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Abstract
Background Glioblastoma (GBM) is an aggressive and heterogeneous brain tumor that currently has no curative treatment. Our group identified CD70, which is overexpressed by low-/high-grade gliomas and associated with poor patient survival.1 2 We established a CAR-T cell therapy platform targeting CD70-expressing gliomas, which showed efficient antitumor activity preclinically. Modification of CD70CAR to express IL-8 receptors (8R-70CAR) enhanced tumor trafficking and persistence, resulting in improved antitumor efficacy and long-lasting immunity to tumor rechallenge.3 These findings culminated in a phase-I trial of 8R-70CAR T cells (NCT05353530) for patients with newly diagnosed GBM that will begin at UF soon. However, CAR T cell therapy currently faces obstacles such as single antigen targeting in heterogeneous tumors and maintenance of activation of CAR T cells. Cytomegalovirus pp65 protein is a tumor-specific target in GBM.4 5 A combinatorial approach against CD70 and pp65 may result in enhanced effect against heterogeneous GBM.
Methods Healthy donor peripheral blood mononuclear cells were stimulated with anti-CD3/CD28 Dynabeads and retrovirally transduced with 8R-70CAR. Frequencies of 8R-70CAR- and pp65-specific T cells were evaluated by flow cytometry.
Results The pp65-specific CD8+ T cell population was expanded post DynaBeads activation to a frequency tenfold over baseline (figure 1). Single-specific (CD70 CAR+ only and pp65-specific only) and double-specific (CD70 CAR+ and pp65-specific) T cells were successfully generated. Importantly, these cells secreted greater IFN-g when tumor cells expressed both targets (figure 2).
Conclusions The CAR T cell production process significantly expands pp65-specific T cells, resulting in enhanced antitumor efficacy through recognition of both tumor targets. Our CAR T cell product may contain T cell repertoires that effectively target multiple tumor antigens.
References
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Scheurer ME, Bondy ML, Aldape KD, et al. Detection of human cytomegalovirus in different histological types of gliomas. Acta Neuropathol. 2008;116(1):79–86.
Schuessler A, Smith C, Beagley L, et al. Autologous T-cell therapy for cytomegalovirus as a consolidative treatment for recurrent glioblastoma. Cancer Res. 2014;74(13):3466–76.
pp65-specific T cell frequency was assessed via flow cytometry using HLA-matched pp65 tetramer at baseline (’Non-Activated’) and after CAR T cell production (‘Activated/CAR-transduced’). These are representative flow cytometry data for three healthy donors (HD1–3).
IFN-y-secreting cells as percentages of the total CD3+ populations after tumor/T-cell coculture. U87 (CD70+/pp65-), U87/pp65 (CD70+/pp65+), and L0 (CD70-/pp65-) GBM lines were used as target cells for coculture with CAR- and vector-transduced T cells. The U87/pp65 line is U87 transduced to overexpress pp65. Cytostim was used as positive control.
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