The figure depicts the role of MTDH and SND1 interaction in breast tumor initiation. Under stress conditions during the formation of tumors (top), MTDH interacts with SND1 and protects it from degradation. This allows cancer stem cells, the root of tumors, to survive and expand, eventually giving rise to large tumors. When MTDH was genetically deleted (bottom), the normal development of mammary glands was unaffected. However, without the interaction with MTDH, SND1 becomes unstable under oncogenic stress and is no longer able to support cancer stem cells. These cells undergo stress-induced cell death and lose the ability to initiate tumors.