2′,2′‐Difluorodeoxycytidine (Gemcitabine) Induces Apoptosis in Myeloma Cell Lines Resistant to Steroids and 2‐Chlorodeoxyadenosine (2‐CdA)

Abstract

Abstract. The paucity of effective cytotoxic agents for the treatment of steroid resistant multiple myeloma explains the ongoing search for alternative substances for chemotherapy of this disease. In the present study, the purine antagonist 2-chlorodeoxyadenosine (2-CdA, cladribine) and the pyrimidine antagonist 2′,2′-difluorodeoxycytidine (gemcitabine) were tested on four myeloma cell lines (i.e., U 266, OPM 2, RPMI 8226, IM 9), one plasma cell leukemia cell line (HS Sultan) and a myeloid control cell line (HL 60), all of which are resistant to 10 -6 M dexamethasone. Gemcitabine has been found to be promising in the chemotherapy of other tumors with low proliferative activity, but its effectiveness against myeloma cells has not been analyzed so far. In our tests, gemcitabine induced a significant degree of apoptosis in all cell lines investigated. After incubation for 48 h with 10 µM gemcitabine, the median numbers of apoptotic cells were in the range of 45% in the OPM 2 and 79% in the U 266 cell line. All of the investigated cell lines were responsive to concentrations of 10 µM gemcitabine even after an exposure of only 30 min, three of them (U 266, HS Sultan, IM 9) also responded to a concentration of 10 nM. Higher concentrations and longer exposure times were necessary to suppress the growth of normal hematopoietic bone marrow progenitor cells. In contrast to gemcitabine, standard concentrations of 2-CdA (i.e., 30 and 300 nM) failed to induce a significant degree of apoptosis in the cell lines investigated but inhibited the growth of myeloid progenitor cells.The results suggest that gemcitabine induces apoptosis in myeloma and plasma cell leukemia lines resistant to steroids and 2-CdA. The fact that tumor cell apoptosis was achieved at concentrations clinically achievable and tolerable, which at the same time do not inhibit the growth of normal CFU-GM progenitor cells, favors the initiation of phase I trials with this drug for the treatment of multiple myeloma.

High-Dose Infusional Gemcitabine Combined with Busulfan and Melphalan with Autologous Stem-Cell Transplantation in Patients with Refractory Lymphoid Malignancies

“…Gemcitabine has potent activity against myeloma cell lines in vitro, including cells resistant to other drugs. [46,47] Unfortunately, gemcitabine has not been adequately tested clinically in this disease. In a small phase 2 trial of weekly 30-minute infusions little activity was observed against refractory tumors.…”

Expression of Apo‐1/Fas (CD95), Bcl‐2, Bax and Bcl‐x in myeloma cell lines: relationship between responsiveness to anti‐Fas mab and p53 functional status

“…1% Triton X-100) for permeabilization and DNA staining. Analysis of cell size and fluorescence intensity was performed in the forward/side scatter program of a Becton Dickinson FACScan as recently described in detail (Nicoletti et al, 1991;Gruber et al, 1996). After exclusion of necrotic debris, apoptotic cells in PI-assays were defined by a decrease in DNA content as compared to G1 phase cells of myeloma cell lines and normal T lymphocytes.…”

“…DNA was extracted from 1 × 10 7 cells, using phenol-chloroform and then electrophoretically separated in a 1 . 8% agarose gel, as described previously (Gruber et al, 1996). Cell pellets were resuspended in 100 ml ice-cold PBS/EDTA, to which 900 ml of lysis buffer (0 .…”

Evolving role of ribonucleoside reductase inhibitors in hematologic malignancies

“…On CML cells, gemcitabine was demonstrated to be more effective than the nucleoside analog cladribine [117]. Gemcitabine induces apoptosis in myeloma and plasma cell leukemia lines resistant to steroids and cladribine [119]. Gemcitabine induces apoptosis in myeloma and plasma cell leukemia lines resistant to steroids and cladribine [119].…”