Transition to Chronic Fibrosis in an Animal Model of Retinal Detachment With Features of Proliferative Vitreoretinopathy.

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 Mϋller 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.

Downregulation of Nodal inhibits metastatic progression in retinoblastoma.

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.

Unbiased Metabolic Profiling Predicts Sensitivity of High MYC-Expressing Atypical Teratoid/Rhabdoid Tumors to Glutamine Inhibition with 6-Diazo-5-Oxo-L-Norleucine.

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.

Inhibition of mTORC1 in pediatric low-grade glioma depletes glutathione and therapeutically synergizes with carboplatin.

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 BRAFV600E mutation, with carboplatin and/or everolimus and performed assays for growth, cell proliferation, and cell death. Immunohistochemistry 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.

The TORC1/2 inhibitor TAK228 sensitizes atypical teratoid rhabdoid tumors to cisplatin-induced cytotoxicity.

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.

DiSCoVERing Innovative Therapies for Rare Tumors: Combining Genetically Accurate Disease Models with In Silico Analysis to Identify Novel Therapeutic Targets.

PURPOSE: 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.

Altered gene expression in conjunctival squamous cell carcinoma.

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.

Disrupting LIN28 in atypical teratoid rhabdoid tumors reveals the importance of the mitogen activated protein kinase pathway as a therapeutic target.

Atypical teratoid rhabdoid tumor (AT/RT) is among the most fatal of all pediatric brain tumors. Aside from loss of function mutations in the SMARCB1 (BAF47/INI1/SNF5) chromatin remodeling gene, little is known of other molecular drivers of AT/RT. LIN28A and LIN28B are stem cell factors that regulate thousands of RNAs and are expressed in aggressive cancers. We identified high-levels of LIN28A and LIN28B in AT/RT primary tumors and cell lines, with corresponding low levels of the LIN28-regulated microRNAs of the let-7 family. Knockdown of LIN28A by lentiviral shRNA in the AT/RT cell lines CHLA-06-ATRT and BT37 inhibited growth, cell proliferation and colony formation and induced apoptosis. Suppression of LIN28A in orthotopic xenograft models led to a more than doubling of median survival compared to empty vector controls (48 vs 115 days). LIN28A knockdown led to increased expression of let-7b and let-7g microRNAs and a down-regulation of KRAS mRNA. AT/RT primary tumors expressed increased mitogen activated protein (MAP) kinase pathway activity, and the MEK inhibitor selumetinib (AZD6244) decreased AT/RT growth and increased apoptosis. These data implicate LIN28/RAS/MAP kinase as key drivers of AT/RT tumorigenesis and indicate that targeting this pathway may be a therapeutic option in this aggressive pediatric malignancy.