Metastatic tumor evolution and organoid modeling implicate TGFBR2as a cancer driver in diffuse gastric cancer

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>Gastric cancer is the second-leading cause of global cancer deaths, with metastatic disease representing the primary cause of mortality. To identify candidate drivers involved in oncogenesis and tumor evolution, we conduct an extensive genome sequencing analysis of metastatic progression in a diffuse gastric cancer. This involves a comparison between a primary tumor from a hereditary diffuse gastric cancer syndrome proband and its recurrence as an ovarian metastasis.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Both the primary tumor and ovarian metastasis have common biallelic loss-of-function of both the <jats:italic>CDH1</jats:italic> and <jats:italic>TP53</jats:italic> tumor suppressors, indicating a common genetic origin. While the primary tumor exhibits amplification of the Fibroblast growth factor receptor 2 (<jats:italic>FGFR2</jats:italic>) gene, the metastasis notably lacks <jats:italic>FGFR2</jats:italic> amplification but rather possesses unique biallelic alterations of Transforming growth factor-beta receptor 2 (<jats:italic>TGFBR2</jats:italic>), indicating the divergent <jats:italic>in vivo</jats:italic> evolution of a <jats:italic>TGFBR2</jats:italic>-mutant metastatic clonal population in this patient. As <jats:italic>TGFBR2</jats:italic> mutations have not previously been functionally validated in gastric cancer, we modeled the metastatic potential of TGFBR2 loss in a murine three-dimensional primary gastric organoid culture. The <jats:italic>Tgfbr2</jats:italic> shRNA knockdown within <jats:italic>Cdh1</jats:italic><jats:sup> <jats:italic>-/-</jats:italic> </jats:sup><jats:italic>; Tp53</jats:italic><jats:sup> <jats:italic>-/-</jats:italic> </jats:sup> organoids generates invasion <jats:italic>in vitro</jats:italic> and robust metastatic tumorigenicity <jats:italic>in vivo</jats:italic>, confirming <jats:italic>Tgfbr2</jats:italic> metastasis suppressor activity.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>We document the metastatic differentiation and genetic heterogeneity of diffuse gastric cancer and reveal the potential metastatic role of <jats:italic>TGFBR2</jats:italic> loss-of-function. In support of this study, we apply a murine primary organoid culture method capable of recapitulating <jats:italic>in vivo</jats:italic> metastatic gastric cancer. Overall, we describe an integrated approach to identify and functionally validate putative cancer drivers involved in metastasis.</jats:p> </jats:sec>