A platform of functional studies of ESCC-associated gene mutations identifies the roles of TGFBR2 in ESCC progression and metastasis

Genomics studies have detected numerous genetic alterations in esophageal squamous cell carcinoma (ESCC). However, the functions of these mutations largely remain elusive, partially due to a lack of feasible animal models. Here, we report a convenient platform with CRISPR-Cas9-mediated introduction of genetic alterations and orthotopic transplantation to generate a series of primary ESCC models in mice. With this platform, we validate multiple frequently mutated genes, including EP300, FAT1/2/4, KMT2D, NOTCH2, and TGFBR2, as tumor-suppressor genes in ESCC. Among them, TGFBR2 loss dramatically promotes tumorigenesis and multi-organ metastasis. Paradoxically, TGFBR2 deficiency leads to Smad3 activation, and disruption of Smad3 partially restrains the progression of Tgfbr2-mutated tumors. Drug screening with tumor organoids identifies that pinaverium bromide represses Smad3 activity and restrains Tgfbr2-deficient ESCC. Our studies provide a highly efficient platform to investigate the in vivo functions of ESCC-associated mutations and develop potential treatments for this miserable malignancy.