Cytotoxic T-lymphocyte (CTL) therapy directed to Epstein-Barr virus (EBV) antigens has produced complete tumor responses in patients with EBV associated Hodgkin disease (HD) without toxicity. Many HD tumors, however, are EBV antigen negative. To extend immunotherapy to patients with such EBV negative HD, we propose to target the CD30 molecule, which is expressed by all malignant cells in both EBV positive and EBV negative HD. We hypothesize that we can exploit and extend the demonstrated effectiveness of EBV CTLs by redirecting them to the CD30 molecule, by forcing expression of a chimeric antigen receptor (CAR) targeting this molecule. We also hypothesize that we will be able to further engineer the CAR+ CTLs to overcome the molecular and cellular barriers that protect HD cells from immune attack. These hypotheses will be tested in three specific aims.
In Aim 1, we propose to improve the homing of CAR+ CTLs to HD tumor cells by overexpressing the receptor (CCR4) for the chemokine TARC, which is constitutively produced by HD tumors, and whose receptor is lacking on CTLs.
In Aim 2 we will evaluate whether expansion and persistence of our CCR4+ and CD30CAR+ CTLs is enhanced if these CTLs are further modified to produce their own growth cytokine (IL-15), which is essential to sustain their function. Finally, in Aim 3 we will analyze the interactions between regulatory T cells and our CAR+ CTLs. We will discover whether the modifications we have made allow the CAR+ CTLs to resist the inhibitory effects of the regulatory T cells that dominate sites of HD tumor, or whether alternative strategies will be required. The modifications we propose will be tested pre-clinically in vitro and in vivo and will form the basis of our continued clinical investigation of T- cell therapy for cancer.
We have had success in treating patients with relapsed Hodgkin disease (HD) by using their own immune cells directed to viral proteins that are often on the tumor cells. We now want to extend the application of this promising treatment by targeting other proteins that are on all HD cells, and by making the immune cells more potent. ? ? ?
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