Car-Modified T Cells Capable of Distinguishing Normal Cells From Malignant Cells

<p>T cells can be redirected to target tumor-associated antigen (TAA) by genetic modification to express a chimeric antigen receptor (CAR), which fuses the specificity derived from an antibody to T-cell activation domains to result in lysis of TAA-expressing cells. Due to the potential for on-target, off-tissue toxicity, CAR⁺ T-cell therapy is currently limited to unique or lineage-restricted TAAs. Glioblastoma, a grade IV brain malignancy, overexpresses epidermal growth factor receptor (EGFR) in 40-50% of patients. EGFR also has widespread normal tissue expression. To target EGFR on glioblastoma while reducing the potential for normal tissue toxicity, EGFR-specific CAR generated from cetuximab, Cetux-CAR, was transiently expressed in T cells by RNA-modification. RNA-modified CAR⁺ T cells demonstrated similar cytotoxicity against EGFR⁺ cells, including normal renal cells, as DNA-modified CAR⁺ T cells. However, RNA-modified T cells lost CAR expression over time, concomitant with loss of functional specificity to EGFR. Transient expression of CAR limits potential for off-tissue toxicity at the expense of anti-tumor activity, and does not protect normal tissue from immediate toxicity. Recognizing that EGFR is overexpressed at a higher density on glioblastoma relative to normal tissue, we generated an EGFR-specific CAR from nimotuzumab, an EGFR-specific antibody with reduced binding to low density EGFR. While Cetux-CAR⁺ T cells produced cytokine and mediated lysis independent of EGFR density, function of Nimo-CAR⁺ T cells directly correlated with the EGFR density of targets, with reduced activity in response to low density EGFR, but equivalent activity in response to high density EGFR relative to Cetux-CAR⁺ T cells. Cetux-CAR⁺ T cells and Nimo-CAR⁺ T cells demonstrated equivalent control of intracranial glioma xenograft with intermediate EGFR density, but only Cetux-CAR⁺ T cells controlled xenografts with low EGFR density. In sum, transient expression of CAR has the potential to reduce long-term toxicity to normal tissue, but at the expense of anti-tumor activity. Rational design of CAR based on an antibody with reduced binding to low density EGFR generated EGFR-specific CAR able to tune T-cell function to antigen density resulting in discrimination of high EGFR density on malignant cells from low EGFR density on normal tissue.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2014

Author dc:creator

• Caruso, Hillary G

Contributors dc:contributor

• Laurence Cooper, M.D., Ph.D.
• Oliver Bogler, Ph.D.
• Bradley McIntyre, Ph.D.

• genetically modified T cells
• cancer immunotherapy
• affinity
• EGFR
• glioma
• Cancer Biology
• Immunity
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/457

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1497