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Medulloblastoma is the most common malignant brain tumor in children. This disease is heterogeneous and is composed of four subtypes of medulloblastoma [WNT, Sonic Hedgehog (SHH), Group 3, and Group 4]. An immediate goal is to identify novel molecular targets for the most aggressive forms of medulloblastoma. Polo-like kinase 1 (PLK1) is an oncogenic kinase that controls cell cycle and proliferation, making it a strong candidate for medulloblastoma treatment. In this study, pediatric medulloblastomas were subtyped in two patient cohorts (discovery cohort, n = 63 patients; validation cohort, n = 57 patients) using NanoString nCounter analysis and PLK1 mRNA was assessed. We determined that the SHH and Group 3 subtypes were independently associated with poor outcomes in children as was PLK1 using Cox regression analyses. Furthermore, we screened a library of 129 compounds in clinical trials using a model of pediatric medulloblastoma and determined that PLK1 inhibitors were the most promising class of agents against the growth of medulloblastoma. In patient-derived primary medulloblastoma isolates, the PLK1 small-molecule inhibitor BI2536 suppressed the self-renewal of cells with high PLK1 but not low PLK1 expression. PLK1 inhibition prevented medulloblastoma cell proliferation, self-renewal, cell-cycle progression, and induced apoptosis. In contrast, the growth of normal neural stem cells was unaffected by BI2536. Finally, BI2536 extended survival in medulloblastoma-bearing mice with efficacy comparable with Headstart, a standard-of-care chemotherapy regimen. We conclude that patients with medulloblastoma expressing high levels of PLK1 are at elevated risk. These preclinical studies pave the way for improving the treatment of medulloblastoma through PLK1 inhibition. Cancer Res; 73(22); 6734–44. ©2013 AACR.

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PDF file - 685K, Supplementary Table S1. Summary of the pediatric MB patients included in the study Discovery cohort. Supplementary Table S2. Summary of the pediatric MB patients included in the study Validation cohort. Supplementary Table S3. PAM class prediction validation for MB subgroup assignment of Discovery cohort and cultured cells. Supplementary Table S4. PAM class prediction validation for MB subgroup assignment of Validation cohort. Supplementary Table S5. Univariate and multivariate analyses of clinical, pathological and biological endpoints in the Validation cohort. Supplementary Figure S1. MB survival in Validation cohort is stratified by molecular subtype. Supplementary Figure S2. PLK1 is invariably expressed between patient cohorts and between MB subgroups. Supplementary Figure S3. BI2536 sensitivity depends on PLK1 expression in primary MB cells. Supplementary Figure S4. MB cells lines expressing PLK1 experience cell cycle arrest and reduced proliferation with PLK1 inhibition. Supplementary Figure S5. MB cell PLK1 inhibition morphology using immunofluorescence. Supplementary Figure S6. MB cell lines treated with anti-cancer drugs.

Atypical teratoid rhabdoid tumors (ATRT) are rare and aggressive embryonal tumors of central nervous system that typically affect children younger than 3 years of age. Given the generally poor outcomes of patients with ATRT and the significant toxicities associated with conventional multi-modal therapies, there is an urgent need for more novel approaches to treat ATRT, one such approach being immunotherapy. The recent rise of large-scale, multicenter interdisciplinary studies has delineated several molecular and genetic characteristics unique to ATRT. This review aims to describe currently available data on the tumor immune microenvironment of ATRT and its specific subtypes and to summarize the emerging clinical and preclinical results of immunotherapy-based approaches. It will also highlight the evolving knowledge of epigenetics on immunomodulation in this epigenetically influenced tumor, which may help guide the development of effective immunotherapeutic approaches in the future.

PURPOSE Retinoblastoma is the most frequent intraocular cancer in children. It is also one of the most common causes for enucleation and carries a significant morbidity rate in affected individuals. Hence, studies on its pathophysiological and growth regulatory mechanisms are urgently needed to identify more effective novel therapeutics. METHODS Using the Y79 retinoblastoma cell line, we investigated the electrophysiological and functional activities of the T-type voltage-gated calcium channel Cav3.1, that is constitutively expressed in these cells. We also analyzed the Akt and MAPK signaling pathways downstream of the epidermal growth factor receptor (EGFR) to understand the mechanism responsible for the inhibition of Cav3.1. RESULTS We demonstrate that the EGFR inhibitor Afatinib significantly reduced cell viability and Cav3.1 mRNA expression and electrophysiological activity. At low concentrations (1 µM), Afatinib reduced the amplitude of Cav3.1 current density, whereas at a high concentration (10 µM), it completely abolished the voltage-gated calcium current. Our results show that inhibition of the MAPK pathway by a specific inhibitor VX-11e affected the Cav3.1 current in a dose-dependent manner. VX-11e (50 nM-1 µM) treatment reduced Cav3.1 current densities in Y79 cells, with complete abolishment of Cav3.1 current at higher concentrations (5 µM). We also demonstrate that the specific inhibition of the Akt kinase (using MK-2206) had no effect on the Cav3.1 currents. CONCLUSION Our study provides a functional relationship between the MAPK pathway and EGFR signaling and indicates that the MAPK signaling pathway mediates the control of Cav3.1 by EGFR in retinoblastoma.

Background: Most children with recurrent metastatic solid tumors have high mortality rates. Recent studies have shown that proteasome inhibition leads to effective tumor killing in cells that have acquired treatment resistance and metastatic properties. Objective: The purpose of this study was to test the potential of Carfilzomib (CFZ), a proteasome inhibitor, in refractory pediatric solid tumors which is currently unknown. Methods: A panel of pediatric solid tumor cell lines, including neuroblastoma, Ewing’s sarcoma, osteosarcoma, rhabdomyosarcoma and atypical teratoid rhabdoid tumor (ATRT), was used to evaluate the cytotoxic and proteasomal inhibitory effects of CFZ. A drug scheduling experiment was performed to determine the optimal dose and time to obtain effective cell killing. Combination studies of CFZ with chemotherapeutic drugs of different classes were performed to determine the extent of synergy. Results: CFZ showed effective cytotoxicity against all cell lines tested (mean IC50 = 7nM, range = 1-20nM) and activity in a fluorophore-tagged cell-based proteasome assay. Drug scheduling experiments showed that the minimum exposure of 4-8 hours/day is needed for effective cumulative killing. CFZ, when combined with chemotherapeutic drugs of different classes, synergistically enhanced the extent of cell death. Conclusions: CFZ showed cytotoxic activity against all the solid pediatric cancer cell lines tested. This study provides initial in vitro data on the potential of CFZ to treat pediatric solid tumors and supports further investigations into the components of drug scheduling, biological correlates and drug combinations for future early phase clinical trials in children.

Objective: The function of the Ras association domain family 1 (RASSF1)/modulator of apoptosis 1 (MOAP-1) molecular tumor suppressor pathway is often perturbed in many solid and blood cancers by epigenetic loss of RASSF1A via promoter specific methylation. However, a detailed analysis of expression and stability of MOAP-1 as well as effect on cellular proliferation and cell death in blood cancers has not been explored. Materials and Methods: Expression of MOAP-1 RASSF1A was performed by immunoblotting analysis, MOAP-1 effect on biology determined by cell proliferation, cell death and tumorigenicity assays. Lastly, proteomic analysis in MOAP-1 in form 1 and 2 expressing cells reveal new interacting partners to MOAP-1. Results: The expression of MOAP-1 appears to be quite varied and exists as two forms, a p39 and p46 form in blood cancers. The higher MOAP-1 p46 form was mainly observed in acute myeloid leukemia (AML) and some acute lymphocytic leukemia (ALL) patients and cell lines. Furthermore, MOAP-1 p46 form can be reduced to the p39 form upon calf intestinal or lambda phosphatase treatment, suggesting post-translational phosphorylation likely produces the slower migrating form. Blood cancer cell lines containing the p46 form of MOAP-1 appears to be more resistant to cell death signals and have increased growth. In addition, we document in vivo protection from tumorigenesis of cells containing MOAP-1 following tail vein injection of cancer cells. Lastly, proteomic analysis revealed several interesting components of the MOAP-1 interactome in blood cancer cells that we validated. Conclusions: MOAP-1 is a bona fide tumor suppressor in blood cancers with functions beyond apoptosis.

Neurotrophic tyrosine receptor kinase gene fusions (NTRK) are oncogenic drivers present at a low frequency in most tumour types (80%) in a small number of rare tumours (e.g., infantile fibrosarcoma [IFS]) and considered mutually exclusive with other common oncogenic drivers. Health Canada recently approved two tyrosine receptor kinase (TRK) inhibitors, larotrectinib (for adults and children) and entrectinib (for adults), for the treatment of solid tumours harbouring NTRK gene fusions. In Phase I/II trials, these TRK inhibitors have demonstrated promising overall response rates and tolerability in patients with TRK fusion cancer who have exhausted other treatment options. In these studies, children appear to have similar responses and tolerability to adults. In this report, we provide a Canadian consensus on when and how to test for NTRK gene fusions and when to consider treatment with a TRK inhibitor for pediatric patients with solid tumours. We focus on three pediatric tumour types: non-rhabdomyosarcoma soft tissue sarcoma/unspecified spindle cell tumours including IFS, differentiated thyroid carcinoma, and glioma. We also propose a tumour-agnostic consensus based on the probability of the tumour harbouring an NTRK gene fusion. For children with locally advanced or metastatic TRK fusion cancer who have either failed upfront therapy or lack satisfactory treatment options, TRK inhibitor therapy should be considered.

Mutations in the CBL gene were first identified in adults with various myeloid malignancies. Some patients with juvenile myelomonocytic leukemia (JMML) were also noted to harbor mutations in CBL, but were found to have generally less aggressive disease courses compared to patients with other forms of Ras pathway-mutant JMML. Importantly, and in contrast to most reports in adults, the majority of CBL mutations in JMML patients are germline with acquired uniparental disomy occurring in affected marrow cells. Here, we systematically studied a large cohort of 33 JMML patients with CBL mutations and found that this disease is highly diverse in presentation and overall outcome. Moreover, we discovered somatically acquired CBL mutations in 15% of pediatric patients who presented with more aggressive disease. Neither clinical features nor methylation profiling were able to distinguish patients with somatic CBL mutations from those with germline CBL mutations, highlighting the need for germline testing. Overall, we demonstrate that disease courses are quite heterogeneous even among patients with germline CBL mutations. Prospective clinical trials are warranted to find ideal treatment strategies for this diverse cohort of patients.

ObjectiveTo examine the relationship between neonatal inflammatory cytokines and perinatal stroke using a systems biology approach analyzing serum and blood-spot cytokines from 47 patients.MethodsThis was a population-based, controlled cohort study with prospective and retrospective case ascertainment. Participants were recruited through the Alberta Perinatal Stroke Project. Stroke was classified as neonatal arterial ischemic stroke (NAIS), arterial presumed perinatal ischemic stroke (APPIS), or periventricular venous infarction (PVI). Biosamples were stored blood spots (retrospective) and acute serum (prospective). Controls had comparable gestational and maternal ages. Sixty-five cytokines were measured (Luminex). Hierarchical clustering analysis was performed to create heat maps. The Fisher linear discriminant analysis was used to create projection models to determine discriminatory boundaries between stroke types and controls.ResultsA total of 197 participants were analyzed (27 with NAIS, 8 with APPIS, 12 with PVI, 150 controls). Cytokines were quantifiable with quality control measures satisfied (standards testing, decay analysis). Linear discriminant analysis had high accuracy in using cytokine profiles to separate groups. Profiles in participants with PVI and controls were similar. NAIS separation was accurate (sensitivity 77%, specificity 97%). APPIS mapping was also distinguishable from NAIS (sensitivity 86%, specificity 99%). Classification tree analysis generated similar diagnostic accuracy.ConclusionsUnique inflammatory biomarker signatures are associated with specific perinatal stroke diseases. Findings support an acquired pathophysiology and suggest the possibility that at-risk pregnancies might be identified to develop prevention strategies.Classification of evidenceThis study provides Class III evidence that differences in acute neonatal serum cytokine profiles can discriminate between patients with specific perinatal stroke diseases and controls.

Central nervous system (CNS) atypical teratoid/rhabdoid tumor (AT/RT) is a rare, aggressive tumor that most often affects very young children. The common decisive molecular defect in AT/RT has been shown to be a single genetic alteration, i.e., the loss of hSNF5 gene that encodes for a subunit of the SWI/SNF complex that modulates chromatin remodeling activities. As a result, AT/RT cells display unregulated cell proliferation due to the dysfunction of an important epigenetic control. We have previously demonstrated the preclinical efficacy of the oncolytic double-deleted vaccinia virus (VVDD) against AT/RT. Here we report the establishment of a modified VVDD engineered to express wild type hSNF5 gene. We show that this reconstructed vaccinia virus retains comparable infectivity and in vitro cytotoxicity of the parent strain. However, in addition, hSNF5-arming of VVDD results in a decreased cell cycle S phase population and down-regulation of cyclin D1. These findings suggest that hSNF5-arming of VVDD may increase the efficacy in the treatment of AT/RT and validates, as a proof-of-concept, an experimental approach to enhance the effective use of novel modified oncolytic viruses in the treatment of tumors with loss of a tumor suppressor gene function.

Although treatment strategies for pediatric leukemia have improved overall survival rates in the recent past, relapse rates in certain subgroups such as infant leukemia remain unacceptably high. Despite undergoing extensive chemotherapy designed to target the rapidly proliferating leukemia cells, many of these children experience relapse. In refractory leukemia, the existence of cell populations with stemness characteristics, termed leukemia stem cells (LSCs), which remain quiescent and subsequently replenish the blast population, has been described. A significant body of evidence exists, derived largely from xenograft models of adult acute myeloid leukemia, to support the idea that LSCs may play a fundamental role in refractory disease. In addition, clinical studies have also linked LSCs with increased minimal residual disease, higher relapse rate, and decreased survival rates in these patients. Recently, a number of reports have addressed effective ways to utilize new-generation genomic sequencing and transcriptomic analyses to identify targeted therapeutic agents aimed at LSCs, while sparing normal hematopoietic stem cells. These data underscore the value of timely translation of knowledge from adult studies to the unique molecular and physiological characteristics seen in pediatric leukemia. We aim to summarize this article in the rapidly expanding field of stem cell biology in hematopoietic malignancies, focusing particularly on relevant preclinical models and novel targeted therapeutics, and their applicability to childhood leukemia.

Background Efficacy and safety data of COVID-19 vaccines among cancer populations have been limited; however, preliminary data from recent studies have emerged regarding their immunogenicity and safety in this population. In this review, we examined current peer-reviewed publications containing serological and safety data following COVID-19 vaccination of patients with cancer. Methods This analysis examined 21 studies with a total of 5,012 cancer patients, of which 2,676 (53%) had hematological malignancies, 2,309 (46%) had solid cancers, and 739 were healthy controls. Serological responses by anti-SARS-CoV-2 spike protein S1/S2 IgG (anti-S IgG) antibody levels and post-vaccination patient questionnaires regarding vaccine-related side effects following the first and second dose were collected and analyzed. Results In general, a single dose of COVID-19 vaccine yields weaker and heterogeneous serological responses in both patients with hematological and solid malignancies. Upon receiving a second dose, serological response rates indicate a substantial increase in seropositivity to the SARS-CoV-2 spike protein in all cancer cohorts, but antibody titers remain reduced in comparison to healthy controls. Furthermore, seroconversion in patients with hematological malignancies was significantly lower compared to patients with solid tumors. COVID-19 vaccines are safe and well-tolerated in cancer patients based on current data of local and systemic effects. Conclusion Together, these data support the prioritization of patients with cancer to receive their first and second doses to minimize the risk of COVID-19 infection and severe complications in this vulnerable population. Additional prophylactic measures must be considered for high-risk patients where current vaccination programs may not mount sufficient protection against SARS-CoV-2 infection.

BACKGROUND Recent studies have shown that cell cycle events are tightly controlled by complex and shared activities of a select group of kinases. Among these, polo-like kinases (Plks) are regulatory mitotic proteins that are overexpressed in several types of cancer and are associated with poor prognosis. MATERIALS AND METHODS We have evaluated, in preclinical in vitro studies, the activity of a panel of Plk inhibitors against cell lines derived from refractory pediatric leukemia, as well as primary leukemia cells, in culture. Through in vitro growth inhibition studies, Western blot analysis for the expression and activation of key regulators of cell growth and survival and gene silencing studies, we specifically examined the ability of these agents to induce cytotoxicity through the activation of apoptosis and their capacity to interact and modulate the expression and phosphorylation of Aurora kinases. RESULTS Our findings show that the various Plk-1 inhibitors in development show potential utility for the treatment of pediatric leukemia and exhibit a wide range of phosphorylation and target modulatory capabilities. Finally, we provide evidence for a complex interregulatory relationship between Plk-1 and Aurora kinases enabling the identification of synergy and biologic correlates of drug combinations targeting the 2 distinct enzyme systems. DISCUSSION This information provide the rationale for the evaluation of Plk-1 as an effective target for therapeutics in refractory pediatric leukemia and indicate compensatory activities between Plk-1 and Aurora kinases, providing insight into some of the complex mechanisms involved in the process of cell division.

High-risk, relapsed and refractory neuroblastoma are associated with poor 5-years survival rates, demonstrating the need for investigational therapeutic agents to treat this disease. Taurolidine is derived from the aminosulfoacid taurine and has known anti-microbial and anti-inflammatory properties. Taurolidine has also demonstrated anti-neoplastic effects in a range of cancers, providing the rationale to investigate the activity of taurolidine against neuroblastoma in preclinical studies. We investigated the in vitro activity of taurolidine against neuroblastoma using the alamar blue cytotoxicity assay, phase-contrast light microscopy, western blotting and analysis of global gene expression by RNA-Seq. In vivo activity of taurolidine was evaluated using mouse xenograft models. In vitro pre-clinical data show that taurolidine is cytotoxic to neuroblastoma cell lines, inducing cell death by apoptosis. Analysis of global gene expression and determination of signaling pathway activation scores using the in silico Pathway Activation Network Decomposition Analysis (iPANDA) platform indicates that taurolidine has an effect on the Notch, mitogen-activated protein kinase (MAPK) and interleukin-10 (IL-10) signaling pathways. In vivo experiments in xenograft mouse models show that taurolidine decreases tumor growth and improves survival. These results provide supportive pre-clinical data on the activity of taurolidine against neuroblastoma. The findings support the rationale for further evaluation of taurolidine for the treatment of relapsed/refractory neuroblastoma patients in an early phase clinical trial.

Background: Neuroblastoma (NB) is one of the most aggressive and common solid tumors in pediatrics. Development of effective new therapeutics for NB is in progress to help reduce mortality...

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in children. Pathogenesis of RMS is associated with aggressive growth pattern and increased risk of morbidity and mortality. There are two main subtypes or RMS: embryonal and alveolar. The embryonal type is characterized by distinct molecular aberrations, including alterations in the activity of certain protein kinases. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that plays a vital role in focal adhesion (FA) assembly to promote cytoskeleton dynamics and regulation of cell motility. It is regulated by multiple phosphorylation sites: tyrosine 397, Tyr 576/577, and Tyr 925. Tyrosine 397 is the autophosphorylation site that regulates FAK localization at the cell periphery to facilitate the assembly and formation of the FA complex. The kinase activity of FAK is mediated by the phosphorylation of Tyr 576/577 within the kinase domain activation loop. Aberrations of FAK phosphorylation have been linked to the pathogenesis of different types of cancers. In this regard, pY397 upregulation is linked to increase ERMS cell motility, invasion, and tumorigenesis. In this study, we have used an established human embryonal muscle rhabdomyosarcoma cell line RD as a model to examine FAK phosphorylation profiles to characterize its role in the pathogenies of RMS. Our findings revealed a significant increase of FAK phosphorylation at pY397 in RD cells compared to control cells (hTERT). On the other hand, Tyr 576/577 phosphorylation levels in RD cells displayed a pronounced reduction. Our data showed that Y925 residue exhibited no detectable change. The in vitro analysis showed that the FAK inhibitor, PF-562271 led to G1 cell-cycle arrest induced cell death (IC50, ~ 12 µM) compared to controls. Importantly, immunostaining analyses displayed a noticeable reduction of Y397 phosphorylation following PF-562271 treatment. Our data also showed that PF-562271 suppressed RD cell migration in a dose-dependent manner associated with a reduction in Y397 phosphorylation. The data presented herein indicate that targeting FAK phosphorylation at distinct sites is a promising strategy in future treatment approaches for defined subgroups of rhabdomyosarcoma.

Purpose Neuroblastoma is the most common extracranial cancer in children. Although the prognosis for low-risk neuroblastoma patients is good, the 5-year survival rates for high-risk and relapsed patients are low. The poor survival rates for these patients demonstrate the need for novel therapeutic approaches to treat this disease. PV-10 is a sterile 10% solution of Rose Bengal that has previously been shown to induce cell death in a range of adult cancers, providing the rationale for studying the activity of PV-10 against neuroblastoma in preclinical studies. Methods The effects of PV-10 on neuroblastoma were investigated in vitro. Cytotoxicity assays were performed using the alamar blue assay on the following cell lines: SK-N-AS, SK-N-BE(2), IMR5, LAN1, SHEP, and SK-N-SH neuroblastoma cells, SK-N-MC neuroepithelioma cells, and normal primary, BJ, and WI38 fibroblasts. Phase-contrast, fluorescence, and time-lapse video microscopy; flow cytometry; and Western blotting were used to investigate the effects of PV-10 on SK-N-AS and IMR5 cells. Synergy with commonly used anticancer drugs was determined by calculation of combination indices in SK-N-AS and IMR5 cells. Mouse xenograft models of SK-N-AS and IMR5 tumors were also used to evaluate the efficacy of PV-10 in vivo. Results In vitro preclinical data demonstrate that pharmacologically relevant concentrations of PV-10 are cytotoxic to neuroblastoma cell lines. Studies to investigate target modulation in neuroblastoma cell lines show that PV-10 disrupts lysosomes, decreases the percentage of cells in S phase, and induces apoptosis in a concentration-, time-, and cell-line-dependent manner, and we also identify agents that are synergistic with PV-10. Furthermore, experiments in xenograft mouse models show that PV-10 induces tumor regression in vivo. Conclusion Our study provides preclinical data on the efficacy of PV-10 against neuroblastoma and provides rationale for the development of an early phase clinical trial of this agent in relapsed and refractory neuroblastoma patients.

Introduction: PV-10 (10% Rose Bengal) is a small molecule agent previously shown to have potent immunotherapeutic and anti-tumor activities against a number of tumors including metastatic melanoma and refractory neuroblastoma, and is currently undergoing clinical testing as a single-agent for refractory metastatic neuroendocrine cancer (NCT02693067) and in combination with checkpoint inhibitors for metastatic melanoma (NCT02557321) and metastatic uveal melanoma (NCT00986661). We have previously determined that PV-10 induces cell death at pharmacologically relevant concentrations in a panel of phenotypically diverse adult solid tumor cell lines. However, the molecular consequences of this phenomenon have not yet been fully elucidated. In this study, we investigated the target validation and modulation of PV-10 on protein kinase signalling and their associated impact on specific oncogenic pathways in these tumor cells. Methods: A panel of human tumor cell lines derived from breast (MCF-7, T-47D, MDA-MB-231), colorectal (LoVo, T-84), head and neck (CAL-27, Detroit-562, FaDu, UM-SCC-1), and testicular (NCC-IT, NTERA-2, TCAM-2) tissues were treated with PV-10 and their cytotoxic and pro-apoptotic effects were described. Protein kinase profiling was performed using the human phospho-kinase antibody array (#ARY003C, R&D Systems). Western blotting was used to investigate autophagic markers and protein kinase activity. Cell migration inhibition was determined by wound healing assay following treatment with a sublethal dose of PV-10 or pan-WNK inhibitor WNK463. Tumor xenograft studies were carried out according to established protocols. Results: Treatment with PV-10 leads to consistent inhibition of WNK lysine deficient protein kinase 1 (WNK1) phosphorylation based on protein kinase profiling of drug-treated cancer cells when compared with vehicle-treated cells. WNK1 has been implicated as an inhibitor of autophagy and a promoter of cell migration and invasion in several cancers. Western blot analysis showed that PV-10 leads to the downregulation of SQSTM1/p62, upregulation of Beclin-1, and conversion of LC3B-I into LC3B-II, indicating activation of autophagy. PV-10 was also found to significantly inhibit the migration of cancer cells similar to the inhibitor WNK463. Significant tumor regression and target modulation was noted in tumor-bearing animals treated with PV-10. Conclusion: In addition to the known activity of PV-10 to mediate tumor-specific immune responses and cytotoxic effects in neoplasms, we have identified novel therapeutic targets for PV-10, such as WNK1, and provide new insights into its effect on autophagy and metastasis. Our data provide essential mechanism-based evidence and biomarkers of activity to formulate effective PV-10 backbone clinical studies in the future. Citation Format: Son Tran, Satbir Thakur, Mohit Jain, Chunfen Zhang, Aru Narendran. Identification and in vivo validation of unique anti-oncogenic properties and mechanisms involving protein kinase signalling and autophagy mediated by the investigational new agent PV-10 [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 1121.

10024 Background: KMT2a rearrangements are a hallmark of infant (less than 1 year of age) leukemia and are associated with poor prognosis. Menin is a ubiquitous protein that binds to the N-terminal of the KMT2a-fusion protein to mediate the oncogenic activity of KMT2a-rearranged leukemia cells. In this study, we evaluated the effect of multiple menin inhibitors and effective drug combinations for the treatment of KMT2A-rearranged infant leukemia. Methods: FISH analysis and immunoblotting confirmed the presence of KMT2a-fusion in the primary patient samples and cell lines studied. Lymphocytes from healthy donors were used as controls. Cells were treated with various concentration of multiple menin inhibitors for 72 hours and growth inhibition was measured using alamar blue assay. Infant leukemia cells were treated with a panel of FDA-approved agents (n = 221) to identify potential synergy, additive- and antagonistic-effects with specific menin inhibitors. Therapeutic drug interaction properties were established by calculating combination indices (CI) using the Chou-Talalay method. Mode of cell death and cellular target modulations were determined by western blot analysis. The effect of targeting menin in the context of the leukemogenic bone marrow microenvironment was determined through stromal cell co-cultures. Results: A comprehensive analysis of menin inhibitors on infant leukemia cell lines and primary patient cells exhibited significant and quantitatively diverse responses in cells with distinct molecular properties. Within the panel of menin inhibitors, infant B-ALL cells were found to be more sensitive to MI-463, MI-503 and MI-136 with a mean IC50 of 5.9µM, 6.1µM and 10.2µM, respectively. On the other hand, MI-3 exhibited an IC50 of 35.6µM. The cytotoxic effect of menin inhibitors on normal lymphocytes was minimal, suggesting a favourable therapeutic window (p < 0.0001). High-throughput screening with a library of > 200 FDA-approved drugs revealed significant sensitivity of distinct infant leukemia cells to proteasome, HDAC and CDK9 inhibitors. Among these, substantial drug synergy was observed between menin and proteasome inhibitors. For example, carfilzomib synergised with menin inhibitors over a broad range of concentrations with a CI value of 0.7. Conclusions: In this study, we present and discuss the initial proof-of-concept preclinical data for the effective anti-leukemic activity of menin inhibition against KMT2A-rearranged infant leukemia cells. Furthermore, the comprehensive drug screen and drug combination studies identified a spectrum of mechanistically-validated synergies, providing usable data for the formulation of multi-agent clinical studies for this currently unmet need in pediatric oncology.

Background: Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase and a catalytic subunit of the polycomb repressive complex 2 (PRC2) that catalyzes the mono-, di-, and tri-methylation of histone H3 at Lys 27 (H3K27me3) to facilitate chromatin remodeling and gene silencing functions. The overexpression of EZH2 is associated with high levels of H3K27me3 in various types of cancers. Previous reports showed a significant association of EZH2 aberrations in pediatric cancers such as soft tissue sarcomas and glioblastoma. Recent reports in human subjects and animal models have also suggested a central role of EZH2 in the induction and progression of acute myeloid leukemia. Methods: In this study, we aimed to investigate the molecular status of EZH in cell lines derived from distinct pediatric leukemia to assess the efficacy of targeting EZH2 to suppress cancer cell survival and proliferation. Cell cytotoxicity and the half maximal inhibitory concentration (IC50) were measured by Alamar blue cytotoxicity assay. The molecular status of EZH2 was profiled by DNA sequencing and western blot analysis of EZH2 protein levels in THP-1, SEM, and MV4:11. In addition, Methylation of histone H3 was evaluated by immunoblotting and immunostaining analyses. Results: Our results showed that EZH2 protein is overexpressed in the pediatric monocytic cell line THP-1 , but not in other leukemia derived cell lines MV4;11 and SEM. Screening a panel of methyltransferase inhibitors revealed that three inhibitors; GSK126, UNC1999 and EPZ-5687 are the most potent inhibitors that suppressed EZH2 activity selectively on lysine 27 which resulted in increased apoptosis and inhibition of AKT and ERK protein phosphorylation in THP-1 cells. Our data demonstrated a significant increase in apoptosis in cells treated with drug combination (EZH2i and selinexor) compared to EZH2i inhibitors alone. Conclusions: Taken together, our data provide initial evidence that targeting EZH2 is a promising therapeutic strategy for the treatment of subtypes of pediatric AML. Also, combining EZH2 inhibitors with selinexor may increase the treatment efficacy in these patients. Findings from this study indicate further evaluation and consideration of these compounds for early phase clinical studies in selected pediatric malignancies in the future.

Background: The function of the Ras association domain family 1 (RASSF1)/modulator of apoptosis 1 (MOAP-1) molecular tumor suppressor pathway is often perturbed in many solid and blood cancers by epigenetic loss of RASSF1A via promoter specific methylation. However, a detailed analysis of expression and stability of MOAP-1 as well as effect on cellular proliferation and cell death in blood cancers has not been explored. Methods: Expression of MOAP-1 RASSF1A was performed by immunoblotting analysis, MOAP-1 effect on biology determined by cell proliferation, cell death and tumorigenicity assays. Lastly, proteomic analysis in MOAP-1 in form 1 and 2 expressing cells reveal new interacting partners to MOAP-1. Results: The expression of MOAP-1 appears to be quite varied and exists as two forms, a p39 and p46 form in blood cancers. The higher MOAP-1 p46 form was mainly observed in acute myeloid leukemia (AML) and some acute lymphocytic leukemia (ALL) patients and cell lines. Furthermore, MOAP-1 p46 form can be reduced to the p39 form upon calf intestinal or lambda phosphatase treatment, suggesting post-translational phosphorylation likely produces the slower migrating form. Blood cancer cell lines containing the p46 form of MOAP-1 appears to be more resistant to cell death signals and have increased growth. In addition, we document in vivo protection from tumorigenesis of cells containing MOAP-1 following tail vein injection of cancer cells. Lastly, proteomic analysis revealed several interesting components of the MOAP-1 interactome in blood cancer cells that we validated. Conclusions: MOAP-1 is a bona fide tumor suppressor in blood cancers with functions beyond apoptosis.

BackgroundPopulation-based examination of comorbidity is an emerging field of study.AimsThe purpose of the present population level study is to expand our understanding of how cancer and mental illness are temporally associated.MethodA sample of 83 648 056 physician billing records for 664 838 (56% female) unique individuals over the age of 18 was stratified on ages 19–49 years and 50+ years, with temporal order of mental disorder and cancer forming the basis of comparison.ResultsMental disorders preceded cancers for both genders within each age strata. The full range of cancers and mental disorders preceding or following each pivot ICD class are described in terms of frequency of diagnosis and duration in days, with specific examples illustrated.ConclusionsThe temporal comorbidity between specific cancers and mental disorders may be useful in screening or clinical planning and may represent indicators of disease mechanism that warrant further screening or investigation.Declaration of interestNone.

BackgroundDecitabine is a deoxycytidine nucleoside derivative inhibitor of DNA-methyltransferases, which has been studied extensively and is approved for myelodysplastic syndrome in adults but with less focus in children. Accordingly, we conducted a phase 1 multicenter, randomized, open-label study to evaluate decitabine pre-treatment before standard induction therapy in children with newly diagnosed AML to assess safety and tolerability and explore a number of biologic endpoints.ResultsTwenty-four patients were fully assessable for all study objectives per protocol (10 in Arm A, 14 in Arm B). All patients experienced neutropenia and thrombocytopenia. The most common grade 3 and 4 non-hematologic adverse events observed were gastrointestinal toxicities and hypophosphatemia. Plasma decitabine PK were similar to previously reported adult data. Overall CR/CRi was similar for the two arms. MRD negativity at end-induction was 85% in Arm A versus 67% in Arm B patients. DNA methylation measured in peripheral blood over the course of treatment tracked with blast clearance and matched marrow aspirates at day 0 and day 21. Unlike end-point marrow analyses, promoter methylation in blood identified an apparent reversal of response in the lone treatment failure, one week prior to the patient’s marrow aspirate confirming non-response. Decitabine-induced effects of end-induction marrows in Arm A were reflected by changes in DNA methylation and gene expression comparison with matched paired marrow diagnostic aspirates.ConclusionsThis first-in-pediatrics trial demonstrates that decitabine prior to standard combination chemotherapy is feasible and well tolerated in children with newly diagnosed AML. Pre-treatment with decitabine may represent a newer therapeutic option for pediatric AML, especially as it appears to induce important epigenetic alterations. The novel biological correlates studied in this trial offer a clinically relevant window into disease progression and remission. Additional studies are needed to definitively assess whether decitabine can enhance durability responses in children with AML. This trial was registered at www.clinicaltrials.gov as NCT01177540.

Introduction: Cancer is one of the most common causes of death in patients with primary immunodeficiencies (PIDs). The immune surveillance concept postulates that PIDs are an important contributor to cancer growth and outcomes. Although several immunodeficiency syndromes are known to be associated with malignancies in children and adults, currently, the molecular mechanisms that link immune functions to cancers are poorly understood. Here we describe distinct molecular characteristics in adult cancers with respect to PID-associated genes that impact survival outcomes in affected patients. Methods: In this study, we integrated transcriptome data of 28 adult cancers from the public database The Cancer Genome Atlas (TCGA) with respective healthy tissues as control from the Genotype-Tissue Expression (GTEx) project. Unified datasets integrating GTEx healthy samples and TCGA cancer data were provided by the Recount2 protocol and differential expression analyses (DEA) were carried out using the integrated limma-voom and edgeR pipelines in the TCGAbiolinks R package. Gene ontology (GO) enrichment analyses were performed using the pathfindR R package. Mutational and clinical data of adult cancer patient samples in TCGA and the AACR Project GENIE were consolidated using cBioPortal and the maftools R package. PID-associated genes were curated from the latest registry by the European Society for Immunodeficiencies (ESID). Results: Of 307 PID-associated genes, 151 (32.0%) up-regulated and 88 (18.6%) down-regulated genes were identified across the 28 unified TCGA-GTEx datasets. From the identified differentially expressed gene sets, GO analysis revealed enrichment in immunological pathways related to complement and coagulation cascades (27/28 datasets), systemic lupus erythematosus (25/28), in addition to Fanconi anemia (22/28). The greatest frequency of mutations in PID-associated genes from the consolidated TCGA and GENIE datasets were KRAS (14.83%), KMT2D (10.03%), TERT (8.99%), PRKDC (7.59%) and PTEN (6.18%) across all cancer types, with a total of 259 affected PID-associated genes. Survival analyses using Cox proportional-hazards and Kaplan-Meier models will assess the clinical implications of the identified molecular alterations in affected patients. Conclusion: Our integrative approach aids in the elucidation of molecular mechanisms that bridge PIDs to tumour biology. These data may help identify important biomarkers and potential future targeted therapeutics. Citation Format: Son Tran, Luis Murguia-Favela, Aru Narendran. The impact of primary immunodeficiency informed molecular landscape on the biology and prognosis of refractory malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2255.

ATRT of the CNS constitute a group of rare and aggressive early childhood tumors with poor prognosis. While there are differing chemotherapeutic regimens for ATRT, high-dose MTX is a crucial component of many therapeutic protocols. Currently, the biological mechanisms contributing to the generation of MTX resistance in ATRT are unknown. To identify genes involved in MTX resistance in ATRT, an unbiased genome-wide RNAi screen on ATRT cell lines was conducted using 24,000 distinct shRNAs covering 8,000 genes. ATRT cells were transfected with a retrovirus containing pRS-shRNA vectors and treated with puromycin for selection. The resulting cells were treated with MTX to identify resistant clones and resistant colonies were then isolated and amplified individually. Presence of shRNA inserts in each colony was determined by PCR using pRS forward and reverse primers. PCR products within each of the three resistant colonies were sequenced, leading to the identification of three distinct genes, TGIF1, HIF3A and PGAM2, as potential indicators of resistance. Western blotting verified depletion of these proteins in their respective colonies. Proliferation assays were then conducted on cells from each resistant colony alongside control cells to confirm that the identified drivers conferred resistance. Sensitivity to MTX was significantly lower in TGIF1-depleted (IC50=212±8.48nM, n=3), HIF3A-depleted (IC50=52±4.68nM, n=3) and PGAM2-depleted (IC50=41±4.13nM, n=3) cells compared to control cells (IC50=19±2.87nM, n=3), (p

10035 Background: Neuroblastoma (NB) is the most common extracranial solid tumor in children. Despite the development of risk stratification tools to improve prognostication, prediction of patient survival outcomes in NB remains poor. In this study we used an unbiased machine-learning algorithm to develop and validate a transcriptomic signature capable of predicting 5-year overall (OS) and event-free survival (EFS) in these patients. Methods: The TARGET-Neuroblastoma dataset (n = 243) was used as the training set. Two independent NB cohorts, E-MTAB-179 (n = 478) and GSE85047 (n = 266) were used as validation sets. Elastic net regression was employed to identify transcripts associated with EFS. Association of the developed signature with EFS and OS was evaluated using univariate Cox proportional hazards (CoxPH), Kaplan-Meier, and 5-year receiver-operator characteristic curves in validation cohorts. Further, the independent prognostic value of the signature was assessed using multivariate CoxPH models with relevant clinicopathologic variables including age, INSS stage, and N-Myc amplification status in both validation sets. Finally, a nomogram was developed to integrate the signature with prognostic clinicopathologic variables to evaluate their combined efficacy for prediction of 5-year EFS and OS. Results: We identified a 21-gene signature that demonstrates significant association with EFS and OS in both E-MTAB-178 and GSE49710 validation cohorts. Moreover, the signature is independent of clinicopathological variables and can be effectively incorporated into a risk model, improving the prognostic performance. Several genes within the signature have been previously implicated in NB, including ECEL1, HOXC9 and ARAF1. Conclusions: To the best of our knowledge, we are the first to use an unbiased machine learning approach to generate a transcriptomic gene signature for neuroblastoma prognosis externally validated in multiple cohorts across platforms. This 21-gene transcriptomic signature significantly associated with EFS and OS in this disease. Combining this signature with current prognostic clinicopathologic variables will improve risk stratification of affected patients and may inform effective clinical decision-making.[Table: see text]

10033 Background: Although survival rates have improved in the recent past, relapse and refractory disease remain a significant cause of death in children with leukemia. This calls for an urgent need for the development of novel therapies that could effectively treat leukemias in children. The E26 transformation specific (ETS) family of transcription factors regulate various normal cellular functions but are abnormally expressed in various cancers, including leukemia. TK216 is an ETS inhibitor, that has shown pre-clinical activity and clinical efficacy in solid tumors. In this study, we explore the feasibility of using TK216 as a therapeutic agent for the treatment of high risk refractory pediatric leukemia. Methods: A panel of pediatric leukemia derived cell lines and primary blast cells representing a spectrum of molecular abnormalities seen in pediatric leukemia were treated in vitro with TK216 to determine cytotoxicity. Normal lymphocytes were used as controls and cell viability was determined 72 hours post-treatment by Alamar blue assay. The induction of tumor cell apoptosis and target modulation were detected by Western blotting. Alterations in the cell cycle were assessed by FACS analysis with PI staining. Drug combination studies were carried out with established anti-leukemic agents to identify synergy for greater therapeutic efficiency. Results: TK216 decreased cell viability in leukemia cells compared to normal lymphocyte controls in a dose-dependent manner with variations in sensitivity noted with inherent molecular abnormalities. The IC50 values observed ranged from 0.22 µM for the most sensitive cell line, MV4-11 to 0.95 µM for least sensitive cell line, SUP-B15. Apoptosis induction upon TK216 treatment was confirmed by PARP cleavage and caspase 3 activation. Cell cycle analysis demonstrated increased sub-G1 population of cells after TK216 treatment. A strong correlation between sub-G1 population and sensitivity of the cell line towards TK216 (47% in MV4-11 vs 3.72% in SUP-B15) was observed. Screening of a panel of 200 FDA approved anti-cancer agents in drug combination studies identified potential agents for drug synergy. Significant drug synergy was noted with TK216 in combination with the epigenetic modifier 5-azacytidine and the Bcl-2 inhibitor, Venetoclax. [Combination Index for Venetoclax and TK216, mean = 0.65 for MV4-11 and 0.33 for SUP-B15]. Conclusions: Data from our study demonstrate that the ETS inhibitor TK216 induces apoptosis and cell cycle arrest in pediatric leukemia cells at physiologically relevant concentrations. Our combination studies identified distinct anti-cancer agents that could be used for developing effective drug combination regimens with TK216. Overall, our findings provide essential preclinical data for the consideration of TK216 in early phase clinical trials for the treatment of selected high-risk and refractory childhood leukemia.

e14544 Background: PV-10 (10% rose bengal disodium; 4,5,6,7-tetrachloro-2’,4’,5’,7’-tetraiodofluorescein) is a novel therapeutic agent previously shown to have potent anti-tumor activity following intratumoral injection in melanoma and refractory neuroblastoma, and currently is undergoing clinical testing as a single-agent for refractory metastatic neuroendocrine cancer (NCT02693067) and in combination with checkpoint inhibitors for metastatic melanoma (NCT02557321) and metastatic uveal melanoma (NCT00986661). Given the established clinical efficacy of PV-10 in adult melanoma and hepatic cancers via intratumoral injection, there is a need to evaluate the therapeutic potential of PV-10 in high-risk and refractory adult solid tumors via systemic administration. Our study aims to identify the clinical potential of systemically-delivered PV-10 by first generating prerequisite in vitro data for adult malignancies. Methods: Cytotoxicity assays were performed using the Alamar Blue assay to study the effects of PV-10 in vitro 96-hours post-treatment against a panel of adult solid tumor cell lines derived from breast (MCF-7, T-47D, MDA-MB-231), colorectal (HCT-116, LoVo, T-84), head and neck (CAL-27, Detroit-562, FaDu, UM-SCC-1), and testicular (NCC-IT, NTERA-2, TCAM-2) tissues. Light microscopy and Western blotting were used to investigate apoptosis induction and target modulation in tumor cells after PV-10 treatment. Results: In vitro results from our study demonstrate that PV-10 is cytotoxic at pharmacologically relevant concentrations across the indicated cell lines. Specifically, tumor cell lines originating from testicular tissues were highly sensitive to PV-10 treatment (Mean ± SD IC50: 37.5 ± 16.4 µM; n = 3) compared to breast (117.5 ± 71.0 µM; n = 3), colorectal (64.79 µM; n = 3), and head and neck (106.6 ± 29.2 µM; n = 4) cell lines. Western blot analyses showed dose- and time-dependent activation of pro-apoptotic protein markers in caspase-3 and PARP cleavage, indicating drug-induced apoptosis. Conclusions: This study provides the first pre-clinical results of PV-10 as a novel systemically-delivered therapeutic agent for a range of high-risk and refractory adult solid tumors. Data obtained from our in vitro experiments using a broad repertoire of cell lines that represent diverse molecular and phenotypic subtypes of solid tumors in adults can serve as prerequisite pre-clinical data to establish clinical testing in these populations.