Abstract 5044: MYC drives formation of primative neuro-ectodermal tumors in human neural stem cells derived from multiple brain regions.
Authors: Taylor Isabella , Kahlert Ulf , Maciaczyk Jarek , Nikkhah Guido , Eberhart Charles , Raabe Eric H. 
Published: August 2014

Abstract
Primitive neuroectodermal tumors (PNET) are thought to arise from neural stem cells. They are highly aggressive tumors, and they can arise in different regions of the brain. A subset of PNET has genomic amplification of MYC, and the MYC-regulator LIN28A is known to define a group of PNET. The AKT/PTEN pathway is commonly altered in aggressive brain tumors. hTERT is expressed in the majority of PNET. Deletion or mutation of p53 is also a common event in PNET. We hypothesized that a combination of dominant negative R248Wp53, c-myc, AKT and hTERT would transform human neural stem cells into a model for PNET. We used lentiviral vectors to infect human neural stem cells derived from hindbrain and cortex with the same packages of oncogenic elements. After antibiotic selection, we performed western blotting and qPCR to verify the presence of MYC and constitutively active AKT. Increased TP53 expression on western blot was used as a proxy for inactivation of the p53 pathway by dominant negative R248W p53. Increased hTERT expression was verified by qPCR. Hindbrain neural stem cells transduced with MYC/R248Wp53/AKT/hTERT proliferated at an increased rate compared to control cells as measured by BrdU incorporation (Hindbrain pBABE vs. Hindbrain MYC/R248Wp53/AKT/hTERT: 4% vs. 50% BrdU positive, t-test p=0.001). Similar results were observed in cortex derived human neural stem cells transduced with MYC/R248Wp53/AKT/hTERT (Cortex pBABE vs Cortex MYC/R248Wp53/AKT/hTERT: 5% vs. 24% BrdU positive, t-test p=0.027). We then tested the tumor forming ability of cortex and hindbrain derived human neural stem cells, by performing orthotopic intracranial injections on immunocompromised mice. No tumors formed from human neural stem cells infected with one or two oncogenic elements. However, both hindbrain and cortex derived human neural stem cells transformed with MYC /R248Wp53/hTERT, and MYC/R248Wp53/hTERT/AKT formed aggressive orthotopic xenograft tumors with histologic characteristics of PNET. The latency of tumor formation decreased with increasing addition of oncogenes. These PNET-like tumors were synaptophysin positive, GFAP negative, had a high proliferative index, and showed signs of leptomeningal dissemination. Taken together, these experiments show that human neural stem cells from different brain regions, when transduced with the same package of oncogenes, form PNET-like orthotopic xenograft tumors. These data suggest that MYC's transforming power may trump loco-regional differences in neural stem and progenitor cells.
Citation Format: Isabella Taylor, Ulf Kahlert, Jarek Maciaczyk, Guido Nikkhah, Charles Eberhart, Eric H. Raabe. MYC drives formation of primative neuro-ectodermal tumors in human neural stem cells derived from multiple brain regions. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5044. doi:10.1158/1538-7445.AM2013-5044