Cyclosporins: immunosuppressive agents with antitumor activity

Immunosuppressive drugs and their effect on experimental tumor growth

The effect of cyclosporin (CyA), FK 506, and mycophenolate mofetil (MPM) on tumor growth was investigated using syngeneic mouse colon carcinoma 38. Mice were laparotomized and the tumor cells were injected into the portal vein to establish liver metastasis. The animals were grouped as follows: groups A-1, B-1, and C-1 were given CyA [15 mg/kg body weight (BW)], FK 506 (0.15 mg/kg BW), and MPM (100 mg/kg BW), respectively, 30 min before tumor inoculation and daily for 5 days by gavage; groups A-2, B-2, and C-2 were given CyA (30 mg/kg BW), FK 506 (0.3 mg/kg BW), and MPM (200 mg/kg BW), respectively, with the same dose timing; and groups A-3, B-3, and C-3 received CyA (30 mg/kg BW), FK 506 (0.3 mg/kg BW), and MPM (200 mg/kg BW), respectively, on the 7th post-tumor inoculation day and on the following 5 days. The mean tumor diameter in groups A-1 and A-2 was greater than that in the control group and in groups C-1 and C-2 at 3 weeks (P < 0.05). The mean tumor numbers in groups A-1 and A-2 were greater than those in the control group and in groups C-1 and C-2 at 4 weeks (P < 0.05). With in vitro MTT assay, all three drugs acted cytostatically on tumor cells with a higher concentration (10(-6)-10(-4) mol/l), while no cytostatic effect was noted with CyA at a lower concentration (10(-9)-10(-7) mol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Growth inhibition of human gastrointestinal cancer cells by cyclosporin A

We have studied the ability of cyclosporin A (CsA) to inhibit the growth of human AGS gastric and HT29 colon carcinoma cells in vitro. Using continuous drug exposure in growth assays of cultured tumour cells we found that CsA produced a dose-dependent growth inhibition in gastric and colon cancer cells with a half-maximal effect at 5 microM and 6 microM CsA respectively. The growth inhibition of CsA was reversible in AGS cells, when the tumour cells were incubated in normal growth medium following CsA treatment. Trypan blue dye exclusion in AGS cells indicated a cytostatic rather than a cytotoxic effect in the concentration range used. Coincubation of CsA-treated cells with 10-400 U/ml interleukin-2 (IL-2) could not abrogate this growth inhibition, suggesting an IL-2 independent mechanism of action. Flow-cytometric analysis did not reveal a phase arrest of the gastric cancer cells within the cell cycle. We conclude from our experiments that CsA cytostatically and reversibly inhibits the growth of human gastric cancer cells in a dose-dependent manner. In contrast to its mechanism of action in lymphocytes, this direct antiproliferative effect of CsA seems not to be mediated by an IL-2-dependent pathway or a cell-cycle-phase arrest of the tumour cells.

Enhancement of tumor proliferation by cyclosporine A in early phase of experimental hepatic metastasis

The effect of cyclosporine A (CsA) on in vivo growth of hepatic metastasis was studied. Murine colon 38 tumor cells (1 x 10(5) were inoculated via the superior mesenteric vein. Mice were grouped depending on CsA dosage and time schedules: Group A: CsA 30 mg/kg body weight on the 7, 8 and 9th post tumor inoculation days by gavage; Group B: CsA 15 mg/kg body weight 30 min before tumor inoculation and 2 times more at 24 h intervals; Group C: CsA 30 mg/kg body weight at the same dose timing as Group B. Measurement of the diameter of the largest tumor serially by weekly laparotomy up to 4 weeks revealed that the tumor growth rates were significantly greater in Groups B and C than those in Group A or the control (without CsA). The mean tumor doubling times in the control, and Groups A, B and C were 2.2 +/- 1.3, 2.0 +/- 0.5, 1.5 +/- 0.4 and 1.3 +/- 0.8 days, respectively. The mean tumor numbers of hepatic metastasis were 13.2 +/- 8.3, 11.3 +/- 7.3, 19.4 +/- 8.7 and 19.6 +/- 6.8, respectively. Values of tumor proliferation index obtained by bromodeoxyuridine immunohistochemistry were 10.0 +/- 6.1%, 14.9 +/- 8.0%, 28.6 +/- 8.2% and 30.1 +/- 12.4%, respectively, with significant differences (Groups B and C vs. A or control, P < 0.05). In vitro MTT assay showed that cell viability rates were greater than 100% in the medium containing CsA concentrations of less than 10(-7) mol/liter. However, a cytostatic effect of CsA was apparent at higher concentrations. In contrast to the previous in vivo finding of a cytostatic effect of CsA on tumor cells, we found a cytoproliferative action when CsA was administered early in the course of metastatic tumor implantation in the liver. The mechanism of cytoproliferative effect of CsA is unknown but may involve multiple factors.

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.

Cyclosporin A exerts a cytostatic effect in vivo on human and murine epithelial cells

Cyclosporin A (CsA) is a potent immunosuppressant that may also affect nonlymphoid cells. Indeed, CsA exerts a growth inhibition in vitro of several human and animal, normal and neoplastic cell types. To assess a possible in vivo direct cytostatic activity of CsA, the authors evaluated the proportion of S-phase (5-bromo-2'-deoxyuridine incorporating) cells of epithelial origin (skin, tongue, esophagus) of congenitally athymic (nude) mice bearing xenografts of human skin and receiving a daily subcutaneous injection of 50 mg/kg of CsA for 3 weeks. As compared with control animals, CsA-treated mice showed a decreased labeling index (LI) of all the epithelial tissues studied, which was statistically significant in the case of epidermis (both human and murine) and the tongue. Because nude mice lack T-cell-mediated immunity, these results suggest that CsA also exerts an immunologically independent antiproliferative activity on epithelial cells in vivo and they also highlight the interest in pursuing studies on cyclosporins as cytostatic agents.

Growth of metastases of the mouse adenocarcinoma EO 771: an allometric relationship between growth of the primary tumors and their metastases

Growth and cell kinetic parameters have been studied of paraaortal lumbar lymph node metastases of the mouse adenocarcinoma EO 771 growing intramuscularly in the thigh. An allometric relationship was found between the growth of the metastasis and that of the primary tumor, i.e. a linear relationship exists between the logarithm of the size of the metastasis and that of the primary tumor which permits the estimation of the growth rate of the metastasis based on the growth curve of the primary tumor. However, growth of metastases differs quantitatively from that of the primary tumor: the specific growth rate (growth rate per unit size) of the metastasis (1) is greater than that of the simultaneously growing primary tumor but (2) is smaller than that of the primary tumor of the same size as the metastasis. The allometric growth relationship further suggests that metastases originate later than is generally predicted presuming exponential growth of metastasis.

The potential of cyclosporin A as an anti-tumour agent

Cyclosporin A (CsA) has become established as the agent of choice for the prevention of organ allograft rejection and has shown considerable promise in the clinical management of certain autoimmune disorders. The impact of CsA as an immunotherapeutic agent of major importance is attributable to its powerful, selective inhibitory action on T-lymphocyte activation and proliferation. Moreover, CsA lacks the myelotoxic and other major side effects associated with cytotoxic immunosuppressive agents, such as cyclophosphamide or azathioprine. It is now clear that CsA has a potential therapeutic role in the treatment of malignancies, especially T-cell cancers. Recent studies suggest that there may be several areas of application for CsA, either as a direct antiproliferative agent or in combination with other drugs, including inhibitors of polyamine biosynthesis or cytotoxic anti-tumour agents, including vincristine and adriamycin. In addition, CsA and non-immunosuppressive analogues have been shown to restore multi-drug sensitivity in cancer cells with acquired drug resistance. A further application of CsA may be to prevent the induction of human immune responses to therapeutic mouse monoclonal antibodies directed against tumour antigens, thereby enhancing the efficiency and safety of this form of cancer immunotherapy. Due to our incomplete understanding of the antiproliferative properties of CsA, further exploration of its potential as an anti-tumour agent must be accompanied by detailed studies aimed at elucidating its action on subcellular molecular events in both normal and malignant cells.

Influence of cyclosporin A and alpha-difluoromethylornithine, an inhibitor of polyamine biosynthesis, on two rodent T-cell cancers in vivo

We have examined the influence of cyclosporin A (CsA), administered together with the polyamine antimetabolite, alpha-difluoromethylornithine (DFMO), on growth of the Roser acute T-cell leukaemia in PVG rats and on growth of the EL4 lymphoma in C57BL/6 mice. CsA or DFMO alone, administered from the time of tumour injection, markedly reduced numbers of circulating lymphoblasts in leukaemic rats, although survival was prolonged only in those animals given DFMO. Drug combination further reduced blood-borne tumour cells, but had no additional effects on tumour growth within organs or on host survival, compared to that achieved with DFMO treatment alone. Neither CsA nor DFMO, administered from the time of tumour-cell injection, nor both drugs in combination, affected peritoneal growth of the EL4 lymphoma or organ infiltration. Host survival was prolonged by DFMO. As anticipated, DFMO inhibited polyamine synthesis in vivo, but the observed anti-tumour effect of CsA was not accompanied by an alteration in polyamine biosynthesis. By reducing polyamine synthesis, however, DFMO may enhance the vulnerability of those malignant T cells which are susceptible to the as yet unexplained selective inhibitory action of CsA in vivo.

Influence of cyclosporin A on growth of an acute T-cell leukaemia in PVG rats

Our objective was to examine the effect of cyclosporin A (CsA; 25 or 12.5 mg/kg) on growth of an acute (Roser) T-cell leukaemia in male PVG rats. The leukaemic blasts were shown (by immunocytochemical analysis) to have a mature, T-helper-cell phenotype, i.e., OX-19 (CD5) +/- , W3/25 (CD4)+, OX44+, MHC-class I+, OX-26+, corresponding to a population comprising 5% of normal rat medullary thymocytes. Animals received 20 X 10(3) viable tumour cells intramuscularly (day 0) and were given either CsA (25 or 12.5 mg/kg) or drug vehicle by gavage from day 0 or day 14, by which latter time leukaemic blasts normally appeared in the circulation. Administration of the higher dose of CsA from day 0 or day 14 significantly delayed the appearance of leukaemic cells in the peripheral circulation, whereas treatment with 12.5 mg/kg was without significant effect. CsA whole blood levels on day 17 were twice as high in leukaemic rats as in normal controls. Leukaemic infiltration of the spleen and the liver was reduced on day 17 after 25 mg/kg CsA, but no such effect was observed in lymph nodes or kidneys. A heterogeneous, host "reactive" cell population, which developed in response to the leukaemia, was inhibited by CsA, indicating that the effect of the drug was probably not mediated by host defence mechanisms. In CsA-treated leukaemic animals, there was biochemical evidence of synergistic impairment of glomerular and tubular function.

Cyclosporine

Cyclosporine is an immunosuppressant used to prevent the rejection of transplanted kidneys, hearts, and livers. Cyclosporine suppresses T-lymphocyte function without causing myelosuppression, and its pharmacokinetics are highly variable. Compared with conventional immunosuppressive drug therapy, both patient and graft survival improved in patients treated with cyclosporine. Patients treated with cyclosporine also had less complicated hospital courses than patients receiving conventional immunosuppressants. The adverse effects from cyclosporine are reversible but include nephrotoxicity, hepatotoxicity, malignancies, hirsutism, and minor neurologic complications. Intravenous cyclosporine doses range from 2-9 mg/kg/d and oral doses range from 10-50 mg/kg/d; the dosage should be individualized based on the clinical status of the patient as well as blood concentrations of the drug. Monitoring cyclosporine blood concentrations is necessary in the postoperative management of transplant patients. Cyclosporine has contributed to the improved success of transplantation and the recognition of transplantation as a new therapeutic option for several diseases.

Cyclosporine: immunology, toxicity and pharmacology in experimental animals

Cyclosporine (CsA) is the first of a new order of pharmacological immune suppressants and represents a significant advance in the clinical control of graft rejection. In laboratory animals, its capacity to prolong allograft survival has been well documented, including reports of indefinite donor-specific immunological tolerance after shortterm CsA treatment. There is also evidence that CsA can inhibit the onset or progress of a variety of experimental autoimmune diseases. Underlying these properties of the drug is its capacity to selectively interfere with T helper cell activation and lymphokine production, although some direct effects on B cells have also been reported. In addition, sparing of suppressor cells may in part explain the mode of action of CsA which, at the molecular level, is not understood. CsA-induced nephrotoxicity in the rat has been extensively studied and is characterized by reversible proximal tubular cell damage. This problem may be aggravated by concomitant administration of other potentially nephrotoxic drugs, such as gentamicin, or by therapeutic agents which interfere with the metabolism of CsA. CsA is metabolized in the liver and excreted in the bile. Although the pathway of hepatic metabolism of CsA has not been precisely elucidated, animal studies suggest that agents capable of inducing metabolism of the drug CsA could be used to alleviate its nephrotoxic properties.

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.