The interaction of tumor cells with extracellular-matrix components is suspected to play an important role in tumorigenesis induction. The tumorigenicity of a poorly tumorigenic human colon-adenocarcinoma cell line (BCS-TC2) was induced by co-injection with Matrigel. A new cell sub-line, BCS-TC2.1, was isolated and established from these tumors. Implantation of these cells in nude mice in the absence of Matrigel-generated tumors which allowed the establishment of another tumorigenic cell sub-line, BCS-TC2.2. Matrigel and laminin, but not collagens, promote the tumorigenicity of BCS-TC2 cells, probably due to specific interactions of a pre-existing minor cell sub-population with laminin, which facilitate the initial growth of these cells in vivo. Cytogenetic analysis reveals that both sub-lines originate from the parental one, but a new marker in chromosome 9 is observed. These sub-lines present a lower degree of differentiation, as deduced from the lower CEA content, 5'-nucleotidase and alkaline-phosphatase activities. No variation is observed in the mRNA and protein expression of the 67-kDa laminin-binding protein. However, an increase in beta1 integrins and a parallel decrease in beta4 integrin were detected. Thus, the new sub-lines, compared to the parental cells, present karyotypic and phenotypic differences such as the expression of a distinctive integrin pattern. This system represents a useful model for understanding the development and progression of tumorigenicity in cancer cells.