Clones of tumor cells derived from a single primary human lung tumor reveal different patterns of β₁ integrin expression

Previously we reported that over 75% of human non-small cell lung cancers overexpress the βi integrin VLA-2 on their surface and show an increase in the mRNA encoding the α2 chain of this integrin. These results suggested the possibility that the overproduction and overexpression of one or more of the β₁ integrin may be involved in the pathogenesis of human lung tumors by modulating the invasive and/or metastatic potential of the tumor. We report here the generation and characterization of multiple clones of tumor cells derived from the primary culture of cells obtained from biopsy tissue of an aggressive human squamous cell lung tumor. We show that these tumor clones (or clonotypes) exhibit seven different yet stable phenotypes with respect to the expression of five members of the βi integrin family. These results illustrate that a primary human lung tumor consists of multiple subpopulations of cells that while indistinguishable by ultrastructure are heterogeneous with respect to their β₁ integrins. The availability of these distinct tumor clonotypes derived from a single tumor biopsy have made it possible to test the assumption that the βi integrins play a role in tumor progression. The feasibility of this approach is demonstrated here by the intravenous inoculation of different human tumor clonotypes into severe combined immunodeficient (scid) mice. Our preliminary results with a pair of tumor clonotypes differing in VLA-1 and VLA-2 expression level reveal that the clonotype with high level of VLA-1 and VLA-2 displays a substantial increase in the experimental engraftment and metastasis of the human tumor cells in scid mice.