SMAD1 and neoplasm: After the BR-SMADs (Smad1, 5) in mice SCs is deleted via tissue-specific ablation, all male Smad1/Smad5 KO mice (14 samples) developed Sertoli-Leydig tumors after 28 weeks of age with 100% metastases to lymph and peritonea, implicating the role of the BR-SMAD signaling pathway as a tumor suppressor in testis155.