Formal synergy studies with DON and carboplatin

PURPOSE. Proliferative vitreoretinopathy (PVR) is the most common cause of failure of surgically repaired rhegmatogenous retinal detachment (RRD). Chemically induced and cell injection PVR models do not fully simulate the clinical characteristics of PVR in the post-RRD context. There is an unmet need for translational models in which to study mechanisms and treatments specific to RRD-PVR. METHODS. RRD was induced in adult Dutch Belted rabbits. Posterior segments were fixed or processed for RNA sequencing at 6 hours and 2, 7, 14, and 35 days after induction. Histochemical staining and immunolabeling for glial fibrillary acidic protein, alpha smooth muscle actin, vascular endothelial growth factor receptor 2, CD68, and RPE 65 kDa protein were performed, and labeling intensity was scored. Single cell RNA sequencing was performed. RESULTS. Acute histopathological changes included intravitreal and intraretinal hemorrhage, leukocytic vitritis, chorioretinitis, and retinal rarefaction. Chronic lesions showed retinal atrophy, gliosis, fibrotic subretinal membranes, and epiretinal fibrovascular proliferation. Fibrillar collagen was present in the fibrocellular and fibrovascular membranes in chronic lesions. Moderate to strong labeling of glia and vasculature was detected in chronic lesions. At day 14, most cells profiled by single cell sequencing were identified as Muller glia and microglia, consistent with immunolabeling. Expression of several fibrillar collagen genes was upregulated in chronic lesions. CONCLUSIONS. Histological and transcriptional features of this rabbit model simulate important features of human RRD-PVR, including the transition to chronic intraretinal and periretinal fibrosis. This animal model of RRD with features of PVR will enable further research on targeted treatment interventions.

Cellular proliferation in high vs low MYC AT/RT cell lines

Growth of cell lines in glutamine-free media

ANNEXIN V assay after DON/Carboplatin treatments

Weight of mice throguhout in vivo treatments

Purpose Proliferative vitreoretinopathy (PVR) is the most common cause of failure of surgically repaired rhegmatogenous retinal detachment (RRD). Chemically-induced and cell-injection PVR models do not fully simulate the clinical characteristics of PVR in the post-RRD context. There is an unmet need for translational models in which to study mechanisms and treatments specific to RRD-PVR. Methods RRD-PVR was induced in adult Dutch Belted rabbits. Posterior segments of enucleated globes were fixed or processed for RNA-Seq at 6 hours and 2, 7, 14, and 35 days post-induction. Histochemical staining and immunolabeling for glial fibrillary acidic protein (GFAP), alpha smooth muscle actin (αSMA), vascular endothelial growth factor receptor 2 (VEGFR2), CD68, and retinal pigment epithelium 65 kDa protein (RPE65) were performed, and labeling intensity was scored. Single cell RNA sequencing was performed. Results Acute histopathologic changes included intravitreal and intraretinal hemorrhage, leukocytic vitritis, chorioretinitis, and retinal rarefaction. Chronic lesions showed retinal atrophy, gliosis, fibrotic subretinal membranes, and epiretinal fibrovascular proliferation. Fibrillar collagen was present in the fibrocellular and fibrovascular membranes in chronic lesions. Moderate to strong labeling of glia and vasculature was detected in chronic lesions. At day 14, most cells profiled by single cell sequencing were identified as Müller glia and microglia, consistent with immunolabeling. Expression of several fibrillar collagen genes were upregulated in chronic lesions. Conclusions Histologic and transcriptional features of this rabbit model simulate important features of human RRD-PVR, including the transition to chronic intra and periretinal fibrosis. This high-fidelity in vivo model of RRD-PVR will enable further research on targeted treatment interventions.

Abstract Purpose: Atypical teratoid/rhabdoid tumors (AT/RT) are aggressive infantile brain tumors with poor survival. Recent advancements have highlighted significant molecular heterogeneity in AT/RT with an aggressive subgroup featuring overexpression of the MYC proto-oncogene. We perform the first comprehensive metabolic profiling of patient-derived AT/RT cell lines to identify therapeutic susceptibilities in high MYC-expressing AT/RT. Experimental Design: Metabolites were extracted from AT/RT cell lines and separated in ultra-high performance liquid chromatography mass spectrometry. Glutamine metabolic inhibition with 6-diazo-5-oxo-L-norleucine (DON) was tested with growth and cell death assays and survival studies in orthotopic mouse models of AT/RT. Metabolic flux analysis was completed to identify combination therapies to act synergistically to improve survival in high MYC AT/RT. Results: Unbiased metabolic profiling of AT/RT cell models identified a unique dependence of high MYC AT/RT on glutamine for survival. The glutamine analogue, DON, selectively targeted high MYC cell lines, slowing cell growth, inducing apoptosis, and extending survival in orthotopic mouse models of AT/RT. Metabolic flux experiments with isotopically labeled glutamine revealed DON inhibition of glutathione (GSH) synthesis. DON combined with carboplatin further slowed cell growth, induced apoptosis, and extended survival in orthotopic mouse models of high MYC AT/RT. Conclusions: Unbiased metabolic profiling of AT/RT identified susceptibility of high MYC AT/RT to glutamine metabolic inhibition with DON therapy. DON inhibited glutamine-dependent synthesis of GSH and synergized with carboplatin to extend survival in high MYC AT/RT. These findings can rapidly translate into new clinical trials to improve survival in high MYC AT/RT.

Atypical teratoid rhabdoid tumors (AT/RT) are deadly tumors of infancy in need of new, targeted therapies to reduce morbidity and improve survival. Molecular analyses have revealed considerable molecular heterogeneity dividing AT/RT into three distinct subgroups. MYC expression is identified in a particularly aggressive subgroup of AT/RT. MYC is challenging to target directly given large, flat, featureless protein-protein binding sites. To identify anomalies that can be targeted in high MYC-expressing AT/RT, we performed unbiased metabolic profiling of each of our 8 AT/RT cell lines using high pressure liquid chromatography mass spectrometry (HPLC-MS). Partial Least Squares-Discriminant Analysis (PLS-DA) identified a distinct metabolic profile in high MYC-expressing cell lines. Further pathway analysis highlighted unique patterns of glutamine utilization in these cell lines. In fact, high-MYC expressing cell lines were more dependent on glutamine for growth and survival (MTS assay, glutamine-free media vs normal media). Due to this dependence on glutamine metabolism, we hypothesized that high-MYC expressing AT/RT would be especially sensitive to glutamine metabolic inhibitors. We showed that the glutamine analogue, 6-diazo-5-oxo-L-norleucine (DON) slowed high-MYC expressing AT/RT cell growth (MTS assay, p<0.001), induced high rates of apoptosis (C-PARP by western blot), and improved survival in orthotopic mouse models (p<0.01 by log-rank test). In contrast, low-MYC expressing models were relatively resistant to DON. Metabolic flux experiments showed that DON inhibited glutamine-dependent synthesis of glutathione, depleting cells of intracellular glutathione. This DON-induced depletion of glutathione sensitized cells to carboplatin, leading to increased AT/RT cell death (cell viability assay, p<0.001 by ANOVA) and extended survival in mice bearing AT/RT orthotopic xenografts (p< 0.001 by log rank test). We aim to translate these findings into a new clinical trial to improve survival in this deadly disease.

Atypical teratoid rhabdoid tumors (AT/RT) are deadly tumors of infancy in need of new, targeted therapies. Molecular analyses have revealed 3 epigenetically distinct subgroups of AT/RT. High MYC-expressing tumors are a particularly aggressive subgroup, with a 5-year median survival of 18.5%. MYC is difficult to directly target given large, flat, featureless protein-protein binding sites. We performed the first unbiased metabolic profile of AT/RT cell models by high-performance liquid chromatography-mass spectrometry. This study revealed that high MYC-expressing AT/RT have a unique metabolic profile (Partial Least Squares-Discriminant Analysis). Pathway analysis highlights a dependence on glutamine metabolism in high-MYC expressing AT/RT. High MYC-expressing cell lines grow poorly in glutamine-free media compared to low-MYC cell lines (MTS assay, glutamine-free media vs normal media). Due to this dependence on glutamine metabolism, we hypothesized that high-MYC expressing AT/RT would be especially sensitive to glutamine metabolic inhibitors. We show that the glutamine analogue, 6-diazo-5-oxo-L-norleucine (DON) slows high-MYC expressing AT/RT cell growth, induces high rates of apoptosis, and improves survival in orthotopic mouse models of high-MYC expressing AT/RT (p =0.0027 by log-rank test). In contrast, low-MYC expressing models are relatively insensitive to DON. In uniformly labeled glutamine metabolic analyses of AT/RT cells, DON treatment led to depletion of glutathione levels by preventing the production of glutamate. DON treatment synergized with carboplatin to kill AT/RT cells in vitro and extend the life of mice bearing AT/RT orthotopic xenografts (p Citation Format: Sabrina Z. Wang, Brad Poore, Jesse Alt, Antoinette Price, Sariah Allen, Brent Orr, Rana Rais, Barbara Slusher, Charles Eberhart, Eric H. Raabe, Jeffrey H. Rubens. Unbiased metabolic profiling of atypical teratoid/rhabdoid tumors predicts sensitivity to the glutamine metabolic inhibitor 6-diazo-5-oxo-L-norleucine [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 5267.

Retinoblastoma is the most common intraocular malignancy in children. We previously found that the ACVR1C/SMAD2 pathway is significantly upregulated in invasive retinoblastoma samples from patients. Here we studied the role of an ACVR1C ligand, Nodal, in regulating growth and metastatic dissemination in retinoblastoma. Inhibition of Nodal using multiple short hairpin (shRNAs) in WERI Rb1 and Y79 retinoblastoma cell cultures reduced growth by more than 90%, as determined by CCK-8 growth assay. Proliferation was also significantly inhibited, as found by Ki67 assay. These effects were paralleled by inhibition in the phosphorylation of the downstream effector SMAD2, as well as induction of apoptosis, as we observed more than three-fold increase in the percentage of cells positive for cleaved-caspase-3 or expressing cleaved-PARP1. Importantly, we found that downregulation of Nodal potently suppressed invasion in vitro, by 50 to 80%, as determined by transwell invasion assay (p = 0.02). Using an orthotopic model of retinoblastoma in zebrafish, we found 34% reduction in the ability of the cells to disseminate outside the eye, when Nodal was knocked down by shRNA (p = 0.0003). These data suggest that Nodal plays an important role in promoting growth, proliferation and invasion in retinoblastoma, and can be considered a new therapeutic target for both primary tumor growth and metastatic progression.

Background. Pediatric low-grade glioma (pLGG) often initially responds to front-line therapies such as carboplatin, but more than 50% of treated tumors eventually progress and require additional therapy. With the discovery that pLGG often contains mammalian target of rapamycin (mTOR) activation, new treatment modalities and combinations are now possible for patients. The purpose of this study was to determine if carboplatin is synergistic with the mTOR complex 1 inhibitor everolimus in pLGG. Methods. We treated 4 pLGG cell lines and 1 patient-derived xenograft line representing various pLGG genotypes, including neurofibromatosis type 1 loss, proto-oncogene B-Raf (BRAF)-KIAA1549 fusion, and BRAF(v)(600E) mutation, with carboplatin and/or everolimus and performed assays for growth, cell proliferation, and cell death. lmmunohistochemistry as well as in vivo and in vitro metabolomics studies were also performed. Results. Carboplatin synergized with everolimus in all of our 4 pLGG cell lines (combination index <1 at Fa 0.5). Combination therapy was superior at inhibiting tumor growth in vivo. Combination treatment increased levels of apoptosis as well as gamma-H2AX phosphorylation compared with either agent alone. Everolimus treatment suppressed the conversion of glutamine and glutamate into glutathione both in vitro and in vivo. Exogenous glutathione reversed the effects of carboplatin and everolimus. Conclusions. The combination of carboplatin and everolimus was effective at inducing cell death and slowing tumor growth in pLGG models. Everolimus decreased the amount of available glutathione inside the cell, preventing the detoxification of carboplatin and inducing increased DNA damage and apoptosis.

Atypical teratoid rhabdoid tumors (AT/RT) are deadly infantile brain tumors in dire need of new, targeted therapies. Recent molecular analyses revealed considerable tumor heterogeneity subdividing AT/RT into 3 distinct sub-groups - TYR, SHH, and MYC. The MYC subgroup is especially aggressive with a dismal survival. Directly targeting MYC has proven to be challenging, but MYC is known to drive reliance on glutamine for cellular metabolism. We hypothesize that high MYC expressing AT/RT can be targeted with glutamine antagonists to improve survival. 6-diazo-5-oxo L-norleucine (DON) is a glutamine analogue that has been well tolerated in phase I clinical trials in children but never tested against MYC-driven pediatric brain tumors. We find that DON slows cell growth in high MYC expressing AT/RT while it has no effect on low MYC expressing AT/RT cell lines (MTS assay; p< 0.01 DON 10uM compared to DMSO control) or normal neural stem cells. DON also causes G2/M cell cycle arrest in high MYC expressing cell lines (MUSE cell cycle analysis) and induces DNA damage and apoptosis (Western blot for pH2A.X and c-PARP respectively). DON treatment of MYC-expressing AT/RT orthotopic xenografts nearly doubles median survival (p<0.001 by log-rank test; median survival extended from 21 to 36 days). DON combines with cisplatin to synergistically slow cell growth (MTS assay, p<0.01) and induce further DNA damage (Western blot pH2A.X). This study takes a novel approach to targeting cancer metabolism and serves as the first therapeutic strategy addressing the most aggressive subgroup of AT/RT. Since the maximum tolerated dose in pediatric phase I trials of DON was never reached, these findings support the rationale for future clinical trials testing DON and similar drugs against the MYC subgroup of AT/RT as well as other deadly MYC-driven brain tumors.

Background: Atypical teratoid/rhabdoid tumors (AT/RTs) are deadly pediatric brain tumors driven by LIN28. Mammalian target of rapamycin (mTOR) is activated in many deadly, drug-resistant cancers and governs important cellular functions such as metabolism and survival. LIN28 regulates mTOR in normal cells. We therefore hypothesized that mTOR is activated downstream of LIN28 in AT/RT, and the brain-penetrating mTOR complex 1 and 2 (mTORC1/2) kinase inhibitor TAK228 would reduce AT/RT tumorigenicity.Methods: Activation of mTOR in AT/RT was determined by measuring pS6 and pAKT (Ser473) by immunohistochemistry on tissue microarray of 18 primary AT/RT tumors. In vitro growth assays (BrdU and MTS), death assays (CC3, c-PARP by western blot), and survival curves of AT/RT orthotopic xenograft models were used to measure the efficacy of TAK228 alone and in combination with cisplatin.Results: Lentiviral short hairpin RNA-mediated knockdown of LIN28A led to decreased mTOR activation. Primary human AT/RT had high levels of pS6 and pAKT (Ser473) in 21% and 87% of tumors by immunohistochemistry. TAK228 slowed cell growth, induced apoptosis in vitro, and nearly doubled median survival of orthotopic xenograft models of AT/RT. TAK228 combined with cisplatin synergistically slowed cell growth and enhanced cisplatin-induced apoptosis. Suppression of AKT sensitized cells to cisplatin-induced apoptosis and forced activation of AKT protected cells. Combined treatment with TAK228 and cisplatin significantly extended survival of orthotopic xenograft models of AT/RT compared with each drug alone.Conclusions: TAK228 has efficacy in AT/RT as a single agent and synergizes with conventional chemotherapies by sensitizing tumors to cisplatin-induced apoptosis. These results suggest TAK228 may be an effective new treatment for AT/RT.

Conjunctival squamous cell carcinoma is a malignancy of the ocular surface. The molecular drivers responsible for the development and progression of this disease are not well understood. We therefore compared the transcriptional profiles of eight snap-frozen conjunctival squamous cell carcinomas and one in situ lesion with normal conjunctival specimens in order to identify diagnostic markers or therapeutic targets. RNA was analyzed using oligonucleotide microarrays, and a wide range of transcripts with altered expression identified, including many dysregulated in carcinomas arising at other sites. Among the upregulated genes, we observed more than 30-fold induction of the matrix metalloproteinases, MMP-9 and MMP-11, as well as a prominent increase in the mRNA level of a calcium-binding protein important for the intracellular calcium signaling, S100A2, which was induced over 20-fold in the tumor cohort. Clusterin was the most downregulated gene, with an approximately 180-fold reduction in the mRNA expression. These alterations were all confirmed by qPCR in the samples used for initial microarray analysis. In addition, immunohistochemical analysis confirmed the overexpression of MMP-11 and S100A2, as well as reductions in clusterin, in several independent in situ carcinomas of conjunctiva. These data identify a number of alterations, including upregulation of MMP-9, MMP-11, and S100A2, as well as downregulation of clusterin, associated with epithelial tumorigenesis in the ocular surface.

Abstract LIN28 is a somatic cell reprogramming and stem cell factor that binds to and regulates RNA involved in growth, invasion and metabolic genes. We have previously shown that LIN28 is upregulated in atypical teratoid rhabdoid tumors (AT/RT) and contributes to the aggressive nature of these tumors. One of the canonical downstream targets of LIN28 is the mTOR pathway. We hypothesized that AT/RT tumorgenicity is dependent on mTOR signaling downstream of LIN28 and inhibition of this pathway would disrupt tumor growth. We found that primary human AT/RT samples have high expression of the mTOR pathway as determined by immunohistochemistry staining for P-S6 and P-AKT Ser473 (21% of tumors with 2+ P-S6 staining; 87% with 2+ p-AKT staining). The dual TORC1/2 inhibitor MLN0128 has good brain penetration and is currently being tested in phase I clinical trials. Treatment of AT/RT cell lines with MLN0128 inhibits TORC1/2 targets in vitro and suppresses cell proliferation at 100nM concentration in multiple AT/RT cell lines (MTS assay for BT12 p<0.005 vs DMSO control; BT37 p = 0.006 vs DMSO control; and CHLA-06 p<0.005 vs DMSO control by t-test). MLN0128 also slows cell proliferation via BrdU assay (BT12 p<0.005 vs DMSO control; BT37 p<0.005 100nM vs DMSO control; CHLA-06 p<0.005 100nM vs DMSO control by t-test) and induces apoptosis measured by Western Blot for cleaved PARP and cleaved caspase 3 assay (BT12 p<0.005 100nM vs DMSO; BT37 p<0.005 100nM vs DMSO; CHLA-06 p = 0.007 100nM vs DMSO by t-test). MLN0128 induces apoptosis synergistically with cisplatin, which is the backbone of conventional AT/RT therapy (CC3 assay BT37 p<0.005 vs DMSO by t-test) and slows cell growth (MTS assay BT37 p<0.005 vs DMSO control by t-test). MLN0128 treatment of AT/RT xenograft mouse models extends overall survival from a median of 23 days to 39 days (Log-rank test p = 0.002). Targeting the mTOR pathway with MLN0128 leads to potent in vitro and in vivo activity against AT/RT and can be combined with conventional chemotherapy to provide an important survival benefit. MLN0128 may be a candidate for future clinical trials to treat this deadly tumor. Citation Format: Jeffrey Rubens, Antoinette Price, Brent Orr, Charles Eberhart, Eric Raabe. Targeting mTOR downstream of LIN28 in atypical teratoid rhabdoid tumors promotes apoptosis and suppresses tumorigenicity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2102.

AbstractPurpose: We used human stem and progenitor cells to develop a genetically accurate novel model of MYC-driven Group 3 medulloblastoma. We also developed a new informatics method, Disease-model Signature versus Compound-Variety Enriched Response (“DiSCoVER”), to identify novel therapeutics that target this specific disease subtype.Experimental Design: Human neural stem and progenitor cells derived from the cerebellar anlage were transduced with oncogenic elements associated with aggressive medulloblastoma. An in silico analysis method for screening drug sensitivity databases (DiSCoVER) was used in multiple drug sensitivity datasets. We validated the top hits from this analysis in vitro and in vivo.Results: Human neural stem and progenitor cells transformed with c-MYC, dominant-negative p53, constitutively active AKT and hTERT formed tumors in mice that recapitulated Group 3 medulloblastoma in terms of pathology and expression profile. DiSCoVER analysis predicted that aggressive MYC-driven Group 3 medulloblastoma would be sensitive to cyclin-dependent kinase (CDK) inhibitors. The CDK 4/6 inhibitor palbociclib decreased proliferation, increased apoptosis, and significantly extended the survival of mice with orthotopic medulloblastoma xenografts.Conclusions: We present a new method to generate genetically accurate models of rare tumors, and a companion computational methodology to find therapeutic interventions that target them. We validated our human neural stem cell model of MYC-driven Group 3 medulloblastoma and showed that CDK 4/6 inhibitors are active against this subgroup. Our results suggest that palbociclib is a potential effective treatment for poor prognosis MYC-driven Group 3 medulloblastoma tumors in carefully selected patients. Clin Cancer Res; 22(15); 3903–14. ©2016 AACR.