TUFT1 stabilizes TGF-β receptor II protein and facilitates activation of hepatic stellate cells into metastasis-promoting myofibroblasts.

Cancer-associated fibroblasts (CAFs) transdifferentiated from hepatic stellate cells (HSCs) are a critical determinant of liver metastasis of colorectal cancer (CRC). However, the mechanisms behind transforming growth factor β (TGF-β)-stimulated activation of HSCs into CAFs remain poorly understood. Immunoprecipitation coupled with mass spectrometry identified tuftelin 1 (TUFT1) as a novel TGF-β receptor II (TβRII) binding protein in primary human HSCs and immortalized LX2 cells. TUFT1 interacts with TβRII via its fragments (amino acids 1-86, 87-157), protecting TβRII from lysosomal degradation to facilitate TGF-β signaling and myofibroblastic activation of HSCs. Mechanistically, TUFT1 competes with caveolin-1 for TβRII binding, retrieving TβRII from the lipid rafts/caveolae-mediated degradation pathway and sorting it into the endosome-mediated trafficking and signaling pathway. Clinically, TUFT1 expression was confirmed in the CAFs of patient-derived colorectal cancer liver metastasis (CRCLM) tissues. Both protein and transcript analyses revealed higher TUFT1 expression in the CAFs of CRCLM than in HSCs. Furthermore, bulk RNA sequencing indicated that knocking down TUFT1 altered the TGF-β transcriptome of HSCs and suppressed HSC expression of tumor-promoting factors. In HSC/CRC co-implantation and portal vein tumor injection mouse models, targeting TUFT1 of HSCs inhibited HSC activation and restricted CRC growth in both subcutaneous and hepatic sites. Taken together, our findings uncover the novel function of TUFT1 in the hepatic tumor microenvironment, highlighting its role as a critical regulator of HSC activation and the pro-metastatic hepatic niche via promoting TβRII protein stability. Targeting TUFT1 in HSCs presents a promising therapeutic approach for combating CRCLM.