| Abstract: | The human lymphoblastoid B-cell line RPMI-6410t was found to synthesize and secrete into the growth medium a factor necessary to maintain the reproduction of these cells. In the condition of low plating density (concentration 1-1000 cells per ml) cell proliferation can be maintained only in the presence of a definite dose of medium conditioned by 6410t cell growth under high concentration. Using such a medium guaranteed almost 100% cloning efficiency of these cells by the method of limiting dilutions. The cloning of 6410t cells in the presence of feeder cells, such as mouse splenocytes and peritoneal cells, failed. The 6410t cells were shown to bind specifically the growth factor secreted by them, thus suggesting the presence of a growth factor acceptor on their surface. With the help of special selective method some clones were derived which did not secrete growth factor but were likely to have growth factor acceptors on their surface. A comparison of growth properties of clones GF- and GF+ supported the idea of autocrine control of proliferation as one of the mechanisms of malignant cell transformation. |
