· Screening of TNA aptamers targeting PD-L1 and its application in tumor immunotherapy
Person in charge: Li Xintong
Blockade of the immune checkpoint proteins such as programmed cell death protein 1 (PD-1) and its ligand PD-L1 has proven an effective cancer immunotherapeutic strategy. However, currently used antibody-based inhibitors suffer from high production cost and potential immune adverse effects. Herein threose nucleic acid (TNA) aptamers were selected to bind PD-L1 and inhibit its interaction with PD-1. Two TNA aptamers N5 and S42 blocked over 50% of PD-1/PD-L1 interaction in an ELISA competition assay. Flow cytometry analysis showed that these TNA aptamers inhibited PD-L1 binding to PD-1 protein on the cell surface. Lastly, when injected into a colon cancer xenograft mouse model, TNA aptamer N5 was specifically accumulated at the tumor site, and significantly inhibited tumor growth in vivo. In summary, these TNA molecules could provide alternative XNA-based immune checkpoint inhibitors for cancer immunotherapy.
TNA aptamers that inhibit PD-1 / PD-L1 interaction can be used in tumor immunotherapy
· Selection of chemically modified aptamers as targeted delivery vehicle for improved bladder cancer therapy
Person in charge: Wang Yao
Clinical therapies that treat non-muscle-invasion bladder cancer are transurethral resection assisted with intravesical chemotherapy. The deficiencies needed to be solved is that nontargeted chemotherapeutic drugs eliminate cancer tumors while distributing indiscriminately into normal tissue, causing visible side effect. With the aim to developing a simple target-specific drug delivery platform with high load capacity, here we designed and assembled the aptamer-grafted DNA nanotrains (aptamer NTrs) as transporter that delivers doxorubicin (Dox) to cancer cells. Cell-internalization selection against T24 bladder cancer cells were performed and obtained the first aptamer targeting bladder cancer, termed aptamer B1, which specifically enter into cancer cells but not normal bladder epithelial cell. Subsequently, the delivery system of aptamer B1 NTrs were constructed and Dox was stably intercalated into double-stranded DNA of nanotrains. This complex yielded effective cells selectivity and outstanding cytotoxicity to cancer cells in vitro, reducing the amount of Dox diffused into normal cells. Further studies confirmed that aptamer B1 NTrs-Dox significantly inhibited bladder tumor growth through intravesical instillation therapy in vivo, indicating this platform was efficient and specific carriers to bladder tumors and expected to be used in clinical cancer therapy.
· Screening of chemically modified functional nucleic acids targeting CTLA-4 and its application in tumor immunotherapy
Person in charge: Lian Enxiao
Cytotoxic T-lymphocyte associated protein 4 (CTLA-4) is one of the hot research objects in immune checkpoint in recent years. It can inhibit the initiation of T cell immune response and avoid the over activation of effector T cells in the normal immune process, and plays an important role in anti-tumor immune response. Here, we propose to use functional unnatural nucleic acid molecules to inhibit the expression and signal transduction of CTLA-4 at gene and protein levels to activate the immune system. Firstly, CTLA-4 protein was selected as the target in vitro, and the unnatural nucleic acid obtained could block the binding of CTLA-4 with B7 receptor; secondly, we designed and synthesized chemically modified deoxyribozyme molecules to selectively bind and catalyze the cleavage reaction of CTLA-4 mRNA to reduce the expression of CTLA-4 protein.
Schematic diagram of the inhibitory effect of functional unnatural nucleic acid molecules on CTLA-4
· TNA enzyme that catalyzes RNA cleavage is used for the magnesium ion detection in living cells
Person in charge: Gao Mingmei
TNA is an artificial nucleic acid resistant to degradation by nucleases, and it can form functional tertiary structures. This subject first obtained magnesium ion-dependent TNA enzymes that specifically catalyze RNA cleavage reactions through in vitro selection. After further characterization and optimization, a biosensor system with TNA enzymes was established for Mg2+ sensing in living cells.
Screening of TNAzyme with RNA cleavage activity and its application in detection of intracellular magnesium concentration
· Screening aptamers of siglec 7 based on cell screening technology
Person in charge: Guo Jiajie
Siglec 7 is a protein expressed on human immune cells, which has the function of distinguishing between the self and non-self, and plays a role in tumor immune escape. However, little is known about the proteins that interact with Siglec 7. Therefore, we want to construct Siglec 7 on Jurkat cells to screen the DNA aptamers of Siglec 7 and try to use them as proximity markers to explore the role of Siglec 7 in tumor immune escape. If the aptamer can block Siglec 7 and the effect is good, the unnatural nucleic acid of Siglec 7 will be developed for further application in vivo.
