Glioblastoma (GBM) is the most common brain cancer and remains largely incurable. The recent identification of chemotherapy and radiotherapy resistant stem cells in GBMs may help explain why conventional therapies are ineffective.
Immunotherapy may be able to kill GBM stem cells since immune-mediated killing does not rely on the conventional mechanisms of cell killing. HER2 is tumor protein is positive in >80% of GBMs, but not by the normal brain, making it an attractive target for immunotherapy.
We have shown that HER2-specific T cells from GBM patients kill GBM stem cells and induce remission of GBMs grown in mice. We now wish to evaluate our approach clinically and test if HER2-specific T cells can be safely given to patients with HER2-positive GBMs (Aim 1) and intend to study their will persistence and antitumor activity in the human body (Aim 2).
While our preclinical studies demonstrated the potent antitumor activity of HER2-specific T cells, tumors recurred in several treated animals. This limitation in T-cell efficacy is most likely due to the inhibitory tumor environment. GBMs (including GBM stem cells) contain high level of the STAT3, a protein which is not only necessary for GBM stem cell survival but also induces the expression of T cell suppressive factors. Thus, Aim 3 will test in preclinical models our hypothesis that combining STAT3 inhibition with HER2-specific T cells will more effectively eradicate GBMs than T cells alone.
Scatter factor/hepatocyte growth factor is a pleiotropic growth factor that binds to c-Met, a proto-oncogene encoded tyrosine kinase receptor ubiquitously present on most malignant gliomas. This grant application seeks to infuse thawed allogeneic T cells that have been rendered c-Met-specific for the treatment of gliomas.
Buidling upon on our experience infusing autologous and allogeneic T cells genetically modified to express a chimeric antigen receptor (CAR) to redirect specificity for a desired cell-surface antigen (such as CD19 on B-cell malignancies) and our novel platform technologies that have been adapted for clinical translation using (i) the Sleeping Beauty (SB) transposon/transposase system to stably express CAR transgenes and (ii) artificial antigen presenting cells (aAPC) derived from K562 cells to propagate genetically modified T cells in a CAR-dependent manner to clinically-sufficient numbers.
We have designed a 2nd generation CAR, designated cMetRCD28, to render T cells specific for c-Met independent of MHC. To conditionally activate cMetRCD28+ T cells under conditions of hypoxia thereby limiting deleterious targeting of normal tissues expressing c-Met, this CAR has been fused to the oxygen-dependent degradation domain (ODDD) which results in degradation of cell-surface CAR-ODDD protein under conditions of normoxia, but not hypoxia found in the tumor microenvironment.
To generate allogeneic T cells from a 3rd party to be infused “on demand” we will co-express the CAR-ODDD with designer zinc finger nuclease (ZFN) (or inhibiting RNA species) to eliminate endogenous expression of alpha/beta T-cell receptor (TCR). The cMetRCD28-ODDD and ZFN transgenes will be electro-transferred into T cells using the SB system and selectively propagated on c-Met+ aAPC.
This approach will be further developed to co-express a mutein of thymidine kinase (sr39TK) from herpes simplex virus-1 for in vivo conditional ablation with ganciclovir and imaging by positron emission tomography (PET). Aim #1 evaluates whether cMetRCD28+TK+TCRneg T cells lyse gliomas. The ability for these T cells to survive/propagate under hypoxia will be determined.
Aim #2 evaluates the ability of cMetRCD28+TK+TCRneg T cells to selectively eliminate hypoxic c-Met+ glioma in an orthotopic xenogeneic mouse tumor model, using bioluminescent imaging and micro-PET to asses T-cell persistence and anti-tumor effect. Aim #3 evaluates in a human Phase I clinical trial the safety, feasibility, persistence and efficacy of thawed allogeneic cMetRCD28+TK+TCRneg T cells delivered loco-regionally after initial resection. PET/CT imaging using [18F]-FHBG metabolized by sr39TK will be used to evaluate the distribution of adoptively transferred T cells.
In aggregate, these studies will develop new targeted cell and gene therapy for gliomas using our established clinical platform technologies and as c-Met is expressed on many extra-cranial solid tumors this approach may have broad application.