CHARACTERIZATION OF SPONTANEOUS FACTOR-INDEPENDENT CELL-LINES DERIVEDFROM THE HUMAN LEUKEMIC-CELL LINE TF-1 - A DOMINANT EVENT

Uncontrolled proliferation of acute myeloid leukemia (AML) cells is an important step during leukemogenesis. However, little is known about the mechanisms leading to growth autonomy. Studies using immortalized murine hematopoietic cell lines have suggested that autocrine producti on of growth factors, or the constitutive activation of molecules in g rowth factor signalling pathways, are involved. We have established si x spontaneous factor-independent cell lines from the human growth fact or-dependent TF-1 cell line. The factor-independent cells showed no de tectable growth factor activity. Immunoblotting analyses of tyrosine p hosphorylation, Raf-1 and extracellular signal-regulated kinase 2 (ERK -2) showed a similar pattern in all the cell lines including TF-1 cell s. Furthermore, somatic-cell hybrids between TF-1 and the factor-indep endent cells grew in absence of growth factor. Taken together this dat a demonstrates that the factor independence in this system is dominant and suggests that the molecular event is located either downstream of the Raf-1 and MAP kinases pathway or on an alternative pathway. Final ly, the karyotype analysis of one factor-independent cell line TF-1i1 and TF-1H(-) (G418 resistant, HAT sensitive TF-1 cells) and their hybr ids demonstrated an unstable derivative chromosome [der(19) t(19;?) (q 13.1;?)] which seemed to correlate with the factor-independence capaci ty. This model may help in our understanding of autonomous proliferati on by human myeloid leukemias.