guanylyl-imidodiphosphate and Neoplasm-Metastasis

The ability of a series of B16 melanoma clones to form experimental lung metastases in syngeneic mice has been shown to correlate positively with adenylate cyclase activity. (Sheppard et al, Int. J. Cancer 37 (1986) 713-722). To begin to identify the components of the adenylate cyclase complex that account for enhanced enzyme activity in highly metastatic tumor populations, cholate extracts containing the GTP-binding protein GS from B16 melanoma clones of different metastatic capacities were reconstituted with membranes prepared from S49 cyc-, a variant lymphoma cell line that lacks GS function. The results revealed that extracts from a highly metastatic B16 clone (F10-C23) reconstituted significantly greater adenylate cyclase activities in S49 cyc- membranes than parallel preparations from a B16 clone (F1-C29) of low metastatic capacity. The data suggest that aberrations in GS function may contribute to the heightened responsiveness of adenylate cyclase observed in B16 melanoma clones of increased metastatic potential.

Topics: Adenylyl Cyclases; Animals; Cell Line; Cell Membrane; Colforsin; GTP-Binding Proteins; Guanylyl Imidodiphosphate; Melanoma; Mice; Molecular Weight; Neoplasm Metastasis

The regulation of adenylate cyclase in murine melanoma tumor cell clones with different metastatic capacities has been studied in intact cells and isolated membrane preparations. Analysis of the responses of intact cells from a number of B16 melanoma clones revealed that treatment with melanocyte-stimulating hormone (MSH) or the diterpene, forskolin, produced significantly greater accumulation of intracellular cyclic adenosine 3',5' monophosphate (cAMP) in strongly metastatic clones than in weakly metastatic tumor cell clones. In contrast, in isolated membranes from the same panel of clones, the extent of activation by forskolin but not by MSH correlated with metastatic capacity. Sodium fluoride and 5'-guanyl-beta-gamma-imidodiphosphate [Gpp(NH)p] also stimulated adenylate cyclase in isolated membranes but the extent of activation did not correlate with the metastatic behavior of the donor cells. A combination of forskolin and Gpp(NH)p proved to be a sensitive prospective indicator for identifying differences in the metastatic capabilities of individual B16 melanoma clones. Adenylate cyclase in membrane preparations from strongly metastatic B16 clones displayed synergistic activation but stimulation of the enzyme from weakly metastatic clones was less than additive. To test the generality of these findings, similar investigations were performed on B16-BL6 melanoma cells, a highly invasive subline of the B16 melanoma, and the K1735, an ultraviolet-light-induced murine melanoma arising in a different mouse strain (C3H). Consistent with their high metastatic potential, clones derived from the B16-BL6 melanoma displayed elevated levels of hormonally-stimulated adenylate cyclase, thereby confirming, for this tumor system, a close association between hormonal responsiveness and metastatic capacity. In contrast, K1735 melanoma cell clones exhibited significant interclonal variation in adenylate cyclase activity and metastatic performance, but no consistent relationship between the two traits was detected. Differences in the regulation and/or the intrinsic catalytic capacity of adenylate cyclase may account, at least in part, for the variation in hormonal responsiveness observed among B16 clones with distinct metastatic properties and suggest that cAMP-dependent molecular processes may be required for the expression of B16 melanoma experimental metastatic potential.(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Adenylyl Cyclases; Animals; Cell Membrane; Clone Cells; Colforsin; Cyclic AMP; Fluorides; Guanylyl Imidodiphosphate; Kinetics; Lung Neoplasms; Melanocyte-Stimulating Hormones; Melanoma; Mice; Neoplasm Metastasis