Armida W. M. Fabius

IDH1 mutation is sufficient to establish the glioma hypermethylator phenotype

Both genome-wide genetic and epigenetic alterations are fundamentally important for the development of cancers, but the interdependence of these aberrations is poorly understood. Glioblastomas and other cancers with the CpG island methylator phenotype (CIMP) constitute a subset of tumours with extensive epigenomic aberrations and a distinct biology. Glioma CIMP (G-CIMP) is a powerful determinant of tumour pathogenicity, but the molecular basis of G-CIMP remains unresolved. Here we show that mutation of a single gene, isocitrate dehydrogenase 1 (IDH1), establishes G-CIMP by remodelling the methylome. This remodelling results in reorganization of the methylome and transcriptome. Examination of the epigenome of a large set of intermediate-grade gliomas demonstrates a distinct G-CIMP phenotype that is highly dependent on the presence of IDH mutation. Introduction of mutant IDH1 into primary human astrocytes alters specific histone marks, induces extensive DNA hypermethylation, and reshapes the methylome in a fashion that mirrors the changes observed in G-CIMP-positive lower-grade gliomas. Furthermore, the epigenomic alterations resulting from mutant IDH1 activate key gene expression programs, characterize G-CIMP-positive proneural glioblastomas but not other glioblastomas, and are predictive of improved survival. Our findings demonstrate that IDH mutation is the molecular basis of CIMP in gliomas, provide a framework for understanding oncogenesis in these gliomas, and highlight the interplay between genomic and epigenomic changes in human cancers.

Loss of the tyrosine phosphatase PTPRD leads to aberrant STAT3 activation and promotes gliomagenesis

Significance Protein tyrosine phosphatase receptor-δ (PTPRD) is a frequently inactivated tumor-suppressor gene. We demonstrate that Ptprd inactivation in the context of Cdkn2a/p16Ink4a deletion is sufficient to promote tumorigenesis in vivo. Our mouse model closely recapitulates the genetic events on chromosome 9p that occur in cancer. We demonstrate that PTPRD is a haploinsufficient tumor suppressor and provide a rationale for the high frequency of heterozygous loss of PTPRD in human glioblastoma. Finally, this study establishes loss of PTPRD, a STAT3 phosphatase, as a cause of STAT3 hyperactivation in gliomas. PTPRD, which encodes the protein tyrosine phosphatase receptor-δ, is one of the most frequently inactivated genes across human cancers, including glioblastoma multiforme (GBM). PTPRD undergoes both deletion and mutation in cancers, with copy number loss comprising the primary mode of inactivation in GBM. However, it is unknown whether loss of PTPRD promotes tumorigenesis in vivo, and the mechanistic basis of PTPRD function in tumors is unclear. Here, using genomic analysis and a glioma mouse model, we demonstrate that loss of Ptprd accelerates tumor formation and define the oncogenic context in which Ptprd loss acts. Specifically, we show that in human GBMs, heterozygous loss of PTPRD is the predominant type of lesion and that loss of PTPRD and the CDKN2A/p16INK4A tumor suppressor frequently co-occur. Accordingly, heterozygous loss of Ptprd cooperates with p16 deletion to drive gliomagenesis in mice. Moreover, loss of the Ptprd phosphatase resulted in phospho-Stat3 accumulation and constitutive activation of Stat3-driven genetic programs. Surprisingly, the consequences of Ptprd loss are maximal in the heterozygous state, demonstrating a tight dependence on gene dosage. Ptprd loss did not increase cell proliferation but rather altered pathways governing the macrophage response. In total, we reveal that PTPRD is a bona fide tumor suppressor, pinpoint PTPRD loss as a cause of aberrant STAT3 activation in gliomas, and establish PTPRD loss, in the setting of CDKN2A/p16INK4A deletion, as a driver of glioma progression.

Protein tyrosine phosphatase receptor delta acts as a neuroblastoma tumor suppressor by destabilizing the aurora kinase a oncogene

BackgroundProtein tyrosine phosphatase receptor delta (PTPRD) is a member of a large family of protein tyrosine phosphatases which negatively regulate tyrosine phosphorylation. Neuroblastoma is a major childhood cancer arising from precursor cells of the sympathetic nervous system which is known to acquire deletions and alterations in the expression patterns of PTPRD, indicating a potential tumor suppressor function for this gene. The molecular mechanism, however, by which PTPRD renders a tumor suppressor effect in neuroblastoma is unknown.ResultsAs a molecular mechanism, we demonstrate that PTPRD interacts with aurora kinase A (AURKA), an oncogenic protein that is over-expressed in multiple forms of cancer, including neuroblastoma. Ectopic up-regulation of PTPRD in neuroblastoma dephosphorylates tyrosine residues in AURKA resulting in a destabilization of this protein culminating in interfering with one of AURKAs primary functions in neuroblastoma, the stabilization of MYCN protein, the gene of which is amplified in approximately 25 to 30% of high risk neuroblastoma.ConclusionsPTPRD has a tumor suppressor function in neuroblastoma through AURKA dephosphorylation and destabilization and a downstream destabilization of MYCN protein, representing a novel mechanism for the function of PTPRD in neuroblastoma.

Advanced Unilateral Retinoblastoma: The Impact of Ophthalmic Artery Chemosurgery on Enucleation Rate and Patient Survival at MSKCC

Purpose To report on the influence of ophthalmic artery chemosurgery (OAC) on enucleation rates, ocular and patient survival from metastasis and impact on practice patterns at Memorial Sloan Kettering for children with advanced intraocular unilateral retinoblastoma. Patients and Methods Single-center retrospective review of all unilateral retinoblastoma patients with advanced intraocular retinoblastoma treated at MSKCC between our introduction of OAC (May 2006) and December 2014. End points were ocular survival, patient survival from metastases and enucleation rates. Results 156 eyes of 156 retinoblastoma patients were included. Primary enucleation rates have progressively decreased from a rate of >95% before OAC to 66.7% in the first year of OAC use to the present rate of 7.4%. The percent of patients receiving OAC has progressively increased from 33.3% in 2006 to 92.6% in 2014. Overall, ocular survival was significantly better in eyes treated with OAC in the years 2010–2014 compared to 2006–2009 (p = 0.023, 92.7% vs 68.0% ocular survival at 48 months). There have been no metastatic deaths in the OAC group but two patients treated with primary enucleation have died of metastatic disease. Conclusion OAC was introduced in 2006 and its impact on patient management is profound. Enucleation rates have decreased from over 95% to less than 10%. Our ocular survival rate has also significantly and progressively improved since May 2006. Despite treating more advanced eyes rather then enucleating them patient survival has not been compromised (there have been no metastatic deaths in the OAC group). In our institution, enucleation is no longer the most common treatment for advanced unilateral retinoblastoma.

Mutant-IDH1-dependent chromatin state reprogramming, reversibility, and persistence

Mutations in IDH1 and IDH2 (encoding isocitrate dehydrogenase 1 and 2) drive the development of gliomas and other human malignancies. Mutant IDH1 induces epigenetic changes that promote tumorigenesis, but the scale and reversibility of these changes are unknown. Here, using human astrocyte and glioma tumorsphere systems, we generate a large-scale atlas of mutant-IDH1-induced epigenomic reprogramming. We characterize the reversibility of the alterations in DNA methylation, the histone landscape, and transcriptional reprogramming that occur following IDH1 mutation. We discover genome-wide coordinate changes in the localization and intensity of multiple histone marks and chromatin states. Mutant IDH1 establishes a CD24+ population with a proliferative advantage and stem-like transcriptional features. Strikingly, prolonged exposure to mutant IDH1 results in irreversible genomic and epigenetic alterations. Together, these observations provide unprecedented high-resolution molecular portraits of mutant-IDH1-dependent epigenomic reprogramming. These findings have substantial implications for understanding of mutant IDH function and for optimizing therapeutic approaches to targeting IDH-mutant tumors.This study uses human astrocytes and glioma tumorspheres to generate an atlas of mutant-IDH1-induced epigenomic reprogramming. The findings have implications for understanding mutant IDH function and for optimizing approaches to target IDH-mutant tumors.

Simultaneous Bilateral Ophthalmic Artery Chemosurgery for Bilateral Retinoblastoma (Tandem Therapy).

Objective Report on the 7-year experience with bilateral ophthalmic artery chemosurgery (OAC-Tandem therapy) for bilateral retinoblastoma. Design Retrospective, single institution study. Subjects 120 eyes of 60 children with bilateral retinoblastoma treated since March 2008. Methods Retrospective review of all children treated at Memorial Sloan Kettering with bilateral ophthalmic artery chemosurgery (Melphalan, Carboplatin, Topotecan, Methotrexate) delivered in the same initial session to both naïve and previously treated eyes. Main Outcome Measures Ocular survival, metastatic disease, patient survival from metastases, second cancers, systemic adverse effects, need for transfusion of blood products, electroretinogram before and after treatment. Results 116 eyes were salvaged (4 eyes were enucleated: 3 because of progressive disease, 1 family choice). Kaplan Meier ocular survival was 99.2% at one year, 96.9% at 2 and 3 years and 94.9% for years 4 through 7. There were no cases of metastatic disease or metastatic deaths with a mean follow-up of 3.01 years. Two children developed second cancers (both pineoblastoma) and one of them died. Transfusion of blood products was required in 3 cases (4 transfusions), 1.9%. Two children developed fever/neutropenia requiring hospitalization (0.95%). ERGs were improved in 21.6% and unchanged after treatment in 52.5% of cases (increase or decrease of less than 25μV). Conclusions Bilateral ophthalmic artery chemosurgery is a safe and effective technique for managing bilateral retinoblastoma-even when eyes are advanced bilaterally, and if both eyes have progressed after systemic chemotherapy. Ocular survival was excellent (94.9% at 8 years), there were no cases of of metastatic disease and no deaths from metastatic disease, but children remain at risk for second cancers. In 21.6% of cases ERG function improved. Despite using chemotherapy in both eyes in the same session, systemic toxicity was low.

OCULAR PHARMACOLOGY OF CHEMOTHERAPY FOR RETINOBLASTOMA.

Purpose: To review preclinical and clinical pharmacokinetic studies of the three most important chemotherapy drugs used for intraocular retinoblastoma and the contribution of the reported results to optimize treatment. Methods: Systemic review of pharmacokinetic studies identified by a literature search at Pubmed using the keywords carboplatin, melphalan, topotecan, intravitreal, ophthalmic artery chemosurgery, pharmacokinetics, and retinoblastoma. Results: A total of 21 studies were reviewed for assessing the preclinical and clinical pharmacokinetics of carboplatin, topotecan, and melphalan delivered by intravenous, periocular, ophthalmic artery, and intravitreal routes. Some preclinical studies were done before translation to the clinics. Others, despite encouraging preclinical data as reported for periocular topotecan did not correlate with clinical use. In addition, as was the case for melphalan after ophthalmic artery chemosurgery and despite nonfavorable preclinical information, some routes of drug delivery are clinically effective. Besides topotecan, complete knowledge of the pharmacokinetics of melphalan and carboplatin is still lacking. Conclusion: Pharmacokinetic knowledge of chemotherapy may aid to guide retinoblastoma treatment in favor of safety and efficacy. Nonetheless, results obtained in preclinical models should be translated with care to the clinics.

Ophthalmic artery chemosurgery for eyes with advanced retinoblastoma

ABSTRACT Background: Surgical removal of one or both eyes has been the most common way to treat children with retinoblastoma worldwide for more than 100 years. Ophthalmic artery chemosurgery (OAC) was introduced 10 years ago and it has been used as an alternative to enucleation for eyes with advanced retinoblastoma. The purpose of this report is to analyze our 9-year experience treating advanced retinoblastoma eyes with OAC. Materials and methods: Single-arm retrospective study from a single center of 226 eyes with eyes of retinoblastoma patients with advanced intraocular disease defined as both Reese-Ellsworth (RE) “Va” or ”Vb” and International Classification Retinoblastoma (ICRb) group “D” or ”E” (COG Classification). Ocular survival, patient survival, second cancers, and electroretinography (ERG) were assessed. Results: Ocular survival at five years for these advanced eyes was 70.2% (95% confidence interval, 57.3%–79.8%). When eyes were divided into groups either by RE classification or ICRb, no significant differences in ocular survival were seen. Ocular survival was significantly better in naïve compared to non-naïve eyes (80.2% vs 58.4%, p = 0.041). The ERG distribution was very similar before and after OAC treatment for the patient population that did not receive intravitreal chemotherapy. Three patients (1.5%) have developed metastatic retinoblastoma (previously reported) and were successfully treated (no deaths). Conclusion: Using OAC for advanced eyes (the majority of such eyes have been enucleated in the past) enables 70% 5-year ocular survival. Treated eyes have a similar ERG distribution before and after treatment. No patient has died of metastatic retinoblastoma.

Second primary malignancies in retinoblastoma patients treated with intra-arterial chemotherapy: the first 10 years

Background/Aims Survivors of retinoblastoma carry a lifetime risk of secondary malignancies. It is well established that external beam radiation increases this risk; however, the risk with ophthalmic artery chemosurgery (OAC) remains unknown. We report on 10 years of experience with OAC and the rate of second primary malignancy (SPM) development. Methods This is a single-centre retrospective review approved by the Memorial Sloan Kettering Cancer Center Institutional Review Board of all patients who received OAC over a 10-year period, from May 2006 to November 2016. The second tumour incidence and survival in patients with germline disease (bilateral and unilateral with family history or confirmed germline mutation) was estimated using the Kaplan-Meier method. Patients who received external beam radiotherapy were excluded from analyses. Results Two hundred and thirty-three patients with heritable retinoblastoma who received OAC were analysed. Nineteen patients were excluded for having received external beam radiation. The Kaplan-Meier estimate of the likelihood for SPM development was 2.7% at 5 years (95% CI 0 to 25). All of the SPMs were pineoblastomas and all patients had bilateral disease in this cohort. Conclusions In our 10-year experience, we have found that SPM development in patients with germline retinoblastoma treated with OAC alone is comparable to previously published rates. In the first 10 years, OAC did not increase the known incidence of SPMs. This cohort will continue to be followed to establish the rate of development with extended follow-up.

Abstract 521: Glioma-associated IDH mutation induces miR-34a repression and stem cell-like physiology through enhanced PDGF signaling

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Point mutations in isocitrate dehydrogenase enzymes (IDH1 and IDH2) have been identified in 70-90% of lower-grade gliomas (LGGs; WHO grade II and III) as foundational genomic alterations. Glioma-associated IDH mutations occur in active site arginine residues and confer a neomorphic activity resulting in overproduction of the oncometabolite R(-)-2-hydroxyglutarate (2HG). The affects of 2HG on cellular physiology are widespread and include global shifts in epigenomic profiles. LGGs have also been repeatedly linked with dysregulated platelet-derived growth factor (PDGF) signaling. We have recently demonstrated that miR-34a is downregulated in gliomas in response to dysregulated PDGF signaling and that miR-34a directly targets the PDGF receptor (PDGFRA) in high-grade gliomas. Analyzing a panel of diffuse gliomas, we find that miR-34a is specifically downregulated in LGG in response to IDH mutation. Similarly, in multiple isogenic cell line systems, IDH mutation induces repression of miR-34a. Also in these contexts, IDH mutation induces neurosphere formation and the expression of stem cell-associated genes. miR-34a has been reported to target pluripotency factors such as LIN28, OCT4 and NANOG. Accordingly, we find that murine neuroglial progenitor cells expressing IDH mutant isoform express higher levels of these factors than isogenic controls. The stem cell-like phenotype of IDH mutant-expressing cells is morphologically reversed by restoring miR-34a expression in the cells. Despite findings that IDH mutation correlates with hypermethylation at the MIR34a locus in LGG tumors, we have not been able to demonstrate the functional relevance of this. Instead, we find that IDH mutation is associated with enhanced PDGF signaling, and we demonstrate that inhibition or stimulation of PDGF signaling in IDH mutant cells increases or decreases miR-34a expression, respectively. Our studies support a model in which glioma-associated IDH mutation induces miR-34a repression and stem cell-like physiology through enhanced PDGF signaling. Citation Format: Joachim Silber, Girish Harinath, Prasanna Tamarapu Parthasarathy, Armida W.M. Fabius, Sevin Turcan, Timothy A. Chan, Jason T. Huse. Glioma-associated IDH mutation induces miR-34a repression and stem cell-like physiology through enhanced PDGF signaling. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 521. doi:10.1158/1538-7445.AM2014-521