The prognosis for primary malignant brain tumor patients remains poor. Due to the infiltrative growth and heterogeneity of gliomas, conventional therapy (surgery, chemo- and radiotherapy) is non-curative, and patient survival has not significantly improved in the past twenty years. Therefore, adjuvant treatment strategies have been sought. Cellular immune therapies have the potential to selectively destroy malignant cells while leaving normal cells unharmed. In a Phase 1 clinical trial, adoptive transfer of alloreactive cytotoxic T lymphocytes (aCTL) sensitized to patient MHC antigens showed promise in the treatment of recurrent high-grade astrocytic tumors. Despite encouraging results, cellular immunotherapy is not an established therapy in the clinic. Cellular immune therapies may not succeed in eradiaticating tumors due to the development of resistance to immune effector cells such as aCTL. In order to improve the current therapy, we will develop human and rat immunotherapy resistant (ITR) glioma cell populations, and then investigate factors to understand what mechanism(s) were used to provide the resistance. Immunoresistant glioma populations will be obtained by repeatedly exposing cultured glioma cells or intracranial rat brain tumor to aCTL. We will monitor for the stability of immunoresistance by cytotoxicity and clonogenic assays. We will characterize the immunoresistant cell populations relative to the parental by cell death criteria, proliferation, adhesive/invasive properties, and MHC expression. T helper 1 and 2 cytokine expression profiles will be examined from supernatants obtained from coincubates of aCTL with immunoresistant and parental lines. At the chromosomal level, cytogenetic analysis will help identify chromosomal alterations that are unique to ITR and parental gliomas. Gene expression analysis will help identify differential gene expression that would allow for the development of resistance. The proposed studies have to potential to lead to the development of strategies to circumvent the development of immunoresistance. As far as we can ascertain, this is the first study to specifically address development of glioma cell models resistant to alloreactive CTL effector cells. If successful, the knowledge gained from these studies may apply to other effector cell types used in immunotherapy, therefore the proposed scientific research merits consideration for funding under the NINDS Exploratory/Developmental Program.
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