Date of Award
8-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biological Sciences
Committee Chair/Advisor
Yanzhang Wei
Committee Member
Lesly A. Temesvari
Committee Member
Charles D. Rice
Committee Member
Zhicheng Dou
Abstract
Cancer immunotherapy has highlighted the importance of immune checkpoint blockade and innate immune cell engagement in battling tumor-mediated immune suppression in the past few decades. However, with cancer development, advanced tumors are often found to develop resistance towards single-target immunotherapy due to the complexity of the immunosuppressive mechanisms within the tumor microenvironment (TME). To address this, we developed a novel bifunctional fusion protein, PDL1sFv/MICAe, which combines the tumor-targeting capability of an anti-PDL1 single-chain variable fragment (sFv) with the NK cells immunostimulatory properties of the MICA extracellular domain.
In vitro functional assays revealed that PDL1sFv/MICAe significantly enhanced cytotoxicity towards natural killer (NK) cells against PD-L1 positive cancer cells despite minimal changes in IFN-γ or granzyme B secretion, suggesting that the PDL1sFv/MICAe promotes NK cell activation via non-canonical mechanisms. Similarly, cytotoxic T cells, which often exhibit suppressed function in PDL1–rich environments, showed rescued cytotoxicity upon treatment, independent of IL-10 regulation.
Post-treatment transcriptomic analysis of NK cells revealed significant upregulation of genes involved in signal transmission pathways rather than genes classically linked to cell-mediated killing or stress responses. These findings suggest a possible alteration in NK cell signaling dynamics in the observed functional enhancement in cytotoxicity.
Although no synergistic effect was observed in co-culture assays involving NK cells and cytotoxic T cells, the fusion protein effectively activated each cell type independently towards PDL1-positive cancer cells. These results highlight the therapeutic potential of PDL1sFv/MICAe as a dual-function protein capable of reactivating suppressed immune responses of T cells while inducing NK cell cytotoxicity within the TME.
By engaging both adaptive and innate immunity, PDL1sFv/MICAe represents a promising strategy for improving immunotherapy outcomes in solid tumors resistant to conventional treatments.
Recommended Citation
Li, Junyi, "Bifunctional Fusion Protein PDL1sFv/MICAe for Cancer Immunothearpy" (2025). All Dissertations. 3988.
https://open.clemson.edu/all_dissertations/3988
Author ORCID Identifier
0009-0006-4807-5118