| Budget Amount *help |
¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1986: ¥3,500,000 (Direct Cost: ¥3,500,000)
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| Research Abstract |
The ability of cancer cells to produce and to respond to their own growth factors (Sutocrine secretion) has become a central concept which is emerging as a unifying theme in the search for the molecular and cellular basis of malignant transformation. A new autocrine growth factor was isolated from a human leukemia cell line, K-562T1, which had been established in a protein-free chemically defined medium. The factor designated as leukemia-derived growth factor (LGF) stimulated the growth of various human leukemia cells, including myeloid, erythroid, lymphoid, and myeloma cells. In the presence of LGF, these cells were able to proliferate in a protein-free chemically defined medium. We report here the purification and molecular characterization of LGF. The purification involved sequential QAE-Sephadex chromatography, gel filtration, and Mono S ion exchange chromatography. The purifed factor showed a single protein band of Mr.=20,000 on NaDoSO_4/polyacrylamide gel electrophoresis, by the silver staining technique. Its amino-terminal sequence was determined as Met-Gln-Ile-Phe-Val-Iys-Thr-Ieu-Thr-Gly-Iys-Thr-Ile-Thr-Leu-Glu-Val-Glu-Pro-. The amino-terminal sequence and molecular size of LGF indicate that the structure of LGF is different from that of other known growth factors. Interestingly, the amino-terminal sequence of LGF was identical to that of ubiquitin (Mr.=8,500), a part of chromosomal semi histones. Ubiquitin purified from bovine thymus did not stimulate proliferation of the human leukemia cells. These results suggest that LGF is a unique autocrine growth factor, having the same amino-terminal amino acid sequence as ubiquitin
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