Fenretinide Cytotoxicity for Ewing’s Sarcoma and Primitive Neuroectodermal Tumor Cell Lines Is Decreased by Hypoxia and Synergistically Enhanced by Ceramide Modulators

Attempts to Improve Lipophilic Drugs' Solubility and Bioavailability: A Focus on Fenretinide

The development of numerous drugs is often arrested at clinical testing stages, due to their unfavorable biopharmaceutical characteristics. It is the case of fenretinide (4-HPR), a second-generation retinoid, that demonstrated promising in vitro cytotoxic activity against several cancer cell lines. Unfortunately, response rates in early clinical trials with 4-HPR did not confirm the in vitro findings, mainly due to the low bioavailability of the oral capsular formulation that was initially developed. Capsular 4-HPR provided variable and insufficient drug plasma levels attributable to the high hepatic first-pass effect and poor drug water solubility. To improve 4-HPR bioavailability, several approaches have been put forward and tested in preclinical and early-phase clinical trials, demonstrating generally improved plasma levels and minimal systemic toxicities, but also modest antitumor efficacy. The challenge is thus currently still far from being met. To redirect the diminished interest of pharmaceutical companies toward 4-HPR and promote its further clinical development, this manuscript reviewed the attempts made so far by researchers to enhance 4-HPR bioavailability. A comparison of the available data was performed, and future directions were proposed.

Phase I trial of intravenous fenretinide (4-HPR) plus safingol in advanced malignancies

PURPOSE

Fenretinide (4-HPR) is a synthetic retinoid that induces cytotoxicity through dihydroceramide production. Safingol, a stereochemical-variant dihydroceramide precursor, exhibits synergistic effects when administered with fenretinide in preclinical studies. We conducted a phase 1 dose-escalation clinical trial of this combination.

METHODS

Fenretinide was administered as a 600 mg/m2 24-h infusion on Day 1 of a 21-day cycle followed by 900 mg/m2/day on Days 2 and 3. Safingol was concurrently administered as a 48-h infusion on Day 1 and 2 using 3 + 3 dose escalation. Primary endpoints were safety and maximum tolerated dose (MTD). Secondary endpoints included pharmacokinetics and efficacy.

RESULTS

A total of 16 patients were enrolled (mean age 63 years, 50% female, median three prior lines of therapy), including 15 patients with refractory solid tumors and one with non-Hodgkin lymphoma. The median number of treatment cycles received was 2 (range 2-6). The most common adverse event (AE) was hypertriglyceridemia (88%; 38% ≥ Grade 3), attributed to the fenretinide intralipid infusion vehicle. Other treatment-related AEs occurring in ≥ 20% of patients included anemia, hypocalcemia, hypoalbuminemia, and hyponatremia. At safingol dose 420 mg/m2, one patient had a dose-limiting toxicity of grade 3 troponinemia and grade 4 myocarditis. Due to limited safingol supply, enrollment was halted at this dose level. Fenretinide and safingol pharmacokinetic profiles resembled those observed in monotherapy trials. Best radiographic response was stable disease (n = 2).

CONCLUSION

Combination fenretinide plus safingol commonly causes hypertriglyceridemia and may be associated with cardiac events at higher safingol levels. Minimal activity in refractory solid tumors was observed.

TRIAL REGISTRATION NUMBER

NCT01553071 (3.13.2012).

Hypoxia and HIFs in Ewing sarcoma: new perspectives on a multi-facetted relationship

Hypoxia develops during the growth of solid tumors and influences tumoral activity in multiple ways. Low oxygen tension is also present in the bone microenvironment where Ewing sarcoma (EwS) - a highly aggressive pediatric cancer - mainly arises. Hypoxia inducible factor 1 subunit alpha (HIF-1-a) is the principal molecular mediator of the hypoxic response in cancer whereas EWSR1::FLI1 constitutes the oncogenic driver of EwS. Interaction of the two proteins has been shown in EwS. Although a growing body of studies investigated hypoxia and HIFs in EwS, their precise role for EwS pathophysiology is not clarified to date. This review summarizes and structures recent findings demonstrating that hypoxia and HIFs play a role in EwS at multiple levels. We propose to view hypoxia and HIFs as independent protagonists in the story of EwS and give a perspective on their potential clinical relevance as prognostic markers and therapeutic targets in EwS treatment.

The unfolding role of ceramide in coordinating retinoid-based cancer therapy

Sphingolipid-mediated regulation in cancer development and treatment is largely ceramide-centered with the complex sphingolipid metabolic pathways unfolding as attractive targets for anticancer drug discovery. The dynamic interconversion of sphingolipids is tightly controlled at the level of enzymes and cellular compartments in response to endogenous or exogenous stimuli, such as anticancer drugs, including retinoids. Over the past two decades, evidence emerged that retinoids owe part of their potency in cancer therapy to modulation of sphingolipid metabolism and ceramide generation. Ceramide has been proposed as a 'tumor-suppressor lipid' that orchestrates cell growth, cell cycle arrest, cell death, senescence, autophagy, and metastasis. There is accumulating evidence that cancer development is promoted by the dysregulation of tumor-promoting sphingolipids whereas cancer treatments can kill tumor cells by inducing the accumulation of endogenous ceramide levels. Resistance to cancer therapy may develop due to a disrupted equilibrium between the opposing roles of tumor-suppressor and tumor-promoter sphingolipids. Despite the undulating effect and complexity of sphingolipid pathways, there are emerging opportunities for a plethora of enzyme-targeted therapeutic interventions that overcome resistance resulting from perturbed sphingolipid pathways. Here, we have revisited the interconnectivity of sphingolipid metabolism and the instrumental role of ceramide-biosynthetic and degradative enzymes, including bioactive sphingolipid products, how they closely relate to cancer treatment and pathogenesis, and the interplay with retinoid signaling in cancer. We focused on retinoid targeting, alone or in combination, of sphingolipid metabolism nodes in cancer to enhance ceramide-based therapeutics. Retinoid and ceramide-based cancer therapy using novel strategies such as combination treatments, synthetic retinoids, ceramide modulators, and delivery formulations hold promise in the battle against cancer.

STAG2 mutations alter CTCF-anchored loop extrusion, reduce cis-regulatory interactions and EWSR1-FLI1 activity in Ewing sarcoma

STAG2, a cohesin family gene, is among the most recurrently mutated genes in cancer. STAG2 loss of function (LOF) is associated with aggressive behavior in Ewing sarcoma, a childhood cancer driven by aberrant transcription induced by the EWSR1-FLI1 fusion oncogene. Here, using isogenic Ewing cells, we show that, while STAG2 LOF profoundly changes the transcriptome, it does not significantly impact EWSR1-FLI1, CTCF/cohesin, or acetylated H3K27 DNA binding patterns. In contrast, it strongly alters the anchored dynamic loop extrusion process at boundary CTCF sites and dramatically decreases promoter-enhancer interactions, particularly affecting the expression of genes regulated by EWSR1-FLI1 at GGAA microsatellite neo-enhancers. Down-modulation of cis-mediated EWSR1-FLI1 activity, observed in STAG2-LOF conditions, is associated with enhanced migration and invasion properties of Ewing cells previously observed in EWSR1-FLI1low cells. Our study illuminates a process whereby STAG2-LOF fine-tunes the activity of an oncogenic transcription factor through altered CTCF-anchored loop extrusion and cis-mediated enhancer mechanisms.

p21-activated kinases as viable therapeutic targets for the treatment of high-risk Ewing sarcoma

Ewing sarcoma (ES) is the second most common bone tumor in children and young adults. Unfortunately, there have been minimal recent advancements in improving patient outcomes, especially in metastatic and recurrent diseases. In this study, we investigated the biological role of p21-activated kinases (PAKs) in ES, and the ability to therapeutically target them in high-risk disease. Via informatics analysis, we established the inverse association of PAK1 and PAK4 expression with clinical stage and outcome in ES patients. Through expression knockdown and small-molecule inhibition of PAKs, utilizing FRAX-597, KPT-9274, and PF-3758309 in multiple ES cell lines and patient-derived xenograft models, we further explored the role of PAKs in ES tumor growth and metastatic capabilities. In vitro studies in several ES cell lines indicated that diminishing PAK1 and PAK4 expression reduces tumor cell viability, migratory, and invasive properties. In vivo studies using PAK4 inhibitors, KPT-9274 and PF-3758309 demonstrated significant inhibition of primary and metastatic tumor formation, while transcriptomic analysis of PAK4-inhibitor-treated tumors identified concomitant suppression of Notch, β-catenin, and hypoxia-mediated signatures. In addition, the analysis showed enrichment of anti-tumor immune regulatory mechanisms, including interferon (IFN)-ɣ and IFN-α responses. Altogether, our molecular and pre-clinical studies are the first to establish a critical role for PAKs in ES development and progression, and consequently as viable therapeutic targets for the treatment of high-risk ES in the near future.

A phase I study of intravenous fenretinide (4-HPR) for patients with malignant solid tumors

BACKGROUND

Fenretinide is a synthetic retinoid that can induce cytotoxicity by several mechanisms. Achieving effective systemic exposure with oral formulations has been challenging. An intravenous lipid emulsion fenretinide formulation was developed to overcome this barrier. We conducted a study to establish the maximum tolerated dose (MTD), preliminary efficacy, and pharmacokinetics of intravenous lipid emulsion fenretinide in patients with advanced solid tumors.

METHODS

Twenty-three patients with advanced solid tumors refractory to standard treatments received fenretinide as a continuous infusion for five consecutive days in 21-day cycles. Five different dose cohorts were evaluated between doses of 905 mg/m² and 1414 mg/m² per day using a 3 + 3 dose escalation design. A priming dose of 600 mg/m² on day 1 was introduced in an attempt to address the asymptomatic serum triglyceride elevations related to the lipid emulsion.

RESULTS

The treatment-related adverse events occurring in ≥ 20% of patients were anemia, hypertriglyceridemia, fatigue, aspartate aminotransferase (AST)/alanine aminotransferase (ALT) increase, thrombocytopenia, bilirubin increase, and dry skin. Five evaluable patients had stable disease as best response, and no patients had objective responses. Plasma steady-state concentrations of the active metabolite were significantly higher than with previous capsule formulations.

CONCLUSION

Fenretinide emulsion intravenous infusion had a manageable safety profile and achieved higher plasma steady-state concentrations of the active metabolite compared to previous capsule formulations. Single-agent activity was minimal but combinatorial approaches are under evaluation.

Endomorphin-2 Analog Inhibits the Growth of DLD-1 and RKO Human Colon Cancer Cells by Inducing Cell Apoptosis

Background

In developed countries, colon cancer is a leading cause of cancer-associated mortality. Dietary changes have resulted in an increased incidence of colon cancer in Asia. This study aimed to investigate the effects of the structural analog of endomorphin-2 (H-Tyr-Pro-Phe-Phe-NH₂) on human colon cancer cells in vitro.

Material/Methods

Human DLD-1 and RKO colon cancer cells and CCD-18Co normal human colonic fibroblasts were treated with increasing doses of the structural analog of endomorphin-2. Cells underwent the MTT assay, fluorescence confocal flow cytometry, and Hoechst 33258 staining to investigate cell proliferation, the cell cycle, and apoptosis. Western blot was used to measure the expression levels of poly(ADP-ribose) polymerase-1 (PARP-1), cytochrome c, caspase-3, and caspase-9. The 2′,7′-dichlorofluorescein diacetate (DCFH-DA) fluorescence method measured reactive oxygen species (ROS).

Results

Cell proliferation of DLD-1 and RKO cells was inhibited by the endomorphin-2 analog in a dose-dependent manner, and a 100 μM dose reduced DLD-1 and RKO cell proliferation by 28% and 23%, respectively, at 72 h. Endomorphin-2 analog induced cell apoptosis and the generation of ROS, activated caspase-3 and caspase-9, and increased the levels of p53 and cytochrome c release, and down-regulated of Akt activation in DLD-1 and RKO cells in a dose-dependent manner. Treatment of the DLD-1 and RKO cells with the endomorphin-2 analog increased the expression of Bax and reduced the expression of Bcl-2.

Conclusions

Endomorphin-2 analog inhibited colon cancer cell proliferation, activated apoptosis, and down-regulated Akt phosphorylation of human DLD-1 and RKO colon cancer cells in vitro in a dose-dependent manner.

Intrinsic Disorder of the BAF Complex: Roles in Chromatin Remodeling and Disease Development

The two-meter-long DNA is compressed into chromatin in the nucleus of every cell, which serves as a significant barrier to transcription. Therefore, for processes such as replication and transcription to occur, the highly compacted chromatin must be relaxed, and the processes required for chromatin reorganization for the aim of replication or transcription are controlled by ATP-dependent nucleosome remodelers. One of the most highly studied remodelers of this kind is the BRG1- or BRM-associated factor complex (BAF complex, also known as SWItch/sucrose non-fermentable (SWI/SNF) complex), which is crucial for the regulation of gene expression and differentiation in eukaryotes. Chromatin remodeling complex BAF is characterized by a highly polymorphic structure, containing from four to 17 subunits encoded by 29 genes. The aim of this paper is to provide an overview of the role of BAF complex in chromatin remodeling and also to use literature mining and a set of computational and bioinformatics tools to analyze structural properties, intrinsic disorder predisposition, and functionalities of its subunits, along with the description of the relations of different BAF complex subunits to the pathogenesis of various human diseases.

Inhibition of Colon Cancer Cell Growth by Imidazole Through Activation of Apoptotic Pathway

Background

This study aimed to investigate the inhibitory effect of imidazole on colon cancer cell proliferation and understand the mechanism involved.

Material/Methods

MTT assay and flow cytometry using Hoechst 33258 staining were used to assess cell proliferation and morphology, respectively. Changes in protein expression was determined by western blotting assay. The reactive oxygen species (ROS) production in DLD-1 cells was analyzed by flow cytometry using DCFH-DA (2′,7′-dichlorofluorescein diacetate) stain.

Results

DLD-1 and HCT-116 cell viability was suppressed by imidazole in a concentration-based manner. At the concentration of 36 μM, imidazole reduced DLD-1 and HCT-116 cell viability to 22% and 28%, respectively. Treatment with imidazole led to chromatin material condensation, detaching of cells, and apoptotic nuclei. In imidazole treated cells, the G1/G0 phase cell proportion increased, whereas in the S and G2/M phases the cell proportion decreased. Imidazole treatment of DLD-1 cells markedly promoted activation of caspase-3, caspase-8, and caspase-9. The level of cleaved PARP1 was also upregulated in DLD-1 cells with imidazole treatment. Treatment of DLD-1 cells with imidazole suppressed Bcl-2 and promoted Bax, p53, and cytc expression. The Akt activation was suppressed by imidazole treatment in DLD-1 cells. ROS generation in DLD-1 cells was enhanced markedly by treatment with imidazole.

Conclusions

The present study demonstrated that imidazole inhibited colon cancer cell viability through activation of apoptosis and cell cycle arrest by increasing the generation of ROS, caspase activation, and apoptotic protein expression. Therefore, imidazole can act as a therapeutic molecule for the treatment of colon cancer.

BORIS promotes chromatin regulatory interactions in treatment-resistant cancer cells

The CCCTC-binding factor (CTCF), which anchors DNA loops that organize the genome into structural domains, has a central role in gene control by facilitating or constraining interactions between genes and their regulatory elements^1,2. In cancer cells, the disruption of CTCF binding at specific loci by somatic mutation^3,4 or DNA hypermethylation⁵ results in the loss of loop anchors and consequent activation of oncogenes. By contrast, the germ-cell-specific paralogue of CTCF, BORIS (brother of the regulator of imprinted sites, also known as CTCFL)⁶, is overexpressed in several cancers^7-9, but its contributions to the malignant phenotype remain unclear. Here we show that aberrant upregulation of BORIS promotes chromatin interactions in ALK-mutated, MYCN-amplified neuroblastoma¹⁰ cells that develop resistance to ALK inhibition. These cells are reprogrammed to a distinct phenotypic state during the acquisition of resistance, a process defined by the initial loss of MYCN expression followed by subsequent overexpression of BORIS and a concomitant switch in cellular dependence from MYCN to BORIS. The resultant BORIS-regulated alterations in chromatin looping lead to the formation of super-enhancers that drive the ectopic expression of a subset of proneural transcription factors that ultimately define the resistance phenotype. These results identify a previously unrecognized role of BORIS-to promote regulatory chromatin interactions that support specific cancer phenotypes.

The Ewing Family of Tumors Relies on BCL-2 and BCL-XL to Escape PARP Inhibitor Toxicity

PURPOSE

It was recently demonstrated that the EWSR1-FLI1 t(11;22)(q24;12) translocation contributes to the hypersensitivity of Ewing sarcoma to PARP inhibitors, prompting clinical evaluation of olaparib in a cohort of heavily pretreated Ewing sarcoma tumors. Unfortunately, olaparib activity was disappointing, suggesting an underappreciated resistance mechanism to PARP inhibition in patients with Ewing sarcoma. We sought to elucidate the resistance factors to PARP inhibitor therapy in Ewing sarcoma and identify a rational drug combination capable of rescuing PARP inhibitor activity.

EXPERIMENTAL DESIGN

We employed a pair of cell lines derived from the same patient with Ewing sarcoma prior to and following chemotherapy, a panel of Ewing sarcoma cell lines, and several patient-derived xenograft (PDX) and cell line xenograft models.

RESULTS

We found olaparib sensitivity was diminished following chemotherapy. The matched cell line pair revealed increased expression of the antiapoptotic protein BCL-2 in the chemotherapy-resistant cells, conferring apoptotic resistance to olaparib. Resistance to olaparib was maintained in this chemotherapy-resistant model in vivo, whereas the addition of the BCL-2/X_L inhibitor navitoclax led to tumor growth inhibition. In 2 PDXs, olaparib and navitoclax were minimally effective as monotherapy, yet induced dramatic tumor growth inhibition when dosed in combination. We found that EWS-FLI1 increases BCL-2 expression; however, inhibition of BCL-2 alone by venetoclax is insufficient to sensitize Ewing sarcoma cells to olaparib, revealing a dual necessity for BCL-2 and BCL-X_L in Ewing sarcoma survival.

CONCLUSIONS

These data reveal BCL-2 and BCL-X_L act together to drive olaparib resistance in Ewing sarcoma and reveal a novel, rational combination therapy that may be put forward for clinical trial testing.

A k-mer based transcriptomics approach for antisense drug discovery targeting the Ewing's family of tumors

Ewing’s sarcoma treatment failures are associated with high mortality indicating a need for new therapeutic approaches. We used a k-mer counting approach to identify cancer-specific mRNA transcripts in 3 Ewing’s Family Tumor (EFT) cell lines not found in the normal human transcriptome. Phosphorodiamidate morpholino oligomers targeting six EFT-specific transcripts were evaluated for cytotoxicity in TC-32 and CHLA-10 EFT lines and in HEK293 renal epithelial control cells. Average morpholino efficacy (EC₅₀) was 0.66 ± 0.13 in TC-32, 0.25 ± 0.14 in CHLA-10 and 3.07 ± 5.02 µM in HEK293 control cells (ANOVA p < 0.01). Synergy was observed for a cocktail of 12 morpholinos at low dose (0.3 µM) in TC-32 cells, but not in CHLA-10 cells. Paired synergy was also observed in both EFT cell lines when the PHGDH pre-mRNA transcript was targeted in combination with XAGE1B or CYP4F22 transcripts. Antagonism was observed when CCND1 was targeted with XAGE1B or CYP4F22, or when IGFBP-2 was targeted with CCND1 or RBM11. This transcriptome profiling approach is highly effective for cancer drug discovery, as it identified new EWS-specific target genes (e.g. CYP4F22, RBM11 and IGBP-2), and predicted effective antisense agents (EC₅₀ < 1 µM) that demonstrate both synergy and antagonism in combination therapy.

Replication Study: Systematic identification of genomic markers of drug sensitivity in cancer cells

In 2016, as part of the Reproducibility Project: Cancer Biology, we published a Registered Report (Vanden Heuvel et al., 2016), that described how we intended to replicate selected experiments from the paper ‘Systematic identification of genomic markers of drug sensitivity in cancer cells’ (Garnett et al., 2012). Here we report the results. We found Ewing’s sarcoma cell lines, overall, were more sensitive to the PARP inhibitor olaparib than osteosarcoma cell lines; however, while the effect was in the same direction as the original study (Figure 4C; Garnett et al., 2012), it was not statistically significant. Further, mouse mesenchymal cells transformed with either the EWS-FLI1 or FUS-CHOP rearrangement displayed similar sensitivities to olaparib, whereas the Ewing’s sarcoma cell line SK-N-MC had increased olaparib sensitivity. In the original study, mouse mesenchymal cells transformed with the EWS-FLI1 rearrangement and SK-N-MC cells were found to have similar sensitivities to olaparib, whereas mesenchymal cells transformed with the FUS-CHOP rearrangement displayed a reduced sensitivity to olaparib (Figure 4E; Garnett et al., 2012). We also studied another Ewing’s sarcoma cell line, A673: A673 cells depleted of EWS-FLI1 or a negative control both displayed similar sensitivities to olaparib, whereas the original study reported a decreased sensitivity to olaparib when EWS-FLI1 was depleted (Figure 4F; Garnett et al., 2012). Differences between the original study and this replication attempt, such as the use of different sarcoma cell lines and level of knockdown efficiency, are factors that might have influenced the outcomes. Finally, where possible, we report meta-analyses for each result.

Neuropeptide Y (NPY) in tumor growth and progression: Lessons learned from pediatric oncology

Neuropeptide Y (NPY) is a sympathetic neurotransmitter with pleiotropic actions, many of which are highly relevant to tumor biology. Consequently, the peptide has been implicated as a factor regulating the growth of a variety of tumors. Among them, two pediatric malignancies with high endogenous NPY synthesis and release - neuroblastoma and Ewing sarcoma - became excellent models to investigate the role of NPY in tumor growth and progression. The stimulatory effect on tumor cell proliferation, survival, and migration, as well as angiogenesis in these tumors, is mediated by two NPY receptors, Y2R and Y5R, which are expressed in either a constitutive or inducible manner. Of particular importance are interactions of the NPY system with the tumor microenvironment, as hypoxic conditions commonly occurring in solid tumors strongly activate the NPY/Y2R/Y5R axis. This activation is triggered by hypoxia-induced up-regulation of Y2R/Y5R expression and stimulation of dipeptidyl peptidase IV (DPPIV), which converts NPY to a selective Y2R/Y5R agonist, NPY(3-36). While previous studies focused mainly on the effects of NPY on tumor growth and vascularization, they also provided insight into the potential role of the peptide in tumor progression into a metastatic and chemoresistant phenotype. This review summarizes our current knowledge of the role of NPY in neuroblastoma and Ewing sarcoma and its interactions with the tumor microenvironment in the context of findings in other malignancies, as well as discusses future directions and potential clinical implications of these discoveries.

The Macrophage Inhibitor CNI-1493 Blocks Metastasis in a Mouse Model of Ewing Sarcoma through Inhibition of Extravasation

Metastatic Ewing Sarcoma carries a poor prognosis, and novel therapeutics to prevent and treat metastatic disease are greatly needed. Recent evidence demonstrates that tumor-associated macrophages in Ewing Sarcoma are associated with more advanced disease. While some macrophage phenotypes (M1) exhibit anti-tumor activity, distinct phenotypes (M2) may contribute to malignant progression and metastasis. In this study, we show that M2 macrophages promote Ewing Sarcoma invasion and extravasation, pointing to a potential target of anti-metastatic therapy. CNI-1493 is a selective inhibitor of macrophage function and has shown to be safe in clinical trials as an anti-inflammatory agent. In a xenograft mouse model of metastatic Ewing Sarcoma, CNI-1493 treatment dramatically reduces metastatic tumor burden. Furthermore, metastases in treated animals have a less invasive morphology. We show in vitro that CNI-1493 decreases M2-stimulated Ewing Sarcoma tumor cell invasion and extravasation, offering a functional mechanism through which CNI-1493 attenuates metastasis. These data indicate that CNI-1493 may be a safe and effective adjuvant agent for the prevention and treatment of metastatic Ewing Sarcoma.

Isoflavone lupiwighteone induces cytotoxic, apoptotic, and antiangiogenic activities in DU-145 prostate cancer cells

Isoflavones constitute a large series of compounds found in many plants. They make up an important part of the diet and have a broad spectrum of biological activities such as cytotoxic and antitumor effects. Lupiwighteone (Lup) is an isoflavone-type compound. It is distributed widely in wild-growing plants such as Glycyrrhiza glabra, Lupinus, and Lotus pedunculatus. On the basis of existing research, Lup shows antioxidant and antimicrobial effects, but its antitumor activity has not been reported as yet. This study aimed to examine the antitumor activity of Lup, explore its antitumor mechanism in a human prostate carcinoma cell line (DU-145), and evaluate its antiangiogenetic activity in the human umbilical vein endothelial cell line (HUVEC). The results showed that Lup could inhibit the growth of DU-145 and HUVEC cells in a concentration-dependent and time-dependent manner by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Flow cytometry analysis indicated that Lup could induce cell cycle arrest, cells apoptosis, mitochondrial membrane potential loss, and an increase in intracellular reactive oxygen species of DU-145 cells. Upregulation of Bax, cytochrome c, caspase-3, and PARP-1 protein expressions and downregulation of Bcl-2, procaspase-9, and p-Akt protein expressions were observed by western blot after the treatment of Lup. Furthermore, the effects of Lup on the cellular behavior of HUVECs were also investigated. Altogether, our data proved the anticancer and antiangiogenesis potential of Lup.

Modification of sphingolipid metabolism by tamoxifen and N-desmethyltamoxifen in acute myelogenous leukemia--Impact on enzyme activity and response to cytotoxics

The triphenylethylene antiestrogen, tamoxifen, can be an effective inhibitor of sphingolipid metabolism. This off-target activity makes tamoxifen an interesting ancillary for boosting the apoptosis-inducing properties of ceramide, a sphingolipid with valuable tumor censoring activity. Here we show for the first time that tamoxifen and metabolite, N-desmethyltamoxifen (DMT), block ceramide glycosylation and inhibit ceramide hydrolysis (by acid ceramidase, AC) in human acute myelogenous leukemia (AML) cell lines and in AML cells derived from patients. Tamoxifen (1-10 μM) inhibition of AC in AML cells was accompanied by decreases in AC protein expression. Tamoxifen also depressed expression and activity of sphingosine kinase 1 (SphK1), the enzyme-catalyzing production of mitogenic sphingosine 1-phosphate (S1-P). Results from mass spectroscopy showed that tamoxifen and DMT (i) increased the levels of endogenous C16:0 and C24:1 ceramide molecular species, (ii) nearly totally halted production of respective glucosylceramide (GC) molecular species, (iii) drastically reduced levels of sphingosine (to 9% of control), and (iv) reduced levels of S1-P by 85%, in vincristine-resistant HL-60/VCR cells. The co-administration of tamoxifen with either N-(4-hydroxyphenyl)retinamide (4-HPR), a ceramide-generating retinoid, or a cell-deliverable form of ceramide, C6-ceramide, resulted in marked decreases in HL-60/VCR cell viability that far exceeded single agent potency. Combination treatments resulted in synergistic apoptotic cell death as gauged by increased Annexin V binding and DNA fragmentation and activation of caspase-3. These results show the versatility of adjuvant triphenylethylene with ceramide-centric therapies for magnifying therapeutic potential in AML. Such drug regimens could serve as effective strategies, even in the multidrug-resistant setting.

Akt/eNOS signaling pathway mediates inhibition of endothelial progenitor cells by palmitate-induced ceramide

Palmitate (PA) impairs endothelial progenitor cells (EPCs). However, the molecular mechanism underlying the suppressive function of PA remains largely unknown. Ceramide, a free fatty acid metabolite, mediates multiple cellular signals. We hypothesized that ceramide acts as an intermediate molecule to mediate inhibition of EPCs by PA. We first demonstrated that PA could inhibit the attachment, migration, and tube formation of EPCs through suppression of the Akt/endothelial nitric oxide (NO) synthase (eNOS) signaling pathway. In addition, we observed that PA could induce ceramide accumulation in EPCs. To test whether the accumulation of ceramide causes EPC dysfunction, the ceramide synthesis inhibitors myriocin and fumonisin B1 were used. We that found both inhibitors could effectively abolish PA-mediated EPC inhibition. Furthermore, the ceramide deacylation inhibitor N-oleoylethanolamine could augment the inhibitory effect of PA on EPCs, indicating that it is ceramide, not its metabolites, that mediates the suppression of EPCs by PA. We have previously shown that Akt/eNOS phosphorylation was reduced after PA treatment, which, in turn, hampered the normal bioavailability of NO, leading to impaired functions of EPCs. To test the role for ceramide in this process, a clinically used NO donor, sodium nitroprusside, was used. We found that sodium nitroprusside could rescue the suppressive effects of ceramide on EPCs, suggesting that ceramide-mediated EPC inhibition might be through reduction of NO production. Taken together, our findings indicated that ceramide-induced reduction of NO might be the molecular mechanism for PA-mediated EPC inhibition; thus, targeting either ceramide or NO production might be an effective means for improvement of EPC functions in diseases.

Hypoxia shifts activity of neuropeptide Y in Ewing sarcoma from growth-inhibitory to growth-promoting effects

Ewing sarcoma (ES) is an aggressive malignancy driven by an oncogenic fusion protein, EWS-FLI1. Neuropeptide Y (NPY), and two of its receptors, Y1R and Y5R are up-regulated by EWS-FLI1 and abundantly expressed in ES cells. Paradoxically, NPY acting via Y1R and Y5R stimulates ES cell death. Here, we demonstrate that these growth-inhibitory actions of NPY are counteracted by hypoxia, which converts the peptide to a growth-promoting factor. In ES cells, hypoxia induces another NPY receptor, Y2R, and increases expression of dipeptidyl peptidase IV (DPPIV), an enzyme that cleaves NPY to a shorter form, NPY3-36. This truncated peptide no longer binds to Y1R and, therefore, does not stimulate ES cell death. Instead, NPY3-36 acts as a selective Y2R/Y5R agonist. The hypoxia-induced increase in DPPIV activity is most evident in a population of ES cells with high aldehyde dehydrogenase (ALDH) activity, rich in cancer stem cells (CSCs). Consequently, NPY, acting via Y2R/Y5Rs, preferentially stimulates proliferation and migration of hypoxic ALDHhigh cells. Hypoxia also enhances the angiogenic potential of ES by inducing Y2Rs in endothelial cells and increasing the release of its ligand, NPY3-36, from ES cells. In summary, hypoxia acts as a molecular switch shifting NPY activity away from Y1R/Y5R-mediated cell death and activating the Y2R/Y5R/DPPIV/NPY3-36 axis, which stimulates ES CSCs and promotes angiogenesis. Hypoxia-driven actions of the peptide such as these may contribute to ES progression. Due to the receptor-specific and multifaceted nature of NPY actions, these findings may inform novel therapeutic approaches to ES.

Clinical and biochemical function of polymorphic NR0B1 GGAA-microsatellites in Ewing sarcoma: a report from the Children's Oncology Group

BACKGROUND

The genetics involved in Ewing sarcoma susceptibility and prognosis are poorly understood. EWS/FLI and related EWS/ETS chimeras upregulate numerous gene targets via promoter-based GGAA-microsatellite response elements. These microsatellites are highly polymorphic in humans, and preliminary evidence suggests EWS/FLI-mediated gene expression is highly dependent on the number of GGAA motifs within the microsatellite.

OBJECTIVES

Here we sought to examine the polymorphic spectrum of a GGAA-microsatellite within the NR0B1 promoter (a critical EWS/FLI target) in primary Ewing sarcoma tumors, and characterize how this polymorphism influences gene expression and clinical outcomes.

RESULTS

A complex, bimodal pattern of EWS/FLI-mediated gene expression was observed across a wide range of GGAA motifs, with maximal expression observed in constructs containing 20-26 GGAA motifs. Relative to white European and African controls, the NR0B1 GGAA-microsatellite in tumor cells demonstrated a strong bias for haplotypes containing 21-25 GGAA motifs suggesting a relationship between microsatellite function and disease susceptibility. This selection bias was not a product of microsatellite instability in tumor samples, nor was there a correlation between NR0B1 GGAA-microsatellite polymorphisms and survival outcomes.

CONCLUSIONS

These data suggest that GGAA-microsatellite polymorphisms observed in human populations modulate EWS/FLI-mediated gene expression and may influence disease susceptibility in Ewing sarcoma.

ChildSeq-RNA: A next-generation sequencing-based diagnostic assay to identify known fusion transcripts in childhood sarcomas

Childhood sarcomas can be extremely difficult to accurately diagnose on the basis of morphological characteristics alone. Ancillary methods, such as RT-PCR or fluorescence in situ hybridization, to detect pathognomonic gene fusions can help to distinguish these tumors. Two major deficiencies of these assays are their inability to identify gene fusions at nucleotide resolution or to detect multiple gene fusions simultaneously. We developed a next-generation sequencing-based assay designated ChildSeq-RNA that uses the Ion Torrent platform to screen for EWSR1-FLI1 and EWSR1-ERG, PAX3-FOXO1 and PAX7-FOXO1, EWSR1-WT1, and ETV6-NTRK3 fusions of Ewing sarcoma (ES), alveolar rhabdomyosarcoma, desmoplastic small round cell tumor, and congenital fibrosarcoma, respectively. To rapidly analyze resulting data, we codeveloped a bioinformatics tool, termed ChildDecode, that operates on a scalable, cloud-computing platform. Total RNA from four ES cell lines plus 33 clinical samples representing ES, alveolar rhabdomyosarcoma, desmoplastic small round cell tumor, and congenital fibrosarcoma tumors was subjected to ChildSeq-RNA. This accurately identified corresponding gene fusions in each tumor type, with no examples of false positive fusion detection in this proof-of-concept study. Comparison with previous RT-PCR findings demonstrated high sensitivity (96.4%; 95% CI, 82.3%-99.4%) and specificity (100%; 95% CI, 56.6%-100%) of ChildSeq-RNA to detect gene fusions. Herein, we propose ChildSeq-RNA as a novel tool to detect gene fusions in childhood sarcomas at single-nucleotide resolution.

Synthetic retinoid fenretinide in breast cancer chemoprevention

Preclinical models suggest that retinoids inhibit mammary carcinogenesis. The induction of apoptosis is a unique feature of fenretinide, the most-studied retinoid in clinical trials of breast cancer chemoprevention, owing to its selective accumulation in breast tissue and its favorable toxicological profile. In a Phase III breast cancer prevention trial, fenretinide showed a strong trend of reduction of incidence of second breast malignancies in premenopausal women, which was confirmed by 15 years of follow-up. This warrants further research on the mechanisms of action and potential efficacy of fenretinide and provides the rationale for a Phase III primary prevention trial in young women at high risk for breast cancer. This review will highlight the role of fenretinide in breast cancer chemoprevention.

Characterization and drug resistance patterns of Ewing's sarcoma family tumor cell lines

Despite intensive treatment with chemotherapy, radiotherapy and surgery, over 70% of patients with metastatic Ewing's Sarcoma Family of Tumors (EFT) will die of their disease. We hypothesize that properly characterized laboratory models reflecting the drug resistance of clinical tumors will facilitate the application of new therapeutic agents to EFT. To determine resistance patterns, we studied newly established EFT cell lines derived from different points in therapy: two established at diagnosis (CHLA-9, CHLA-32), two after chemotherapy and progressive disease (CHLA-10, CHLA-25), and two at relapse after myeloablative therapy and autologous bone marrow transplantation (post-ABMT) (CHLA-258, COG-E-352). The new lines were compared to widely studied EFT lines TC-71, TC-32, SK-N-MC, and A-673. These lines were extensively characterized with regard to identity (short tandem repeat (STR) analysis), p53, p16/14 status, and EWS/ETS breakpoint and target gene expression profile. The DIMSCAN cytotoxicity assay was used to assess in vitro drug sensitivity to standard chemotherapy agents. No association was found between drug resistance and the expression of EWS/ETS regulated genes in the EFT cell lines. No consistent association was observed between drug sensitivity and p53 functionality or between drug sensitivity and p16/14 functionality across the cell lines. Exposure to chemotherapy prior to cell line initiation correlated with drug resistance of EFT cell lines in 5/8 tested agents at clinically achievable concentrations (CAC) or the lower tested concentration (LTC): (cyclophosphamide (as 4-HC) and doxorubicin at CAC, etoposide, irinotecan (as SN-38) and melphalan at LTC; P<0.1 for one agent, and P<0.05 for four agents. This panel of well-characterized drug-sensitive and drug-resistant cell lines will facilitate in vitro preclinical testing of new agents for EFT.

Optimal management of Ewing sarcoma family of tumors: recent developments in systemic therapy

The Ewing sarcoma family of tumors (ESFT) is defined by cell surface expression of CD99 and a translocation involving EWS and an ETS partner. Cytotoxic chemotherapy remains the benchmark of first- and second-line therapy, and although the majority of patients with localized disease are cured, almost one third of patients relapse or progress from their disease. Moreover, cure remains elusive in most patients who present with distant metastases. In recent years, the ESFT literature has been dominated by reports of attempts at modulating the insulin-like growth factor (IGF) receptor (IGFR). Unfortunately, three phase II studies examining inhibiting antibodies to IGFR-1 published disappointing results. Whether these results were due to failure to modulate the pathway or other limitations in study design and/or patient selection remain unclear. Other novel strategies currently being investigated in ESFT include tyrosine kinase, mammalian target of rapamycin (mTOR), and poly(ADP-ribose) polymerase (PARP) inhibitors.

Phase I trial of fenretinide delivered orally in a novel organized lipid complex in patients with relapsed/refractory neuroblastoma: a report from the New Approaches to Neuroblastoma Therapy (NANT) consortium

BACKGROUND

A phase I study was conducted to determine the maximum-tolerated dose, dose-limiting toxicities (DLTs), and pharmacokinetics of fenretinide (4-HPR) delivered in an oral powderized lipid complex (LXS) in patients with relapsed/refractory neuroblastoma.

PROCEDURE

4-HPR/LXS powder (352-2,210 mg/m(2) /day) was administered on Days 0-6, in 21-day courses, by standard 3 + 3 design.

RESULTS

Thirty-two patients (median age = 8 years, range 3-27 years) enrolled with 30 evaluable for dose escalation. Prior therapies included stem cell transplantation/support (n = 26), 13-cis-retinoic acid (n = 22), (125/131) I-MIBG (n = 13), and anti-GD2 antibody (n = 6). 170+ courses were delivered. Course 1 DLTs were a Grade 3 (n = 1) alkaline phosphatase at 352 mg/m(2) /day. Other major toxicities were Grade 4 (n = 1) alkaline phosphatases on Courses 5 and 6 at 774 mg/m(2) /day, and Grade 3 (n = 1) ALT/AST elevation on Course 2 at 1,700 mg/m(2) /day. Of 29 response-evaluable patients, six had stable disease (SD) (4-26 courses); four with marrow- or bone disease-only had complete responses (CR) (10-46 courses). 4-HPR plasma levels were several folds higher (P < 0.05) than previously reported using capsular fenretinide. The Day 6 mean peak 4-HPR plasma level at 1,700 mg/m(2) /day was 21 µM. An MTD was not reached.

CONCLUSIONS

4-HPR/LXS oral powder obtained higher plasma levels, with minimal toxicity and evidence of anti-tumor activity, than a previous capsule formulation. A recommended phase II schedule of 4-HPR/LXS powder is 1,500 mg/m(2) /day, TID, on Days 0-6, of a 21-day course.

Aminoferrocene-based prodrugs and their effects on human normal and cancer cells as well as bacterial cells

Aminoferrocene-based prodrugs are activated under cancer-specific conditions (high concentration of reactive oxygen species, ROS) with the formation of glutathione scavengers (p-quinone methide) and ROS-generating iron complexes. Herein, we explored three structural modifications of these prodrugs in an attempt to improve their properties: (a) the attachment of a -COOH function to the ferrocene fragment leads to the improvement of water solubility and reactivity in vitro but also decreases cell-membrane permeability and biological activity, (b) the alkylation of the N-benzyl residue does not show any significant affect, and (c) the attachment of the second arylboronic acid fragment improves the toxicity (IC50) of the prodrugs toward human promyelocytic leukemia cells (HL-60) from 52 to 12 μM. Finally, we demonstrated that the prodrugs are active against primary chronic lymphocytic leukemia (CLL) cells, with the best compounds exhibiting an IC50 value of 1.5 μM. The most active compounds were found to not affect mononuclear cells and representative bacterial cells.

ERBB4 confers metastatic capacity in Ewing sarcoma

Metastatic spread is the single-most powerful predictor of poor outcome in Ewing sarcoma (ES). Therefore targeting pathways that drive metastasis has tremendous potential to reduce the burden of disease in ES. We previously showed that activation of the ERBB4 tyrosine kinase suppresses anoikis, or detachment-induced cell death, and induces chemoresistance in ES cell lines in vitro. We now show that ERBB4 is transcriptionally overexpressed in ES cell lines derived from chemoresistant or metastatic ES tumours. ERBB4 activates the PI3K-Akt cascade and focal adhesion kinase (FAK), and both pathways contribute to ERBB4-mediated activation of the Rac1 GTPase in vitro and in vivo. ERBB4 augments tumour invasion and metastasis in vivo, and these effects are blocked by ERBB4 knockdown. ERBB4 expression correlates significantly with reduced disease-free survival, and increased expression is observed in metastatic compared to primary patient-matched ES biopsies. Our findings identify a novel ERBB4-PI3K-Akt-FAK-Rac1 pathway associated with aggressive disease in ES. These results predict that therapeutic targeting of ERBB4, alone or in combination with cytotoxic agents, may suppress the metastatic phenotype in ES.

Dihydroceramide accumulation and reactive oxygen species are distinct and nonessential events in 4-HPR-mediated leukemia cell death

4-(Hydroxyphenyl)retinamide (4-HPR) is a synthetic retinoid with a strong apoptotic effect towards different cancer cell lines in vitro, and it is currently tested in clinical trials. Increases of reactive oxygen species (ROS) and modulation of endogenous sphingolipid levels are well-described events observed upon 4-HPR treatment, but there is still a lack of understanding of their relationship and their contribution to cell death. LC-MS analysis of sphingolipids revealed that in human leukemia CCRF-CEM and Jurkat cells, 4-HPR induced dihydroceramide but not ceramide accumulation even at sublethal concentrations. Myriocin prevented the 4-HPR-induced dihydroceramide accumulation, but it did not prevent the loss of viability and increase of intracellular ROS production. On the other hand, ascorbic acid, Trolox, and vitamin E reversed 4-HPR effects on cell death but not dihydroceramide accumulation. NDGA, described as a lipoxygenase inhibitor, exerted a significantly higher antioxidant activity than vitamin E and abrogated 4-HPR-mediated ROS. It did not however rescue cellular viability. Taken together, this study demonstrates that early changes observed upon 4-HPR treatment, i.e., sphingolipid modulation and ROS production, are mechanistically independent events. Furthermore, the results indicate that 4-HPR-driven cell death may occur even in the absence of dihydroceramide or ROS accumulation. These observations should be taken into account for an improved design of drug combinations.

Fenretinide (4-HPR): a preventive chance for women at genetic and familial risk?

The incidence and mortality of breast cancer have been recently influenced by several new therapeutic strategies. In particular our knowledge on cancer precursors, risk biomarkers, and genetics has considerably increased, and prevention strategies are being successfully explored. Since their discovery, retinoids, the natural and synthetic derivatives of vitamin A, have been known to play a crucial role in cell and tissue differentiation and their ability to inhibit carcinogenesis has made them the ideal chemopreventive agents studied in several preclinical and clinical trials. Fenretinide (4-HPR) is the most studied retinoid in breast cancer chemoprevention clinical trials due to its selective accumulation in breast tissue and its favorable toxicological profile. This agent showed a significative reduction of the incidence of second breast tumors in premenopausal women confirmed after 15-year followups. Considering Fenretinide protective action, a similar trend on ovarian cancer, this drug warrants reevaluations as a preventive agent for high-risk young women, such as BRCA-1 and 2 mutation carriers or with a high familial risk. This favorable effect therefore provides a strong rationale for a primary prevention trial in these unaffected cohort of women.

A central role for long non-coding RNA in cancer

Long non-coding RNAs (ncRNAs) have been shown to regulate important biological processes that support normal cellular functions. Aberrant regulation of these essential functions can promote tumor development. In this review, we underscore the importance of the regulatory role played by this distinct class of ncRNAs in cancer-associated pathways that govern mechanisms such as cell growth, invasion, and metastasis. We also highlight the possibility of using these unique RNAs as diagnostic and prognostic biomarkers in malignancies.

Heterogeneous role of the glutathione antioxidant system in modulating the response of ESFT to fenretinide in normoxia and hypoxia

Glutathione (GSH) is implicated in drug resistance mechanisms of several cancers and is a key regulator of cell death pathways within cells. We studied Ewing's sarcoma family of tumours (ESFT) cell lines and three mechanistically distinct anticancer agents (fenretinide, doxorubicin, and vincristine) to investigate whether the GSH antioxidant system is involved in the reduced sensitivity to these chemotherapeutic agents in hypoxia. Cell viability and death were assessed by the trypan blue exclusion assay and annexin V-PI staining, respectively. Hypoxia significantly decreased the sensitivity of all ESFT cell lines to fenretinide-induced death, whereas the effect of doxorubicin or vincristine was marginal and cell-line-specific. The response of the GSH antioxidant system in ESFT cell lines to hypoxia was variable and also cell-line-specific, although the level of GSH appeared to be most dependent on de novo biosynthesis rather than recycling. RNAi-mediated knockdown of key GSH regulatory enzymes γ-glutamylcysteine synthetase or glutathione disulfide reductase partially reversed the hypoxia-induced resistance to fenretinide, and increasing GSH levels using N-acetylcysteine augmented the hypoxia-induced resistance in a cell line-specific manner. These observations are consistent with the conclusion that the role of the GSH antioxidant system in modulating the sensitivity of ESFT cells to fenretinide is heterogeneous depending on environment and cell type. This is likely to limit the value of targeting GSH as a therapeutic strategy to overcome hypoxia-induced drug resistance in ESFT. Whether targeting the GSH antioxidant system in conjunction with other therapeutics may benefit some patients with ESFT remains to be seen.

Factors Affecting EWS-FLI1 Activity in Ewing's Sarcoma

Ewing's sarcoma family tumors (ESFT) are characterized by specific chromosomal translocations, which give rise to EWS-ETS chimeric proteins. These aberrant transcription factors are the main pathogenic drivers of ESFT. Elucidation of the factors influencing EWS-ETS expression and/or activity will guide the development of novel therapeutic agents against this fatal disease.

Evaluation of bioactive sphingolipids in 4-HPR-resistant leukemia cells

Background

N-(4-hydroxyphenyl)retinamide (4-HPR, fenretinide) is a synthetic retinoid with potent pro-apoptotic activity against several types of cancer, but little is known regarding mechanisms leading to chemoresistance. Ceramide and, more recently, other sphingolipid species (e.g., dihydroceramide and dihydrosphingosine) have been implicated in 4-HPR-mediated tumor cell death. Because sphingolipid metabolism has been reported to be altered in drug-resistant tumor cells, we studied the implication of sphingolipids in acquired resistance to 4-HPR based on an acute lymphoblastic leukemia model.

Methods

CCRF-CEM cell lines resistant to 4-HPR were obtained by gradual selection. Endogenous sphingolipid profiles and in situ enzymatic activities were determined by LC/MS, and resistance to 4-HPR or to alternative treatments was measured using the XTT viability assay and annexin V-FITC/propidium iodide labeling.

Results

No major crossresistance was observed against other antitumoral compounds (i.e. paclitaxel, cisplatin, doxorubicin hydrochloride) or agents (i.e. ultra violet C, hydrogen peroxide) also described as sphingolipid modulators. CCRF-CEM cell lines resistant to 4-HPR exhibited a distinctive endogenous sphingolipid profile that correlated with inhibition of dihydroceramide desaturase. Cells maintained acquired resistance to 4-HPR after the removal of 4-HPR though the sphingolipid profile returned to control levels. On the other hand, combined treatment with sphingosine kinase inhibitors (unnatural (dihydro)sphingosines ((dh)Sph)) and glucosylceramide synthase inhibitor (PPMP) in the presence or absence of 4-HPR increased cellular (dh)Sph (but not ceramide) levels and were highly toxic for both parental and resistant cells.

Conclusions

In the leukemia model, acquired resistance to 4-HPR is selective and persists in the absence of sphingolipid profile alteration. Therapeutically, the data demonstrate that alternative sphingolipid-modulating antitumoral strategies are suitable for both 4-HPR-resistant and sensitive leukemia cells. Thus, whereas sphingolipids may not be critical for maintaining resistance to 4-HPR, manipulation of cytotoxic sphingolipids should be considered a viable approach for overcoming resistance.

Characteristics of human Ewing/PNET sarcoma models

Ewing/PNET (peripheral neuroepithelioma) tumors are rare aggressive bone sarcomas occurring in young people. Rare-disease clinical trials can require global collaborations and many years. In vivo models that as accurately as possible reflect the clinical disease are helpful in selecting therapeutics with the most promise of positive clinical impact. Human Ewing/PNET sarcoma cell lines developed over the past 45 years are described. Several of these have undergone genetic analysis and have been confirmed to be those of Ewing/PNET sarcoma. The A673 Ewing sarcoma line has proven to be particularly useful in understanding the biology of this disease in the mouse. The chromosomal translocation producing the EWS/FLI1 fusion transcript characterizes clinical Ewing sarcoma. Cell lines that express this genetic profile are confirmed to be those of Ewing sarcoma. The A673 Ewing sarcoma line grows in culture and as a xenograft in immunodeficient mice. The A673 model has been used to study Ewing sarcoma angiogenesis and response to antiangiogenic agents. Many Ewing sarcoma clinical specimens express the cell surface protein endosialin. Several Ewing sarcoma cell lines, including the A673 line, also express cell surface endosialin when grown as subcutaneous tumor nodules and as disseminated disease; thus the A673 is a useful model for the study of endosialin biology and endosialin-directed therapies. With the advent of tools that allow characterization of clinical disease to facilitate optimal treatment, it becomes imperative, especially for rare tumors, to develop preclinical models reflecting disease subsets. Ewing PNET sarcomas are a rare disease where models are available.

National Cancer Institute pediatric preclinical testing program: model description for in vitro cytotoxicity testing

BACKGROUND

The National Cancer Institute (NCI) has established the Pediatric Preclinical Testing Program (PPTP) for testing drugs against in vitro and in vivo childhood cancer models to aid in the prioritization of drugs considered for early phase pediatric clinical trials.

PROCEDURES

In vitro cytotoxicity testing employs a semi-automated fluorescence-based digital imaging cytotoxicity assay (DIMSCAN) that has a 4-log dynamic range of detection. Curve fitting of the fractional survival data of the cell lines in response to various concentrations of the agents was used to calculate relative IC(50) , absolute IC(50) , and Y(min) values. The panel of 23 pediatric cancer cell lines included leukemia (n = 6), lymphoma (n = 2), rhabdomyosarcoma (n = 4), brain tumors (n = 3), Ewing family of tumors (EFT, n = 4), and neuroblastoma (n = 4). The doubling times obtained using DIMSCAN were incorporated into data analyses to estimate the relationship between input cell numbers and final cell number.

RESULTS

We report in vitro activity data for three drugs (vincristine, melphalan, and etoposide) that are commonly used for pediatric cancer and for the mTOR inhibitor rapamycin, an agent that is currently under preclinical investigation for cancer. To date, the PPTP has completed in vitro testing of 39 investigational and approved agents for single drug activity and two investigational agents in combination with various "standard" chemotherapy drugs.

CONCLUSIONS

This robust in vitro cytotoxicity testing system for pediatric cancers will enable comparisons to response data for novel agents obtained from xenograft studies and from clinical trials.

Preferential involvement of both ROS and ceramide in fenretinide-induced apoptosis of HL60 rather than NB4 and U937 cells

Leukemic cells responding to apoptosis-inducing drugs can be varied in terms of the mechanisms of action. Fenretinide, a synthetic retinoid, is worth of study as a promising candidate for apoptosis-based therapy of leukemia. Yet, it remains unclear whether this drug exerts the similar mechanisms on different leukemic cells. Here, we report a comparative analysis of fenretinide-induced apoptosis in three acute myeloid leukemic (AML) cell lines including HL60, NB4 and U937. Through a series of antagonist assays, we revealed similarities and differences of mechanisms involved in these three cell lines. Antioxidant vitamin C completely abrogated fenretinide-induced apoptosis in all cell lines, demonstrating that ROS is an essential and common mediator. However, the apoptotic effects of fenretinide could be blocked by ceramide synthase inhibitor fumonisin B1 only in HL60 rather than the other two. Moreover, fumonisin B1 was unable to inhibit the generation of ROS in fenretinide-treated HL60 cells, indicating that ROS may function as upstream stimulus of ceramide-mediated apoptosis. These comparative results strongly suggest that the apoptotic response induced by fenretinide in HL60 involves both ROS and ceramide, whereas drug-induced apoptosis in NB4 and U937 requires ROS but is independent of ceramide. Differentiated modes of action exerting on AML may guide the use of this apoptosis-inducing drug, and hence advance our knowledge about the nature of cancer-specific responses to this drug.

Induction of Mitochondrial Pathways and Endoplasmic Reticulum Stress for Increasing Apoptosis in Ectopic and Orthotopic Neuroblastoma Xenografts

Cancers are characterized by dysregulation of multiple signaling pathways and thus monotherapies are hardly effective. Neuroblastoma, which often occurs in adrenal glands, is the most common childhood malignancy. Malignant neuroblastoma resists traditional treatments and further studies are needed for effective therapeutic interventions. We evaluated synergistic efficacy of N-(4-hydroxyphenyl) retinamide (4-HPR) and genistein (GST) for induction of apoptosis in human malignant neuroblastoma SH-SY5Y and SK-N-BE2 cells in culture and activation of multiple pathways for increasing apoptosis in ectopic and orthotopic neuroblastoma xenografts in nude mice. Combination of 4-HPR and GST synergistically reduced cell viability, caused subG1 accumulation, increased caspase-3 activity for apoptosis in vitro and reduced tumor growth in vivo. Western blotting indicated that combination therapy down regulated Id2 to induce differentiation, increased pro-apoptotic Bax and decreased anti-apoptotic Bcl-2 leading to an increase in Bax:Bcl-2 ratio, increased mitochondrial Bax level, caused mitochondrial release of Smac/Diablo, down regulation of the baculovirus inhibitor-of-apoptosis repeat containing (BIRC) proteins such as BIRC-2 and BIRC-3, and activation of calpain and caspase-3 in SH-SY5Y xenografts. Accumulation of apoptosis-inducing-factor (AIF) in cytosol and increase in caspase-4 activation suggested involvement of mitochondrial pathway and endoplasmic reticulum (ER) stress, respectively, for apoptosis in SH-SY5Y xenografts. In situ immunofluorescent labelings of SH-SY5Y and SK-N-BE2 xenograft sections showed overexpression of calpain, caspase-12, and caspase-3, and AIF, suggesting induction of mitochondrial caspase-dependent and caspase-independent pathways for apoptosis. Collectively, synergistic effects of 4-HPR and GST induced mitochondrial pathways and also ER stress for increasing apoptosis in ectopic and orthotopic neuroblastoma xenografts in nude mice.

N-(4-Hydroxyphenyl) Retinamide Potentiated Anti-tumor Efficacy of Genistein in Human Ewing's Sarcoma Xenografts

Background

Ewing’s sarcoma is a pediatric tumor that mainly occurs in soft tissues and bones. New therapeutic strategies are urgently needed for treatment of Ewing’s sarcoma. We examined for the first time the efficacy of N-(4-hydroxyphenyl) retinamide (4-HPR) and genistein (GST) alone and also in combination for controlling growth of human Ewing’s sarcoma SK-N-MC and RD-ES xenografts.

Methods

Efficacy of combination therapy was evaluated using histopathological parameters. Molecular mechanisms of combination therapy were detected using Western blotting and immunofluorescence microscopy.

Results

Histopathological examination of tumor sections showed that control group maintained characteristic growth of tumors, 4-HPR alone inhibited proliferation of tumor cells, GST alone induced apoptosis to some extent, and combination of 4-HPR and GST significantly induced apoptosis in both Ewing’s sarcoma xenografts. Time-dependent reductions in body weight, tumor volume, and tumor weight were also found. Combination therapy increased Bax : Bcl-2 ratio to trigger mitochondrial release of Smac/Diablo into the cytosol to downregulate the baculovirus inhibitor-of-apoptosis repeat containing (BIRC) proteins such as BIRC-2 and BIRC-3 and thereby promote apoptosis. Activation of caspase-3 and mitochondrial release of apoptosis-inducing factor (AIF) occurred in course of apoptosis. Downregulation of the survival factor NF-κB and the angiogenic factors VEGF and FGF2 and increase in caspase-3 activity controlled tumor growth. In situ immunofluorescent labelings showed overexpression of calpain, caspase-12 and caspase-3, and AIF in xenografts, indicating induction of cysteine proteases and AIF for apoptosis.

Conclusions

Results revealed that combination of 4-HPR and GST could be highly effective treatment for inhibiting Ewing’s sarcomas in vivo.

The majority of total nuclear-encoded non-ribosomal RNA in a human cell is 'dark matter' un-annotated RNA

Background

Discovery that the transcriptional output of the human genome is far more complex than predicted by the current set of protein-coding annotations and that most RNAs produced do not appear to encode proteins has transformed our understanding of genome complexity and suggests new paradigms of genome regulation. However, the fraction of all cellular RNA whose function we do not understand and the fraction of the genome that is utilized to produce that RNA remain controversial. This is not simply a bookkeeping issue because the degree to which this un-annotated transcription is present has important implications with respect to its biologic function and to the general architecture of genome regulation. For example, efforts to elucidate how non-coding RNAs (ncRNAs) regulate genome function will be compromised if that class of RNAs is dismissed as simply 'transcriptional noise'.

Results

We show that the relative mass of RNA whose function and/or structure we do not understand (the so called 'dark matter' RNAs), as a proportion of all non-ribosomal, non-mitochondrial human RNA (mt-RNA), can be greater than that of protein-encoding transcripts. This observation is obscured in studies that focus only on polyA-selected RNA, a method that enriches for protein coding RNAs and at the same time discards the vast majority of RNA prior to analysis. We further show the presence of a large number of very long, abundantly-transcribed regions (100's of kb) in intergenic space and further show that expression of these regions is associated with neoplastic transformation. These overlap some regions found previously in normal human embryonic tissues and raises an interesting hypothesis as to the function of these ncRNAs in both early development and neoplastic transformation.

Conclusions

We conclude that 'dark matter' RNA can constitute the majority of non-ribosomal, non-mitochondrial-RNA and a significant fraction arises from numerous very long, intergenic transcribed regions that could be involved in neoplastic transformation.

Hypoxia-induced neuronal apoptosis is mediated by de novo synthesis of ceramide through activation of serine palmitoyltransferase

Cellular hypoxia can lead to cell death or adaptation and has important effects on development, physiology, and pathology. Here, we investigated the role and regulation of ceramide in hypoxia-induced apoptosis of SH-SY5Y neuroblastoma cells. Hypoxia increased the ceramide concentration; subsequently, we observed biochemical changes indicative of apoptosis, such as DNA fragmentation, nuclear staining, and poly ADP-ribose polymerase (PARP) cleavage. The hypoxic cell death was potently inhibited by a caspase inhibitor, zVAD-fmk (benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone). l-Cycloserine, a serine palmitoyltransferase (SPT) inhibitor, and fumonisin B(1) (FB(1)), a ceramide synthase inhibitor, inhibited the hypoxia-induced increase in ceramide, indicating that the increase occurred via the de novo pathway. Hypoxia increased the activity and protein levels of SPT2, suggesting that the hypoxia-induced increase in ceramide is due to the transcriptional up-regulation of SPT2. Specific siRNA of SPT2 prevented hypoxia-induced cell death and ceramide production. However, hypoxia also increased the cellular level of glucosylceramide, which was inhibited by a glucosylceramide synthase (GCS) inhibitor and specific siRNA, but not a ceramidase inhibitor. The increase in glucosylceramide was accompanied by increases in both PARP cleavage and DNA fragmentation. Together, the current results suggest that both SPT and GCS may regulate the cellular level of ceramide, and thus may be critical enzymes for deciding the fate of the cells exposed to hypoxia.

Oral fenretinide in biochemically recurrent prostate cancer: a California cancer consortium phase II trial

BACKGROUND

Fenretinide is a synthetic retinoid that is cytotoxic to a variety of cancers. We conducted a phase II trial of oral fenretinide in patients with biochemically recurrent prostate cancer.

PATIENTS AND METHODS

Eligible patients had histologically confirmed prostate cancer and a confirmed rising prostate-specific antigen (PSA) >or= 2 ng/mL following either radical prostatectomy and/or pelvic radiation therapy, without clinical or radiographic evidence of metastasis. The primary endpoint was PSA response, which was defined as a confirmed decrease by >or=50%, and >or=5 ng/mL, from the pretreatment value. Treatment comprised oral fenretinide 900 mg/m2 twice daily for 1 week, every 3 weeks, for 1 year.

RESULTS

After a median follow-up of 17.7 months, out of 23 patients, 7 (30%) patients had PSA stable disease (SD), 11 (48%) patients had PSA progression within 3 months, 4 patients had minimal increases over 3 months that did not qualify as SD or progression (17%), and one patient (4%) was not evaluable. Median time to PSA progression was 4.6 months (95% CI, 3.2-8.2 months). Observed grade 3 toxicities included fatigue, pain, hypermagnesemia, a rise in lipase, and nyctalopia.

CONCLUSION

Although well-tolerated, oral fenretinide did not meet prespecified PSA criteria for response in biochemically recurrent prostate cancer; however, 30% of patients had SD, which suggests modest single-agent clinical activity. The role of different formulations of fenretinide, which might allow for higher serum concentrations of the drug, is currently under investigation.