Methods and compositions for the prevention and/or treatment of metastatic cancer by tumor encapsulation achieved by introducing a physical obstacle to prevent cancerous cells from escaping the original site and invading other tissues. Physical obstacle is introduced as a pre-formed matter or its assembly by the treated organism is induced. In the preferred embodiment the composition of matter is disclosed, which enables formation of the obstacle in a form of basement membrane (BM). Said composition enables tissue cells to assemble BM on their surfaces, and supplies ECM components for said assembly, whereby BM is assembled de novo or the existing BM is strengthens. The composition comprises soy phytoestrogens, including genistein, daidzein, glycitein, biochantin A, and derivative thereof, actin cytoskeleton reorganization inhibitors, such as Cytochalasin D, and PTK inhibitors, in combination with ECM proteins, such as laminins and type IV collagens, or their derivatives.
