Novel PROTACs targeting tissue transglutaminase (TG2) suppress tumorigenicity of ovarian cancer cells.

Tissue transglutaminase (TG2), a multifunctional enzyme involved in protein crosslinking through transamidation, fibronectin-integrin interactions and GTP hydrolysis, is upregulated in cancer. Due to its diverse functions, TG2 has been a challenging therapeutic target. Here, we investigate the use of PROteolysis TArgeting Chimeras (PROTACs) to degrade TG2 and inhibit its tumor-promoting functions in ovarian cancer models. We describe a novel family of VHL based PROTACs using a ligand that binds to the TG2 fibronectin interacting domain and a thiol ether PEG linker. Three structurally related PROTACs-P374, P404, and P405-induced significant proteasome dependent TG2 degradation at 24 h (p < 0.05), with stable effects at 48 h. These compounds also potently inhibited cell adhesion and migration (p < 0.005), outside-in signaling, and blocked TG2 enzymatic activity (p < 0.001). An unbiased evaluation using reverse phase protein array of P374-treated cells revealed 136 differentially expressed proteins, including protein networks related to cell adhesion and involved in extracellular matrix (ECM) interactions. P374 and P405 reduced omental colonization in vivo and P374 inhibited intraperitoneal tumor dissemination and growth. Visium HD based spatial profiling of human ovarian tumors identified TG2 as a highly enriched protein at the tumors invasive edge and the interface with the ECM. Together, our findings put forward novel TG2-targeting PROTACs which effectively degrade TG2, impair its functions, and block in-vivo tumor dissemination. These results highlight the potential development of TG2 degraders towards therapeutic targeting in ovarian cancer.