Periostin (encoded by Postn) is a matricellular protein secreted by cancer-associated fibroblasts (CAFs), which may promote cancer stemness, initiation, and progression19,20, and is overexpressed in many cancers, such as breast cancer, colon cancer, glioblastoma, gastric cancer, and liver cancer21–25. The gene discussed is POSTN; the disease is breast carcinoma.