Emerging treatment options for the treatment of neuroblastoma: potential role of perifosine

Targeting Oncogenic Transcriptional Networks in Neuroblastoma: From N-Myc to Epigenetic Drugs

Neuroblastoma (NB) is one of the most frequently occurring neurogenic extracranial solid cancers in childhood and infancy. Over the years, many pieces of evidence suggested that NB development is controlled by gene expression dysregulation. These unleashed programs that outline NB cancer cells make them highly dependent on specific tuning of gene expression, which can act co-operatively to define the differentiation state, cell identity, and specialized functions. The peculiar regulation is mainly caused by genetic and epigenetic alterations, resulting in the dependency on a small set of key master transcriptional regulators as the convergence point of multiple signalling pathways. In this review, we provide a comprehensive blueprint of transcriptional regulation bearing NB initiation and progression, unveiling the complexity of novel oncogenic and tumour suppressive regulatory networks of this pathology. Furthermore, we underline the significance of multi-target therapies against these hallmarks, showing how novel approaches, together with chemotherapy, surgery, or radiotherapy, can have substantial antineoplastic effects, disrupting a wide variety of tumorigenic pathways through combinations of different treatments.

Multiple Facets of Autophagy and the Emerging Role of Alkylphosphocholines as Autophagy Modulators

Autophagy is a highly conserved multistep process and functions as passage for degrading and recycling protein aggregates and defective organelles in eukaryotic cells. Based on the nature of these materials, their size and degradation rate, four types of autophagy have been described, i.e. chaperone mediated autophagy, microautophagy, macroautophagy, and selective autophagy. One of the major regulators of this process is mTOR, which inhibits the downstream pathway of autophagy following the activation of its complex 1 (mTORC1). Alkylphosphocholine (APC) derivatives represent a novel class of antineoplastic agents that inhibit the serine-threonine kinase Akt (i.e. protein kinase B), which mediates cell survival and cause cell cycle arrest. They induce autophagy through inhibition of the Akt/mTOR cascade. They interfere with phospholipid turnover and thus modify signaling chains, which start from the cell membrane and modulate PI3K/Akt/mTOR, Ras-Raf-MAPK/ERK and SAPK/JNK pathways. APCs include miltefosine, perifosine, and erufosine, which represent the first-, second- and third generation of this class, respectively. In a high fraction of human cancers, constitutively active oncoprotein Akt1 suppresses autophagy in vitro and in vivo. mTOR is a down-stream target for Akt, the activation of which suppresses autophagy. However, treatment with APC derivatives will lead to dephosphorylation (hence deactivation) of mTOR and thus induces autophagy. Autophagy is a double-edged sword and may result in chemotherapeutic resistance as well as cancer cell death when apoptotic pathways are inactive. APCs display differential autophagy induction capabilities in different cancer cell types. Therefore, autophagy-dependent cellular responses need to be well understood in order to improve the chemotherapeutic outcome.

Selective elimination of neuroblastoma cells by synergistic effect of Akt kinase inhibitor and tetrathiomolybdate

Neuroblastoma is the most common extracranial solid tumour of infancy. Pathological activation of glucose consumption, glycolysis and glycolysis‐activating Akt kinase occur frequently in neuroblastoma cells, and these changes correlate with poor prognosis of patients. Therefore, several inhibitors of glucose utilization and the Akt kinase activity are in preclinical trials as potential anti‐cancer drugs. However, metabolic plasticity of cancer cells might undermine efficacy of this approach. In this work, we identified oxidative phosphorylation as compensatory mechanism preserving viability of neuroblastoma cells with inhibited glucose uptake/Akt kinase. It was oxidative phosphorylation that maintained intracellular level of ATP and proliferative capacity of these cells. The oxidative phosphorylation inhibitors (rotenone, tetrathiomolybdate) synergized with inhibitor of the Akt kinase/glucose uptake in down‐regulation of both viability of neuroblastoma cells and clonogenic potential of cells forming neuroblastoma spheroids. Interestingly, tetrathiomolybdate acted as highly specific inhibitor of oxygen consumption and activator of lactate production in neuroblastoma cells, but not in normal fibroblasts and neuronal cells. Moreover, the reducing effect of tetrathiomolybdate on cell viability and the level of ATP in the cells with inhibited Akt kinase/glucose uptake was also selective for neuroblastoma cells. Therefore, efficient elimination of neuroblastoma cells requires inhibition of both glucose uptake/Akt kinase and oxidative phosphorylation activities. The use of tetrathiomolybdate as a mitochondrial inhibitor contributes to selectivity of this combined treatment, preferentially targeting neuroblastoma cells.

A phase I/Ib trial targeting the Pi3k/Akt pathway using perifosine: Long-term progression-free survival of patients with resistant neuroblastoma

AKT plays a pivotal role in driving the malignant phenotype of many cancers, including high-risk neuroblastoma (HR-NB). AKT signaling, however, is active in normal tissues, raising concern about excessive toxicity from its suppression. The oral AKT inhibitor perifosine showed tolerable toxicity in adults and in our phase I trial in children with solid tumors (clinicaltrials.gov NCT00776867). We now report on the HR-NB experience. HR-NB patients received perifosine 50-75 mg m^-2  day^-1 after a loading dose of 100-200 mg m^-2 on day 1, and continued on study until progressive disease. The 27 HR-NB patients included three treated for primary refractory disease and 24 with disease resistant to salvage therapy after 1-5 (median 2) relapses; only one had MYCN-amplified HR-NB. Pharmacokinetic studies showed μM concentrations consistent with cytotoxic levels in preclinical models. Nine patients (all MYCN-non-amplified) remained progression-free through 43+ to 74+ (median 54+) months from study entry, including the sole patient to show a complete response and eight patients who had persistence of abnormal ¹²³ I-metaiodobenzylguanidine skeletal uptake but never developed progressive disease. Toxicity was negligible in all 27 patients, even with the prolonged treatment (11-62 months, median 38) in the nine long-term progression-free survivors. The clinical findings (i) confirm the safety of therapeutic serum levels of an AKT inhibitor in children; (ii) support perifosine for MYCN-non-amplified HR-NB as monotherapy after completion of standard treatment or combined with other agents (based on preclinical studies) to maximize antitumor effects; and (iii) highlight the welcome possibility that refractory or relapsed MYCN-non-amplified HR-NB is potentially curable.

Anti-tumor activity of safranal against neuroblastoma cells

Objective:

Safranal (2,6,6-trimethyl-1,3-cyclohexadiene-1-carboxaldehyde, C10H14O) is an active ingredient in the saffron, which is used in traditional medicine, and also, the biological activity of saffron in anti-cancer is in development. It has been reported to have anti-oxidant effects, but its anti-tumor effects remain uncertain. The aim of this study was to evaluate effects of safranal on anti-tumor on neuroblastoma cells.

Materials and Methods:

Neuroblastoma cells were cultured and exposed to safranal (0, 10, 15, 20, 50 μg/ml). Cell proliferation was examined using the 3-(4, 5-dimethyl thiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. Apoptotic cells, cell cycle distribution, and sub-G1 fraction were analyzed using flow cytometric analysis after propidium iodide staining.

Results:

Safranal inhibited the growth of malignant cells in a dose-and time-dependent manner. The IC (50) values against the neuroblastoma cell line were determined as 11.1 and 23.3 μg/ml after 24 and 48 h, respectively. Safranal induced a sub-G1 peak in the flow cytometry histogram of treated cells compared to control cells indicating that apoptotic cell death is involved in safranal toxicity.

Conclusions:

Our pre-clinical study demonstrated a neuroblastoma cell line to be highly sensitive to safranal-mediated growth inhibition and apoptotic cell death. Although the molecular mechanisms of safranal action are not yet clearly understood, it appears to have potential as a therapeutic agent.

Cell survival signaling in neuroblastoma

Neuroblastoma is the most common extracranial solid tumor of childhood and is responsible for over 15% of pediatric cancer deaths. Neuroblastoma tumorigenesis and malignant transformation is driven by overexpression and dominance of cell survival pathways and a lack of normal cellular senescence or apoptosis. Therefore, manipulation of cell survival pathways may decrease the malignant potential of these tumors and provide avenues for the development of novel therapeutics. This review focuses on several facets of cell survival pathways including protein kinases (PI3K, AKT, ALK, and FAK), transcription factors (NF-κB, MYCN and p53), and growth factors (IGF, EGF, PDGF, and VEGF). Modulation of each of these factors decreases the growth or otherwise hinders the malignant potential of neuroblastoma, and many therapeutics targeting these pathways are already in the clinical trial phase of development. Continued research and discovery of effective modulators of these pathways will revolutionize the treatment of neuroblastoma.

Physiology and pathophysiology of the blood-brain barrier: P-glycoprotein and occludin trafficking as therapeutic targets to optimize central nervous system drug delivery

The blood-brain barrier (BBB) is a physical and metabolic barrier that separates the central nervous system from the peripheral circulation. Central nervous system drug delivery across the BBB is challenging, primarily because of the physical restriction of paracellular diffusion between the endothelial cells that comprise the microvessels of the BBB and the activity of efflux transporters that quickly expel back into the capillary lumen a wide variety of xenobiotics. Therapeutic manipulation of protein trafficking is emerging as a novel means of modulating protein function, and in this minireview, the targeting of the trafficking of 2 key BBB proteins, P-glycoprotein and occludin, is presented as a novel, reversible means of optimizing central nervous system drug delivery.

Establishment and characterization of xenograft models of human neuroblastoma bone metastasis

OBJECTS

To improve the therapy of advanced neuroblastoma (NB), it is critical to develop animal models that mimic NB bone metastases. Unlike the human disease, NB xenograft models rarely metastasize spontaneously to bone from the orthotopic site of primary tumor growth.

METHODS

Single-cell suspensions of SY5Y, KCNR NB cells were injected directly into the femur of nude mice. Radiological and histological analyses and immunohistochemistry analyses were performed to characterize these osseous NB models. SY5Y and KCNR result in osteolytic responses.

RESULTS

We have detected osteoprotegerin, receptor activator of nuclear factor kappa B ligand, parathyroid hormone-related protein, and endothelin-1, proteins associated with bone growth and osteolysis, and C-X-C chemokine receptor type 4 (CXCR4) involved in tumor growth and tumor cell migration in the NB cells grown in the bone.

CONCLUSIONS

These animal models can be used to study biological interactions, pathways, and potential therapeutic targets and also to evaluate new agents for treatment and prevention of NB bone metastasis.

Physiology and pathophysiology of the blood-brain barrier: P-glycoprotein and occludin trafficking as therapeutic targets to optimize central nervous system drug delivery

The blood-brain barrier (BBB) is a physical and metabolic barrier that separates the central nervous system from the peripheral circulation. Central nervous system drug delivery across the BBB is challenging, primarily because of the physical restriction of paracellular diffusion between the endothelial cells that comprise the microvessels of the BBB and the activity of efflux transporters that quickly expel back into the capillary lumen a wide variety of xenobiotics. Therapeutic manipulation of protein trafficking is emerging as a novel means of modulating protein function, and in this minireview, the targeting of the trafficking of 2 key BBB proteins, P-glycoprotein and occludin, is presented as a novel, reversible means of optimizing central nervous system drug delivery.