize that hydroxylysine release upon adhesion is the result of the activation of lysyl hydroxylase in interaction with matrix metalloproteinase, the PI3K/Akt pathway and intact actin cytoskeleton, which play important roles in the recruitment of neutrophils into tissue through extracellular matrix remodeling.

Thrombospondin-1 mimetics are promising novel therapeutics for MYC-associated medulloblastoma

BACKGROUND

Medulloblastoma (MB) comprises four subtypes of which group 3 MB are the most aggressive. Although overall survival for MB has improved, the outcome of group 3 MB remains dismal. C-MYC (MYC) amplification or MYC overexpression which characterizes group 3 MB is a strong negative prognostic factor and is frequently associated with metastases and relapses. We previously reported that MYC expression alone promotes highly aggressive MB phenotypes, in part via repression of thrombospondin-1 (TSP-1), a potent tumor suppressor.

METHODS

In this study, we examined the potential role of TSP-1 and TSP-1 peptidomimetic ABT-898 in MYC-amplified human MB cell lines and two distinct murine models of MYC-driven group 3 MBs.

RESULTS

We found that TSP-1 reconstitution diminished metastases and prolonged survival in orthotopic xenografts and promoted chemo- and radio-sensitivity via AKT signaling. Furthermore, we demonstrate that ABT-898 can recapitulate the effects of TSP-1 expression in MB cells in vitro and specifically induced apoptosis in murine group 3 MB tumor cells.

CONCLUSION

Our data underscore the importance of TSP-1 as a critical tumor suppressor in MB and highlight TSP-1 peptidomimetics as promising novel therapeutics for the most lethal subtype of MB.

Incremental prognostic value and underlying biological pathways of radiomics patterns in medulloblastoma

Background

To develop a radiomics signature for predicting overall survival (OS)/progression-free survival (PFS) in patients with medulloblastoma (MB), and to investigate the incremental prognostic value and biological pathways of the radiomics patterns.

Methods

A radiomics signature was constructed based on magnetic resonance imaging (MRI) from a training cohort (n = 83), and evaluated on a testing cohort (n = 83). Key pathways associated with the signature were identified by RNA-seq (GSE151519). Prognostic value of pathway genes was assessed in a public GSE85218 cohort.

Findings

The radiomics-clinicomolecular signature predicted OS (C-index 0.762) and PFS (C-index 0.697) better than either the radiomics signature (C-index: OS: 0.649; PFS: 0.593) or the clinicomolecular signature (C-index: OS: 0.725; PFS: 0.691) alone, with a better calibration and classification accuracy (net reclassification improvement: OS: 0.298, P = 0.022; PFS: 0.252, P = 0.026). Nine pathways were significantly correlated with the radiomics signature. Average expression value of pathway genes achieved significant risk stratification in GSE85218 cohort (log-rank P = 0.016).

Interpretation

This study demonstrated radiomics signature, which associated with dysregulated pathways, was an independent parameter conferring incremental value over clinicomolecular factors in survival predictions for MB patients.

Funding

A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.

LINC00922 regulates epithelial-mesenchymal transition, invasive and migratory capacities in breast cancer through promoting NKD2 methylation

Breast cancer ranks as the major reason for mortality in women populations, accounting for 23% of all cancer deaths. One in every three Asian women encounters the risk of this cancer in their lifetime. Long intergenic non-coding RNAs (lincRNAs) have emerged as tumor promoters and suppressors. The molecular mechanism of breast cancer remains elusive. Therefore, the current study aimed to explore the role lincRNA LINC00922 plays in the development of breast cancer. Breast cancer tissues and adjacent tissues were obtained from 109 patients with breast cancer. The RNA extraction and quantification and immunohistochemical staining characterized the high expression of LINC00922 and low expression of NKD2 in breast cancer tissues in comparison to its adjacent counterparts. Furthermore, the ectopic expression and knockdown experiments were conducted to figure out the in vivo and in vitro effects of LINC00922 on breast cancer progression. The ectopically expressed LINC00922 activated the Wnt signaling pathway, promoted epithelial-mesenchymal transition, cell proliferative, invasive and migratory capacities, tumor growth and metastasis. Additionally, the RIP and ChIP assay identified that LINC00922 recruited DNMT1, DNMT3A and DNMT3B proteins in the promoter region of NKD2 to promote NKD2 promoter methylation, thus reducing the NKD2 expression. Moreover, the Wnt signaling pathway was activated subsequent to NKD2 silencing, which was reversed by LINC00922 silencing. Lastly, the anti-oncogenic effects of LINC00922 inhibition was antagonized after NKD2 knocked down. The current study provides evidence that LINC00922 acts as a tumor promoter by promoting NKD2 methylation. Hopefully, it provides a novel potential gene target for the treatment of breast cancer.

Tubeimoside‑1 induces apoptosis in human glioma U251 cells by suppressing PI3K/Akt‑mediated signaling pathways

Tubeimoside-1 (TBMS1), a traditional Chinese herb extracted from Bolbostemma paniculatum (Maxim.), induces apoptosis in a number of human cancer cell lines. TBMS1 has been reported to induce apoptosis in human glioma cells, however the mechanism remains to be elucidated. The present study explored TBMS1-induced PI3K/Akt-related pathways in human glioma cells. The human glioma U251 and the human astrocyte (HA) cell lines were treated with various concentrations of TBMS1. MTT assays were conducted to analyze cell viability. Cell cycle distribution and the rate of apoptosis were assessed using flow cytometry. BrdU incorporation and Hoechst 33342 staining were performed to analyze the cell cycle and apoptosis, respectively. Western blotting was performed to investigate protein expression levels. The results demonstrated that TBMS1 reduced cell viability in human glioma cells U251 by suppressing Akt phosphorylation. Subsequently, TBMS1 inhibited DNA synthesis and induced G2/M phase arrest by targeting the PI3K/Akt/p21 and the cyclin-dependent kinase 1/cyclin B1 signaling cascades. In addition, TBMS1 triggered apoptosis via the PI3K/Akt-mediated Bcl-2 signaling pathway. These results demonstrated that TBMS1 prevented the progression of gliomas via the PI3K/Akt-dependent pathway, which provided a theoretical basis for in vivo studies to use TBMS1 as potential therapy for the prevention of cancer.

Cleistanthin A inhibits the invasion of MDA-MB-231 human breast cancer cells: involvement of the β-catenin pathway

BACKGROUND

Cleistanthin A (CleA), a natural diphyllin glycoside, has been shown to suppress the invasion of cancer cells, but the underlying mechanisms remain unclear. Here, the inhibitory effect of CleA on the invasion of MDA-MB-231 human breast cancer cells was investigated, and the mechanisms involved were clarified.

METHODS

Cell viability was studied by MTT assay. The migration and invasion of MDA-MB-231 cells were assessed by wound healing assay and transwell assay, respectively. The enzymatic activity of matrix metalloproteinases (MMPs) was detected by gelatin zymography. mRNA and protein levels were detected by qRT-PCR and Western blotting, respectively. Nuclear translocation of β-catenin was observed by immunofluorescence and detected by Western blotting.

RESULTS

CleA effectively inhibited the migration and invasion of MDA-MB-231 cells and suppressed the expression and activation of MMP-2/9. Moreover, the expression and nuclear translocation of β-catenin were reduced by CleA treatment, as well as transcription of the Cyclin D1 and c-myc genes. In addition, the inhibitory effect of CleA on the β-catenin pathway was attributed to the promotion of β-catenin degradation by inhibition of GSK3β phosphorylation. When the phosphorylation of GSK3β was induced by LiCl, the inhibitory effect of CleA on the β-catenin pathway and the invasion of MDA-MB-231 cells were almost reversed.

CONCLUSION

CleA suppressed the invasion of MDA-MB-231 cells, likely through the β-catenin pathway.

Pristimerin suppresses colorectal cancer through inhibiting inflammatory responses and Wnt/β-catenin signaling

Pristimerin, a triterpenoid, has exhibited potential anti-inflammatory and anti-tumor activities. Nevertheless, the role and mechanism of pristimerin in intestinal inflammation and colon cancer require further investigation. Here, we found that pristimerin protected mice from dextran sulfate sodium (DSS)-induced colitis, restoring epithelial damage and reducing tissue inflammation and inflammatory cell infiltration. In addition, pristimerin dramatically reduced the number and size of the tumors in a azoxymethane (AOM)/DSS-induced colitis-associated colorectal cancer (CAC) model. Furthermore, we found that pristimerin suppressed Wnt/β-catenin signaling by RNA-Seq. Pristimerin inhibited Wnt/β-catenin signaling via activation of GSK3β, thereby suppressing Wnt target gene expression in colon cancer HCT116 and HT-29 cells. In HCT116 colon cancer xenografts and APC^min/+ mice, which undergo spontaneous intestinal tumorigenesis, administration of pristimerin reduced the tumor progression and decreased the expression of phosphorylated GSK3β Ser 9, β-catenin, cyclin D1 and c-Myc. These results suggest that pristimerin is a potent agent for preventing colon inflammation and carcinogenesis.

Wnt Signaling in Ovarian Cancer Stemness, EMT, and Therapy Resistance

Ovarian cancers represent the deadliest among gynecologic malignancies and are characterized by a hierarchical structure with cancer stem cells (CSCs) endowed with self-renewal and the capacity to differentiate. The Wnt/β-catenin signaling pathway, known to regulate stemness in a broad spectrum of stem cell niches including the ovary, is thought to play an important role in ovarian cancer. Importantly, Wnt activity was shown to correlate with grade, epithelial to mesenchymal transition, chemotherapy resistance, and poor prognosis in ovarian cancer. This review will discuss the current knowledge of the role of Wnt signaling in ovarian cancer stemness, epithelial to mesenchymal transition (EMT), and therapy resistance. In addition, the alleged role of exosomes in the paracrine activation of Wnt signaling and pre-metastatic niche formation will be reviewed. Finally, novel potential treatment options based on Wnt inhibition will be highlighted.

Hedgehog pathway and smoothened inhibitors in cancer therapies

The hedgehog (Hh) pathway plays an important role in cancer development and maintenance, as ~25% of all cancers have aberrant Hh pathway activation. Targeted therapy for inhibition of the Hh pathway was thought to be promising for achieving clinical response in the Hh-dependent cancers. However, the results of new clinical trials with smoothened (SMO) antagonists do not show much success in cancers other than basal cell carcinoma. The studies suggest that the Hh pathway involves multiple mechanisms of activation or inhibition in primary cilia and interactions between several related pathways in different types of cells, which makes this pathway extremely complex. The SMO-specific antagonists may not stop all relevant pathways that may lead to escape or development of resistance. Therefore, in the Hh-dependent cancers, the inhibition of two or more oncogenic pathways (including the Hh pathway) with use of a single agent of a suitable multitarget profile or a combination of drugs seems promising for achieving clinical response in patients and decrease in resistance development with prolonged use of the specific SMO antagonists. Furthermore, for studying the effect of new treatments, the inclusion criteria should be more specific for selection of patients with aberrant Hh pathway activity confirmed by tests. These considerations will be very helpful for choosing the right patients and the right drugs for the best therapeutic outcome.

Long noncoding RNA OIP5-AS1 targets Wnt-7b to affect glioma progression via modulation of miR-410

The present study was undertaken to investigate the underlying mechanisms of long noncoding RNA OIP5-AS1 via regulating miR-410 to modulate Wnt-7b in the progression of glioma. To address this problem, we measured the expression of OIP5-AS1 and miR-410 in glioma tissues by qRT-PCR. Glioma U87 cells were transfected with OIP5-AS1 siRNA or miR-410 inhibitors. The targeting relationships among miR-410, OIP5-AS1 and Wnt-7b were verified by luciferase reporter assays. Western blotting was employed to determine the expression of Wnt-7b/β-catenin pathway-related proteins, while MTT, flow cytometry, Transwell assays and wound-healing assays were used to measure the biological characteristics of glioma cells. The results showed that OIP5-AS1 expression was higher and miR-410 was lower in glioma tissues. Luciferase reporter assays confirmed a targeting relationship between OIP5-AS1 and miR-410, as well as between miR-410 and Wnt-7b. Silencing OIP5-AS1 reduced cell proliferation, invasion and migration of glioma U87 cells and led to depressed expression levels of miR-410, Wnt-7b, p-β-catenin, GSK-3β-pS9, c-Myc and cyclin D1. Furthermore, down-regulation of OIP5-AS1 induced G0/G1 phase cell cycle arrest and apoptosis of glioma cells. Inhibitors of miR-410 abolished the biological effects of OIP5-AS1 siRNA in glioma cells. In vivo, OIP5-AS1 knockdown also inhibited tumor growth. Taken together, this research suggested that silencing OIP5-AS1 may specifically block the Wnt-7b/β-catenin pathway via targeted up-regulating miR-410, thereby inhibiting growth, invasion and migration while promoting apoptosis in glioma cells.

Improving Diagnostic and Therapeutic Outcomes in Pediatric Brain Tumors

Pediatric brain tumors are the primary cause of cancer-related death during childhood. Unfortunately, the number of primary and metastatic brain tumors is steadily increasing while the mortality rates for many central nervous system (CNS) lesions have remained stagnant. Molecularly defined tumor classes have been added to the most recent 2016 World Health Organization (WHO) Classification System of Central Nervous System Brain Tumors, driving potential new treatments and identifying targets to improve survival for these patients. Focusing on the genetic mutations most commonly seen in the pediatric CNS tumor population provides the ability to better define tumors based on shared molecular characteristics. Consequently, there is the potential for greater efficacy in targeted therapy to treat these identified genetic aberrations. Understanding the growing importance of molecular diagnosis in pediatric CNS tumors is vital to successfully using novel targeted therapies and improving patient outcomes.

CYP24A1 depletion facilitates the antitumor effect of vitamin D3 on thyroid cancer cells

It has been demonstrated that 25-hydroxyvitamin-D3-24-hydroxylase (CYP24A1) is a key enzyme that neutralizes vitamin D activity, which may have an anti-tumor effect. Therefore, the aim of the current study was to explore the effect of the active metabolite of vitamin D, 1,25-dihydroxyvitamin D (1,25-D3) on thyroid cancer cells following the downregulation of CYP24A1. A Cell Counting Kit-8 assay identified that CYP24A1 knockdown enhanced the anti-proliferative effects of 1,25-D3 on thyroid cancer cells. Furthermore, the results of the scratch wound and Transwell assays indicated that CYP24A1 knockdown enhanced the inhibitory effect of 1,25-D3 on cell migration. The results from reverse transcription-quantitative polymerase chain reaction and western blot analysis indicated that treatment with 1,25-D3 and CYP24A1 knockdown synergistically enhanced the expression of the epithelial-related gene E-cadherin and decreased the expression of the mesenchymal-related genes N-cadherin and vimentin. Following CYP24A1 knockdown and treatment with 1,25-D3, the expression of matrix metalloproteinase 2 and metalloproteinase inhibitor 1 were significantly decreased and increased, respectively, compared with the group that underwent treatment with 25-D3 alone. Furthermore, protein kinase B (Akt) and β-catenin activity was significantly decreased by this synergetic effect compared with the group that underwent treatment with 1,25-D3 alone. The results of the current study suggest that CYP24A1 knockdown contributes to the anti-tumor effect of 1,25-D3 and that this effect may be due to deactivation of the Akt and β-catenin signaling pathways. Therefore, CYP24A1 knockdown and 1,25-D3 treatment may be used synergistically as a novel therapeutic strategy to treat patients with thyroid cancer.

Small Molecules Identified from a Quantitative Drug Combinational Screen Resensitize Cisplatin's Response in Drug-Resistant Ovarian Cancer Cells

Drug resistance to chemotherapy occurs in many ovarian cancer patients resulting in failure of treatment. Exploration of drug resistance mechanisms and identification of new therapeutics that overcome the drug resistance can improve patient prognosis. Following a quantitative combination screen of 6060 approved drugs and bioactive compounds in a cisplatin-resistant A2780-cis ovarian cancer cell line, 38 active compounds with IC₅₀s under 1 μM suppressed the growth of cisplatin-resistant ovarian cancer cells. Among these confirmed compounds, CUDC-101, OSU-03012, oligomycin A, VE-821, or Torin2 in a combination with cisplatin restored cisplatin's apoptotic response in the A2780-cis cells, while SR-3306, GSK-923295, SNX-5422, AT-13387, and PF-05212384 directly suppressed the growth of A2780-cis cells. One of the mechanisms for overcoming cisplatin resistance in these cells is mediated by the inhibition of epidermal growth factor receptor (EGFR), though not all the EGFR inhibitors are equally active. The increased levels of total EGFR and phosphorylated-EGFR (p-EGFR) in the A2780-cis cells were reduced after the combined treatment of cisplatin with EGFR inhibitors. In addition, a knockdown of EGFR mRNA reduced cisplatin resistance in the A2780-cis cells. Therefore, the top active compounds identified in this work can be studied further as potential treatments for cisplatin-resistant ovarian cancer. The quantitative combinational screening approach is a useful method for identifying effective compounds and drug combinations against drug-resistant cancer cells.

LncRNA LOXL1-AS1 Promotes the Proliferation and Metastasis of Medulloblastoma by Activating the PI3K/AKT Pathway

Medulloblastoma is the most common malignant brain tumor of childhood, with great potential to metastasize. However, the mechanisms of how medulloblastoma develops and progresses remain to be elucidated. The present study assessed the role of long noncoding RNA LOXL1-AS1 (lncRNA LOXL1-AS1) in the cell proliferation and metastasis in human medulloblastoma. It was initially found that LOXL1-AS1 was significantly overexpressed in clinical medulloblastoma tissues compared with the adjacent noncancerous tissues. LOXL1-AS1 was also highly expressed in medulloblastoma at advanced stages and differentially expressed in a series of medulloblastoma cell lines. Knockdown of LOXL1-AS1 using shRNAs significantly inhibited cell viability and colony formation capacities in D283 and D341 cells. Moreover, the cell proportion in the S phase was significantly increased, while the cell proportion in the G2/M phase was decreased after knockdown of LOXL1-AS1 in D283 cells and D341 cells. Cell cycle arrest led to eventual cell apoptosis by LOXL1-AS1 knockdown. Moreover, in a xenograft model of human medulloblastoma, knockdown of LOXL1-AS1 significantly inhibited tumor growth and promoted tumor cell apoptosis. In addition, knockdown of LOXL1-AS1 inhibited cell migration and reversed epithelial-to-mesenchymal transition (EMT). Western blot analysis further revealed that knockdown of LOXL1-AS1 decreased the phosphorylated levels of PI3K and AKT without affecting their total protein levels. These results suggest that LncRNA LOXL1-AS1 promoted the proliferation and metastasis of medulloblastoma by activating the PI3K-AKT pathway, providing evidence that knockdown of LncRNA LOXL1-AS1 might be a potential therapeutic strategy against medulloblastoma.

Hypoxia-induced PLOD2 promotes proliferation, migration and invasion via PI3K/Akt signaling in glioma

Gliomas are the most common form of malignant primary brain tumors with poor 5-year survival rate. Dysregulation of procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2) was observed in gliomas, but the specific role and molecular mechanism of PLOD2 in glioma have not been reported yet. In this study, PLOD2 was found to be frequently up-regulated in glioma and could serve as an independent prognostic marker to identify patients with poor clinical outcome. Knockdown of PLOD2 inhibited proliferation, migration and invasion of glioma cells in vitro and in vivo. Mechanistically, inhibition of PLOD2 inactivated PI3K/AKT signaling pathway and thus regulated the expression of its downstream epithelial–mesenchymal transition (EMT)-associated regulators, including E-cadherin, vimentin, N-cadherin, β-catenin, snail and slug in glioma cells. Moreover, PLOD2 could be induced by hypoxia-inducible factor-1α (HIF-1α) via hypoxia, thereby promoting hypoxia-induced EMT in glioma cells. Our data suggests that PLOD2 may be a potential therapeutic target for patients with glioma.

TRIM59 induces epithelial-to-mesenchymal transition and promotes migration and invasion by PI3K/AKT signaling pathway in medulloblastoma

Medulloblastoma is the most common malignant brain tumor in children. Despite remarkable advances over previous decades, the long-term survival of patients with medulloblastoma remains poor due to the frequent metastatic nature of this malignancy. The aim of the present study was to examine the role of tripartite motif containing 59 (TRIM59) in cell metastasis in medulloblastoma. It was initially demonstrated that TRIM59 expression was significantly increased in clinical medulloblastoma tissues compared with adjacent non-cancerous tissues and differentially expressed in a series of medulloblastoma cell lines. The knockdown of TRIM59 in D283 cells resulted in epithelial-to-mesenchymal transition (EMT), and decreased cell migratory and invasive capacities. By contrast, the overexpression of TRIM59 in Daoy cells was able to inhibit the EMT process and increase migratory and invasive capacities of the cells. Notably, the knockdown of TRIM59 was able to decrease the protein level of matrix metalloproteinase (MMP)-2 without altering the levels of MMP-9, and conversely the overexpression of TRIM59 was able to increase the protein level of MMP-2. Importantly, the downregulation of TRIM59 in D283 cells was able to inhibit the levels of phosphorylated (p)-AKT (Ser473), glycogen synthase kinase 3 β(GSK3β; Ser9) and phosphoinositide 3-kinase (PI3K) p85 (Tyr458) without altering the levels of total protein. The data from the present study suggest that TRIM59 induces epithelial-to-mesenchymal transition and promotes migration and invasion by PI3K/AKT signaling pathway in medulloblastoma. This data may provide novel insight into tumor metastasis and pave the way for the development of therapeutic strategies for the treatment of medulloblastoma in the clinic.

Signaling pathways and mesenchymal transition in pediatric high-grade glioma

Pediatric high-grade gliomas (pHGG), including diffuse intrinsic pontine gliomas (DIPG), are the most lethal types of cancer in children. In recent years, it has become evident that these tumors are driven by epigenetic events, mainly mutations involving genes encoding Histone 3, setting them apart from their adult counterparts. These tumors are exceptionally resistant to chemotherapy and respond only temporarily to radiotherapy. Moreover, their delicate location and diffuse growth pattern make complete surgical resection impossible. In many other forms of cancer, chemo- and radioresistance, in combination with a diffuse, invasive phenotype, are associated with a transcriptional program termed the epithelial-to-mesenchymal transition (EMT). Activation of this program allows cancer cells to survive individually, invade surrounding tissues and metastasize. It also enables them to survive exposure to cytotoxic therapy, including chemotherapeutic drugs and radiation. We here suggest that EMT plays an important, yet poorly understood role in the biology and therapy resistance of pHGG and DIPG. This review summarizes the current knowledge on the major signal transduction pathways and transcription factors involved in the epithelial-to-mesenchymal transition in cancer in general and in pediatric HGG and DIPG in particular. Despite the fact that the mesenchymal transition has not yet been specifically studied in pHGG and DIPG, activation of pathways and high levels of transcription factors involved in EMT have been described. We conclude that the mesenchymal transition is likely to be an important element of the biology of pHGG and DIPG and warrants further investigation for the development of novel therapeutics.

The therapeutic potential of targeting the PI3K pathway in pediatric brain tumors

Central nervous system tumors are the most common cancer type in children and the leading cause of cancer related deaths. There is therefore a need to develop novel treatments. Large scale profiling studies have begun to identify alterations that could be targeted therapeutically, including the phosphoinositide 3-kinase (PI3K) signaling pathway, which is one of the most commonly activated pathways in cancer with many inhibitors under clinical development. PI3K signaling has been shown to be aberrantly activated in many pediatric CNS neoplasms. Pre-clinical analysis supports a role for PI3K signaling in the control of tumor growth, survival and migration as well as enhancing the cytotoxic effects of current treatments. Based on this evidence agents targeting PI3K signaling have begun to be tested in clinical trials of pediatric cancer patients. Overall, targeting the PI3K pathway presents as a promising strategy for the treatment of pediatric CNS tumors. In this review we examine the genetic alterations found in the PI3K pathway in pediatric CNS tumors and the pathological role it plays, as well as summarizing the current pre-clinical and clinical data supporting the use of PI3K pathway inhibitors for the treatment of these tumors.

ETV4 collaborates with Wnt/β-catenin signaling to alter cell cycle activity and promote tumor aggressiveness in gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST) is the most common sarcoma, often resulting from a KIT or platelet-derived growth factor receptor alpha (PDGFRA) mutation. The lineage transcription factor ETV1 is expressed similarly in GISTs regardless of malignant potential. Although the related transcription factor ETV4 has been associated with metastasis and tumor progression in other cancers, its role in GIST is unknown. In this study, we found that ETV4 levels were high in a subset of human GISTs and correlated with high mitotic rate. Through Gene Set Enrichment Analysis in selected human GISTs, we identified a relationship between ETV4 levels and β-catenin signaling, especially in advanced GISTs. GIST specimens with high ETV4 levels overexpressed cell cycle regulating genes and had aberrant activation of the canonical Wnt pathway. In human GIST cell lines, ETV4 RNA interference suppressed cell cycle genes and Wnt/β-catenin signaling. ETV4 knockdown also reduced tumor cell proliferation, invasion, and tumor growth in vivo. Conversely, ETV4 overexpression increased cyclin D1 expression and Wnt/β-catenin signaling. Moreover, we determined that ETV4 knockdown destabilized nuclear β-catenin and increased its degradation via COP1, an E3 ligase involved in both ETV4 and β-catenin turnover. Aberrant accumulation of ETV4 and nuclear β-catenin was found in patient derived xenografts created from metastatic GISTs that became resistant to tyrosine kinase inhibitors. Collectively, our findings highlight the significance of ETV4 expression in GIST and identify ETV4 as a biomarker in human GISTs.

A promising natural product, pristimerin, results in cytotoxicity against breast cancer stem cells in vitro and xenografts in vivo through apoptosis and an incomplete autopaghy in breast cancer

Several natural products have been suggested as effective agents for the treatment of cancer. Given the important role of CSCs (Cancer Stem Cells) in cancer, which is a trendy hypothesis, it is worth investigating the effects of pristimerin on CSCs as well as on the other malignant cells (MCF-7 and MDA-MB-231) of breast cancer. The anti-growth activity of pristimerin against MCF-7 and MCF-7s (cancer stem cell enriched population) cells was investigated by real time viability monitorization (xCELLigence System^®) and ATP assay, respectively. Mode of cell death was evaluated using electron and fluorescence microscopies, western blotting (autophagy, apoptosis and ER-stress related markers) and flow cytometry (annexin-V staining, caspase 3/7 activity, BCL-2 and PI3K expressions). Pristimerin showed an anti-growth effect on cancer cells and cancer stem cells with IC₅₀ values ranging at 0.38-1.75μM. It inhibited sphere formation at relatively lower doses (<1.56μM). Apoptosis was induced in MCF-7 and MCF-7s cells. In addition, extensive cytoplasmic vacuolation was observed, implying an incompleted autophagy as evidenced by the increase of autophagy-related proteins (p62 and LC3-II) with an unfolded protein response (UPR). Pristimerin inhibited the growth of MCF-7 and MDA-MB-231-originated xenografts in NOD.CB17-Prkdc^scid/J mice. In mice, apoptosis was further confirmed by cleavage of PARP, activation of caspase 3 and/or 7 and TUNEL staining. Taken together, pristimerin shows cytotoxic activity on breast cancer both in vitro and in vivo. It seems to represent a robust promising agent for the treatment of breast cancer. Pristimerin's itself or synthetic novel derivatives should be taken into consideration for novel potent anticancer agent(s).

Exon 3 mutations of CTNNB1 drive tumorigenesis: a review

The canonical Wnt/β-catenin signaling pathway, an important modulator of progenitor cell proliferation and differentiation, is highly regulated for the maintenance of critical biological homeostasis. Decades of studies in cancer genetics and genomics have demonstrated that multiple genes encoding key proteins in this signaling pathway serve as targets for recurrent mutational alterations. Among these proteins, β-catenin and adenomatosis polyposis coli (APC) are two key nodes. β-catenin contributes in transporting extracellular signals for nuclear programming. Mutations of the CTNNB1 gene that encodes β-catenin occur in a wide spectrum of cancers. These mutations alter the spatial characteristics of the β-catenin protein, leading to drastic reprogramming of the nuclear transcriptional network. Among the outcomes of this reprogramming are increased cell proliferation, enhanced immunosuppression, and disruption of metabolic regulation. Herein we review the current understanding of CTNNB1 mutations, their roles in tumorigenesis and discuss their possible therapeutic implications for cancer.

Targeting WNT Signaling for Multifaceted Glioblastoma Therapy

The WNT signaling pathway has been of great interest to developmental biologists for decades and has more recently become a central topic for study in cancer biology. It is vital for cell growth and regulation of embryogenesis in many organ systems, particularly the CNS and its associated vasculature. We summarize the role of WNT in CNS development and describe how WNT signaling makes key contributions to malignant glioma stemness, invasiveness, therapeutic resistance, and angiogenesis. The role of WNT in these mechanisms, along with creation and maintainance of the blood-brain barrier (BBB), points to the potential of WNT as a multi-faceted target in malignant glioma therapy.

Knowledge-guided gene prioritization reveals new insights into the mechanisms of chemoresistance

BACKGROUND

Identification of genes whose basal mRNA expression predicts the sensitivity of tumor cells to cytotoxic treatments can play an important role in individualized cancer medicine. It enables detailed characterization of the mechanism of action of drugs. Furthermore, screening the expression of these genes in the tumor tissue may suggest the best course of chemotherapy or a combination of drugs to overcome drug resistance.

RESULTS

We developed a computational method called ProGENI to identify genes most associated with the variation of drug response across different individuals, based on gene expression data. In contrast to existing methods, ProGENI also utilizes prior knowledge of protein-protein and genetic interactions, using random walk techniques. Analysis of two relatively new and large datasets including gene expression data on hundreds of cell lines and their cytotoxic responses to a large compendium of drugs reveals a significant improvement in prediction of drug sensitivity using genes identified by ProGENI compared to other methods. Our siRNA knockdown experiments on ProGENI-identified genes confirmed the role of many new genes in sensitivity to three chemotherapy drugs: cisplatin, docetaxel, and doxorubicin. Based on such experiments and extensive literature survey, we demonstrate that about 73% of our top predicted genes modulate drug response in selected cancer cell lines. In addition, global analysis of genes associated with groups of drugs uncovered pathways of cytotoxic response shared by each group.

CONCLUSIONS

Our results suggest that knowledge-guided prioritization of genes using ProGENI gives new insight into mechanisms of drug resistance and identifies genes that may be targeted to overcome this phenomenon.

BKM120 induces apoptosis and inhibits tumor growth in medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor in children, accounting for nearly 20 percent of all childhood brain tumors. New treatment strategies are needed to improve patient survival outcomes and to reduce adverse effects of current therapy. The phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) intracellular signaling pathway plays a key role in cellular metabolism, proliferation, survival and angiogenesis, and is often constitutively activated in human cancers, providing unique opportunities for anticancer therapeutic intervention. The aim of this study was to evaluate the pre-clinical activity of BKM120, a selective pan-class I PI3K inhibitor, on MB cell lines and primary samples. IC50 values of BKM120 in the twelve MB cell lines tested ranged from 0.279 to 4.38 μM as determined by cell viability assay. IncuCyte ZOOM Live-Cell Imaging system was used for kinetic monitoring of cytotoxicity of BKM120 and apoptosis in MB cells. BKM120 exhibited cytotoxicity in MB cells in a dose and time-dependent manner by inhibiting activation of downstream signaling molecules AKT and mTOR, and activating caspase-mediated apoptotic pathways. Furthermore, BKM120 decreased cellular glycolytic metabolic activity in MB cell lines in a dose-dependent manner demonstrated by ATP level per cell. In MB xenograft mouse study, DAOY cells were implanted in the flank of nude mice and treated with vehicle, BKM120 at 30 mg/kg and 60 mg/kg via oral gavage daily. BKM120 significantly suppressed tumor growth and prolonged mouse survival. These findings help to establish a basis for clinical trials of BKM120, which could be a novel therapy for the treatment of medulloblastoma patients.

Posterior Fossa Tumors

Pediatric brain tumors are the leading cause of death from solid tumors in childhood. The most common posterior fossa tumors in children are medulloblastoma, atypical teratoid/rhabdoid tumor, cerebellar pilocytic astrocytoma, ependymoma, and brainstem glioma. Location, and imaging findings on computed tomography (CT) and conventional MR (cMR) imaging may provide important clues to the most likely diagnosis. Moreover, information obtained from advanced MR imaging techniques increase diagnostic confidence and help distinguish between different histologic tumor types. Here we discuss the most common posterior fossa tumors in children, including typical imaging findings on CT, cMR imaging, and advanced MR imaging studies.

Modeling and Targeting MYC Genes in Childhood Brain Tumors

Brain tumors are the second most common group of childhood cancers, accounting for about 20%–25% of all pediatric tumors. Deregulated expression of the MYC family of transcription factors, particularly c-MYC and MYCN genes, has been found in many of these neoplasms, and their expression levels are often correlated with poor prognosis. Elevated c-MYC/MYCN initiates and drives tumorigenesis in many in vivo model systems of pediatric brain tumors. Therefore, inhibition of their oncogenic function is an attractive therapeutic target. In this review, we explore the roles of MYC oncoproteins and their molecular targets during the formation, maintenance, and recurrence of childhood brain tumors. We also briefly summarize recent progress in the development of therapeutic approaches for pharmacological inhibition of MYC activity in these tumors.

Molecular insights into cancer therapeutic effects of the dietary medicinal phytochemical withaferin A

Despite the worldwide research efforts to combat cancer, it remains a leading cause of death. Although various specific kinase inhibitors already have been approved for clinical cancer treatment, occurrence of intrinsic or acquired resistance and intermittent response over longer periods limits long-term success of single kinase-targeted therapies. In this respect, there is a renewed interest in polypharmaceutical natural compounds, which simultaneously target various hyperactivated kinases involved in tumour-inflammation, angiogenesis, cell survival, proliferation, metastasis and angiogenesis. The dietary medicinal phytochemical withaferin A (WA), isolated from Withaferin somnifera (popular Indian name Ashwagandha), holds promise as a novel anti-cancer agent, which targets multiple cell survival kinase pathways, including IκB kinase/NF-κB, PI3 kinase/protein kinase B/mammalian target of rapamycin and mitogen-activated protein kinase/extracellular signal-regulated kinase amongst others. In this review, we propose a novel mechanism of WA-dependent kinase inhibition via electrophilic covalent targeting of cysteine residues in conserved kinase activation domains (kinase cysteinome), which could underlie its pleiotropic therapeutic effects in cancer signalling.

Mesoporous titanium dioxide nanocarrier with magnetic-targeting and high loading efficiency for dual-modal imaging and photodynamic therapy

Photodynamic therapy (PDT), by producing reactive oxygen species (ROS), inhibits cancer cells and is an emerging and pioneering cancer therapeutic modality which can eliminate some of the drawbacks of other traditional anticancer therapies.

Inhibition of mTOR-kinase destabilizes MYCN and is a potential therapy for MYCN-dependent tumors

MYC oncoproteins deliver a potent oncogenic stimulus in several human cancers, making them major targets for drug development, but efforts to deliver clinically practical therapeutics have not yet been realized. In childhood cancer, aberrant expression of MYC and MYCN genes delineates a group of aggressive tumours responsible for a major proportion of pediatric cancer deaths. We designed a chemical-genetic screen that identifies compounds capable of enhancing proteasomal elimination of MYCN oncoprotein. We isolated several classes of compound that selectively kill MYCN expressing cells and we focus on inhibitors of PI3K/mTOR pathway in this study. We show that PI3K/mTOR inhibitors selectively killed MYCN-expressing neuroblastoma tumor cells, and induced significant apoptosis of transgenic MYCN-driven neuroblastoma tumors concomitant with elimination of MYCN protein in vivo. Mechanistically, the ability of these compounds to degrade MYCN requires complete blockade of mTOR but not PI3 kinase activity and we highlight NVP-BEZ235 as a PI3K/mTOR inhibitor with an ideal activity profile. These data establish that MYCN expression is a marker indicative of likely clinical sensitivity to mTOR inhibition, and provide a rationale for the selection of clinical candidate MYCN-destabilizers likely to be useful for the treatment of MYCN-driven cancers.

JPO2/CDCA7L and LEDGF/p75 Are Novel Mediators of PI3K/AKT Signaling and Aggressive Phenotypes in Medulloblastoma

Substantial evidence links Myc-PI3K/AKT signaling to the most aggressive subtype of medulloblastoma and this axis in medulloblastoma therapy. In this study, we advance understanding of how Myc-PI3K/AKT signaling contributes to this malignancy, specifically, in identifying the Myc-interacting protein JPO2 and its partner binding protein LEDGF/p75 as critical modulators of PI3K/AKT signaling and metastasis in medulloblastoma. JPO2 overexpression induced metastatic medulloblastoma in vivo through two synergistic feed-forward regulatory circuits involving LEDGF/p75 and AKT that promote metastatic phenotypes in this setting. Overall, our findings highlight two novel prometastatic loci in medulloblastoma and point to the JPO2:LEDGF/p75 protein complex as a potentially new targetable component of PI3K/AKT signaling in medulloblastoma. Cancer Res; 76(9); 2802-12. ©2016 AACR.

The evolving roles of canonical WNT signaling in stem cells and tumorigenesis: implications in targeted cancer therapies

The canonical WNT/β-catenin signaling pathway governs a myriad of biological processes underlying the development and maintenance of adult tissue homeostasis, including regulation of stem cell self-renewal, cell proliferation, differentiation, and apoptosis. WNTs are secreted lipid-modified glycoproteins that act as short-range ligands to activate receptor-mediated signaling pathways. The hallmark of the canonical pathway is the activation of β-catenin-mediated transcriptional activity. Canonical WNTs control the β-catenin dynamics as the cytoplasmic level of β-catenin is tightly regulated via phosphorylation by the 'destruction complex', consisting of glycogen synthase kinase 3β (GSK3β), casein kinase 1α (CK1α), the scaffold protein AXIN, and the tumor suppressor adenomatous polyposis coli (APC). Aberrant regulation of this signaling cascade is associated with varieties of human diseases, especially cancers. Over the past decade, significant progress has been made in understanding the mechanisms of canonical WNT signaling. In this review, we focus on the current understanding of WNT signaling at the extracellular, cytoplasmic membrane, and intracellular/nuclear levels, including the emerging knowledge of cross-talk with other pathways. Recent progresses in developing novel WNT pathway-targeted therapies will also be reviewed. Thus, this review is intended to serve as a refresher of the current understanding about the physiologic and pathogenic roles of WNT/β-catenin signaling pathway, and to outline potential therapeutic opportunities by targeting the canonical WNT pathway.

Medulloblastoma development: tumor biology informs treatment decisions

Medulloblastoma is the most common malignant pediatric brain tumor. Current treatments including surgery, craniospinal radiation and high-dose chemotherapy have led to improvement in survival. However, the risk for recurrence as well as significant long-term neurocognitive and endocrine sequelae associated with current treatment modalities underscore the urgent need for novel tumor-specific, normal brain-sparing therapies. It has also provided the impetus for research focused on providing a better understanding of medulloblastoma biology. The expectation is that such studies will lead to the identification of new therapeutic targets and eventually to an increase in personalized treatment approaches.

Evolving molecular era of childhood medulloblastoma: time to revisit therapy

Currently medulloblastoma is treated with a uniform therapeutic approach based on histopathology and clinico-radiological risk stratification, resulting in unpredictable treatment failure and relapses. Improved understanding of the biological, molecular and genetic make-up of these tumors now clearly identifies it as a compendium of four distinct subtypes (WNT, SHH, group 3 and 4). Advances in utilization of the genomic and epigenomic machinery have now delineated genetic aberrations and epigenetic perturbations in each subgroup as potential druggable targets. This has resulted in endeavors to profile targeted therapy. The challenge and future of medulloblastoma therapeutics will be to keep pace with the evolving novel biological insights and translating them into optimal targeted treatment regimens.

The PI3K inhibitor GDC-0941 displays promising in vitro and in vivo efficacy for targeted medulloblastoma therapy

Deregulation of the Phosphoinositide 3-kinase (PI3K)/AKT signalling network is a hallmark of oncogenesis. Also medulloblastoma, the most common malignant brain tumor in children, is characterized by high levels of AKT phosphorylation and activated PI3K signalling in medulloblastoma is associated with enhanced cellular motility, survival and chemoresistency underscoring its role of as a potential therapeutic target. Here we demonstrate that GDC-0941, a highly specific PI3K inhibitor with good clinical tolerability and promising anti-neoplastic activity in adult cancer, also displays anti-proliferative and pro-apoptotic effects in pediatric human medulloblastoma cell lines. Loss in cell viability is accompanied by reduced phosphorylation of AKT, a downstream target of PI3K. Furthermore, we show that GDC-0941 attenuates the migratory capacity of medulloblastoma cells and targets subpopulations expressing the stem cell marker CD133. GDC-0941 also synergizes with the standard medulloblastoma chemotherapeutic etoposide. In an orthotopic xenograft model of the most aggressive human medulloblastoma variant we document that oral adminstration of GDC-0941 impairs tumor growth and significantly prolongs survival. These findings provide a rational to further investigate GDC-0941 alone and in combination with standard chemotherapeutics for medulloblastoma treatment.