erbstatin and Cell-Transformation--Neoplastic

Somatic mutation of the FLT3 gene, in which the juxtamembrane domain has an internal tandem duplication, is found in 20% of human acute myeloid leukemias and causes constitutive tyrosine phosphorylation of the products. In this study, we observed that the transfection of mutant FLT3 gene into an IL3-dependent murine cell line, 32D, abrogated the IL3-dependency. Subcutaneous injection of the transformed 32D cells caused leukemia in addition to subcutaneous tumors in C3H/HeJ mice. To develop a FLT3-targeted therapy, we examined tyrosine kinase inhibitors for in vitro growth suppression of the transformed 32D cells. A tyrosine kinase inhibitor, herbimycin A, remarkably inhibited the growth of the transformed 32D cells at 0.1 microM, at which concentration it was ineffective in parental 32D cells. Herbimycin A suppressed the constitutive tyrosine phosphorylation of the mutant FLT3 but not the phosphorylation of the ligand-stimulated wild-type FLT3. In mice transplanted with the transformed 32D cells, the administration of herbimycin A prolonged the latency of disease or completely prevented leukemia, depending on the number of cells inoculated and schedule of drug administration. These results suggest that mutant FLT3 is a promising target for tyrosine kinase inhibitors in the treatment of leukemia.

Topics: Animals; Antineoplastic Agents; Benzoquinones; Cell Line, Transformed; Cell Transformation, Neoplastic; Drug Screening Assays, Antitumor; Enzyme Inhibitors; Female; fms-Like Tyrosine Kinase 3; Genistein; Humans; Hydroquinones; Interleukin-3; Lactams, Macrocyclic; Leukemia, Experimental; Mice; Mice, Inbred C3H; Neoplasm Proteins; Neoplasm Transplantation; Phosphorylation; Phthalimides; Protein Processing, Post-Translational; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Quinones; Receptor Protein-Tyrosine Kinases; Rifabutin; Signal Transduction; Transfection; Tyrphostins

Phosphatidylinositol (PI) synthesis was activated in Rous sarcoma virus-infected NIH3T3 or activated erbB2-transformed NIH3T3 cells. The in vitro activity of CDP-DG:inositol transferase prepared from these cells was also higher than that from normal parent NIH3T3 cells, although phospholipase C and PI kinase activities were not significantly different among these cells. A tyrosine kinase inhibitor, erbstatin, inhibited the PI synthesis in cultured cells, suggesting that Src and ErbB2-associated tyrosine kinases are involved in activation of CDP-DG:inositol transferase in these cell lines.

Topics: 1-Phosphatidylinositol 4-Kinase; 3T3 Cells; Animals; CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; Cell Line, Transformed; Cell Transformation, Neoplastic; Genes, src; Hydroquinones; Mice; Oncogene Proteins, Viral; Phosphatidylinositols; Phosphotransferases (Alcohol Group Acceptor); Protein-Tyrosine Kinases; Receptor, ErbB-2; Transferases (Other Substituted Phosphate Groups); Type C Phospholipases

Topics: Animals; Benzoquinones; Cell Transformation, Neoplastic; Flavonoids; Genistein; Hydroquinones; Isoflavones; Lactams, Macrocyclic; Oncogenes; Phospholipids; Protein-Tyrosine Kinases; Quinones; Rifabutin