In vitro induction of apoptosis of neoplastic cells in low-grade non-Hodgkin's lymphomas using combinations of established cytotoxic drugs with bendamustine

Background and Objectives, Regulation of apoptotic cell death is being incr easingly recognized as a mechanism by which cytostatic agents mediate tumor cell death. Preliminary clinical studies with bendamustine, an alkylating agent with a purine nucleus, provide strong evidence that this drug is a hi ghly effective cytostatic in low grade lymphomas, We, therefore, investigat ed the in vitro activity of bendamustine in combination with other establis hed cytotoxic drugs. Design and Methods. Two cell lines (DOHH-2, WSU-NHL) and mononuclear cells (MNC) from patients with leukemic low-grade B-non-Hodgkin's lymphoma (NHL) (n=10), T-NHL (n=7) and chronic lymphocytic leukemia (CU) (n=12). Apoptosis (7-AAD), depolarization of mitochondrial membrane potential (MMP, JC-1), c aspase-3-activity (FIENA) and cell proliferation (XTT/WST-1) were determine d, Several incubation times and drug dosages (for IC30/50/70/90) were studi ed, Synergistic, additive or antagonistic effects were calculated by a medi an plot effect and the combination index (CI) method. Results. In general, combinations of bendamustine with mitoxantrone or doxo rubicin resulted in antagonistic effects in the tested cell lines and the M NC from the patients. CI-calculation failed in these cases since there was not a sufficient dose response. On the other hand, the combination of benda mustine with 2-CdA showed synergistic in vitro activity on the tested cell lines, neoplastic lymphocytes from patients with peripheral T-cell lymphoma s and partially on MNC from patients with CU. and B-NHL The antagonism of t he combination of bendamustine and anthracyclines appeared to be due to inh ibition of depolarization of mitochondrial membrane potential and caspase-3 -activity during apoptosis of the studied cell lines. Interpretation and Conclusions. In conclusion, our results suggest that sch edules using combinations of bendamustine and anthracyclines should not be recommended for the treatment of low-grade NHL whereas bendamustine combine d with 2-CdA could be considered for the development of future treatment st rategies. (C) 2001, Ferrata Storti Foundation.