BX-795 inhibits neuroblastoma growth and enhances sensitivity towards chemotherapy

High-risk neuroblastoma (NB) represents a major clinical challenge in pediatric oncology due to relapse of metastatic, drug-resistant disease, and treatment-related toxicities. An analysis of 1235 primary NB patient dataset revealed significant increase in AKT1 and AKT2 gene expression with cancer stage progression. Additionally, Both AKT1 and AKT2 expression inversely correlate with poor overall survival of NB patients. AKT1 and AKT2 genes code for AKT that drive a major oncogenic cell signaling pathway known in many cancers, including NB. To inhibit AKT pathway, we repurposed an antiviral inhibitor BX-795 that inhibits PDK1, an upstream activator of AKT. BX-795 potently inhibits NB cell proliferation and colony growth in a dose-dependent manner. BX-795 significantly enhances apoptosis and blocks cell cycle progression at mitosis phase in NB. Additionally, BX-795 potently inhibits tumor formation and growth in a NB spheroid tumor model. We further tested dual therapeutic approaches by combining BX-795 with either doxorubicin or crizotinib and found synergistic and significant inhibition of NB growth, in contrast to either drug alone. Overall, our data demonstrate that BX-795 inhibits AKT pathway to inhibit NB growth, and combining BX-795 with current therapies is an effective and clinically tractable therapeutic approach for NB.     

Pantoprazole Induces Mitochondrial Apoptosis and Attenuates NF-κB Signaling in Glioma Cells

Gastric H⁺/K⁺-ATPase or vacuolar-ATPases (V-ATPases) are critical for the cancer cells survival and growth in the ischemic microenvironment by extruding protons from the cell. The drugs which inhibit V-ATPases are known as proton pump inhibitors (PPIs). In the present study, we aimed to evaluate the anticancer efficacy of pantoprazole (PPZ) and its consequences on NF-κB signaling in glioma cells. We have used MTT and clonogenic assay to show PPZ effect on glioma cell growth. Propidium iodide and rhodamine 123 staining were performed to demonstrate cell cycle arrest and mitochondrial depolarization. TUNEL staining was used to evidence apoptosis after PPZ treatment. Immunoblotting and immunofluorescence microscopy were performed to depict protein levels and localization, respectively. Luciferase assay was performed to confirm NF-κB suppression by PPZ. Our results revealed PPZ treatment inhibits cell viability or growth and induced cell death in a dose- and time-dependent manner. PPZ exposure arrested G0/G1 cyclic phase and increased TUNEL positivity, caspase-3 and PARP cleavage with altered pro and anti-apoptotic proteins. PPZ also induced ROS levels and depolarized mitochondria (Δψm) with increased cytosolic cytochrome c level. Further, PPZ suppressed TNF-α stimulated NF-κB signaling by repressing p65 nuclear translocation. NF-κB luciferase reporter assays revealed significant inhibition of NF-κB gene upon PPZ treatment. PPZ exposure also reduced the expression of NF-κB-associated genes, such as cyclin-D1, iNOS, and COX-2, which indicate NF-κB inhibition. Altogether, the present study disclosed that PPZ exerts mitochondrial apoptosis and attenuates NF-κB signaling suggesting PPZ can be an effective and safe anticancer drug for glioma.     

Quantitative Phosphoproteomic Analysis Identifies Activation of the RET and IGF-1R/IR Signaling Pathways in Neuroblastoma

Neuroblastoma is an embryonal tumor of childhood with a heterogenous clinical presentation that reflects differences in activation of complex biological signaling pathways. Protein phosphorylation is a key component of cellular signal transduction and plays a critical role in processes that control cancer cell growth and survival. We used shotgun LC/MS to compare phosphorylation between a human MYCN amplified neuroblastoma cell line (NB10), modeling a resistant tumor, and a human neural precursor cell line (NPC), modeling a normal baseline neural crest cell. 2181 unique phosphorylation sites representing 1171 proteins and 2598 phosphopeptides were found. Protein kinases accounted for 6% of the proteome, with a predominance of tyrosine kinases, supporting their prominent role in oncogenic signaling pathways. Highly abundant receptor tyrosine kinase (RTK) phosphopeptides in the NB10 cell line relative to the NPC cell line included RET, insulin-like growth factor 1 receptor/insulin receptor (IGF-1R/IR), and fibroblast growth factor receptor 1 (FGFR1). Multiple phosphorylated peptides from downstream mediators of the PI3K/AKT/mTOR and RAS pathways were also highly abundant in NB10 relative to NPC. Our analysis highlights the importance of RET, IGF-1R/IR and FGFR1 as RTKs in neuroblastoma and suggests a methodology that can be used to identify potential novel biological therapeutic targets. Furthermore, application of this previously unexploited technology in the clinic opens the possibility of providing a new wide-scale molecular signature to assess disease progression and prognosis.     

Identification of Host-Targeted Small Molecules That Restrict Intracellular Mycobacterium tuberculosis Growth

Mycobacterium tuberculosis remains a significant threat to global health. Macrophages are the host cell for M. tuberculosis infection, and although bacteria are able to replicate intracellularly under certain conditions, it is also clear that macrophages are capable of killing M. tuberculosis if appropriately activated. The outcome of infection is determined at least in part by the host-pathogen interaction within the macrophage; however, we lack a complete understanding of which host pathways are critical for bacterial survival and replication. To add to our understanding of the molecular processes involved in intracellular infection, we performed a chemical screen using a high-content microscopic assay to identify small molecules that restrict mycobacterial growth in macrophages by targeting host functions and pathways. The identified host-targeted inhibitors restrict bacterial growth exclusively in the context of macrophage infection and predominantly fall into five categories: G-protein coupled receptor modulators, ion channel inhibitors, membrane transport proteins, anti-inflammatories, and kinase modulators. We found that fluoxetine, a selective serotonin reuptake inhibitor, enhances secretion of pro-inflammatory cytokine TNF-α and induces autophagy in infected macrophages, and gefitinib, an inhibitor of the Epidermal Growth Factor Receptor (EGFR), also activates autophagy and restricts growth. We demonstrate that during infection signaling through EGFR activates a p38 MAPK signaling pathway that prevents macrophages from effectively responding to infection. Inhibition of this pathway using gefitinib during in vivo infection reduces growth of M. tuberculosis in the lungs of infected mice. Our results support the concept that screening for inhibitors using intracellular models results in the identification of tool compounds for probing pathways during in vivo infection and may also result in the identification of new anti-tuberculosis agents that work by modulating host pathways. Given the existing experience with some of our identified compounds for other therapeutic indications, further clinically-directed study of these compounds is merited.     

Design and synthesis of mono-and di-pyrazolyl-s-triazine derivatives,their anticancer profile in human cancer cell lines,and in vivo toxicity in zebrafish embryos

s-Triazine is considered a privileged structure, as it is found in several FDA-approved drugs. In the framework of our ongoing medicinal chemistry project based on the use of s-triazine as a scaffold, we synthesized a series of mono- and di-pyrazolyl-s-triazine derivatives and tested them against four human cancer cell lines, namely Human breast carcinoma (MCF 7 and MDA-MB-231), hepatocellular carcinoma (HepG2), colorectal carcinoma (LoVo), and leukemia (K562). The cell viability assay revealed that most of the s-triazine compounds induced cytotoxicity in all four types of human cancer cell lines, however, compounds 4a, and 6g, both of them have a piperidine moiety in their structure were most effective. These two compounds affected the cell viability of cancer cells, with IC₅₀ values within the range between 5 to 9 µM. The cell cycle analysis showed that 4a and 6g induced S and G2/M phase cell cycle arrest in K562 cells. This could be the mechanism by which these molecules induced cytotoxicity in tested cancer cells. The prepared compounds were tested in zebrafish embryos to evaluate in vivo and developmental toxicity of the pyrazolyl-s-triazine derivatives in animals. None of the derivatives were lethal in the concentration range tested.     

High-Throughput Screening for the Identification of New Therapeutic Options for Metastatic Pheochromocytoma and Paraganglioma

Drug repurposing or repositioning is an important part of drug discovery that has been growing in the last few years for the development of therapeutic options in oncology. We applied this paradigm in a screening of a library of about 3,800 compounds (including FDA-approved drugs and pharmacologically active compounds) employing a model of metastatic pheochromocytoma, the most common tumor of the adrenal medulla in children and adults. The collection of approved drugs was screened in quantitative mode, testing the compounds in compound-titration series (dose-response curves). Analysis of the dose-response screening data facilitated the selection of 50 molecules with potential bioactivity in pheochromocytoma cells. These drugs were classified based on molecular/cellular targets and signaling pathways affected, and selected drugs were further validated in a proliferation assay and by flow cytometric cell death analysis. Using meta-analysis information from molecular targets of the top drugs identified by our screening with gene expression data from human and murine microarrays, we identified potential drugs to be used as single drugs or in combination. An example of a combination with a synergistic effect is presented. Our study exemplifies a promising model to identify potential drugs from a group of clinically approved compounds that can more rapidly be implemented into clinical trials in patients with metastatic pheochromocytoma or paraganglioma.     

Knockdown of LncRNA PVT1 inhibits tumorigenesis in non-small-cell lung cancer by regulating miR-497 expression

Plasmacytoma variant translocation1 (PVT1) was reported to be upregulated in non-small-cell lung cancer (NSCLC) tissues, serve as a promising biomarker for diagnosis and prognosis of NSCLC, and promoted NSCLC cell proliferation. However, the detailed molecular mechanism of PVT1 involved in the pathogenesis and development of NSCLC remains largely unknown. In this study, the expression levels of PVT1 and miR-497 in NSCLC cells were determined by qRT-PCR. Cell viability, invasion and apoptosis were detected by MTT assay, cell invasion assay and flow cytometry analysis, respectively. RNA immunoprecipitation (RIP) and luciferase reporter assay were performed to confirm whether PVT1 directly interacts with miR-497. A xenograft mouse model was established to confirm the effect of PVT1 on tumor growth in vivo and the underlying molecular mechanism. Our findings indicated that PVT1 was significantly upregulated and miR-497 was markedly downregulated in NSCLC cell lines. si-PVT1 effectively decreased the expression of PVT1 and increased the expression of miR-497. PVT1 knockdown remarkably inhibited cell viability, invasion and promoted apoptosis in NSCLC cells. RIP and luciferase reporter assay demonstrated that PVT1 could directly interact with miR-497. Moreover, PVT1 overexpression reversed the inhibitory effect of miR-497 on cell viability, invasion and promotion effect on apoptosis of NSCLC cells. Furthermore, in vivo experiment showed that knockdown of PVT1 inhibited tumor growth in vivo and promoted miR-497 expression. In conclusion, knockdown of PVT1 inhibited cell viability, invasion and induced apoptosis in NSCLC by regulating miR-497 expression, elucidating the molecular mechanism of the oncogenic role of PVT1 in NSCLC and providing an lncRNA-directed target for NSCLC.     

Essential Roles for Soluble Virion-Associated Heparan Sulfonated Proteoglycans and Growth Factors in Human Papillomavirus Infections

A subset of human papillomavirus (HPV) infections is causally related to the development of human epithelial tumors and cancers. Like a number of pathogens, HPV entry into target cells is initiated by first binding to heparan sulfonated proteoglycan (HSPG) cell surface attachment factors. The virus must then move to distinct secondary receptors, which are responsible for particle internalization. Despite intensive investigation, the mechanism of HPV movement to and the nature of the secondary receptors have been unclear. We report that HPV16 particles are not liberated from bound HSPG attachment factors by dissociation, but rather are released by a process previously unreported for pathogen-host cell interactions. Virus particles reside in infectious soluble high molecular weight complexes with HSPG, including syndecan-1 and bioactive compounds, like growth factors. Matrix mellatoproteinase inhibitors that block HSPG and virus release from cells interfere with virus infection. Employing a co-culture assay, we demonstrate HPV associated with soluble HSPG-growth factor complexes can infect cells lacking HSPG. Interaction of HPV-HSPG-growth factor complexes with growth factor receptors leads to rapid activation of signaling pathways important for infection, whereas a variety of growth factor receptor inhibitors impede virus-induced signaling and infection. Depletion of syndecan-1 or epidermal growth factor and removal of serum factors reduce infection, while replenishment of growth factors restores infection. Our findings support an infection model whereby HPV usurps normal host mechanisms for presenting growth factors to cells via soluble HSPG complexes as a novel method for interacting with entry receptors independent of direct virus-cell receptor interactions.     

Medicinal Chemistry Perspectives on Recent Advances in Src Kinase Inhibitors as a Potential Target for the Development of Anticancer Agents: Biological Profile,Selectivity, Structure-Activity Relationship

The physiological Src proto-oncogene is a protein tyrosine kinase receptor that served as the essential signaling pathway in different types of cancer. Src kinase receptor is divided into different domains: a unique domain, an SH3 domain, an SH2 domain, a protein tyrosine kinase domain, and a regulatory tail, which runs from the N-terminus to the C-terminus. Src kinase inhibitors bind in the kinase domain and are activated by phosphorylation. The etiology of cancer involved various signaling pathways and Src signaling pathways are also involved in those clusters. Although the dysregulation of Src kinase resulted in cancer being discovered in the late 19^th century it is still considered a cult pathway because it is not much explored by different medicinal chemists and oncologists. The Src kinase regulated through different kinase pathways (MAPK, PI3K/Akt/mTOR, JAK/STAT3, Hippo kinase, PEAK1, and Rho/ROCK pathways) and proceeded downstream signaling to conduct cell proliferation, angiogenesis, migration, invasion, and metastasis of cancer cells. There are numerous FDA-approved drugs flooded the market but still, there is a huge demand for the creation of novel anticancer drugs. As the existing drugs are accompanied by several adverse effects and drug resistance due to rapid mutation in proteins. In this review, we have elaborated about the structure and activation of Src kinase, as well as the development of Src kinase inhibitors. Our group also provided a comprehensive overview of Src inhibitors throughout the last two decades, including their biological activity, structure-activity relationship, and Src kinase selectivity. The Src binding pocket has been investigated in detail to better comprehend the interaction of Src inhibitors with amino acid residues. We have strengthened the literature with our contribution in terms of molecular docking and ADMET studies of top compounds. We hope that the current analysis will be a useful resource for researchers and provide glimpse of direction toward the design and development of more specific, selective, and potent Src kinase inhibitors.     

Establishment of a luciferase assay-based screening system: fumitremorgin C selectively inhibits cellular proliferation of immortalized astrocytes expressing an active form of AKT

The AKT pathway is frequently activated in glioblastoma, and as such, inhibitors of this pathway could prove very useful as anti-glioblastoma therapies. Here we established immortalized astrocytes expressing Renilla luciferase as well as those expressing both an active form of AKT and firefly luciferase. Since both luciferase activities represent the numbers of corresponding cell lines, novel inhibitors of the AKT pathway can be identified by treating co-cultures containing the two types of luciferase-expressing cells with individual compounds. Indeed, such a screening system succeeded in identifying fumitremorgin C as an efficient inhibitor of the AKT pathway, which was further confirmed by the ability of fumitremorgin C to selectively inhibit the growth of immortalized astrocytes expressing an active form of AKT. The present study proposes a broadly applicable approach for identifying therapeutic agents that target the pathways and/or molecules responsible for cancer development.     

Close Interactions between Mesenchymal Stem Cells and Neuroblastoma Cell Lines Lead to Tumor Growth Inhibition

Mesenchymal stem cells (MSCs) have attracted much interest in oncology since they exhibit marked tropism for the tumor microenvironment and support or suppress malignant cell growth depending on the tumor model tested. The aim of this study was to investigate the role of MSCs in the control of the growth of neuroblastoma (NB), which is the second most common solid tumor in children. In vivo experiments showed that systemically administered MSCs, under our experimental conditions, did not home to tumor sites and did not affect tumor growth or survival. However, MSCs injected intratumorally in an established subcutaneous NB model reduced tumor growth through inhibition of proliferation and induction of apoptosis of NB cells and prolonged the survival of hMSC-treated mice. The need for contact between MSCs and NB cells was further supported by in vitro experiments. In particular, MSCs were found to be attracted by NB cells, and to affect NB cell proliferation with different results depending on the cell line tested. Moreover, NB cells, after pre-incubation with hMSCs, acquired a more invasive behavior towards CXCL12 and the bone marrow, i.e., the primary site of NB metastases. In conclusion, this study demonstrates that functional cross-talk between MSCs and NB cell lines used in our experiments can occur only within short range interaction. Thus, this report does not support the clinical use of MSCs as vehicles for selective delivery of antitumor drugs at the NB site unless chemotherapy and/or radiotherapy create suitable local conditions for MSCs recruitment.     

A cell-based small molecule screening method for identifying inhibitors of epithelial-mesenchymal transition in carcinoma

Epithelial Mesenchymal Transition (EMT) is a crucial mechanism for carcinoma progression, as it provides routes for in situ carcinoma cells to dissociate and become motile, leading to localized invasion and metastatic spread. Targeting EMT therefore represents an important therapeutic strategy for cancer treatment. The discovery of oncogene addiction in sustaining tumor growth has led to the rapid development of targeted therapeutics. Whilst initially optimized as anti-proliferative agents, it is likely that some of these compounds may inhibit EMT initiation or sustenance, since EMT is also modulated by similar signaling pathways that these compounds were designed to target. We have developed a novel screening assay that can lead to the identification of compounds that can inhibit EMT initiated by growth factor signaling. This assay is designed as a high-content screening assay where both cell growth and cell migration can be analyzed simultaneously via time-course imaging in multi-well plates. Using this assay, we have validated several compounds as viable EMT inhibitors. In particular, we have identified compounds targeting ALK5, MEK, and SRC as potent inhibitors that can interfere with EGF, HGF, and IGF-1 induced EMT signaling. Overall, this EMT screening method provides a foundation for improving the therapeutic value of recently developed compounds in advanced stage carcinoma.     

Sphingosine Kinase Activity Is Not Required for Tumor Cell Viability

Sphingosine kinases (SPHKs) are enzymes that phosphorylate the lipid sphingosine, leading to the formation of sphingosine-1-phosphate (S1P). In addition to the well established role of extracellular S1P as a mitogen and potent chemoattractant, SPHK activity has been postulated to be an important intracellular regulator of apoptosis. According to the proposed rheostat theory, SPHK activity shifts the intracellular balance from the pro-apoptotic sphingolipids ceramide and sphingosine to the mitogenic S1P, thereby determining the susceptibility of a cell to apoptotic stress. Despite numerous publications with supporting evidence, a clear experimental confirmation of the impact of this mechanism on tumor cell viability in vitro and in vivo has been hampered by the lack of suitable tool reagents. Utilizing a structure based design approach, we developed potent and specific SPHK1/2 inhibitors. These compounds completely inhibited intracellular S1P production in human cells and attenuated vascular permeability in mice, but did not lead to reduced tumor cell growth in vitro or in vivo. In addition, siRNA experiments targeting either SPHK1 or SPHK2 in a large panel of cell lines failed to demonstrate any statistically significant effects on cell viability. These results show that the SPHK rheostat does not play a major role in tumor cell viability, and that SPHKs might not be attractive targets for pharmacological intervention in the area of oncology.