Antiproliferative activity of cyclosporin A on human T-lymphoblastic leukaemia cell line

Cyclosporin A Induces Apoptosis in Childhood Acute Lymphoblastic Leukemia Cells

In an effort to identify novel antileukemic agents that can bypass the mechanisms of multidrug resistance, we found that cyclosporin A ([CyA] 5 μmol/L) produced a median cell kill of 69% (range, 47% to 85%) in seven B-lineage acute lymphoblastic leukemia (ALL) cell lines (OP-1, SUP-B15, KOPN-55bi, RS4;11, NALM6, REH, and 380) and three T-lineage ALL cell lines (MOLT4, CCRF-CEM, and CEM-C7) after 4 days of culture. At 10 μmol/L, median CyA toxicity was 99% (range, 88% to >99%). CyA was equally toxic to both a multidrug-resistant cell line, CEM-VLB100, which overexpresses gp-170 P-glycoprotein, and one resistant to topoisomerase II inhibitors, CEM-VM1-5, which has a mutation in the topoisomerase II gene. CyA was also toxic to primary leukemic cells maintained in stroma-based culture, a system that substantially prolongs in vitro cell survival. Against lymphoblasts from 21 patients with B-lineage ALL, the compound (at 5 μmol/L) reduced the leukemic cell number by a median of 87% (range, 27% to >99%) compared with results for parallel control cultures lacking CyA. Seven of these samples were from cases with unfavorable genetic features (eg, Philadelphia-chromosome orMLL gene rearrangements); three were obtained at relapse. Against T lymphoblasts (from six patients), the median reduction in cell number was 79% (range, 30% to >99%). At 10 μmol/L, the cell kill exceeded 97% in all cases studied. The mechanism of CyA cytotoxicity was found to be the activation of apoptosis, which was suppressed by phorbol myristate acetate but not by inhibitors of ceramide-mediated apoptosis, phosphatidyl inositol-3 kinase activity, or tyrosine kinase activity. These findings demonstrate high levels of CyA-induced toxicity against ALL cells at concentrations achievable in vivo, thus providing a strong rationale for clinical testing of this agent in patients with ALL.

Cyclosporin A Induces Apoptosis in Childhood Acute Lymphoblastic Leukemia Cells

In an effort to identify novel antileukemic agents that can bypass the mechanisms of multidrug resistance, we found that cyclosporin A ([CyA] 5 μmol/L) produced a median cell kill of 69% (range, 47% to 85%) in seven B-lineage acute lymphoblastic leukemia (ALL) cell lines (OP-1, SUP-B15, KOPN-55bi, RS4;11, NALM6, REH, and 380) and three T-lineage ALL cell lines (MOLT4, CCRF-CEM, and CEM-C7) after 4 days of culture. At 10 μmol/L, median CyA toxicity was 99% (range, 88% to >99%). CyA was equally toxic to both a multidrug-resistant cell line, CEM-VLB100, which overexpresses gp-170 P-glycoprotein, and one resistant to topoisomerase II inhibitors, CEM-VM1-5, which has a mutation in the topoisomerase II gene. CyA was also toxic to primary leukemic cells maintained in stroma-based culture, a system that substantially prolongs in vitro cell survival. Against lymphoblasts from 21 patients with B-lineage ALL, the compound (at 5 μmol/L) reduced the leukemic cell number by a median of 87% (range, 27% to >99%) compared with results for parallel control cultures lacking CyA. Seven of these samples were from cases with unfavorable genetic features (eg, Philadelphia-chromosome orMLL gene rearrangements); three were obtained at relapse. Against T lymphoblasts (from six patients), the median reduction in cell number was 79% (range, 30% to >99%). At 10 μmol/L, the cell kill exceeded 97% in all cases studied. The mechanism of CyA cytotoxicity was found to be the activation of apoptosis, which was suppressed by phorbol myristate acetate but not by inhibitors of ceramide-mediated apoptosis, phosphatidyl inositol-3 kinase activity, or tyrosine kinase activity. These findings demonstrate high levels of CyA-induced toxicity against ALL cells at concentrations achievable in vivo, thus providing a strong rationale for clinical testing of this agent in patients with ALL.

Effects of cyclosporin A and a non-immunosuppressive analogue, O-acetyl cyclosporin A, upon the growth of parent and multidrug resistant human lung cancer cells in vitro

We have studied the ability of cyclosporin A (CsA) and a non-immunosuppressive analogue, O-acetyl cyclosporin A (OACsA, B3-243) to inhibit the growth of human lung cancer cells in vitro. Using continuous drug exposure and the MTT colorimetric assay to determine cell growth we found that CsA produced partial growth inhibition at doses ranging from 0.5 to 3.0 micrograms ml-1 (0.4-2.4 microM). At progressively higher doses, complete growth inhibition and in situ cell lysis were seen. The P-glycoprotein expressing multidrug resistant (MDR) variant H69/LX4 of the small cell line H69/P was less sensitive to cyclosporins than the parent line, but this was not true of the non-P-glycoprotein expressing MDR variants of large cell line COR-L23 or adenocarcinoma line MOR. Sensitivity to OACsA was approximately 2-fold higher than that to CsA in most of the lines although not in the most sensitive line, COR-L88. Even in COR-L88, exposed to CsA or OACsA for 24 h, clonogenic cell survival was reduced only to 50%. There was no reduction in polyamine content of COR-L23 or COR-L88 cells following 48 h of exposure to CsA or OACsA. The effects on cell growth could not be inhibited by the addition of exogenous putrescine, nor could they be enhanced by the addition of alpha-difluoromethylorthinine. It does not appear therefore that inhibition of polyamine synthesis is the basis of the observed growth inhibition.

A method for preparing biologically active aqueous cyclosporin A solutions avoiding the use of detergents or organic solvents

The immunosuppressive agent cyclosporin A (CsA) is highly hydrophobic and is, therefore, being taken for in vitro use directly from ethanolic stock solutions. In the present study it is demonstrated that ethanol itself affects several immunological activities in vitro, thus interfering with the immunosuppressive effects of CsA. As an alternative, it is demonstrated that CsA can be solubilized and retain its activity in aqueous solutions of polyvinyl pyrrolidone (PVP). Unlike ethanol, PVP has no effect on the various immunological activities in vitro and therefore the immunosuppressive effects of CsA can be evaluated without interference.

Pharmacological modification of multi-drug resistance (MDR) in vitro detected by a novel fluorometric microculture cytotoxicity assay. Reversal of resistance and selective cytotoxic actions of cyclosporin A and verapamil on MDR leukemia T-cells

A novel fluorometric microculture cytotoxicity assay (FMCA), based on measurements of fluorescein diacetate (FDA) hydrolysis and DNA staining by Hoechst 33342, was used for drug sensitivity testing and detection of resistance reversal in acute lymphoblastic leukemia (ALL) cell lines. The 72-hr assay was found to be sensitive, reproducible and linearly related to the number of viable cells within a broad range of cell concentrations. At clinically achievable drug concentrations, the calcium channel blocker Verapamil (ver) and the immunosuppressant Cyclosporin A (csA) were found to partly reverse acquired Vincristine (vcr) resistance in multi-drug resistant (MDR) T-ALL L100 cells with little or no effect on the drug-sensitive parental L0 cell line. By combining the fluorometric indices, we found that low concentrations of csA were growth-inhibitory, whereas higher concentrations (greater than 10 micrograms/ml) were progressively cytotoxic for drug-sensitive L0 cells. In MDR L100 cells, on the other hand, csA produced significant cell kill even at low drug concentrations. Ver had no effects on sensitive L0 cells but showed considerable cytotoxic action towards MDR L100 cells. There was no apparent relationship between drug reversal of vcr resistance and the cytotoxic actions of the drug per se since the calcium channel blocker diltiazem (dil) significantly potentiated the actions of vcr on MDR L100 cells without being more toxic to these cells (compared to vcr-sensitive L0 cells).

On the potential role of cyclosporin in the treatment of lymphoproliferative diseases

Lymphomas and leukemias, as cancers of the immune system, may still retain some susceptibility to regulatory mechanisms which govern the proliferation of their cells of origin. According to this concept, an enhanced immune suppression as induced by irradiation and chemotherapy may contribute to their cytotoxic effect in inducing and maintaining a remission of the disease. Cyclosporin selectively and reversibly inhibits activation and proliferation of both normal and neoplastic T lymphocytes. In-vitro experiments and preliminary clinical data from small uncontrolled studies indicate that cyclosporin might be a promising agent in the treatment of mycosis fungoides, Hodgkin's disease, acute leukemia, and possibly other lymphoproliferative disorders, but the experience is still limited and no definitive conclusions may be made. In addition to its direct effect on lymphocytes, cyclosporin reverses the resistance of cancer cells to several antineoplastic agents and may thus find its place in combination with chemotherapy. It is hoped that a more systematic basic and clinical research will help define the role of this new therapeutic approach.

Effect of cyclosporine on carcinogenesis induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine

Cyclosporine administration has been associated with the development of lymphomas in human transplant patients as well as animals. Its effect on the genesis of common epithelial carcinomas is unknown. To investigate this N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was administered in drinking water to Wistar rats. Seventy-five young healthy male animals were divided into six groups and received cyclosporine alone, cyclosporine followed by MNNG, MNNG alone, cyclosporine during MNNG administration, MNNG followed by cyclosporine, and no treatment. Cyclosporine seemed to have minimal overall health effects and no cancers were encountered in the group receiving this agent alone. Animals in all carcinogen-treated groups developed gastric and upper intestinal carcinomas by Week 39. No statistically significant differences among carcinogen-treated groups were evident with respect to tumor incidence, histology, or distribution. There appeared to be trends (not statistically significant) toward a greater incidence of small bowel carcinomas in animals receiving cyclosporine plus MNNG as compared to those receiving MNNG alone; greater multiplicity of small intestinal carcinomas in animals receiving cyclosporine after MNNG as compared to all other groups; and greater incidence of small bowel tumors greater than 1 cm3 in animals receiving cyclosporine after MNNG as compared to all other groups. The median total tumor volume in the animals receiving cyclosporine following carcinogen was significantly greater than in any other group. This study does not support a policy of aggressive surveillance for gastrointestinal carcinoma in the human population receiving cyclosporine.

In vitro effects of cyclosporin A (CSA) on human hemopoietic cell lines

The sensitivity of 18 permanent hemopoietic cell lines to Cyclosporin A (CsA) was tested in a 3H-thymidine incorporation rate assay. Two human T cell lines (Molt4 and CEM) were significantly inhibited by a CsA concentration of 0.5 microgram/ml. Not affected at all or only inhibited by 10 to 20 times higher CsA concentrations were: three human B cell lines (4413a, Daudi, Raji), a monkey B cell line (B95-8), a mouse plasmocytoma line (X63-Ag8/653), a human non-B T cell line (Reh), four human myeloid lines (HL-60, ML-1, ML-2, ML-3), a human myelomonocytic line (Karpas 230), four human monoblastic lines (U 937, SU-DHL-1, THP-1, Karpas 241) and a human erythroid line (K 562). It therefore seems that among permanently growing hemopoietic cells a cell type specificity for T cells also exists.