dicumarol and Leukemia--Myeloid

In this study, we have characterized quinone reductase (QR), glutathione (GSH), glutathione S-transferase (GST) and their induction by a chemoprotector, 1,2-dithiole-3-thione (D3T), in the human myeloid cell lines ML-1 and HL-60. In addition, we also examined the toxicity of hydroquinone (HQ), a benzene metabolite, to these two cell lines. Both of the cell lines contain a basal level of cellular GSH, which is similar in the two cell lines. Although ML-1 cells contain much higher QR specific activity than HL-60 cells, which are relatively QR deficient, the GST specific activity of ML-1 cells is 1.8 times less than that of HL-60 cells. Immunoblot experiments showed that the GST in these two cell lines is GST pi. In addition, HL-60 cells exhibit 4.5 times more myeloperoxidase specific activity than ML-1 cells. Inclusion of D3T in the cultures could induce significant increases in cellular GSH content and QR activity, but not GST activity in either cell line. Treatment with HQ caused both inhibition of cell proliferation and loss of cell viability in these two myeloid cell lines. HQ treatment also resulted in a significant depletion of cellular GSH, which preceded the loss of cell viability. Pretreatment of both cell lines with buthionine sulfoximine, an inhibitor of GSH biosynthesis, markedly increased HQ-induced toxicity. In contrast, the presence of dicumarol, a QR inhibitor, failed to potentiate HQ-induced toxicity in ML-1 cells. On the other hand, pretreatment of these two myeloid cell lines with D3T significantly protected against HQ-induced inhibition of cell proliferation and cell death. Therefore, the above results suggest that GSH but not QR is an important factor involved in the toxicodynamics of HQ in these myeloid cells.

Topics: Antimetabolites, Antineoplastic; Antineoplastic Agents; Buthionine Sulfoximine; Dicumarol; Drug Synergism; Enzyme Induction; Glutathione; Glutathione Transferase; Humans; Hydroquinones; Leukemia, Myeloid; Methionine Sulfoximine; Models, Chemical; NAD(P)H Dehydrogenase (Quinone); Peroxidase; Thiones; Thiophenes; Tumor Cells, Cultured

Using 4 human cancer cell lines, the relevance of NAD(P)H: quinone oxidoreductase (DT-diaphorase) activity to mitomycin C (MMC)-induced cytotoxicity was investigated. KB cells (oral epidermoid carcinoma) had more than 4 times higher DT-diaphorase activity than PH101 (pancreatic cancer), SH 101 (gastric cancer), or K562 (myelogenous leukemia) cells. The sensitivity to MMC was greatest in KB cells. Concentrations causing 50% inhibition of cell growth (IC50 value: microgram/ml) by 30 min treatment with MMC were 0.4 in KB, 1.1 in PH101, 1.6 in SH 101, and 1.9 in K 562. Treatment with 1.5 micrograms/ml of MMC induced DNA total cross links, and the indices were 0.18 in KB, 0.10 in SH101, 0.09 in SH101, and 0.06 in K 562. When DT-diaphorase activity was inhibited by non-toxic dicoumarol (50 microM), DNA damage and cytotoxic activity induced by MMC were decreased in all cells examined. Especially in KB cells, it was remarkable. Since it was shown that the level of cellular DT-diaphorase activities were correlated with the responses to MMC, we suggest that bioreduction by DT-diaphorase may activate MMC.

Topics: Carcinoma, Squamous Cell; Cell Division; Dicumarol; DNA Damage; Humans; Leukemia, Myeloid; Mitomycin; Mouth Neoplasms; NAD(P)H Dehydrogenase (Quinone); Pancreatic Neoplasms; Stomach Neoplasms; Tumor Cells, Cultured