Jonathan Yun

MRI-localized biopsies reveal subtype-specific differences in molecular and cellular composition at the margins of glioblastoma.

Significance Molecular analysis of surgically resected glioblastomas (GBM) samples has uncovered phenotypically and clinically distinct tumor subtypes. However, little is known about the molecular features of the glioma margins that are left behind after surgery. To address this key issue, we performed RNA-sequencing (RNA-seq) and histological analysis on MRI-guided biopsies from the contrast-enhancing core and nonenhancing margins of GBM. Computational deconvolution of the RNA-seq data revealed that cellular composition, including nonneoplastic cells, is a major determinant of the expression patterns at the margins of GBM. The different GBM subtypes show distinct expression patterns that relate the contrast enhancing centers to the nonenhancing margins of tumors. Understanding these patterns may provide a means to infer the molecular and cellular features of residual disease. Glioblastomas (GBMs) diffusely infiltrate the brain, making complete removal by surgical resection impossible. The mixture of neoplastic and nonneoplastic cells that remain after surgery form the biological context for adjuvant therapeutic intervention and recurrence. We performed RNA-sequencing (RNA-seq) and histological analysis on radiographically guided biopsies taken from different regions of GBM and showed that the tissue contained within the contrast-enhancing (CE) core of tumors have different cellular and molecular compositions compared with tissue from the nonenhancing (NE) margins of tumors. Comparisons with the The Cancer Genome Atlas dataset showed that the samples from CE regions resembled the proneural, classical, or mesenchymal subtypes of GBM, whereas the samples from the NE regions predominantly resembled the neural subtype. Computational deconvolution of the RNA-seq data revealed that contributions from nonneoplastic brain cells significantly influence the expression pattern in the NE samples. Gene ontology analysis showed that the cell type-specific expression patterns were functionally distinct and highly enriched in genes associated with the corresponding cell phenotypes. Comparing the RNA-seq data from the GBM samples to that of nonneoplastic brain revealed that the differentially expressed genes are distributed across multiple cell types. Notably, the patterns of cell type-specific alterations varied between the different GBM subtypes: the NE regions of proneural tumors were enriched in oligodendrocyte progenitor genes, whereas the NE regions of mesenchymal GBM were enriched in astrocytic and microglial genes. These subtype-specific patterns provide new insights into molecular and cellular composition of the infiltrative margins of GBM.

Regression of Recurrent Malignant Gliomas with Convection-Enhanced Delivery of Topotecan.

BACKGROUND Convection-enhanced delivery of chemotherapeutics for the treatment of malignant glioma is a technique that delivers drugs directly into a tumor and the surrounding interstitium through continuous, low-grade positive-pressure infusion. This allows high local concentrations of drug while overcoming the limitations imposed by toxicity and the blood-brain barrier in systemic therapies that prevent the use of many potentially effective drugs. OBJECTIVE To examine the safety profile of a conventional chemotherapeutic agent, topotecan, via convection-enhanced delivery in the treatment of recurrent malignant gliomas and secondarily to assess radiographic response and survival. METHODS We performed a prospective, dose-escalation phase Ib study of the topoisomerase-I inhibitor topotecan given by convection-enhanced delivery in patients with recurrent malignant gliomas. RESULTS Significant antitumor activity as described by radiographic changes and prolonged overall survival with minimal drug-associated toxicity was demonstrated. A maximum tolerated dose was established for future phase II studies. CONCLUSION Topotecan by convection-enhanced delivery has significant antitumor activity at concentrations that are nontoxic to normal brain. The potential for use of this therapy as a generally effective treatment option for malignant gliomas will be tested in subsequent phase II and III trials.

Convection-Enhanced Delivery of Topotecan into a PDGF-Driven Model of Glioblastoma Prolongs Survival and Ablates Both Tumor-Initiating Cells and Recruited Glial Progenitors

The contribution of microenvironment to tumor growth has important implications for optimizing chemotherapeutic response and understanding the biology of recurrent tumors. In this study, we tested the effects of locally administered topotecan on a rat model of glioblastoma that is induced by intracerebral injection of PDGF (platelet-derived growth factor)-IRES (internal ribosome entry site)-GFP (green fluorescent protein)-expressing retrovirus, treated the tumors by convection-enhanced delivery (CED) of topotecan (136 μmol/L) for 1, 4, or 7 days, and then characterized the effects on both the retrovirus-transformed tumor cells (GFP(+) cells) as well as the uninfected glial progenitor cells (GFP(-) cells) that are recruited to the tumor. Topotecan treatment reduced GFP(+) cells about 10-fold and recruited progenitors by about 80-fold while providing a significant survival advantage that improved with greater treatment duration. Regions of glial progenitor ablation occurred corresponding to the anatomic distribution of topotecan as predicted by MRI of a surrogate tracer. Histopathologic changes in recurrent tumors point to a decrease in recruitment, most likely due to the chemotherapeutic ablation of the recruitable progenitor pool.

The Transcriptional Regulatory Network of Proneural Glioma Determines the Genetic Alterations Selected During Tumor Progression

Proneural glioblastoma is defined by an expression pattern resembling that of oligodendrocyte progenitor cells and carries a distinctive set of genetic alterations. Whether there is a functional relationship between the proneural phenotype and the associated genetic alterations is unknown. To evaluate this possible relationship, we performed a longitudinal molecular characterization of tumor progression in a mouse model of proneural glioma. In this setting, the tumors acquired remarkably consistent genetic deletions at late stages of progression, similar to those deleted in human proneural glioblastoma. Further investigations revealed that p53 is a master regulator of the transcriptional network underlying the proneural phenotype. This p53-centric transcriptional network and its associated phenotype were observed at both the early and late stages of progression, and preceded the proneural-specific deletions. Remarkably, deletion of p53 at the time of tumor initiation obviated the acquisition of later deletions, establishing a link between the proneural transcriptional network and the subtype-specific deletions selected during glioma progression.

Prolonged intracerebral convection-enhanced delivery of topotecan with a subcutaneously implantable infusion pump

Intracerebral convection-enhanced delivery (CED) of chemotherapeutic agents currently requires an externalized catheter and infusion system, which limits its duration because of the need for hospitalization and the risk of infection. To evaluate the feasibility of prolonged topotecan administration by CED in a large animal brain with the use of a subcutaneous implantable pump. Medtronic Synchromed-II pumps were implanted subcutaneously for intracerebral CED in pigs. Gadodiamide (28.7 mg/mL), with or without topotecan (136 μM), was infused at 0.7 mL/24 h for 3 or 10 days. Pigs underwent magnetic resonance imaging before and at 6 times points after surgery. Enhancement and FLAIR+ volumes were calculated in a semi-automated fashion. Magnetic resonance spectroscopy-based topotecan signature was also investigated. Brain histology was analyzed by hematoxylin and eosin staining and with immunoperoxidase for a microglial antigen. CED of topotecan/gadolinium was well tolerated in all cases (n = 6). Maximum enhancement volume was reached at day 3 and remained stable if CED was continued for 10 days, but it decreased if CED was stopped at day 3. Magnetic resonance spectroscopy revealed a decrease in parenchymal metabolites in the presence of topotecan. Similarly, the combination of topotecan and gadolinium infusion led to a FLAIR+ volume that tended to be larger than that seen after the infusion of gadolinium alone. Histological analysis of the brains showed an area of macrophage infiltrate in the ipsilateral white matter upon infusion with topotecan/gadolinium. Intracerebral topotecan CED is well tolerated in a large animal brain for up to 10 days. Intracerebral long-term CED can be achieved with a subcutaneously implanted pump and provides a stable volume of distribution. This work constitutes a proof of principle for the safety and feasibility for prolonged CED, providing a means of continuous local drug delivery that is accessible to the practicing neuro-oncologist.

A novel adenoviral vector labeled with superparamagnetic iron oxide nanoparticles for real-time tracking of viral delivery.

In vivo tracking of gene therapy vectors challenges the investigation and improvement of biodistribution of these agents in the brain, a key feature for their targeting of infiltrative malignant gliomas. The glioma-targeting Ad5/3-cRGD gene therapy vector was covalently bound to super-paramagnetic iron oxide (Fe(3)O(4)) nanoparticles (SPION) to monitor its distribution by MRI. Transduction of labeled and unlabeled vectors was assessed on the U87 glioma cell line and normal human astrocytes (NHA), and was higher in U87 compared to NHA, but was similar between labeled and unlabeled virus. An in vivo study was performed by intracranial subcortical injection of labeled-Ad5/3-cRGD particles into a pig brain. The labeled vector appeared in vivo as a T2-weighted hyperintensity and a T2-gradient echo signal at the injection site, persisting up to 72 hours post-injection. We describe a glioma-targeting vector that is labeled with SPION, thereby allowing for MRI detection with no change in transduction capability.

Convection-Enhanced Delivery for Targeted Delivery of Antiglioma Agents: The Translational Experience

Recent improvements in the understanding of glioblastoma (GBM) have allowed for increased ability to develop specific, targeted therapies. In parallel, however, there is a need for effective methods of delivery to circumvent the therapeutic obstacles presented by the blood-brain barrier and systemic side effects. The ideal delivery system should allow for adequate targeting of the tumor while minimizing systemic exposure, applicability across a wide range of potential therapies, and have existing safe and efficacious systems that allow for widespread application. Though many alternatives to systemic delivery have been developed, this paper will focus on our experience with convection-enhanced delivery (CED) and our focus on translating this technology from pre-clinical studies to the treatment of human GBM.

Convection-enhanced delivery of etoposide is effective against murine proneural glioblastoma

BACKGROUND Glioblastoma subtypes have been defined based on transcriptional profiling, yet personalized care based on molecular classification remains unexploited. Topoisomerase II (TOP2) contributes to the transcriptional signature of the proneural glioma subtype. Thus, we targeted TOP2 pharmacologically with etoposide in proneural glioma models. METHODS TOP2 gene expression was evaluated in mouse platelet derived growth factor (PDGF)(+)phosphatase and tensin homolog (PTEN)(-/-)p53(-/-) and PDGF(+)PTEN(-/-) proneural gliomas and cell lines, as well as human glioblastoma from The Cancer Genome Atlas. Correlation between TOP2 transcript levels and etoposide susceptibility was investigated in 139 human cancer cell lines from the Cancer Cell Line Encyclopedia public dataset and in mouse proneural glioma cell lines. Convection-enhanced delivery (CED) of etoposide was tested on cell-based PDGF(+)PTEN(-/-)p53(-/-) and retroviral-based PDGF(+)PTEN(-/-) mouse proneural glioma models. RESULTS TOP2 expression was significantly higher in human proneural glioblastoma and in mouse proneural tumors at early as well as late stages of development compared with normal brain. TOP2B transcript correlated with susceptibility to etoposide in mouse proneural cell lines and in 139 human cancer cell lines from the Cancer Cell Line Encyclopedia. Intracranial etoposide CED treatment (680 μM) was well tolerated by mice and led to a significant survival benefit in the PDGF(+)PTEN(-/-)p53(-/-) glioma model. Moreover, etoposide CED treatment at 80 μM but not 4 μM led to a significant survival advantage in the PDGF(+)PTEN(-/-) glioma model. CONCLUSIONS TOP2 is highly expressed in proneural gliomas, rendering its pharmacological targeting by intratumoral administration of etoposide by CED effective on murine proneural gliomas. We provide evidence supporting clinical testing of CED of etoposide with a molecular-based patient selection approach.

The safety of resection for primary central nervous system lymphoma: a single institution retrospective analysis.

Surgical resection is not the standard of care for primary central nervous system lymphoma (PCNSL), as historical studies have demonstrated unfavorable complication rates and limited benefits. Some recent studies suggest that resection may provide a therapeutic benefit, yet the safety of these procedures has not been systematically investigated in the setting of modern neurosurgery. We examined the safety of surgical resection for PCNSL. We retrospectively analyzed all patients with PCNSL treated at Columbia University Medical Center between 2000 and 2015 to assess complications rates following biopsy or resection using the Glioma Outcomes Project system. We identified predictors of complications and selection for resection. Well-validated scales were used to quantify patients’ baseline clinical characteristics, including functional status, comorbid disease burden, and cardiac risk. The overall complication rate was 17.2% after resection, and 28.2% after biopsy. Cardiac risk (p = 0.047, OR 1.72 [1.01, 2.95]), and comorbid diagnoses (p = 0.004, OR 3.05 [1.42, 6.57]) predicted complications on multivariable regression. Patients who underwent resection had better KPS scores (median 70 v. 80, p = 0.0068, ∆ 10 [0.0, 10.00]), and were less likely to have multiple (46.5% v. 27.6%, p = 0.030, OR 1.42 [1.05, 1.92]) or deep lesions (70.4% v. 39.7%, p = 0.001, OR 1.83 [1.26, 2.65]). Age (p = 0.048, OR 0.75 per 10-year increase [0.56, 1.00]) and deep lesions (p = 0.003, OR 0.29 [0.13, 0.65]) influenced selection for resection on multivariable regression. Surgical resection of PCNSL is safe for select patients, with complication rates comparable to rates for other intracranial neoplasms. Whether there is a clinical benefit to resection cannot be concluded.

Primary Central Nervous System Lymphoma: A Critical Review of the Role of Surgery for Resection

BACKGROUND Primary central nervous system lymphomas (PCNSL) are rare CNS tumors that carry a poor prognosis, with most patients suffering recurrence. Progress has been made in the treatment of this pathology, notably with the widespread use of systemic high dose methotrexate. However, unlike most other malignant CNS neoplasms, surgery for cytoreduction is not routinely performed for this disease, mainly as a result of negative experiences decades ago. Since these studies were published, the availability of intraoperative monitoring, MR imaging and neuro-navigation as well as surgical adjuncts such as fluorescence- guided resection have greatly improved the safety of intracranial procedures. More recent data is suggestive of a potential survival benefit for resection of single PCNSL lesions when patients are subsequently treated with modern regimen high-dose methotrexate, yet this evidence is limited, and should be interpreted conservatively. METHODS AND FINDINGS A systematic review of the literature was performed to identify trials evaluating surgical options for the treatment of PCNSL. CONCLUSION In this review, we provide a critical overview of the evidence favoring and discouraging resection for PCNSL. This literature suffers from several biases and limitations that must be considered in the context of the extrapolation of this literature into clinical decision-making.