Background
T cell receptor (TCR)-based immunotherapy is a promising cancer treatment particularly as the TCR antigen repertoire detects both intracellular and extracellular tumor antigens. Our newly identified cancer-testis antigen (CTA) is an intracellular antigen exclusively expressed by cancer and reproductive tissue making it an ideal target for TCR-T cell therapy. Here, we aim to isolate a TCR against an HLA-A*02:01 restricted CTA epitope from the human HLA-A*02:01 negative repertoire to evaluate its safety and efficacy in vitro and in vivo.
Materials and Methods
CTA expression and epitope presentation is analyzed in hematological and solid neoplasms by immunohistochemistry, qRT-PCR, and mass spectrometry. TCRs are isolated using a co-culture of naive HLA-A*02:01 negative CD8+ T cells with antigen-presenting cells. Epitope-specific cells are identified by multimer staining and sorted by fluorescence-activated cell sorting followed by sequencing of TCR alpha and beta chains to identify mutation-specific TCRs. Functional avidity of TCR transduced CD8+ T cells is determined by measuring IFN release (ELISA). Cross-reactivity is evaluated by the Alanine- and Glycine-Scan-Assay, and alloreactivity is determined by co-culturing immortalized B lymphoblastoid cell lines holding different haplotypes with TCR-transduced T cells.
Results
CTA expression was detected in patient samples of colorectal, breast, and head and neck cancer by immunohistochemistry and qRT-PCR. Epitope presentation was quantified by mass spectrometry and PDX models of breast cancer and is ongoing in PDX models of colorectal cancer. Thus far, four potential CTA-specific TCRs containing minimally murinized constant regions have been identified and constructed, awaiting further safety evaluation and efficacy testing in established PDX models.
Conclusions
We have identified an undescribed epitope of a CTA not yet targeted by immunotherapy and isolated four potential high avidity epitope-specific TCRs from human HLA-A*02:01 negative donors. We confirmed the expression of the target CTA as well as epitope presentation in several common solid neoplasms. This indicates a huge therapeutic potential of our identified TCRs in a wide patient population with relapsed/refractory solid tumors in a tumor agnostic manner.
E. Sivro: None. M. Klatt: None. S. Elezkurtaj: None. C. Freund: None. C. Grunert: None. U. Keller: None. A. Busse: None.