Levamisole has been employed as an immunomodulatory agent in conjunction with 5-fluorouracil in the treatment of colon cancer relapse. At high doses, levamisole has been shown to have both anti-cancer and immunosuppressive activities. In vitro, levamisole has been shown to potentiate the anti-proliferative effect of 5-fluorouracil in several types of tumor cell lines; however, its mechanism of cytotoxic action and its molecular targets in cells remains to be elucidated. Here, the effect of levamisole on the proliferative response of the human multiple myeloma cell lines RPMI 8226 and U266B1 was studied in vitro. Treatment of both lines with varying concentrations of levamisole for 48 and 72 h in culture resulted in a significant inhibition of proliferation (unstimulated) in a dose-dependent manner, as assessed by an 3-[(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide dye assay. Furthermore, measurements of cell viability (using a trypan blue dye exclusion assay) clearly showed that the levamisole was cytotoxic. The preliminary evaluation of the mechanism of this cytotoxic effect revealed that this drug induced apoptosis in the myeloma cells, as evidenced by increases in the levels of DNA fragmentation, release of cytochrome c into the cytoplasm, and the activation of caspase-3 activity in the cells. The results of these studies strongly suggest that levamisole could be a potent anti-myeloma agent and might be considered in the treatment of multiple myeloma in the future.
Bone marrow aspirates form patients with multiple myeloma were obtained and lymphocytes were isolated using density gradient centrifugation. The APase activity of the samples ranged from 12 to 88 nmol/ 0.2 9 10 6 cells as compared to the very low activity present in normal human peripheral blood lymphocytes PBL. Neither the unstimulated nor the mitogen stimulated lymphocytes from peripheral blood of normal humans showed appreciable APase activity. The lymphocytes from bone marrow of multiple myeloma patients as well as myeloma cell lines-RPMI 8226 and U266 B1 express APase activity constitutively. The results of the present investigation are discussed in the light of existing literature.Keywords Alkaline phosphatase Á Human peripheral blood lymphocytes Á U266B1 and RPMI 8226
Materials and MethodsCell Lines and Culture Conditions U266B1 and RPMI 8226 cell lines were obtained from
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