PLGA Foundation Grant Proposal March 31, Pediatric Low Grade Astrocytoma: Dedicated Tumor Banking And Establishment Of Cell Lines And Xenografts

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1 PLG Foundation Grant Proposal March 31, 2009 Pediatric Low Grade strocytoma: Dedicated Tumor anking nd Establishment Of Cell Lines nd Xenografts Charles G. Eberhart M.D., Ph.D., Kenneth Cohen M.D., Eli ar Ph.D., and Peter urger M.D. Introduction Pediatric Low Grade strocytoma (PLG) are a heterogeneous group of generally slow-growing glial neoplasms, including pilocytic astrocytomas, grade II fibrillary astrocytomas and tumors of mixed (often poorly defined) phenotype with an astrocytic component. Most common are pilocytic/pilomyxoid astrocytomas. Infiltrating WHO grade II fibrillary astrocytomas represent the next most common type of PLG. Some tumors also appear to have an oligodendroglial component, although these generally lack the genetic changes found in adult oligodendrogliomas and oligoastrocytomas, and likely represent unique pediatric tumors. Indeed, relatively little is known about the genetic alterations that differentiate grade II fibrillary astrocytomas from other PLG, or cause any of these tumors to form. However, the molecular biology and clinical behavior of grade II fibrillary astrocytomas arising in children seems to be different from that observed in adult cases. major roadblock hindering investigations into the various types of PLG is the lack of frozen tissue or renewable tumor models such as cell lines and xenografts. Several factors have contributed to this. First, such tumors are rare, and have not been a research priority at most institutions. Second, surgical resections are often small, and the limited tissue available has gone to pathology for diagnosis, with little or none reserved for research. Finally, because of their relatively indolent growth, it has been difficult to develop cell line or xenograft models. elow, we describe a strategy designed to harvest tissue from the majority of PLG and other pediatric brain tumors resected at Johns Hopkins. We feel we can overcome the barriers listed above by (1) the commitment of sufficient resources, including dedicated personnel, (2) by better integration between neurosurgery, neuropathology and neurooncology, and (3) by the utilization of improved laboratory technologies enabling the establishment of cell lines and xenografts. im 1 ank Frozen Samples From Most PLG Cases. Rationale: We plan to utilize funds requested in this proposal, as well as existing resources in neuropathology and neuro-oncology, to hire a technician dedicated to the banking of pediatric brain tumors. No such individual currently exists, and tumor banking has therefore in the past been dependent on having an otherwise committed scientist or technician from the Eberhart laboratory stop their ongoing experiments on short notice in 1

2 order to obtain and process clinical specimens. ecause freezers, tumor bank labeling equipment, and a relational database are already in place, the costs will be limited to the dedicated technician for this im. n additional key component of this plan is the commitment of Dr. Peter urger, a world expert in brain tumor diagnosis, to actively assist in the determination of which specimens to bank while operations are still being performed, as well as serving as final reviewer of pathology diagnoses. We anticipate banking tissue from the majority of cases. Some biopsies, however, may be so small that all surgical tissue will be required for diagnosis. Tumor ank Design: The Surgical Neuropathology Division is located adjacent to the neurosurgical operating rooms, pathology reference laboratory, and research laboratories. This proximity, facilitates the rapid, accurate processing and storage of specimens. Drs. urger or Eberhart are directly involved in most frozen section diagnoses, and frequently communicate with the neurosurgeons in the operating room during surgical procedures. This close interaction during specimen processing ensures the highest tissue quality for molecular and research studies. The frozen specimens are stored in -80 o C freezers, which are protected by both local and telephone alarms and housed in a secure area in the Neuropathology division located on the 5 th floor of the Ross uilding. The Eberhart Laboratory maintains two -80 o C freezers in this area, with additional designated open modules for temporarily storing specimens should one or more units fail. 135 o C ultralow freezer provides additional storage capacity. The tumor bank is managed using a dedicated Microsoft ccess database housed on a specially protected server within Pathology reserved for files containing patient data. Estimate of the number of PLG/pediatric brain tumor cases to be banked each year: The Johns Hopkins surgical pathology laboratory processed over 600 brain specimens in pproximately 15% of the specimens were stereotactic biopsies, and the remaining were open craniotomy or other types of surgical specimens. The number of pediatric surgical cases (both tumor and non-tumor) over the last three years are as follows: 60 in 2006, 70 in 2007, 78 in The recent increases are due to the growing practices of the well-established pediatric neurosurgeons Dr. Carson, Dr. Jallo, and Dr. Weingart. The breakdown of pediatric brain tumor types for 2008 is: PLG 28 Medullo/PNETs 6 Ependymoma 6 Craniopharyngioma 8 /GM 12 T/RT 2 Neurocytic 2 Hemangioblastoma 2 2

3 Choroid Plexus Papilloma 2 Other 4 mong the PLG, 17 were well-defined Pilocytic strocytomas, 2 were other Piloid tumors, 5 were well-defined Diffuse strocytomas (WHO Grade II), and 4 were low grade astrocytomas of indeterminate type. ased on these numbers, and the fact that many diffuse astrocytomas yield limited diagnostic tissue, we hope to bank tissue and/or attempt to establish lines from 6-8 pediatric Diffuse strcytomas (WHO grade II) over the two years covered by this proposal. im 2 Generate PLG Cell Lines and Xenografts The goal of this aim is to generate new models of PLG, especially Diffuse strocytomas (WHO grade II) and other non-piloid tumors, which can be used for clinical testing. Hypotheses: () Pilocytic and piloyxoid astrocytomas can be grown in neurosphere media or as intracranial xenografts in athymic nude mice. () Their growth will be augmented by lentiviral delivery of htert, c-myc, and/or large T antigen. Rationale: In order to examine the functional effects of potential tumor suppressor genes and oncogenes, or test new targeted therapies, it will be necessary to develop cell culture and/or xenograft based models of pilocytic and pilomyxoid astrocytomas. To our knowledge, no wellcharacterized cell culture or xenograft models of pilocytic astrocytomas currently exist. We and others have had preliminary success in growing freshly resected pilocytic astrocytomas for a period of weeks or months as tumor neurospheres in a special media supplemented with EGF and FGF (Figure 1). However, the first two such pilocytic cultures we have attempted to establish do not grow as robustly as Figure 1. Pilocytic strocytoma Grown in neurosphere media and immunolabelled with GFP (green) and nestin (red) antibodies glioblastoma neurospheres, and it has not been possible to passage them continuously for more than three months. We have had somewhat better luck growing the cells as adherent cultures, and have recently confirmed the presence of the KI/RF fusion transcript in some of these lines, which means they may be useful in modeling this common molecular change. We therefore plan to try several additional genetic manipulations of these cells in culture in order to induce and perpetuate their long-term growth ( immortalize the 3

4 cells ). We will infect the cultures with lentivirus encoding c-myc or Large T antigen, both singly and in combination with htert. These inserts are flanked in the constructs we use with Lox sites, thus we can subsequently excise them using CRE and revert the culture to its initial genetic state. This will allow us to perform some assays without the potentially confounding presence of the immortalizing proteins. It has recently been shown that c-myc can immortalize neural progenitor cells without causing transformation, suggesting that this approach may be most promising in terms of changing the growth characteristinc of the culture without significantly altering the underlying tumor phenotype. Finally, we plan to inject freshly resected pilocytic astrocytoma cells (and immortalized cultures) into the brains of athymic (nude) mice and attempt to derive a xenograft-based model of these tumors. Experimental Design/Methods and Preliminary Data: Pilocytic and pilomyxoid astrocytomas resected at Johns Hopkins will be grown as neurospheres using previously published methods (17). In brief, primary tumors resected at Johns Hopkins Hospital, with IR approval, will be minced with scissors and digested for minutes in papain solution, then neutralized, triturated, and plated in Neurocult complete medium containing hegf, hfgf and buffering agents. Cells are grown at high density in T25 flasks until spheres form (2-14 days) at which point they are triturated and passaged. For intracranial injections, 100,000 tumor cells suspended in 2 ul of culture media are injected into the cerebrum or cerebellum with a 10-uL Hamilton syringe and 26 gauge needle using a stereotactic apparatus. Mice are sacrificed when they show symptoms of tumor formation (ataxia, somnolence, cachexia) and the brains removed and examined grossly and microscopically. To immortalize primary human pilocytic and pilomyxoid astrocytoma cells, we will use a Lox-site containing lentiviral vector. The backbone of this vector is HLox.CMV.GFP.IRES.TK.Lox. htert or T antigen will be used for the immortalization process and it replaces the GFP gene in the vector backbone. There are several benefits for this system. First, the lenti vector transduction/integration is very efficient and will result in immortalization of most of the original sample. Second, the flanking Lox sites allow the construct to be excised at a future time using Cre, reverting the cells to their original state. Finally, the utilization of HSV-1 TK permits selection against cells Figure 2. Lentiviral Infection of U87 Glioma Cells which contain the lentivirus DN and transgene, serving as an internal safety control. We have already acquired these constructs and packaged them into lentivirus. Shown in Figure 2 is a Western blot documenting high-level expression of large T antigen in U87 glioma cells infected with the virus. We will need to generate a similar c-myc construct. We W Should we successfully derive a strongly-growing pilocytic cell line or xenograft, we will compare its karyotype to the primary tumor from which it is derived using array CGH. This will ensure that our model(s) have not shown excessive genetic drift compared to the progenitor lesion(s). 4

5 Resource Sharing Plan: We are committed to sharing precious pediatric brain tumor tissue with as many institutions as possible, and have a strong history of collaborative endevours. Show below is a record of tissue distributions by Drs. Eberhart and urger from Table 1. Specimen distribution within Johns Hopkins Unstained Slides DN RN Frozen rray Sidransky C C aylin Small Rigamonti Herman C Perlman C Laterra Dang eachy Snyder C Sukamar Rothstein Shah C Resar Pasternack C Legend: - up to 10 specimens; 11 to 20 specimens; C over 20 specimens Table 2. Specimen distribution outside Johns Hopkins Unstained Slides DN RN Frozen rray Upsalla, Sweden ilbao, Spain Texas Childrens Hosp NIH C UCSD Duke St. Jude C Mayo Clinic Hong Kong, China Temple UCSF Ohio State Wake Forest Zurich, Switzerlnd 5

6 Roswell Park C Legend: - up to 10 specimens; 11 to 20 specimens; C over 20 specimens Overlap: The tumor banking effort does not overlap with any other grants. The attempts to grow PLG as cell lines and xenografts overlaps slightly with our recent Children s Cancer Foundation of altimore wards. However, that grant will expire in approximately 6 months, and focuses on RF changes in pilocytic astrocytomas rather than the generation of novel models of Diffuse strocytoma as this project does. Timetable and Performance Goals: We request funds for two years, in order to give us time to optimize our cell culture and xenograft techniques, and to bank a reasonable number of specimens. Over this time, we will attempt to secure more permanent funding for this project from the NIH or DOD. We understand that the second year of funding is contingent on adequate performance during the first year in terms of the number/percentage of PLG banked. Specifically, we agree that at least 50% of PLG tumors resected at Johns Hopkins, a minimum of 14 cases based on historical norms, must be banked to meet the performance goal. greement Regarding Distribution and Data Sharing: We agree to send a portion of all frozen PLG over 50 mg in size to Drs. Keith Ligon and Chuck Stiles at the Dana Farber so they can test the lesions for genetic changes. 30% of frozen PLG tissue over 50 mg will be sent (up to a total of 200 mg mailed for each case). For example, from a 250 mg tumor 60 mg would be sent. If possible, DN/RN extracted from the tumors smaller than 50 mg will be sent as well. In addition, our group at Johns Hopkins will make reasonable efforts to collaborate and share data resulting from this and other PLG-related projects with researchers at the Dana Farber Cancer Institute. 6