Senescent Fibroblasts Potentiate Peritoneal Metastasis of Diffuse-type Gastric Cancer Cells via IL-8-mediated Crosstalk

Background/Aim: Diffuse-type gastric cancer (DGC) often forms peritoneal metastases, leading to poor prognosis. However, the underlying mechanism of DGCmediated peritoneal metastasis is poorly understood. DGC is characterized by desmoplastic stroma, in which heterogeneous cancer-associated fibroblasts (CAFs), including myofibroblastic CAFs (myCAFs) and senescent CAFs (sCAFs), play a crucial role during tumor progression. This study investigated the CAF subtypes induced by GC cells and the role of sCAFs in peritoneal metastasis of DGC cells. Materials and Methods: Conditioned medium of human DGC cells (KATOIII, NUGC-4) and human intestinal-type GC (IGC) cells (MKN-7, N87) was used to induce CAFs. CAF subtypes were evaluated by analyzing the expression of alpha-smooth muscle actin (alpha-SMA), senescence-associated beta galactosidase (SA-beta-gal), and p16 in human normal fibroblasts (GF, FEF-3). A cytokine array was used to explore the underlying mechanism of GC-induced CAF subtype development. The role of sCAFs in peritoneal metastasis of DGC cells was analyzed using a peritoneally metastatic DGC tumor model. The relationships between GC subtypes and CAF-related markers were evaluated using publicly available datasets. Results: IGC cells significantly induced alpha-SMA+ myCAFs by secreting transforming growth factor-beta, whereas DGC cells induced SA-beta-gal+/p16+ sCAFs by secreting interleukin (IL)-8. sCAFs further secreted IL-8 to promote DGC cell migration. In vivo