Insulin receptors on cultured murine lymphoid tumor cell lines

Eight murine lymphoid tumor cell lines have been examined for the presence of high-affinity insulin receptors. The eight cell lines included two Abelson murine leukemia virus-transformed pre-B cell lines, three plasmacytoma cell lines, and three spontaneous T-cell lymphomas from AKR mice. All of the cell lines in the B-cell series had high-affinity insulin binding sites. The apparent equilibrium association constant (Ka) for the high-affinity binding sites on these cells was 1.3-3.3 X 10(9) M-1. Two of the T-cell lymphomas had high-affinity receptor levels so low as to be undetectable in the whole cell binding assay under the conditions used for assaying the other cell lines, although in binding assays performed at very high cell densities, these two cell lines did appear to have a small number of high-affinity insulin binding sites. These results indicate that the growth stimulus provided by the tumor virus in neoplastic transformation of the AKR thymic lymphocytes differs from that provided by lectins in blast transformation of lymphocytes in that the neoplastic transforming event does not always result in the emergence of large numbers of high-affinity insulin receptors. In addition, the existence of cell lines such as the T-cell lymphomas that have nearly exclusively low-affinity binding sites suggests that the low-affinity sites may represent a distinct receptor that is not freely interconvertible with the high-affinity receptor.