SMAD1 and neoplasm: Since we have shown that RTKs and ERK1/2 are upregulated by SOCS1 in murine melanoma cells and that the expression of matrix metallo-proteases (MMPs) and CD10, which are involved in the neoplastic transformation and tumor progression32, can occur by activation of MAPKs through a Smad independent pathway33, 34, we analyzed the expression of total and phosphorylated Smad 2/3, activated by TGF-β; as well as Smad1/5/8, by BMP signaling.