Tumor necrosis factor-alpha, transforming growth factor-beta, and tetradecanoylphorbol acetate: competence factors for ML-1 human myeloblastic leukemia cell differentiation.

ML-1 human myeloblastic leukemia cells, suspended in RPMI-1640 medium, differentiated to monocyte or macrophage-like cells when either tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), or tetradecanoylphorbol acetate (TPA) was added prior to or simultaneously with fetal bovine serum (FBS). When FBS was applied first, and followed, after washing, by the cytokines or by TPA, maturation did not occur. A 77 kDa glycoprotein (DF77), isolated from human leukocyte-conditioned medium and present in FBS, was capable of replacing FBS for induction of differentiation. Thus, in this cell system, TNF-alpha, TGF-beta, and TPA acted as competence factors, whereas DF77 acted as the progression signal. Optimal competence was established after exposure of the cells to TPA or to either of the cytokines for approximately 2 or 30 min, respectively. After removal of the factors, competence was retained for approximately 3 hr before it declined. These results demonstrate that the initiation of ML-1 human myeloblastic leukemia cell differentiation relied upon the sequential and ordered input of competence and progression signals.

Comparison of the effects of treatment with the polyamine analogue N1,N8 bis(ethyl)spermidine (BESpd) or difluoromethylornithine (DFMO) on the Topoisomerase II mediated formation of 4'-(9-acridinylamino) methanesulfon-m-anisidide (m-AMSA) induced cleavable complex in the human lung carcinoma line NCI H157.

The positively charged polyamines putrescine, spermidine, and spermine are thought to be important in the maintenance of chromosomal structure. Polyamine depletion by the ornithine decarboxylase inhibitor, 2-difluoromethyl-ornithine (DFMO) is known to alter the effect of several DNA active agents, presumably resulting from the altered conformation of the polyamine depleted DNA. Here we compare the polyamine depletion effects of DFMO and the spermidine analogue N1,N8 bis(ethyl)spermidine (BESpd) on the formation of Topoisomerase II mediated, 4'-(9-acridinylamino) methanesulfon-m-anisidide (m-AMSA) induced cleavable complex formation in human large cell undifferentiated lung carcinoma NCI H157 cells. This human cell line responds in the normal cytostatic manner to DFMO, whereas it responds in an unusual cytotoxic manner to treatment with BESpd. Here we report that neither DFMO nor BESpd alone affects the formation of cleavable complex. However, both compounds significantly enhance the m-AMSA induced formation of cleavable complex, each by approximately 1.6 fold. These results indicate that both DFMO and BESpd lead to a similar depletion of nuclear polyamines. Additionally, although BESpd closely resembles the natural polyamine spermidine, it appears that it cannot substitute for Spd at the level of DNA.

Cell cycle dependence of sister chromatid exchange induction by DNA topoisomerase II inhibitors in Chinese hamster V79 cells.

The cell cycle dependence of sister chromatid exchange (SCE) induced by topoisomerase II inhibitors was studied in Chinese hamster V79 cells. 4'-(9-Acridinylamino)methansulfon-m-anisidide, which increases the concentration of covalently linked DNA-topoisomerase II complexes (cleavable complexes), induces SCE strongly in only a short period of the cell cycle. The sensitive period was identified an occurring in early to mid-S phase through the use of labeled thymidine incorporation and flow cytometry. Novobiocin, an inhibitor which prevents formation of the cleavable complex, did not induce SCEs in any part of the cell cycle. However, novobiocin did decrease the level of 4'-(9-acridinylamino)methansulfon-m-anisidide-induced SCEs. These results indicate that the cleavable complex may be important in 4'-(9-acridinylamino)methansulfon-m-anisidide-induced SCE.