Targeting glioblastoma stem-like cells with custom-designed viral vectors

Glioblastoma (GBM) is the most lethal form of adult brain cancers with a median survival of andlt;15 months
despite aggressive standard chemoradiation. GBM are formed by GBM stem-like cells (GSCs) - a major
contributor to tumor recurrence and a natural focus for therapeutic development. There are two main reasons
responsible for treatment failure: 1) high intra- and inter-tumor cellular and molecular heterogeneity with
multiple subclones possessing distinct genetic determinants; 2) GSCs exhibit multiple redundant signaling
pathways requiring simultaneous targeting of overlapping pathways. We have invented and biologically
validated a novel tandem computational platform, GeneRep-nSCORE that integrates large-scale gene
expression profiles with genomic changes to identify common founding alterations or master regulators of
GSCs that span a large number, if not all, GSC subclones within and across GBM tumors. We discovered such
a core set of four common master regulators in GCSs that are outstanding targets for clinical development.
Expression of these four factors was sufficient to reprogram normal astrocytes to GSCs, whereas their
depletion profoundly abrogated GSCs, and thus tumor development in vivo, in all eight lines of patient-derived
GSCs of varied genetic and molecular backgrounds examined to date.
The goal of this application is to develop a customized set of Adeno-associated virus (AAV)-based genetic
tools to target the whole spectrum of GSCs (Phase I) for the purpose of delivering targeting constructs to
deplete the four common master regulators responsible for malignant transformation and proliferation in GSCs
(Phase II). The specific objectives of this proposal are: (i) using directed evolution and available combinatorial
AAV capsid library, and for the first time, introducing a dynamic mode of administration of a library reagent
over the time course of tumor progression, to greatly increase the probability of identifying novel AAV variants
specifically targeting slow-, and fast-cycling GSCs in patient-derived xenograft models (PDX) (Phase I); (ii) To
design and validate a panel of AAV vectors that express shRNAs targeting core master regulators of GSCs to
identify leads for preclinical testing; (iii) To optimize modes of viral delivery, pharmacokinetics and
pharmacodynamics parameters, and safety and toxicity in normal and PDX treated with lead targeting AAV
cassettes; and (iv) Based on these results, tools and basic DMPK data created, to conduct preclinical efficacy
studies in PDX treated with lead targeting AAV cassettes either alone or in combination with standard
chemoradiotherapy (Phase II) to prepare for an investigative new drug application for clinical testing in patients
with GBM, and for commercial development of this novel technology.Glioblastoma (GBM) is the most lethal form of adult human brain cancers. The goal of this proposal is to
develop a customized set of viral vectors specifically targeting GBM stem-like cells. These novel viral vectors
will express targeting constructs to deplete common master regulators responsible for malignant
transformation and proliferation of these GBM stem cells such as tumor control and survival can be improved.