[Role of growth factors in the autonomous growth of XXXX cells].

@entity2594 @entity242 @entity5 @entity2140 @entity1492 @entity35
Typical characteristic of @entity5 cells is a decreased dependence on the growth factors for promotion of their growth. @entity2140 independence and autonomous growth of @entity5 cells has been thought to be due to the ability of the cells to produce growth factors. According to an autocrine hypothesis, @entity2140 can be secreted by @entity5 cells and then binds to its receptor on the same cells to create an uncontrolled growth stimulation. Although there has been much circumstantial evidence to support this hypothesis, an autocrine mechanism is still uncertain. We purified DSF (DNA synthesis factor) from an extract of @entity35 Rhodamine @entity1492 . This factor with strong affinity for heparin-Sepharose was a basic protein with molecular weight of 17,000. These properties were similar to those of basic FGF (fibroblast @entity2140 ). We found that primary cells from the @entity242 could grow in serum-free medium supplemented with the extract of the same @entity242 tissue. The extract was fractionated to purify proteins which supported the growth of primary cells. DSF, @entity2594 and albumin which localized in the tissue, not due to contamination of blood, were purified. When they were added to the serum-free medium, the cells grew at a similar rate to that in medium supplemented with serum. This finding suggests that the growth of @entity242 cells is stimulated by their own @entity2140 and by some environmental factors.
