The crosstalk between non-coding RNAs and cell-cycle events: A new frontier in cancer therapy

The cell cycle comprises sequential events during which a cell duplicates its genome and divides it into two daughter cells. This process is tightly regulated to ensure that the daughter cell receives identical copied chromosomal DNA and that any errors in the DNA during replication are correctly repaired. Cyclins and their enzyme partners, cyclin-dependent kinases (CDKs), are critical regulators of G- to M-phase transitions during the cell cycle. Mitogenic signals induce the formation of the cyclin/CDK complexes, resulting in phosphorylation and activation of the CDKs. Once activated, cyclin/CDK complexes phosphorylate specific substrates that drive the cell cycle forward. The sequential activation and inactivation of cyclin-CDK complexes are tightly controlled by activating and inactivating phosphorylation events induced by cell-cycle proteins. The non-coding RNAs (ncRNAs), which do not code for proteins, regulate cell-cycle proteins at the transcriptional and translational levels, thereby controlling their expression at different cell-cycle phases. Deregulation of ncRNAs can cause abnormal expression patterns of cell-cycle-regulating proteins, resulting in abnormalities in cell-cycle regulation and cancer development. This review explores how ncRNA dysregulation can disrupt cell division balance and discusses potential therapeutic approaches targeting these ncRNAs to control cell-cycle events in cancer treatment.

Marinopyrrole derivative MP1 as a novel anti-cancer agent in group 3 MYC-amplified Medulloblastoma

BACKGROUND

Medulloblastoma (MB) patients with MYC oncogene amplification or overexpression exhibit extremely poor prognoses and therapy resistance. However, MYC itself has been one of the most challenging targets for cancer treatment. Here, we identify a novel marinopyrrole natural derivative, MP1, that shows desirable anti-MYC and anti-cancer activities in MB.

METHODS

In this study, using MYC-amplified (Group 3) and non-MYC amplified MB cell lines in vitro and in vivo, we evaluated anti-cancer efficacies and molecular mechanism(s) of MP1.

RESULTS

MP1 significantly suppressed MB cell growth and sphere counts and induced G2 cell cycle arrest and apoptosis in a MYC-dependent manner. Mechanistically, MP1 strongly downregulated the expression of MYC protein. Our results with RNA-seq revealed that MP1 significantly modulated global gene expression and inhibited MYC-associated transcriptional targets including translation/mTOR targets. In addition, MP1 inhibited MYC-target metabolism, leading to declined energy levels. The combination of MP1 with an FDA-approved mTOR inhibitor temsirolimus synergistically inhibited MB cell growth/survival by downregulating the expression of MYC and mTOR signaling components. Our results further showed that as single agents, both MP1 and temsirolimus, were able to significantly inhibit tumor growth and MYC expression in subcutaneously or orthotopically MYC-amplified MB bearing mice. In combination, there were further anti-MB effects on the tumor growth and MYC expression in mice.

CONCLUSION

These preclinical findings highlight the promise of marinopyrrole MP1 as a novel MYC inhibition approach for MYC-amplified MB.

PRMT5 as a Potential Therapeutic Target in MYC-Amplified Medulloblastoma

MYC amplification or overexpression is most common in Group 3 medulloblastomas and is positively associated with poor clinical outcomes. Recently, protein arginine methyltransferase 5 (PRMT5) overexpression has been shown to be associated with tumorigenic MYC functions in cancers, particularly in brain cancers such as glioblastoma and medulloblastoma. PRMT5 regulates oncogenes, including MYC, that are often deregulated in medulloblastomas. However, the role of PRMT5-mediated post-translational modification in the stabilization of these oncoproteins remains poorly understood. The potential impact of PRMT5 inhibition on MYC makes it an attractive target in various cancers. PRMT5 inhibitors are a promising class of anti-cancer drugs demonstrating preclinical and preliminary clinical efficacies. Here, we review the publicly available preclinical and clinical studies on PRMT5 targeting using small molecule inhibitors and discuss the prospects of using them in medulloblastoma therapy.

Low Motor Dexterity and Significant Behaviors Following Hospitalized Isolation in Children

The main objective of this study was to describe the cortical patterns of brain activity during a gross dexterity task and develop a behavioral profile of children experiencing isolation. A cross-sectional assessment was conducted during one visit. Sample: Four pediatric patients who had undergone isolation within a hospital comprised the full data collection. During the collection, participants completed the Box and Blocks Test of gross manual dexterity while undergoing imaging of the motor cortex using functional near-infrared spectroscopy. Participants also completed a Behavioral Assessment System for Children, Third Edition (BASC-3) self-report, which was analyzed along with a parent report to quantify their emotional and social behaviors. All participants displayed lower gross dexterity levels than normative data. Furthermore, three out of the four participants displayed ipsilateral dominance of the motor cortex during the dexterity task. Three of the participants displayed behavioral measures reported within clinically significant or at-risk scores. Clinically significant behavioral scores coupled with lower than expected manual dexterity values and ipsilateral hemispheric dominance indicate that neuroplastic changes can occur in populations undergoing hospitalized isolation. While the impacts of the treatments and isolation in this case cannot be separated, further studies should be conducted to understand these impacts of isolation.

STAT3 Inhibition Attenuates MYC Expression by Modulating Co-Activator Recruitment and Suppresses Medulloblastoma Tumor Growth by Augmenting Cisplatin Efficacy In Vivo

MB is a common childhood malignancy of the central nervous system, with significant morbidity and mortality. Among the four molecular subgroups, MYC-amplified Group 3 MB is the most aggressive type and has the worst prognosis due to therapy resistance. The present study aimed to investigate the role of activated STAT3 in promoting MB pathogenesis and chemoresistance via inducing the cancer hallmark MYC oncogene. Targeting STAT3 function either by inducible genetic knockdown (KD) or with a clinically relevant small molecule inhibitor reduced tumorigenic attributes in MB cells, including survival, proliferation, anti-apoptosis, migration, stemness and expression of MYC and its targets. STAT3 inhibition attenuates MYC expression by affecting recruitment of histone acetyltransferase p300, thereby reducing enrichment of H3K27 acetylation in the MYC promoter. Concomitantly, it also decreases the occupancy of the bromodomain containing protein-4 (BRD4) and phosphoSer2-RNA Pol II (pSer2-RNAPol II) on MYC, resulting in reduced transcription. Importantly, inhibition of STAT3 signaling significantly attenuated MB tumor growth in subcutaneous and intracranial orthotopic xenografts, increased the sensitivity of MB tumors to cisplatin, and improved the survival of mice bearing high-risk MYC-amplified tumors. Together, the results of our study demonstrate that targeting STAT3 may be a promising adjuvant therapy and chemo-sensitizer to augment treatment efficacy, reduce therapy-related toxicity and improve quality of life in high-risk pediatric patients.

A novel dual epigenetic approach targeting BET proteins and HDACs in Group 3 (MYC-driven) Medulloblastoma

Background

Medulloblastoma (MB) patients with MYC oncogene amplification or overexpression exhibit extremely poor clinical outcomes and respond poorly to current therapies. Epigenetic deregulation is very common in MYC-driven MB. The bromodomain extra-terminal (BET) proteins and histone deacetylases (HDACs) are epigenetic regulators of MYC transcription and its associated tumorigenic programs. This study aimed to investigate the therapeutic potential of inhibiting the BET proteins and HDACs together in MB.

Methods

Using clinically relevant BET inhibitors (JQ1 or OTX015) and a pan-HDAC inhibitor (panobinostat), we evaluated the effects of combined inhibition on cell growth/survival in MYC-amplified MB cell lines and xenografts and examined underlying molecular mechanism(s).

Results

Co-treatment of JQ1 or OTX015 with panobinostat synergistically suppressed growth/survival of MYC-amplified MB cells by inducing G2 cell cycle arrest and apoptosis. Mechanistic investigation using RNA-seq revealed that co-treatment of JQ1 with panobinostat synergistically modulated global gene expression including MYC/HDAC targets. SYK and MSI1 oncogenes were among the top 50 genes synergistically downregulated by JQ1 and panobinostat. RT-PCR and western blot analyses confirmed that JQ1 and panobinostat synergistically inhibited the mRNA and protein expression of MSI1/SYK along with MYC expression. Reduced SYK/MSI expression after BET (specifically, BRD4) gene-knockdown further confirmed the epigenetic regulation of SYK and MSI1 genes. In addition, the combination of OTX015 and panobinostat significantly inhibited tumor growth in MYC-amplified MB xenografted mice by downregulating expression of MYC, compared to single-agent therapy.

Conclusions

Together, our findings demonstrated that dual-inhibition of BET and HDAC proteins of the epigenetic pathway can be a novel therapeutic approach against MYC-driven MB.

Multifarious Functions of Butyrylcholinesterase in Neuroblastoma: Impact of BCHE Deletion on the Neuroblastoma Growth In Vitro and In Vivo

The physiological functions of butyrylcholinesterase (BChE) and its role in malignancy remain unexplained. Our studies in children newly diagnosed with neuroblastoma indicated that BChE expressions is proportional to MYCN amplification suggesting that pathogenesis of high-risk disease may be related to the persistent expression of abnormally high levels of tumor-associated BChE. BChE-deficient neuroblastoma cells (KO [knockout]) were produced from MYCN -amplified BE(2)-C cells (WT [wild-type]) by the CRISPR-Cas9 targeted disruption of the BCHE locus. KO cells have no detectable BChE activity. The compensatory acetylcholinesterase activity was not detected. The average population doubling time of KO cells is 47.0±2.4 hours, >2× longer than WT cells. Reduced proliferation rates of KO cells were accompanied by the loss of N-Myc protein and a significant deactivation of tyrosine kinase receptors associated with the aggressive neuroblastoma phenotype including Ros1, TrkB, and Ltk. Tumorigenicity of WT and KO cells in male mice was essentially identical. In contrast, KO xenografts in female mice were very small (0.37±0.10 g), ~3× smaller compared with WT xenografts (1.11±0.30 g). Unexpectedly, KO xenografts produced changes in plasma BChE similarly to WT tumors but lesser in magnitude. The disruption of BCHE locus in MYCN -amplified neuroblastoma cells decelerates proliferation and produces neuroblastoma cells that are less aggressive in female mice.

Immune checkpoint molecules in neuroblastoma: A clinical perspective

High-risk neuroblastoma (NB) is challenging to treat with 5-year long-term survival in patients remaining below 50% and low chances of survival after tumor relapse or recurrence. Different strategies are being tested or under evaluation to destroy resistant tumors and improve survival outcomes in NB patients. Immunotherapy, which uses certain parts of a person's immune system to recognize or kill tumor cells, effectively improves patient outcomes in several types of cancer, including NB. One of the immunotherapy strategies is to block immune checkpoint signaling in tumors to increase tumor immunogenicity and anti-tumor immunity. Immune checkpoint proteins put brakes on immune cell functions to regulate immune activation, but this activity is exploited in tumors to evade immune surveillance and attack. Immune checkpoint proteins play an essential role in NB biology and immune escape mechanisms, which makes these tumors immunologically cold. Therapeutic strategies to block immune checkpoint signaling have shown promising outcomes in NB but only in a subset of patients. However, combining immune checkpoint blockade with other therapies, including conjugated antibody-based immunotherapy, radioimmunotherapy, tumor vaccines, or cellular therapies like modified T or natural killer (NK) cells, has shown encouraging results in enhancing anti-tumor immunity in the preclinical setting. An analysis of publicly available dataset using computational tools has unraveled the complexity of multiple cancer including NB. This review comprehensively summarizes the current information on immune checkpoint molecules, their biology, role in immune suppression and tumor development, and novel therapeutic approaches combining immune checkpoint inhibitors with other therapies to combat high-risk NB.

Abstract 2349: SAP30, a novel drug response specific transcription factor in high-risk neuroblastoma

Neuroblastoma is the most devastating extracranial solid malignancy in children. Despite an intense treatment regimen, the prognosis for high-risk neuroblastoma patients remains poor, with less than 40% survival. So far, MYCN status/amplification is considered the most prognostic factor but corresponds to only 25% of neuroblastoma patients. Therefore, it is essential to identify a better prognosis and prediction marker of therapy response in neuroblastoma patients. The identification of master regulators with good prognostic and drug response abilities are not successful due to the complexity and lack of data-driven bioinformatic workflows. We applied robust bioinformatic data mining tools such as Weighted Gene Co-expression Network Analysis, cisTarget, and Single-Cell rEgulatory Network Inference and Clustering on three neuroblastoma patient datasets (n=1252). We found Sin3A Associated Protein 30 (Sap30), a driver transcription factor positively associated with high-risk, progression, stage 4, and poor survival in high-risk neuroblastoma patient cohorts. Tumors of high-risk neuroblastoma patients and relapse-specific patient-derived xenografts showed higher Sap30 levels. The Genomics of Drug Sensitivity in Cancer, The Cancer Cell Line Encyclopedia, and CRISPR-Cas9 screens indicated that Sap30 essentiality is associated with Cisplatin resistance and further showed higher levels in Cisplatin resistant patient-derived xenograft tumor cell lines. The silencing of Sap30 in cells reduced cell growth, induced cell death, mitochondrial membrane potential loss in vitro, and reduced tumorigenicity in vivo. Altogether, these results indicate that Sap30 is a novel prognostic and Cisplatin resistant marker and thus a potential drug target in high-risk neuroblastoma patients.

Citation Format: Philip Prathipati, Anup S. Pathania, Nagendra K. Chaturvedi, Subash C. Gupta, Siddappa N. Byrareddy, Don W. Coulter, Kishore B. Challagundla. SAP30, a novel drug response specific transcription factor in high-risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2349.

miR-15a and miR-15b modulate natural killer and CD8+T-cell activation and anti-tumor immune response by targeting PD-L1 in neuroblastoma

Neuroblastoma (NB) is an enigmatic and deadliest pediatric cancer to treat. The major obstacles to the effective immunotherapy treatments in NB are defective immune cells and the immune evasion tactics deployed by the tumor cells and the stromal microenvironment. Nervous system development during embryonic and pediatric stages is critically mediated by non-coding RNAs such as micro RNAs (miR). Hence, we explored the role of miRs in anti-tumor immune response via a range of data-driven workflows and in vitro & in vivo experiments. Using the TARGET, NB patient dataset (n=249), we applied the robust bioinformatic workflows incorporating differential expression, co-expression, survival, heatmaps, and box plots. We initially demonstrated the role of miR-15a-5p (miR-15a) and miR-15b-5p (miR-15b) as tumor suppressors, followed by their negative association with stromal cell percentages and a statistically significant negative regulation of T and natural killer (NK) cell signature genes, especially CD274 (PD-L1) in stromal-low patient subsets. The NB phase-specific expression of the miR-15a/miR-15b-PD-L1 axis was further corroborated using the PDX (n=24) dataset. We demonstrated miR-15a/miR-15b mediated degradation of PD-L1 mRNA through its interaction with the 3'-untranslated region and the RNA-induced silencing complex using sequence-specific luciferase activity and Ago2 RNA immunoprecipitation assays. In addition, we established miR-15a/miR-15b induced CD8⁺T and NK cell activation and cytotoxicity against NB in vitro. Moreover, injection of murine cells expressing miR-15a reduced tumor size, tumor vasculature and enhanced the activation and infiltration of CD8⁺T and NK cells into the tumors in vivo. We further established that blocking the surface PD-L1 using an anti-PD-L1 antibody rescued miR-15a/miR-15b induced CD8⁺T and NK cell-mediated anti-tumor responses. These findings demonstrate that miR-15a and miR-15b induce an anti-tumor immune response by targeting PD-L1 in NB.

Histiocytic Neoplasms, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

Histiocytic neoplasms are rare hematologic disorders accounting for less than 1% of cancers of the soft tissue and lymph nodes. Clinical presentation and prognosis of these disorders can be highly variable, leading to challenges for diagnosis and optimal management of these patients. Treatment often consists of systemic therapy, and recent studies support use of targeted therapies for patients with these disorders. Observation ("watch and wait") may be sufficient for select patients with mild disease. These NCCN Guidelines for Histiocytic Neoplasms include recommendations for diagnosis and treatment of adults with the most common histiocytic disorders: Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease.

Synergistic efficacy of inhibiting MYCN and mTOR signaling against neuroblastoma

BACKGROUND

Neuroblastoma (NB) patients with MYCN amplification or overexpression respond poorly to current therapies and exhibit extremely poor clinical outcomes. PI3K-mTOR signaling-driven deregulation of protein synthesis is very common in NB and various other cancers that promote MYCN stabilization. In addition, both the MYCN and mTOR signaling axes can directly regulate a common translation pathway that leads to increased protein synthesis and cell proliferation. However, a strategy of concurrently targeting MYCN and mTOR signaling in NB remains unexplored. This study aimed to investigate the therapeutic potential of targeting dysregulated protein synthesis pathways by inhibiting the MYCN and mTOR pathways together in NB.

METHODS

Using small molecule/pharmacologic approaches, we evaluated the effects of combined inhibition of MYCN transcription and mTOR signaling on NB cell growth/survival and associated molecular mechanism(s) in NB cell lines. We used two well-established BET (bromodomain extra-terminal) protein inhibitors (JQ1, OTX-015), and a clinically relevant mTOR inhibitor, temsirolimus, to target MYCN transcription and mTOR signaling, respectively. The single agent and combined efficacies of these inhibitors on NB cell growth, apoptosis, cell cycle and neurospheres were assessed using MTT, Annexin-V, propidium-iodide staining and sphere assays, respectively. Effects of inhibitors on global protein synthesis were quantified using a fluorescence-based (FamAzide)-based protein synthesis assay. Further, we investigated the specificities of these inhibitors in targeting the associated pathways/molecules using western blot analyses.

RESULTS

Co-treatment of JQ1 or OTX-015 with temsirolimus synergistically suppressed NB cell growth/survival by inducing G1 cell cycle arrest and apoptosis with greatest efficacy in MYCN-amplified NB cells. Mechanistically, the co-treatment of JQ1 or OTX-015 with temsirolimus significantly downregulated the expression levels of phosphorylated 4EBP1/p70-S6K/eIF4E (mTOR components) and BRD4 (BET protein)/MYCN proteins. Further, this combination significantly inhibited global protein synthesis, compared to single agents. Our findings also demonstrated that both JQ1 and temsirolimus chemosensitized NB cells when tested in combination with cisplatin chemotherapy.

CONCLUSIONS

Together, our findings demonstrate synergistic efficacy of JQ1 or OTX-015 and temsirolimus against MYCN-driven NB, by dual-inhibition of MYCN (targeting transcription) and mTOR (targeting translation). Additional preclinical evaluation is warranted to determine the clinical utility of targeted therapy for high-risk NB patients.

Pediatric Hodgkin Lymphoma, Version 3.2021

Hodgkin lymphoma (HL) is a highly curable form of cancer, and current treatment regimens are focused on improving treatment efficacy while decreasing the risk of late effects of treatment. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for pediatric HL provide recommendations on the workup, diagnostic evaluation, and treatment of classic HL, including principles of pathology, imaging, staging, systemic therapy, and radiation therapy. This portion of the NCCN Guidelines focuses on the management of pediatric classic HL in the upfront and relapsed/refractory settings.

The emerging role of non-coding RNAs in the epigenetic regulation of pediatric cancers

Epigenetics is a process that involves the regulation of gene expression without altering the sequence of DNA. Numerous studies have documented that epigenetic mechanisms play a critical role in cell growth, differentiation, and cancer over the past decade. The well-known epigenetic modifications are either on DNA or at the histone proteins. Although several studies have focused on regulating gene expression by non-coding RNAs, the current understanding of their biological functions in various human diseases, particularly in cancers, is inadequate. Only about two percent of DNA is involved in coding the protein-coding genes, and leaving the rest 98 percent is non-coding and the scientific community regarded as junk or noise with no known purpose. Most non-coding RNAs are derived from such junk DNA and are known to be involved in various signaling pathways involving cancer initiation, progression, and the development of therapy resistance in many human cancer types. Recent studies have suggested that non-coding RNAs, especially microRNAs, piwi-interactingRNAs, and long non-coding RNAs, play a significant role in controlling epigenetic mechanism(s), indicating the potential effect of epigenetic modulation of non-coding RNAs on cancer progression. In this review article, we briefly presented epigenetic marks' characteristics, crosstalk between epigenetic modifications and microRNAs, piwi-interactingRNAs, and long non-coding RNAs to uncover the effect on the phenotype of pediatric cancers. Further, current knowledge on understanding the RNA epigenetics will help design novel therapeutics that target epigenetic regulatory networks to benefit cancer patients in the clinic.

Preliminary preclinical study of Chol-DsiRNA polyplexes formed with PLL[30]-PEG[5K] for the RNAi-based therapy of breast cancer

RNA interference molecules have tremendous potential for cancer therapy but are limited by insufficient potency after i.v. administration. We previously found that Chol-DsiRNA polyplexes formed between cholesterol-modified dicer-substrate siRNA (Chol-DsiRNA) and the cationic diblock copolymer PLL[30]-PEG[5K] greatly increase the activity of Chol-DsiRNA against a stably expressed reporter mRNA in primary murine syngeneic breast tumors after daily i.v. dosing. Here, we provide a more thorough preliminary preclinical study of Chol-DsiRNA polyplexes against the therapeutically relevant target protein, STAT3. We found that Chol-DsiSTAT3 polyplexes greatly increase plasma exposure, distribution, potency, and therapeutic activity of Chol-DsiSTAT3 in primary murine syngeneic 4T1 breast tumors after i.v. administration. Furthermore, inactive Chol-DsiCTRL polyplexes are well tolerated by healthy female BALB/c mice after chronic i.v. administration at 50 mg Chol-DsiCTRL/kg over 28 days. Thus, Chol-DsiRNA polyplexes may be a good candidate for Phase I clinical trials to improve the treatment of breast cancer and other solid tumors.

Amino Acids Regulate Cisplatin Insensitivity in Neuroblastoma

Simple Summary

Neuroblastomas mostly show poor response to the Cisplatin therapy. Amino acids serve as building blocks for proteins, which are acquired either through diet or protein breakdown. Our study reveals high amino acid pools and dependence of Cisplatin-tolerant neuroblastomas cells on amino acids for their survival, especially, in drug treated conditions. Our study also demonstrates that response of neuroblastomas to Cisplatin can be improved by decreasing cellular amino acid levels either by reducing amino acid supplements or by applying autophagy inhibitor, Hydroxychloroquine. Thus, our findings establish that neuroblastomas can be sensitized to Cisplatin by targeting amino acid metabolism.

Abstract

Neuroblastoma are pediatric, extracranial malignancies showing alarming survival prognosis outcomes due to their resilience to current aggressive treatment regimens, including chemotherapies with cisplatin (CDDP) provided in the first line of therapy regimens. Metabolic deregulation supports tumor cell survival in drug-treated conditions. However, metabolic pathways underlying cisplatin-resistance are least studied in neuroblastoma. Our metabolomics analysis revealed that cisplatin-insensitive cells alter their metabolism; especially, the metabolism of amino acids was upregulated in cisplatin-insensitive cells compared to the cisplatin-sensitive neuroblastoma cell line. A significant increase in amino acid levels in cisplatin-insensitive cells led us to hypothesize that the mechanisms upregulating intracellular amino acid pools facilitate insensitivity in neuroblastoma. We hereby report that amino acid depletion reduces cell survival and cisplatin-insensitivity in neuroblastoma cells. Since cells regulate their amino acids levels through processes, such as autophagy, we evaluated the effects of hydroxychloroquine (HCQ), a terminal autophagy inhibitor, on the survival and amino acid metabolism of cisplatin-insensitive neuroblastoma cells. Our results demonstrate that combining HCQ with CDDP abrogated the amino acid metabolism in cisplatin-insensitive cells and sensitized neuroblastoma cells to sub-lethal doses of cisplatin. Our results suggest that targeting of amino acid replenishing mechanisms could be considered as a potential approach in developing combination therapies for treating neuroblastomas.

Long non-coding RNA profiling of pediatric Medulloblastoma

Background

Medulloblastoma (MB) is one of the most common malignant cancers in children. MB is primarily classified into four subgroups based on molecular and clinical characteristics as (1) WNT (2) Sonic-hedgehog (SHH) (3) Group 3 (4) Group 4. Molecular characteristics used for MB classification are based on genomic and mRNAs profiles. MB subgroups share genomic and mRNA profiles and require multiple molecular markers for differentiation from each other. Long non-coding RNAs (lncRNAs) are more than 200 nucleotide long RNAs and primarily involve in gene regulation at epigenetic and post-transcriptional levels. LncRNAs have been recognized as diagnostic and prognostic markers in several cancers. However, the lncRNA expression profile of MB is unknown.

Methods

We used the publicly available gene expression datasets for the profiling of lncRNA expression across MB subgroups. Functional analysis of differentially expressed lncRNAs was accomplished by Ingenuity pathway analysis (IPA).

Results

In the current study, we have identified and validated the lncRNA expression profile across pediatric MB subgroups and associated molecular pathways. We have also identified the prognostic significance of lncRNAs and unique lncRNAs associated with each MB subgroup.

Conclusions

Identified lncRNAs can be used as single biomarkers for molecular identification of MB subgroups that warrant further investigation and functional validation.

A Novel Combination Approach Targeting an Enhanced Protein Synthesis Pathway in MYC-driven (Group 3) Medulloblastoma

The MYC oncogene is frequently amplified in patients with medulloblastoma, particularly in group 3 patients, who have the worst prognosis. mTOR signaling-driven deregulated protein synthesis is very common in various cancers, including medulloblastoma, that can promote MYC stabilization. As a transcription factor, MYC itself is further known to regulate transcription of several components of protein synthesis machinery, leading to an enhanced protein synthesis rate and proliferation. Thus, inhibiting enhanced protein synthesis by targeting the MYC and mTOR pathways together may represent a highly relevant strategy for the treatment of MYC-driven medulloblastoma. Here, using siRNA and small-molecule inhibitor approaches, we evaluated the effects of combined inhibition of MYC transcription and mTOR signaling on medulloblastoma cell growth/survival and associated molecular mechanism(s) in MYC-amplified (group 3) medulloblastoma cell lines and xenografts. Combined inhibition of MYC and mTOR synergistically suppressed medulloblastoma cell growth and induced G₁ cell-cycle arrest and apoptosis. Mechanistically, the combined inhibition significantly downregulated the expression levels of key target proteins of MYC and mTOR signaling. Our results with RNA-sequencing revealed that combined inhibition synergistically modulated global gene expression including MYC/mTOR components. In addition, the combination treatment significantly delayed tumor growth and prolonged survival of MYC-amplified medulloblastoma xenografted mice by downregulating expression of MYC and the key downstream components of mTOR signaling, compared with single-agent therapy. Together, our findings demonstrated that dual inhibition of MYC (transcription) and mTOR (translation) of the protein synthesis pathway can be a novel therapeutic approach against MYC-driven medulloblastoma.

Radiolabeled (R)-(-)-5-iodo-3'-O-[2-(ε-guanidinohexanoyl)-2-phenylacetyl]-2'-deoxyuridine: A new theranostic for neuroblastoma

Neuroblastoma, the most common extracranial solid tumor in children, accounts for nearly 8% of childhood cancers in the United States. It is a disease with pronounced clinical and biological heterogeneities. The amplification of MYCN, whose key tumorigenic functions include the promotion of proliferation, facilitation of the cell's entry into the S phase, and prevention of cells from leaving the cell cycle, correlates with poor prognosis. Patients with a high proliferation index disease have low survival rates. Neuroblastoma is one of the most radioresponsive of all human tumors. To exploit this radiosensitivity, radioactive guanidine (R)-(-)-5-[125 I]iodo-3'-O-[2-(ε-guanidinohexanoyl)-2-phenylacetyl]-2'-deoxyuridine (9, GPAID) was designed. This compound enters neuroblastoma cells much like metaiodobenzylguanidine (MIBG). Additionally, it cotargets DNA of proliferating cells, an attribute especially advantageous in the treatment of MYCN-amplified tumors. GPAID was synthesized from the trimethylstannyl precursor with an average yield of >90% at the no-carrier-added specific activities. The norepinephrine transporter-aided delivery of GPAID to neuroblastoma cells was established in the competitive uptake studies with nonradioactive MIBG. The intracellular processing and DNA targeting properties were confirmed in the subcellular distribution experiments. Studies in a mouse model of neuroblastoma demonstrated the therapeutic potential of GPAID. The tin precursor of GPAID can be used to prepare compounds radiolabeled with single-photon emission computed tomography (SPECT)- and positron-emission tomography (PET)-compatible radionuclides. Accordingly, these reagents can function as theranostics useful in the individualized and comprehensive treatment strategies comprising treatment planning and the assessment of tumor responses as well as the targeted molecular radiotherapy employing treatment doses derived from the imaging data.

Alpha-Particle Therapy for Multifocal Osteosarcoma: A Hypothesis

Osteosarcoma (OST) is the most common bone tumor in children and adolescents with a second peak of incidence in elderly adults usually diagnosed as secondary tumors in Paget's disease or irradiated bone. Subjects with metastatic disease or whose disease relapses after the initial therapy have a poor prognosis. Moreover, multifocal OST contains tumor-initiating cells that are resistant to chemotherapy. The use of aggressive therapies in an attempt to eradicate these cells can have long-term negative consequences in these vulnerable patient populations. ²²⁷Th-labeled molecular probes based on ligands to OST-associated receptors such as IGF-1R (insulin-like growth factor receptor 1), HER2 (human epidermal growth factor receptor 2), and PSMA (prostate-specific membrane antigen) are expected to detect and treat osseous and nonosseous sites of multifocal OST. Published reports indicate that ²²⁷Th has limited myelotoxicity, can be stably chelated to its carriers and, as it decays at targeted sites, ²²⁷Th produces ²²³Ra that is subsequently incorporated into the areas of increased osteoblastic activity, that is, osseous metastatic lesions. Linear energy transfer of α particles emitted by ²²⁷Th and its daughter ²²³Ra is within the range of the optimum relative biological effectiveness. The radiotoxicity of α particles is virtually independent of the phase in the cell cycle, oxygenation, and the dose rate. For these reasons, even resistant OST cells remain susceptible to killing by high-energy α particles, which can also kill adjacent quiescent OST cells or cells with low expression of targeted receptors. Systemic side effects are minimized by the limited range of these intense radiations. Quantitative single-photon emission computed tomography of ²²⁷Th and ²²³Ra is feasible. Additionally, the availability of radionuclide pairs, for example, ⁸⁹Zr for positron emission tomography and ²²⁷Th for therapy, establish a strong basis for the theranostic use of ²²⁷Th in the individualized treatment of multifocal OST.

miR-15a-5p, miR-15b-5p, and miR-16-5p inhibit tumor progression by directly targeting MYCN in neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid malignancy in children. Despite current aggressive treatment regimens, the prognosis for high-risk NB patients remains poor, with the survival of less than 40%. Amplification/stabilization of MYCN oncogene, in NB is associated with a high risk of recurrence. Thus, there is an urgent need for novel therapeutics. The deregulated expression of microRNA (miR) is reported in NB; nonetheless, its effect on MYCN regulation is poorly understood. First, we identified that miR-15a-5p, miR-15b-5p, and miR-16-5p (hereafter miR-15a, miR-15b or miR-16) were down-regulated in patient-derived xenografts (PDX) with high MYCN expression. MiR targeting sequences on MYCN mRNA were predicted using online databases such as TargetScan and miR database. The R2 database, containing 105 NB patients, showed an inverse correlation between MYCN mRNA and deleted in lymphocytic leukemia (DLEU) 2, a host gene of miR-15. Moreover, overexpression of miR-15a, miR-15b or miR-16 significantly reduced the levels of MYCN mRNA and N-Myc protein. Conversely, inhibiting miR dramatically enhanced MYCN mRNA and N-Myc protein levels, as well as increasing mRNA half-life in NB cells. By performing immunoprecipitation assays of argonaute-2 (Ago2), a core component of the RNA-induced silencing complex, we showed that miR-15a, miR-15b and miR-16 interact with MYCN mRNA. Luciferase reporter assays showed that miR-15a, miR-15b and miR-16 bind with 3'UTR of MYCN mRNA, resulting in MYCN suppression. Moreover, induced expression of miR-15a, miR-15b and miR-16 significantly reduced the proliferation, migration, and invasion of NB cells. Finally, transplanting miR-15a-, miR-15b- and miR-16-expressing NB cells into NSG mice repressed tumor formation and MYCN expression. These data suggest that miR-15a, miR-15b and miR-16 exert a tumor-suppressive function in NB by targeting MYCN. Therefore, these miRs could be considered as potential targets for NB treatment.

Biological Evaluation of a Potential Anticancer Agent Methyl N-[5-(3'-Iodobenzoyl)-1H-Benzimidazol-2-yl]Carbamate

Background: Resistance of cancer to chemo- and radiotherapy remains a major clinical problem. This study contributes to the ongoing search for agents that can bypass this resistance by developing a novel antimitotic theranostic. Materials and Methods: Methyl N-[5-(3'-iodobenzoyl)-1H-benzimidazol-2-yl]carbamates 1 and 2 were synthesized from a common precursor 3 or its 3'-stannylated derivative. The cytotoxicity of compound 1 was evaluated in several neuroblastoma and glioblastoma cell lines and in the NCI 60-cell assay. Biodistribution was conducted in mice after oral administration of compound 2 to determine tissue and brain uptake. Result: Lethal concentrations (LC₅₀s) of compound 1 in neuroblastoma and glioblastoma are >15 × lower compared with compound 3, a drug currently tested in clinical studies in pediatric and adult brain tumors. Growth inhibition concentrations (GI₅₀) are in the nanomolar range in 60 cancer cell lines. When compound 1 is combined with a 4-Gy dose of radiation, <0.5% of cells retain their reproductive integrity. Increased hydrophobicity of new agents greatly enhances their brain uptake after oral administration. Conclusions: Compound 1 is potently cytotoxic in a wide range of human cancer cell lines. Its structure allows incorporation of imaging and therapeutic radionuclides. It is therefore expected that compound 1 can be developed into a novel theranostic modality across a wide range of malignancies.

Role of protein arginine methyltransferase 5 in group 3 (MYC-driven) Medulloblastoma

BACKGROUND

MYC amplification or overexpression is common in Group 3 medulloblastoma and is associated with the worst prognosis. Recently, protein arginine methyl transferase (PRMT) 5 expression has been closely associated with aberrant MYC function in various cancers, including brain tumors such as glioblastoma. However, the role of PRMT5 and its association with MYC in medulloblastoma have not been explored. Here, we report the role of PRMT5 as a novel regulator of MYC and implicate PRMT5 as a potential therapeutic target in MYC-driven medulloblastoma.

METHODS

Expression and association between PRMT5 and MYC in primary medulloblastoma tumors were investigated using publicly available databases. Expression levels of PRMT5 protein were also examined using medulloblastoma cell lines and primary tumors by western blotting and immunohistochemistry, respectively. Using MYC-driven medulloblastoma cells, we examined the physical interaction between PRMT5 and MYC by co-immunoprecipitation and co-localization experiments. To determine the functional role of PRMT5 in MYC-driven medulloblastoma, PRMT5 was knocked-down in MYC-amplified cells using siRNA and the consequences of knockdown on cell growth and MYC expression/stability were investigated. In vitro therapeutic potential of PRMT5 in medulloblastoma was also evaluated using a small molecule inhibitor, EPZ015666.

RESULTS

We observed overexpression of PRMT5 in MYC-driven primary medulloblastoma tumors and cell lines compared to non-MYC medulloblastoma tumors and adjacent normal tissues. We also found that high expression of PRMT5 is inversely correlated with patient survival. Knockdown of PRMT5 using siRNA in MYC-driven medulloblastoma cells significantly decreased cell growth and MYC expression. Mechanistically, we found that PRMT5 physically associated with MYC by direct protein-protein interaction. In addition, a cycloheximide chase experiment showed that PRMT5 post-translationally regulated MYC stability. In the context of therapeutics, we observed dose-dependent efficacy of PRMT5 inhibitor EPZ015666 in suppressing cell growth and inducing apoptosis in MYC-driven medulloblastoma cells. Further, the expression levels of PRMT5 and MYC protein were downregulated upon EPZ015666 treatment. We also observed a superior efficacy of this inhibitor against MYC-amplified medulloblastoma cells compared to non-MYC-amplified medulloblastoma cells, indicating specificity.

CONCLUSION

Our results reveal the regulation of MYC oncoprotein by PRMT5 and suggest that targeting PRMT5 could be a potential therapeutic strategy for MYC-driven medulloblastoma.

In vitro and in vivo evaluation of radiolabeled methyl N-[5-(3'-halobenzoyl)-1H-benzimidazol-2-yl]carbamate for cancer radiotherapy

The role of theranostics in cancer management is growing so is the selection of vectors used to deliver these modalities to cancer cells. We describe biological evaluation of a novel theranostic agent targeted to microtubules. Methyl N-[5-(3'-[¹³¹ I]iodobenzoyl)-1H-benzimidazol-2-yl]carbamate (1) and methyl N-[5-(3'-[¹²⁵ I]iodobenzoyl)-1H-benzimidazol-2-yl]carbamate (2) were synthesized from a common precursor 3'-stannylated derivative (4). Antiproliferative effects and radiotoxicity of ¹³¹ I-labeled β-particle emitting 1 were examined in vitro in human neuroblastoma and glioblastoma cells lines. The therapeutic potential of 1 was also examined in a subcutaneous mouse model of human glioblastoma U-87 MG. Compound 1 at the extracellular radioactive concentration of 0.35 MBq/mL, easily achievable in vivo, kills >90% of neuroblastoma cells and >60% glioblastoma cells as measured in a clonogenic assay. D₁₀ doses established for 1 indicate that as few as 3,000 decays are sufficient to kill 90% of BE(2)-C cells. Even U-87 MG cells, the least sensitive of the tested cell lines, require <20,000 decays of intracellular ¹³¹ I to reduce number of clonogenic cells by 90%. Biodistribution studies of 2 delivered either intratumorally or intraperitoneally show a similar tissue distribution for both routes of the drug administration. The whole body clearance half-lives were on average 6 hr. Intratumor administration of 1 produces significant tumor growth delay. After a single dose of 8.4 ± 0.3 MBq of compound 1, the tumor doubling times were 3.2 ± 0.1 and 7.9 ± 0.6 days in control and treated mice, respectively. Methyl N-[5-(3'-radiohalobenzoyl)-1H-benzimidazol-2-yl]carbamates have properties compatible with a theranostic approach to cancer management.

Effects of novel pyrrolomycin MP1 in MYCN amplified chemoresistant neuroblastoma cell lines alone and combined with temsirolimus

BACKGROUND

The activity of MP1, a pyrrolomycin, was studied in MYCN amplified neuroblastoma (NB) alone and combined with temsirolimus (TEM).

METHODS

Activity of MP1 was tested in MYCN amplified (BE-2c, IMR) and non amplified (SKN-AS) NB cells. The effect of MP1 on MYCN, MCL-1, cleaved PARP, LC3II/LC3I, bcl-2, BAX, and BRD-4 were determined by western blot and RNAseq. The effect of MP1 on metabolism, mitochondrial morphology, and cell cycle was determined. Toxicology and efficacy of MP1 plus TEM were evaluated.

RESULTS

The IC50 of MP1 was 0.096 μM in BE-2c cells compared to 0.89 μM in IMR, and >50 μM in SKN-AS. The IC50 of MP1 plus TEM in BE-2c cells was 0.023 μM. MP1 inhibited metabolism leading to quiescence and produced a decline in cell cycle S-phase. Electron microscopy showed cristae loss and rounding up of mitochondria. Gene and protein expression for MYCN and MCL-1 declined while LCII and cleaved PARP increased. Protein expression of BAX, bcl-2, and BRD-4 were not significantly changed after MP1 treatment. The in-vivo concentrations of MP1 in blood and tumor were sufficient to produce the biologic effects seen in-vitro. MP1 plus TEM produced a complete response in 3 out of 5 tumor bearing mice. In a second mouse study, the combination of MP1 and TEM slowed tumor growth compared to control.

CONCLUSIONS

MP1 has a potent inhibitory effect on the viability of MYCN amplified NB. Inhibition of metabolism by MP1 induced quiescence and autophagy with a favorable toxicology and drug distribution profile. When combined with TEM anti-tumor activity was potentiated in-vitro and in-vivo.

Abstract 1249: The role of PRMT5 in MYC-driven medulloblastoma

Medulloblastoma (MB) is the most common pediatric brain tumor, accounting for about 20% of all brain tumors in children. Children with Group 3 MB (aberrant MYC) show the worst prognosis, with &lt;50% survival. Recently, the role and association of protein arginine methyl transferase (PRMT) 5 have been closely associated with aberrant MYC function in various cancers including other brain tumors such as glioblastoma. However, the role of PRMT5 and its association with MYC in MB have not been explored. Here we provide preliminary data indicating PRMT5 as a novel regulator of MYC and implicating PRMT5 as a potential therapeutic target in MYC-driven MB. Using cell lines, our results showed PRMT5 overexpression in MYC-driven MB compared to non-MYC MB. The results from co-immunoprecipitation experiment in MYC-driven MB cells demonstrated that MYC physically associates with PRMT5 by direct protein-protein interaction. In addition, cycloheximide chase experiment showed that PRMT5 regulates MYC stability. Knockdown of PRMT5 using siRNA in MYC-driven MB cells significantly decreased cell growth and MYC expression. We also tested the therapeutic potential of targeting PRMT5 against MB cell lines using a small molecule inhibitor EPZ015666. We observed a dose-dependent efficacy of EPZ015666 in suppressing cell growth in MYC-driven MB cell lines. We also observed a superior efficacy of this inhibitor against MYC-driven MB cells compared to non-MYC MB cells. Together, our results implicate the regulation of MYC oncoprotein by PRMT5, and suggest that targeting PRMT5 could be a potential therapeutic strategy for MYC-driven MB and other MYC-driven cancers.

Citation Format: Nagendra K. Chaturvedi, Varun Kesherwani, Matthew J. Kling, Sutapa Ray, Timothy R. McGuire, Shantaram S. Joshi, J. Graham Sharp, Don W. Coulter. The role of PRMT5 in MYC-driven medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1249.

Abstract 5859: Enhanced therapy for MYC-driven medulloblastoma by targeting protein translation pathway

Medulloblastoma is the most frequent pediatric brain tumor of neuroectodermal cerebellar origin. High-risk MB patients with MYC overexpression and amplification usually show an extremely poor clinical outcome responding poorly to current therapies. Recent preclinical studies have revealed that the aberrant activation and interactions of PI3K/AKT/mTOR signaling is frequently associated with MYC-driven MB therapy-resistance. In addition, it is evident that both MYC and mTOR components of the PI3K/AKT/mTOR signaling axis can directly control and share a common translation pathway in increasing protein synthesis by regulating the expression of multiple components of the protein synthesis machinery, including ribosomal proteins and initiation factors of translation. Thus, inhibiting enhanced protein synthesis may represent a highly relevant strategy for the treatment of MYC-driven MB. Therefore, in this study, we investigated the single agents and combined anti-MB efficacies of a recently well-established BRD4 (bromodomain-containing protein 4)/MYC inhibitor JQ1 and PI3K-mTOR dual inhibitor BEZ235. Using four MB cell lines including three MYC amplified cell lines, the in vitro efficacy of this combined approach on cell growth/apoptosis and cell cycle along with associated molecular mechanism(s) were investigated. We used an MTT assay to measure survival and proliferation, flow-cytometric-based propidium-iodide staining to determine the effects of these inhibitors on cell-cycle, Annexin-V analyses to examine the cells undergoing apoptosis following treatments and western blot analyses to determine the expression levels of target molecules. Our results showed that both inhibitors as single agents, significantly decreased MB cell growth and induced apoptosis by targeting the key molecules of the associated pathways. Combined treatment of JQ1 and BEZ235 significantly decreased MB cell growth/survival in a dose-dependent fashion compared to single agent activity. Moreover, JQ1 and BEZ235 alone or combined significantly induced G1 cell-cycle arrest which coincided with decreased expression of cyclin-D1 and increased expression of p21 proteins in MYC-driven MB cells. Mechanistically, the co-treatment of JQ1 and BEZ235 significantly downregulated the expression levels of phosphorylated 4EBP1/p70-S6K (mTOR components) and BRD4/MYC proteins. Together, our findings demonstrate that the combination of JQ1 and BEZ235 showed significant synergistic efficacy against MYC-driven MB, by enhancing the inhibition of protein synthesis (translation) pathway. Initial evidence from this targeted approach, suggests that additional preclinical evaluation is warranted to determine likely clinical utility of targeted therapy for high-risk MB patients.

Citation Format: Nagendra K. Chaturvedi, Don W. Coulter, Matthew J. Kling, Sutapa Ray, Timothy R. McGuire, Shantaram S. Joshi, J. Graham Sharp. Enhanced therapy for MYC-driven medulloblastoma by targeting protein translation pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5859.

Improved therapy for medulloblastoma: targeting hedgehog and PI3K-mTOR signaling pathways in combination with chemotherapy

Aberrant activation and interactions of hedgehog (HH) and PI3K/AKT/mTOR signaling pathways are frequently associated with high-risk medulloblastoma (MB). Thus, combined targeting of the HH and PI3K/AKT/mTOR pathways could be a viable therapeutic strategy to treat high-risk patients. Therefore, we investigated the anti-MB efficacies of combined HH inhibitor Vismodegib and PI3K-mTOR dual-inhibitor BEZ235 together or combined individually with cisplatin against high-risk MB. Using non-MYC- and MYC-amplified cell lines, and a xenograft mouse model, the in vitro and in vivo efficacies of these therapies on cell growth/survival and associated molecular mechanism(s) were investigated. Results showed that combined treatment of Vismodegib and BEZ235 together, or with cisplatin, significantly decreased MB cell growth/survival in a dose-dependent-fashion. Corresponding changes in the expression of targeted molecules following therapy were observed. Results demonstrated that inhibitors not only suppressed MB cell growth/survival when combined, but also significantly enhanced cisplatin-mediated cytotoxicity. Of these combinations, BEZ235 exhibited a significantly greater efficacy in enhancing cisplatin-mediated MB cytotoxicity. Results also demonstrated that the MYC-amplified MB lines showed a higher sensitivity to combined therapies compared to non-MYC-amplified cell lines. Therefore, we tested the efficacy of combined approaches against MYC-amplified MB growing in NSG mice. In vivo results showed that combination of Vismodegib and BEZ235 or their combination with cisplatin, significantly delayed MB tumor growth and increased survival of xenografted mice by targeting HH and mTOR pathways. Thus, our studies lay a foundation for translating these combined therapeutic strategies to the clinical setting to determine their efficacies in high-risk MB patients.

Suppression of STAT3 NH2 -terminal domain chemosensitizes medulloblastoma cells by activation of protein inhibitor of activated STAT3 via de-repression by microRNA-21

Medulloblastoma (MB) is a malignant pediatric brain tumor with poor prognosis. Signal transducers and activators of transcription-3 (STAT3) is constitutively activated in MB where it functions as an oncoprotein, mediating cancer progression and metastasis. Here, we have delineated the functional role of activated STAT3 in MB, by using a cell permeable STAT3-NH₂ terminal domain inhibitor (S3-NTDi) that specifically perturbs the structure/function of STAT3. We have implemented several biochemical experiments using human MB tumor microarray (TMA) and pediatric MB cell lines, derived from high-risk SHH-TP53-mutated and MYC-amplified Non-WNT/SHH tumors. Treatment of MB cells with S3-NTDi leads to growth inhibition, cell cycle arrest, and apoptosis. S3-NTDi downregulated expression of STAT3 target genes, delayed migration of MB cells, attenuated epithelial-mesenchymal transition (EMT) marker expressions and reduced cancer stem-cell associated protein expressions in MB-spheres. To elucidate mechanisms, we showed that S3-NTDi induce expression of pro-apoptotic gene, C/EBP-homologous protein (CHOP), and decrease association of STAT3 to the proximal promoter of CCND1 and BCL2. Of note, S3-NTDi downregulated microRNA-21, which in turn, de-repressed Protein Inhibitor of Activated STAT3 (PIAS3), a negative regulator of STAT3 signaling pathway. Furthermore, combination therapy with S3-NTDi and cisplatin significantly decreased highly aggressive MYC-amplified MB cell growth and induced apoptosis by downregulating STAT3 regulated proliferation and anti-apoptotic gene expression. Together, our results revealed an important role of STAT3 in regulating MB pathogenesis. Disruption of this pathway with S3-NTDi, therefore, may serves as a promising candidate for targeted MB therapy by enhancing chemosensitivity of MB cells and potentially improving outcomes in high-risk patients.

Temporal and geospatial trends of pediatric cancer incidence in Nebraska over a 24-year period

BACKGROUND

Data from the Surveillance, Epidemiology, and End Results (SEER) revealed that the incidence of pediatric cancer in Nebraska exceeded the national average during 2009-2013. Further investigation could help understand these patterns.

METHODS

This retrospective cohort study investigated pediatric cancer (0-19 years old) age adjusted incidence rates (AAR) in Nebraska using the Nebraska Cancer Registry. SEER AARs were also calculated as a proxy for pediatric cancer incidence in the United States (1990-2013) and compared to the Nebraska data. Geographic Information System (GIS) mapping was also used to display the spatial distribution of cancer in Nebraska at the county level. Finally, location-allocation analysis (LAA) was performed to identify a site for the placement of a medical center to best accommodate rural pediatric cancer cases.

RESULTS

The AAR of pediatric cancers was 173.3 per 1,000,000 in Nebraska compared to 167.1 per 1,000,000 in SEER. The AAR for lymphoma was significantly higher in Nebraska (28.1 vs. 24.6 per 1,000,000; p = 0.009). For the 15-19 age group, the AAR for the 3 most common pediatric cancers were higher in Nebraska (p < 0.05). Twenty-three counties located >2 h driving distance to care facilities showed at least a 10% higher incidence than the overall state AAR. GIS mapping identified a second potential treatment site that would alleviate this geographic burden.

CONCLUSIONS

Regional differences within Nebraska present a challenge for rural populations. Novel use of GIS mapping to highlight regional differences and identify solutions for access to care issues could be used by similar states.

Abstract 1064: STAT3 NH2-terminal domain inhibition sensitizes medulloblastoma cells to chemotherapy

Medulloblastoma (MB) is the most common malignant brain tumor in children that arises from cerebellar neuronal progenitor cells. Despite aggressive treatment involving radiation and chemotherapy, the prognosis for high-risk MB remains poor and long-term complications from current therapies are common. Therefore, new effective therapies based on the molecular features of MB are needed to improve therapeutic outcomes. The STAT3 transcription factor is known to be constitutively activated in a variety of human cancers, including MB and functions as an oncoprotein, mediating cancer cell survival, proliferation, migration and drug-resistance. We have delineated the functional role of STAT3 NH2-Terminal Domain (NTD) in MB by using a cell permeable peptide derivative of the STAT3 second helix that specifically binds and perturbs the structure/function of STAT3 and interferes with tetramerization of STAT3 dimers, protein-protein interactions and target genes transcription. Herein, we report that treatment of MB cells with STAT3-NTD inhibitor (S3-NTDi) leads to growth inhibition, cell cycle arrest and apoptosis. The inhibition of STAT3 signaling was also confirmed by downregulation of its downstream targets, including MYC, CCND1, BCl2L1, BCL2, PIM1 and APEX1. Moreover, we observed that S3-NTDi exposure attenuated the migration of MB cells in a wound-healing assay, a prerequisite for tumor invasion and metastasis. We also found that S3-NTDi abrogated IL-6 induced epithelial-mesenchymal transition (EMT) marker protein expression and inhibition of EMT-related transcription factors SNAIL and TWIST. Most importantly, we observed that combination therapy with S3-NTDi and cisplatin significantly decreased the highly aggressive MYC-driven MB cell growth in a dose dependent manner and induced apoptosis by downregulating STAT3 regulated anti-proliferative and anti-apoptotic gene expression. To elucidate the mechanisms of S3-NTDi mediated inhibition, we showed that S3-NTDi upregulated expression of pro-apoptotic gene C/EBP-homologous protein (CHOP) and concomitantly decreased association of the STAT3 transcription factor to endogenous proximal promoter of CCND1 and BCL2 in chromatin immunoprecipitation assay. Furthermore, we determined that S3-NTDi mediated downregulation of miRNA-21 in MB cells, de-repressed Protein Inhibitor of Activated STAT3 (PIAS3), a negative regulator of STAT3 which, in turn, attenuated STAT3 signaling pathway. Overall, our results revealed an important role of STAT3 NTD and its downstream effector molecules in regulating MB pathogenesis and disruption of this pathway with S3-NTDi may serves as a promising new candidate for therapeutic interventions in MB therapy, thereby improving the outcomesin high-risk pediatric MB patients.

Citation Format: Sutapa Ray, Don W. Coulter, Shawn D. Gray, Jason A. Sughroue, Nagendra K. Chaturvedi, Shantaram S. Joshi, Kishor K. Bhakat, Timothy R. McGuire, John G. Sharp. STAT3 NH2-terminal domain inhibition sensitizes medulloblastoma cells to chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1064. doi:10.1158/1538-7445.AM2017-1064

Abstract 161: Medulloblastoma therapy targeting Hedgehog and PI3K-mTOR signaling pathways in combination with chemotherapy

Medulloblastoma (MB) is the most frequent malignant brain tumor in children. MB patients with high-risk disease have poorly understood biology and few targeted therapies available. Preclinical studies and molecular profiling of MB have revealed that the aberrant activation and interaction of the SHH and PI3K/AKT/mTOR signaling networks are frequently associated with poor prognosis MB cases. Emerging evidence also demonstrate the key role of activated PI3K/AKT/mTOR pathway components in SHH-driven MB therapy-resistance, thus combined targeting of the SHH and PI3K/AKT/mTOR pathways may be a viable therapeutic strategy to treat high-risk patients. Therefore, we investigated the combined efficacy of SHH inhibitor vismodegib and PI3K-mTOR dual inhibitor BEZ235 or their combination, individually with the chemotherapeutic drug cisplatin against high-risk MB. Using four MB cell lines, including non-MYC and MYC amplified cell lines, and a xenograft mouse model, the in vitro and in vivo efficacies of the proposed therapies on cell growth/survival along with associated molecular mechanism(s) were investigated. Our results showed that both inhibitors as single agents significantly decreased MB cell growth and induced apoptosis by targeting the key molecules of the associated pathways in vitro. BEZ235 as single agent showed a greater anti-MB efficacy compared to vismodegib. Combined treatment of vismodegib and BEZ235 together or with cisplatin significantly decreased MB cell growth/survival and anchorage-independent growth in a dose-dependent fashion compared to single agent activity. Corresponding changes in the expression of the targeted molecules following therapy were observed. Results from the combined approach suggested that the inhibitors not only suppressed MB cell growth/survival when combined, but also significantly enhanced the cytotoxic effects of cisplatin. Of these combinations, BEZ235 exhibited a significantly greater efficacy in enhancing the cisplatin-mediated MB cytotoxicity. In vitro studies also demonstrated that the MYC amplified MB cell lines showed a higher sensitivity to these combined therapies compared to relatively non-MYC amplified cell lines. Therefore, as a next logical step, we tested the efficacy of above combined approaches against MYC-amplified MB in vivo using NSG mice. Our in vivo results showed that the combination of vismodegib and BEZ235 or their combinations individually with cisplatin significantly delayed tumor growth and increased survival of xenograft mice compared to single agent activity. These combination not only significantly reduced tumor growth and increased survival of the mice but also significantly enhanced anti-MB efficacy by targeting SHH and mTOR pathways in MB in vivo. Thus, our studies lay a foundation for translating these combined therapeutic strategies to the clinical setting to determine their efficacies in high-risk MB patients.

Citation Format: Nagendra K. Chaturvedi, Don W. Coulter, Timothy R. McGuire, Matthew J. Kling, Sutapa Ray, Shantaram S. Joshi, John G. Sharp. Medulloblastoma therapy targeting Hedgehog and PI3K-mTOR signaling pathways in combination with chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 161. doi:10.1158/1538-7445.AM2017-161

Treatment of a chemoresistant neuroblastoma cell line with the antimalarial ozonide OZ513

BACKGROUND

Evaluate the anti-tumor activity of ozonide antimalarials using a chemoresistant neuroblastoma cell line, BE (2)-c.

METHODS

The activity of 12 ozonides, artemisinin, and two semisynthetic artemisinins were tested for activity against two neuroblastoma cell-lines (BE (2)-c and IMR-32) and the Ewing's Sarcoma cell line A673 in an MTT viability assay. Time course data indicated that peak effect was seen 18 h after the start of treatment thus 18 h pre-treatment was used for all subsequent experiments. The most active ozonide (OZ513) was assessed in a propidium iodide cell cycle flow cytometry analysis which measured cell cycle transit and apoptosis. Metabolic effects of OZ513 in BE (2)-c cells was evaluated. Western blots for the apoptotic proteins cleaved capase-3 and cleaved PARP, the highly amplified oncogene MYCN, and the cell cycle regulator CyclinD1, were performed. These in-vitro experiments were followed by an in-vivo experiment in which NOD-scid gamma immunodeficient mice were injected subcutaneously with 1 × 10⁶ BE (2)-c cells followed by immediate treatment with 50-100 mg/kg/day doses of OZ513 administered IP three times per week out to 23 days after injection of tumor. Incidence of tumor development, time to tumor development, and rate of tumor growth were assessed in DMSO treated controls (N = 6), and OZ513 treated mice (N = 5).

RESULTS

It was confirmed that five commonly used chemotherapy drugs had no cytotoxic activity in BE (2)-c cells. Six of 12 ozonides tested were active in-vitro at concentrations achievable in vivo with OZ513 being most active (IC50 = 0.5 mcg/ml). OZ513 activity was confirmed in IMR-32 and A673 cells. The Ao peak on cell-cycle analysis was increased after treatment with OZ513 in a concentration dependent fashion which when coupled with results from western blot analysis which showed an increase in cleaved capase-3 and cleaved PARP supported an increase in apoptosis. There was a concentration dependent decline in the MYCN and a cyclinD1 protein indicative of anti-proliferative activity and cell cycle disruption. OXPHOS metabolism was unaffected by OZ513 treatment while glycolysis was increased. There was a significant delay in time to tumor development in mice treated with OZ513 and a decline in the rate of tumor growth.

CONCLUSIONS

The antimalarial ozonide OZ513 has effective in-vitro and in-vivo activity against a pleiotropic drug resistant neuroblastoma cell-line. Treatment with OZ513 increased apoptotic markers and glycolysis with a decline in the MYCN oncogene and the cell cycle regulator cyclinD1. These effects suggest adaptation to cellular stress by mechanism which remain unclear.

Abstract B07: Treatment of a chemoresistant human neuroblastoma cell-line (BE-2c) with experimental ozonide antimalarials

Objective: To evaluate the anti-tumor activity of a class of experimental antimalarial drugs in an MYCN amplified chemoresistant neuroblastoma cell line (BE-2c) intended to model poor prognostic neuroblastoma.

Methods: Etoposide cytotoxicity was studied at concentrations (250 ng/ml,500 ng/ml, 1 mcg/ml, 2 mcg/ml, and 3 mcg/ml) to confirm chemoresistance to a commonly used cytotoxic agent in the treatment of neuroblastoma. Concentrations chosen for the ozonide antimalarials were those that have been achieved in-vivo when studied in a malarial model in rodents. Ozonide antimalarial drugs were tested in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay which measures cell viability colorimetrically. A series of 13 ozonide compounds were evaluated for activity using a concentration response scheme (0, 250 ng/ml, 500 ng/ml, 1 mcg/ml, 5 mcg/ml, and 10 mcg/ml) that allowed the generation of IC50 for each agent based on mean MTT absorption values from 10 replicates at each concentration. The most active ozonide (OZ513) identified was then studied in a cell cycle flow cytometry analysis using propidium idodide with measurement of the A0 peak which estimates apoptosis. A neurosphere assay was also used which is considered enriched for “cancer stem cells” and is able to model movement of drug into a small avascular tumor was used to further evaluate the activity of OZ513. Spheres were counted and characterized after treatment and compared to non-treatment controls. Because it has been postulated that the anti-cancer mechanism of action of the ozonide antimalarials is the modulation of cancer cell metabolism (autophagy, disruption of oxidative metabolism) the effect of OZ513 on mitochondrial oxidative metabolism and glycolysis was evaluated in BE-2c cells using Seahorse metabolic analysis.

Results: Etoposide had no cytotoxic activity at any of the concentrations studied. OZ513 antimalarials were consistently active in BE-2c cell culture with the MTT assay generating IC50s on two separate experiments of 0.03 and 0.05 mcg/ml. The MTT results were confirmed using trypan blue staining to directly measure cell death. The Ao peak on PI flow cytometry increased after treatment with OZ513 indicating an increase in apoptosis. In addition, 5 mcg/ml of OZ513 increased G1, S, and G2 aneuploid fraction on propidium iodide cell cycle analysis. OZ513 disrupted BE-2c neurospheres confirming their activity in these multicellular tumorspheres. Metabolic studies demonstrated little effect on mitochondria based oxidative metabolism or glycolysis. Structure activity relationship suggests that the alcohol of the ozonide structure is required for optimal activity.

Conclusion: The antimalarial agent OZ513 has promising activity against the chemoresistant neuroblastoma cell-line BE-2c by increasing apoptosis by mechanisms that remain unclear, but increased cell cycle aneuploidy with treatment of cells with 5 mcg/ml of OZ513 indicates defects in mitosis and cytokinesis.

Citation Format: Don W. Coulter, Timothy R. McGuire, John G. Sharp, Yuxiang Dong, Xiaofang Wang, Erin McIntyre, Xiaoyu Chen, Jon Vennerstrom. Treatment of a chemoresistant human neuroblastoma cell-line (BE-2c) with experimental ozonide antimalarials. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B07.

Abstract B05: Improved therapy for neuroblastoma using small molecule inhibitors in combination with chemotherapy

Neuroblastoma is the most common pediatric malignancy with poor response to current therapy. The NF-kB/mTOR, hedgehog and PLK1 pathways/molecules are aberrantly expressed and activated in high-risk neuroblastoma, thereby targeting these pathways/molecules is an attractive therapeutic strategy. Therefore, we investigated the efficacy and associated molecular mechanism(s) of NF-kB/mTOR dual inhibitor 13-197, hedgehog inhibitor Vismodegib and PLK1 inhibitor BI2536 alone or in combination with Topotecan against high-risk neuroblastoma in vitro and in vivo. Using three neuroblastoma cell lines, the in vitro efficacy of the inhibitors as single agents or in combination with Topotecan on cell growth and apoptosis along with associated molecular mechanism(s) were investigated. In addition, the combined efficacy of Vismodegib and Topotecan was determined in vivo using a xenograft mouse model. Results showed that 13-197, BI2536 and Vismodegib significantly decreased neuroblastoma cell growth and induced apoptosis by targeting associated pathways and molecules in vitro. The 13-197 and BI2536 as single agents showed similar efficacies and were most potent in inhibiting cell growth and survival of neuroblastoma cells. In combination with Topotecan, BI2536 or Vismodegib further significantly decreased neuroblastoma cell growth/survival and neurospheres formation. Corresponding changes in the expression of targeted molecules following therapy were observed. Together, in vitro data demonstrated that hedgehog pathway inhibitor Vismodegib was most efficacious in potentiating Topotecan-induced antineuroblastoma effects. Therefore, as a next logical step, we tested the combined efficacy of Vismodegib and Topotecan against neuroblastoma in vivo using NOD-SCID Gamma deleted (NSG) mice. Our in vivo results showed that Vismodegib combined with Topotecan significantly (p&lt;0.001) reduced tumor growth and increased survival of xenograft mice compared to single agent activity. This combination not only significantly reduced tumor growth and increased survival of the mice but also significantly enhanced antineuroblastoma efficacy by targeting hedgehog pathway components in neuroblastoma in vivo. Thus our studies lay a foundation for taking this therapeutic strategy to clinical setting to determine their efficacies in high-risk neuroblastoma patients.

Citation Format: Nagendra K. Chaturvedi, McGuire R. Timothy, Don W. Coulter, Ashima Shukla, Erin M. McIntyre, J. Graham Sharp, Shantaram S. Joshi. Improved therapy for neuroblastoma using small molecule inhibitors in combination with chemotherapy. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B05.

Abstract 4362: Screening of investigational antimalarials for anticancer activity in high risk N-MYC amplified neuroblastoma (NB)

Introduction: NB is a pediatric tumor of neural crest origin. Patients who have N-MYC amplified metastatic tumors have poor outcomes. The importance of autophagy in protecting NB cells from chemotherapy has been postulated. In the following study we screened bisquinoline (BQ) and ozonide (OZ) antimalarials (potential autophagy inhibitors) in a highly N-MYC amplified NB cell line (BE-2) and a moderately amplified N-MYC NB cell line (IMR-32). A combination of monolayer cell culture and neurospheres were used to screen activity.

Methods: Using a 96 well MMT based assay and 16 hour treatment with compounds dissolved in DMSO, cytotoxicity was calculated as a percent decline in absorbance compared to DMSO controls. 32 BQ and 13 OZ antimalarials were tested. All compounds were tested at a concentration of 1 mcg/ml; an achievable concentration in patients. Selected compounds that were cytotoxic in monolayer culture will be tested in neurosphere culture and then in a mouse xenograft model alone and combined with chemotherapy.

Results: The bisquinolone antimalarials were consistently active in both BE-2 and IMR cell culture. Among the bisquinolones, Q1-9, Q2-5, Q2-61, and Q3-75 had the greatest cytotoxicity. There was no clear structure-activity-relationship for this small bisquinoline library. Among the ozonides, OZ465, OZ513, and OZ521 were the most active. From these data, we could infer that the presence of a weak base functional group was required, but was insufficient for cytotoxicity. Initial studies in BE-2 and IMR neurosphere culture using an LDH assay for cytotoxicity suggests similar activity. Monolayer results are shown in the Table below:

SymbolDrug ClassBE-2*IMR-32*Q1-9BQ38.535.8Q2-5BQ29.844.4Q2-61BQ40.731.4Q3-75BQ40.619.3OZ465OZ3820.6OZ513OZ73.627.7OZ521OZ4415.9

*Percent decline in absorbance compared to DMSO control

Conclusion: The above data indicates that two classes of antimalarials had moderate cytotoxicity in both 96-well monolayer assays as well as in a neurosphere assay (data not shown). The results suggest cytotoxic activity in high and moderately amplified N-MYC NB in both monolayers and neurospheres.

Note: This abstract was not presented at the meeting.

Citation Format: Don W. Coulter, Jonathan Vennerstrom, John G. Sharp, Yuxiang Dong, Xiaofang Wang, Erin McIntyre, Tim McGuire. Screening of investigational antimalarials for anticancer activity in high risk N-MYC amplified neuroblastoma (NB). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4362. doi:10.1158/1538-7445.AM2015-4362

Refractory autoimmune hemolytic anemia after intestinal transplant responding to conversion from a calcineurin to mTOR inhibitor

AIHA is a rare and serious complication of solid organ transplantation. Herein, we report four cases of warm or mixed AIHA in pediatric patients following combined liver, small bowel and pancreas transplant. The hemolysis was refractory to multiple treatment modalities including steroids, rituximab, IVIG, plasmapheresis, cytoxan, discontinuation of prophylactic penicillin, and a change in immunosuppression from tacrolimus to cyclosporine. All patients had resolution or marked improvement of hemolysis after discontinuation of maintenance of CNI and initiation of sirolimus immunosuppression. One patient developed nephrotic syndrome but responded to a change in immunosuppression to everolimus. Three of the four patients continue on immunosuppression with sirolimus or everolimus without further hemolysis, evidence of rejection or medication side effects. Based on our experience and review of similar cases in the literature, we have proposed a treatment algorithm for AIHA in the pediatric intestinal transplant patient population that recommends an early change in immunosuppressive regimen from CNIs to sirolimus therapy.

Parenteral nutrition-induced hypersensitivity in an adolescent

A case report of a 15-year-old adolescent male who developed a hypersensitivity reaction to a parenteral nutrition (PN) solution containing multivitamins (MVI) is presented. Within 30 minutes after initiation of PN and lipids, the patient developed a total-body pruritic urticarial rash that resolved after discontinuation of the infusions and administration of diphenhydramine. Rechallenge with the same PN solution excluding heparin, as well as lipids, resulted in a similar urticarial reaction that also resolved within 30 minutes after discontinuation of the infusions and administration of diphenhydramine. Another rechallenge with a solution containing dextrose and amino acids at the same concentrations contained in the original PN solution did not elicit an allergic reaction, whereas addition of MVI to the dextrose and amino acids resulted in a similar allergic reaction 20 minutes after the start of the infusion. It was determined that the MVI component of the PN was the most likely causative agent of this patient's urticarial reaction.

Inhibition of IGF-I receptor signaling in combination with rapamycin or temsirolimus increases MYC-N phosphorylation

BACKGROUND

It has been previously shown that blockade of the type 1 insulin-like growth factor receptor (IGF1R) signaling combined with mTOR inhibition decreased neuroblastoma proliferation in vitro. MYC-N inactivation occurs through phosphorylation by downstream elements of the IGF1R signaling pathway. It was hypothesized that inhibition of IGF1R signaling would increase the inactivation of MYC-N.

MATERIALS AND METHODS

BE-2(c) and IMR-32 neuroblastoma cell lines were treated with varying concentrations of alphaIR3, rapamycin and temsirolimus either alone or in combination and the expression of MYC-N and phosphorylated MYC-N proteins were evaluated by Western blotting. The number of apoptotic cells was evaluated through cleaved caspase-3 expression.

RESULTS

IGF1R signaling blockade in combination with mTOR inhibition decreased MYC-N protein expression, increased MYC-N phosphorylation and significantly increased cleaved caspase-3 expression in treated cells.

CONCLUSION

The combination of rapamycin or temsirolimus with alphaIR3 decreases MYC-N expression, increases MYC-N phosphorylation and induces apoptosis in vitro which may have clinical relevance to children with neuroblastoma.

IGF-I receptor inhibition combined with rapamycin or temsirolimus inhibits neuroblastoma cell growth

BACKGROUND

Neuroblastoma is the third most common solid tumor in children. Treatment continues to be challenging. The pathogenesis of neuroblastoma has been related to expression of the type 1 insulin-like growth factor receptor (IGF1R) and to transcription factor MYC-N amplification. Previous studies have shown that MYC-N expression is disrupted by blockade of the IGF1R with a specific monoclonal antibody, alphaIR3. Inhibition of IGF1R signaling can be accomplished by other agents, including rapamycin or temsirolimus, which target mTOR (mammalian target of rapamycin).

MATERIALS AND METHODS

BE-2(c) and IMR-32 neuroblastoma cell lines were treated with varying concentrations of alphaIR3, rapamycin and temsirolimus alone or in combination and the viable cells were counted.

RESULTS

Blockade of IGF1R signaling significantly inhibited cell growth as compared to untreated controls (p < 0.05), and a combination of agents was more effective than each agent alone.

CONCLUSION

The combination of rapamycin or temsirolimus with alphaIR3 blocks the IGF1R signaling pathway and has an antiproliferative effect on neuroblastoma cells warranting further investigations using inhibitors of IGF1R signaling as novel combination therapy for neuroblastoma.