Cytogenetic effects of methotrexate on human cells in vivo: comparison between results obtained by chromosome studies on bone-marrow cells and blood lymphocytes and by the micronucleus test

A systematic overview of the spermatotoxic and genotoxic effects of methotrexate, ganciclovir and mycophenolate mofetil

INTRODUCTION

Immunosuppressant drugs are increasingly being used in the reproductive years. Theoretically, such medications could affect fetal health either through changes in the sperm DNA or through fetal exposure caused by a presence in the seminal fluid. This systematic overview summarizes existing literature on the spermatotoxic and genotoxic potentials of methotrexate (MTX), a drug widely used to treat rheumatic and dermatologic diseases, and mycophenolate mofetil (MMF), which alone or supplemented with ganciclovir (GCV) may be crucial for the survival of organ transplants.

MATERIAL AND METHODS

The systematic overview was performed in accordance with the PRISMA guidelines: A systematic literature search of the MEDLINE and Embase databases was done using a combination of relevant terms to search for studies on spermatotoxic or genotoxic changes related to treatment with MTX, GCV or MMF. The search was restricted to English language literature, and to in vivo animal studies (mammalian species) and clinical human studies.

RESULTS

A total of 102 studies were identified, hereof 25 human and 77 animal studies. For MTX, human studies of immunosuppressive dosages show transient effect on sperm quality parameters, which return to reference values within 3 months. No human studies have investigated the sperm DNA damaging effect of MTX, but in other organs the genotoxic effects of immunosuppressive doses of MTX are fluctuating. In animals, immunosuppressive and cytotoxic doses of MTX adversely affect sperm quality parameters and show widespread genotoxic damages in various organs. Cytotoxic doses transiently change the DNA material in all cell stages of spermatogenesis in rodents. For GCV and MMF, data are limited and the results are indeterminate, for which reason spermatotoxic and genotoxic potentials cannot be excluded.

CONCLUSIONS

Data from human and animal studies indicate transient spermatotoxic and genotoxic potentials of immunosuppressive and cytotoxic doses of MTX. There are a limited number of studies investigating GCV and MMF.

Mutagenicity monitoring in humans: Global versus specific origin of mutations

An underappreciated aspect of human mutagenicity biomonitoring is tissue specificity reflected in different assays, especially those that measure events that can only occur in developing bone marrow (BM) cells. Reviewed here are 9 currently-employed human mutagenicity biomonitoring assays. Several assays measure chromosome-level events in circulating T-lymphocytes (T-cells), i.e., traditional analyses of aberrations, translocation studies involving chromosome painting and fluorescence in situ hybridization (FISH) and determinations of micronuclei (MN). Other T-cell assays measure gene mutations. i.e., hypoxanthine-guanine phosphoriboslytransferase (HPRT) and phosphoribosylinositol glycan class A (PIGA). In addition to the T-cell assays, also reviewed are those assays that measure events in peripheral blood cells that necessarily arose in BM cells, i.e., MN in reticulocytes; glycophorin A (GPA) gene mutations in red blood cells (RBCs), and PIGA gene mutations in RBC or granulocytes. This review considers only cell culture- or cytometry-based assays to describe endpoints measured, methods, optimal sampling times, and sample summaries of typical quantitative and qualitative results. However, to achieve its intended focus on the target cells where events occur, kinetics of the cells of peripheral blood that derive at some point from precursor cells are reviewed to identify body sites and tissues where the genotoxic events originate. Kinetics indicate that in normal adults, measured events in T-cells afford global assessments of in vivo mutagenicity but are not specific for BM effects. Therefore, an agent's capacity for inducing mutations in BM cells cannot be reliably inferred from T-cell assays as the magnitude of effect in BM, if any, is unknown. By contrast, chromosome or gene level mutations measured in RBCs/reticulocytes or granulocytes must originate in BM cells, i.e. in RBC or granulocyte precursors, thereby making them specific indicators for effects in BM. Assays of mutations arising directly in BM cells may quantitatively reflect the mutagenicity of potential leukemogenic agents.

Double trouble: Cyclosporine-induced thrombocytosis in a patient with methotrexate toxicity: Are they related?

Psoriasis is a common, chronic, disfiguring, inflammatory, and proliferative condition of the skin. It manifests with varying degrees of severity and can be treated with various immune modulators. This is a case report of a 57-year-old male patient of psoriasis on long-term oral methotrexate, who developed methotrexate toxicity when given an injection of methotrexate for unstable psoriasis. After recovery, the patient was started on cyclosporine 100 mg twice a day. After a week, he developed thrombocytosis, which reverted a week after cyclosporine was stopped. The patient is currently being managed with acitretin. The aim of this case report is to emphasize the various unpredictable adverse reactions encountered during treatment of psoriasis, especially when a combination or sequential treatment is used. There is a need for caution, as late sequelae of long-term administration of the systemic agents used in the treatment of psoriasis are still unknown.

Genotoxicity of pemetrexed in human peripheral blood lymphocytes

Pemetrexed (PMX) is an antineoplastic antifolate used in the treatment of non-small cell lung cancer, mesothelioma and several types of neoplasms. Its toxicity in tumor cells has been linked with the potent inhibition of thymidylate synthase, dihydrofolate reductase and glycinamide ribonucleotide formyl transferase, and subsequent depletion of both purine and pyrimidine nucleotides. However, cytogenetic toxicity of PMX in non-diseased cells has not been adequately studied; despite the increasing data on the DNA-damaging potential of antineoplastic agents on normal cells. In the present study, the genotoxic potential of PMX was evaluated in peripheral blood lymphocytes obtained from healthy human subjects using chromosome aberration (CA), sister chromatid exchange (SCE) and micronucleus (MN) assays as the cytogenetic damage markers. Human peripheral blood lymphocytes were exposed to four different concentrations (25, 50, 75 and 100 μg/mL) of PMX for 24- and 48-h treatment periods. PMX significantly increased the formation of CA in 24-h treatment, but not in 48-h treatment. PMX did not increase the mean SCE frequency in 24- and 48-h treatment periods; however, there was a striking increase (although not statistically significant, p > 0.05) in the number of SCEs at 25 μg/mL (24- and 48-h treatment) and 50 μg/mL (24-h treatment) due to an increase of SCE at the single-cell level. Interestingly, PMX did not induce MN formation in either 24- or 48-h treatment periods. PMX strongly decreased the mitotic index (MI), proliferation index (PI) and nuclear division index (NDI) in 24- and 48-h treatment periods. Our results suggest that PMX has a potent cytotoxic effect against human peripheral blood lymphocytes at concentrations which are reached in vivo in the blood plasma.

Chlorophyll derivative mediated PDT versus methotrexate: an in vitro study using MCF-7 cells

BACKGROUND

Breast cancer is the most common cause of cancer deaths among women worldwide. Although chemotherapy is a standard method for the treatment of breast cancer, the photodynamic therapy (PDT) is a recent promising modality for cancer diagnosis and treatment. Its major advantages over chemotherapy are better selectivity of tumour tissue destruction and lack of severe local and systemic complications. This work is directed towards evaluation of the efficacy of Photodynamic therapy using chlorophyll derivative (CHL) as a photosensitizer in treatment of breast cancer. It also aims at investigation of the genetic safety of chlorophyll mediated PDT in comparison to the conventional chemotherapy.

METHODS

Both methotrexate (MTX) and light activated chlorophyll derivative were used to target MCF-7 breast cancer cell line. Standard karyotyping and alkaline single cell microgel electrophoresis assay (Comet assay) were applied on normal human peripheral blood lymphocytes (HPL) in order to investigate the respective possible mutagenic and genotoxic side effects that might result from application of each therapeutic modality.

RESULTS

Results obtained from this study showed that 50% of MCF-7 tumour cell death (LC(50)) was reached by using a concentration of chlorophyll derivative that is 138 times lower than MTX. Moreover, chlorophyll derivative exerted no genetic side effects as compared to MTX that resulted into several types of chromosomal breakages.

CONCLUSIONS

Compared to MTX, light activated chlorophyll derivative proved to be a better candidate for breast cancer cell toxicity, referring to its higher efficacy at tumour cells killing, safety to normal cells and simple method of extraction.

Biological dosimetry after radiosynoviorthesis with rhenium-186 sulphide and erbium-169 citrate

Radiosynoviorthesis (RSO) with the nuclides rhenium-186 sulphide (186Re) and erbium-169 citrate (169Er) is an established concept for the treatment of persistent synovitis of medium and small sized joints. THE AIM of the present studies was to investigate the biological radiation effect based on analysing chromosome aberrations.

PATIENTS, METHODS

Immediately before and 17 to 19 days (186Re) or 45 to 50 (169Er) days after RSO with 186Re or 169Er colloid and subsequent immobilisation of the treated joint, blood samples of a total of 23 patients were collected. The yield of dicentric chromosomes in lymphocytes was determined exclusively in metaphases of the first cell cycle in vitro. In addition, for 186Re the activity leakage was measured three days after RSO by whole-body scintigraphy.

RESULTS

No statistically significant increase in the number of dicentric chromosomes (40 and 88 before and 59 and 105 after treatment with 186Re and 169Er, respectively) in a total of 47017 cells analysed from 46 blood samples could be found as a result of RSO. For 186Re an activity leakage of 3.9%±7% with a maximum of 23.4% corresponding to an effective dose of 2.8±4.5 mSv , respectively 13.8 mSv, was determined. Also in the case of the maximum leakage no significant increase of dicentric chromosomes were detected.

CONCLUSIONS

No significant biological radiation effect can be detected after RSO with 186Re and 169Er, also in cases of high leakage. Therefore, RSO can be classified as a save therapeutic procedure without a relevant radiation risk.

Therapy-related myelodysplastic syndrome following cyclophosphamide pulse and/or methotrexate therapy in a patient with systemic lupus erythematosus

A 27-year-old woman exhibited progressive pancytopenia during cyclophosphamide pulse therapy for lupus nephritis and low-dose methotrexate therapy for severe arthralgia. Bone marrow aspiration revealed highly abnormal cell morphology, indicating therapy-related myelodysplastic syndrome. Pancytopenia and bone marrow cell morphology improved 3 months after discontinuation of cyclophosphamide. It is necessary to promptly examine bone marrow cell morphology and chromosomal aberration in cases with connective tissue diseases complicated by sudden cytopenia during immunosuppressive therapy with chemotherapeutic agents.

Paternal exposure to methotrexate and pregnancy outcomes

OBJECTIVE

To assess the risk of major malformation in the case of paternal exposure to methotrexate (MTX) at the time of conception.

METHODS

Using prospective data of our Teratology Information Service, we analyzed outcomes of paternal MTX exposure at the time of conception or up to 3 months before conception.

RESULTS

We report on the outcomes of 42 pregnancies involving 40 men treated with MTX at the time of conception. Twenty-three men were treated for an inflammatory disease (54.8%), 9 for psoriasis (21.4%), and 8 for a malignant disease (19.0%). Weekly dosages varied between 7.5 mg and 30 mg. The pregnancies resulted in 36 live births, 3 spontaneous abortions, and 3 voluntary abortions. No congenital malformation was observed at birth.

CONCLUSION

Based on our results and case reports in literature, paternal MTX exposure at the time of conception does not seem to raise any major concern for offspring.

Effect of gene polymorphisms and ethanol consumption on micronucleus frequency in human reticulocytes: a preliminary study

OBJECTIVE

Results from previous studies suggest that alcohol consumption can be genotoxic on peripheral lymphocytes. The aim of our study was to examine the association of alcohol consumption and its genotoxic effect on hematopoietic stem cells in vivo.

METHODS

We investigated 156 healthy Japanese males in a cross-sectional study. Lifestyles, including alcohol drinking behavior and cigarette smoking status, were investigated by means of a self-completed questionnaire. Polymorphisms of ADH1B and ALDH2 were identified by PCR-restriction fragment length polymorphism (RFLP) analysis. The presence of micronuclei in transferrin-positive reticulocytes (MN-RET) was detected with a single-laser flow cytometer. Associations between the genetic polymorphisms, lifestyle factors, and MN-RET frequency were statistically analyzed.

RESULTS

We found a significant difference in the mean frequencies of MN-RET between habitual drinkers and non-habitual drinkers (P = 0.043), and between the ALDH2*1/*1 and ALDH2*2/*2 genotype (P = 0.015). The ADH1B*2 and ALDH2*2 haplotype was estimated to have a significantly higher influence on MN-RET frequency than the ADH1B*2 and ALDH2*1 haplotype (P = 0.00035), and the frequency of alcohol consumption played a significant role in MN-RET frequency on the background of the ADH1B*2 and ALDH2*1 haplotype (P = 0.012).

CONCLUSION

The results of our study suggest a possible association between the ADH1B and ALDH2 polymorphism and the genotoxic effects of alcohol drinking on hematopoietic stem cells.

A comparison of vitamin A and leucovorin for the prevention of methotrexate-induced micronuclei production in rat bone marrow

INTRODUCTION

Methotrexate, a folate antagonist, is a mainstay treatment for childhood acute lymphoblastic leukemia. It is also widely used in a low dose formulation to treat patients with rheumatoid arthritis. In rats, methotrexate is known to induce micronuclei formation, leading to genetic damage, while vitamin A is known to protect against such methotrexate-induced genetic damage. Leucovorin (folinic acid) is generally administered with methotrexate to decrease methotrexate-induced toxicity.

OBJECTIVES

We aimed to determine whether vitamin A and leucovorin differed in their capacity to prevent formation of methotrexate-induced micronuclei in rat bone marrow erythrocytes. The present study also aimed to evaluate the effect of combined treatment with vitamin A and leucovorin on the formation of methotrexate-induced micronuclei.

METHODS

Male and female Wistar rats (n=8) were injected with 20 mg/kg methotrexate (single i.p. dose). The control group received an equal volume of distilled water. The third and fourth groups of rats received vitamin A (5000 IU daily dose for 4 successive days) and leucovorin (0.5 mg/kg i.p. dose for 4 successive days), respectively. The fifth and sixth groups of rats received a combination of vitamin A and a single dose of methotrexate and a combination of leucovorin and methotrexate, respectively. The last group of rats received a combination of leucovorin, vitamin A and single dose of methotrexate. Samples were collected at 24 hours after the last dose of the treatment into 5% bovine albumin. Smears were obtained and stained with May-Grunwald and Giemsa. One thousand polychromatic erythrocytes were counted per animal for the presence of micronuclei and the percentage of polychromatic erythrocyte was determined.

RESULTS

Comparison of methotrexate-treated rats with the control group showed a significant increase in the percentage of cells with micronuclei and a significant decrease polychromatic erythrocyte percentage. Combined methotrexate and vitamin A therapy and combined methotrexate and leucovorin therapy led to significant decreases in the micronuclei percentage and an increase in polychromatic erythrocyte percentage when compared to rats treated with methotrexate alone. Leucovorin was found to be more effective than vitamin A against the formation of methotrexate-induced micronuclei.

CONCLUSIONS

Both vitamin A and leucovorin provided significant protection against genetic damage induced by methotrexate.

Automated human blood micronucleated reticulocyte measurements for rapid assessment of chromosomal damage

This study evaluated the utility of human blood micronucleated reticulocyte (MNCD71+) frequency measurement as a cytogenetic damage biomarker. The analytical methodology was flow cytometry in conjunction with a previously described three color fluorescence labeling technique that includes anti-CD71 to focus analyses on the most immature fraction of reticulocytes [S.D. Dertinger, K. Camphausen, J.T. MacGregor, M.E. Bishop, D.K. Torous, S. Avlasevich, et al., Three-color labeling method for flow cytometric measurement of cytogenetic damage in rodent and human blood, Environ. Mol. Mutagen. 44 (2004) 427-435]. Blood specimens from 50 self-reported healthy adult volunteers were studied. In addition to MNCD71+ measurements, blood plasma folate and B12 levels were assessed, since these variables tend to influence other indices of cytogenetic damage. Time-course data are also provided for 10 cancer patients undergoing treatment. For these subjects, frequency of MNCD71+ was measured immediately before therapy, and daily during the first week of chemotherapy and/or fractionated radiotherapy. For the group of healthy volunteers, the variables of age, and folate and B12 levels demonstrated no significant effect on MNCD71+ frequency. In addition, no difference was observed between pre-treatment MNCD71+ values for cancer patients compared with healthy volunteers. Regarding chemotherapy and/or partial body radiotherapy, elevated frequencies were observed upon initiation of treatment for 9 of the 10 patients studied. Maximal effects were observed 3-5 days following initiation of therapy. The largest increases in frequency of MNCD71+ (up to 25.9-fold) were observed in those patients exposed to anti-neoplastic drugs, presumably due to the systemic red marrow exposure provided by these agents. Taken together, these data support the hypothesis that the MNCD71+ endpoint represents a valuable biomarker of cytogenetic damage that does not require cell culture or microscopy-based scoring.

Analysis of micronuclei in the transferrin-receptor positive reticulocytes from peripheral blood of nasopharyngeal cancer patients undergoing radiotherapy by a single-laser flow cytometer

The automated micronucleus test is now accepted as a simple, objective, and accurate method for evaluating potential mutagenic effects caused by physical, chemical or biotic factors. This paper describes a single-laser flow cytometry, based on an immunomagnetic isolation technique in combination with acridine orange staining, to detect frequencies of micronucleated transferrin-receptor positive reticulocytes from human peripheral blood. Using this flow cytometric system, we detected the frequencies of micronucleated transferrin-receptor positive reticulocytes from 10 nasopharyngeal cancer patients undergoing radiotherapy and the baseline of the frequencies of micronucleated transferrin-receptor positive reticulocytes from 7 healthy donors. The results showed that the mean frequency of micronucleated transferrin-receptor positive reticulocytes from healthy donors was 0.236% and that from nasopharyngeal cancer patients before radiotherapy was 0.297%. After radiotherapy it was significantly elevated. When the cumulative dose of radiotherapy was about 20Gy, it reached a maximum of 6.905%, and then, as the cumulative dose of radiotherapy continued to increase to 30Gy, 40Gy and 50Gy, the frequency decreased to 6.258%, 5.119% and 5.007% respectively. Our results indicated that the single-laser flow cytometric system was quick, reasonable and acceptable for detecting the frequency of micronucleated transferrin-receptor positive reticulocytes from human peripheral blood.

A de novo, apparently balanced reciprocal translocation in a child with developmental delay whose mother was being treated with low-dose methotrexate at the time of conception

BACKGROUND

Methotrexate is a proven teratogen and its use periconceptually is strongly advised against. Concerns about possible chromosomal effects in the offspring of women treated with this agent have been raised, but they have not been reported. In vivo and in vitro studies have supported this possibility, however.

CASE

A 32-year-old primigravida was treated with low-dose methotrexate for rheumatoid arthritis from prior to conception until six weeks postconception. Her child was born without congenital malformations but subsequently developed seizures and was diagnosed with developmental delay. He was found to have a de novo, apparently balanced, reciprocal translocation between chromosomes 5 and 20 (46,XY,t(5:20)(q15;p12)). Other investigations failed to reveal another cause for his developmental delay.

CONCLUSIONS

The possible association between maternal methotrexate exposure and a de novo chromosomal anomaly in an offspring supports the recommendation that women should be advised to cease taking this drug for at least six months prior to conception.

Micronucleated CD71-positive reticulocytes: a blood-based endpoint of cytogenetic damage in humans

The frequency of micronuclei (also known as Howell-Jolly bodies) in peripheral blood erythrocytes of humans is extremely low due to the efficiency with which the spleen sequesters and destroys these aberrant cells. In the past, this has precluded erythrocyte-based analyses from effectively measuring chromosome damage. In this report, we describe a high-throughput, single-laser flow cytometric system for scoring the incidence of micronucleated reticulocytes (MN-RET) in human blood. Differential staining of these cells was accomplished by combining the immunochemical reagent anti-CD71-FITC with a nucleic acid dye (propidium iodide plus RNase). The immunochemical reagent anti-CD42b-PE was also incorporated into the procedure in order to exclude platelets which can interfere with analysis. This analytical system was evaluated with blood samples from ten healthy volunteers, one splenectomized subject, as well as samples collected from nine cancer patients before and over the course of radio- or chemotherapy. The mean frequency of MN-RET observed for the healthy subjects was 0.09%. This value is nearly two orders of magnitude higher than frequencies observed in mature erythrocytes, and is approximately half the MN-RET frequency observed for the splenectomized subject (0.20%). This suggests that the spleen's effect on micronucleated cell incidence can be minimized by restricting analyses to the youngest (CD71-positive) fraction of reticulocytes. Furthermore, MN-RET frequencies were significantly elevated in patients undergoing cancer therapy. Collectively, these data establish that micronuclei can be quantified in human peripheral blood reticulocytes with a single-laser flow cytometer, and that these measurements reflect the level of chromosome damage which has occurred in red marrow space.

Enumeration of micronucleated CD71-positive human reticulocytes with a single-laser flow cytometer

The extreme rarity of micronucleated reticulocytes (RETs) in the peripheral blood of non-splenectomized humans has precluded facile enumeration of these cells, as well as evaluation of this endpoint as an index of cytogenetic damage. In this report, we describe a high-throughput, single-laser flow cytometric system for scoring the incidence of micronuclei (MN) in newly formed human RETs. The procedure is based on an immunochemical reagent that differentially labels the most immature fraction of RETs from mature erythrocytes based on the expression level of the transferrin receptor (also known as CD71). The resolution of four erythrocyte populations (young RETs and mature erythrocytes, with and without MN) was achieved for human blood cells treated with phycoerythrin-conjugated anti-CD71, RNase, and either SYTOX Green or SYBR Green I nucleic acid dyes. Anti-glycophorin A labeling of erythroid cells (CyChrome conjugate) was also incorporated into the staining procedure to ensure that debris or other potential artifacts did not adversely impact the analyses. Instrument calibration procedures utilizing malaria-infected rodent erythrocytes were also developed, and are described. Using this analytical system, blood samples from 10 healthy non-splenectomized human volunteers were analyzed for micronucleus frequencies with a single-laser flow cytometer. Average micronucleus frequencies in the mature and most immature fraction of RETs were 0.016 and 0.19%, respectively. Blood samples from three healthy splenectomized volunteers were also evaluated. As expected, these samples exhibited higher micronucleus frequencies in the mature subset of erythrocytes (range 0.03-0.18%). The resulting data suggest that MN can be quantified in human erythrocyte populations with a single-laser flow cytometer, and that the frequency of MN cells in the youngest reticulocyte population approaches values expected in the absence of splenic selection against MN-erythrocytes. This high throughput system is potentially important for evaluating the value of the micronucleated reticulocyte endpoint as an index of chromosome breakage and/or chromosome segregational abnormalities in human populations.

Acute myeloid leukemia in the setting of low dose weekly methotrexate therapy for rheumatoid arthritis

Methotrexate is in widespread use as second-line therapy for rheumatoid arthritis. Treatment with methotrexate in this and other settings has not been associated with the development of therapy-related leukemias. Four patients with rheumatoid arthritis are reported who developed acute myeloid leukemia (AML) while receiving low dose weekly methotrexate therapy in the absence of previous or concomitant treatment with known leukemogenic agents. AML in these four patients was of different morphologic subtypes and was associated with heterogeneous cytogenetic abnormalities, cell surface marker expression and multidrug resistance protein expression. None of the recognized features of therapy-related leukemia were present in these four nor in five previously-reported patients. It is likely that the occurrence of AML in patients with rheumatoid arthritis in the setting of methotrexate therapy represents the coincidence of these two diseases, and does not reflect a causal relationship.

Genotoxic evaluation of the antimicrobial drug, trimethoprim, in cultured human lymphocytes

The antimicrobial drug, trimethoprim, was evaluated for genotoxicity in human peripheral blood lymphocyte cultures set-up from two healthy donors. Sister-chromatid exchanges (SCE) and micronuclei (MN) were scored as genetic endpoints. The treatment was done using different trimethoprim concentrations ranging from 1 to 100 microg/ml. From our results, we can conclude that this drug is able to induce both cytotoxic and moderate genotoxic effects, as revealed by the increases seen in SCE and MN frequencies in cultures from the two donors and, at least, at one of the concentrations tested.

Induction of cytogenetic damage in human lymphocytes in vitro and of antineoplastic effects in Ehrlich ascites tumor cells in vivo treated by methotrexate, hyperthermia and/or caffeine

The synergistic effect of methotrexate (at concentrations between 3. 1 and 100 nM) and its combinations with caffeine (618 microM) and/or hyperthermia (42 degreesC for 2 h) on the frequency of sister chromatid exchanges (SCEs), the proliferating rate index and the mitotic index in cultured human lymphocytes, was examined. Also, the in vivo antineoplastic effects of methotrexate (at a concentration of 0.45 microg/g body weight) and its combination with caffeine (120 microg/g body weight), both on the survival time and the increase of the weight of tumor of BALB/c mice inoculated with Ehrlich ascites tumor cells was examined in the present study. The results indicated that: (a) the triple combination of methotrexate, caffeine and hyperthermia synergistically increased the levels of SCEs and exerted cytostatic and cytotoxic action and (b) the combination of methotrexate and caffeine significantly increased the survival span of the mice inoculated with Ehrlich ascites tumor cells and reduced the increase of the weight of their tumors at rates higher than in the case of methotrexate by itself. It is suggested that the above triple combination (methotrexate plus caffeine plus hyperthermia) could achieve increased effectiveness of methotrexate, better therapy results, and could be successfully applied in the treatment of various types of cancer.

Does methotrexate increase the risk of infection or malignancy?

Most patients do not exhibit overt signs of immunosuppression. Studies cited in this article support a modest increase in the rate of bacterial respiratory and skin infections. Opportunistic infections occur rarely, however, and may be life threatening. The case for MTX carcinogenicity is less clear. The risk for malignancy other than lymphoproliferative disorders does not seem to be elevated, although multiple sporadic malignancies have been reported in treated patients. MTX is a superb agent for the therapy of a large group of immune-mediated diseases. Although an increased risk for infection and possible malignancy exists, the risk is small compared with the potential clinical benefit.

Lymphoma in patients with rheumatoid arthritis: association with the disease state or methotrexate treatment

Although long-term clinical studies have shown no excessive risk of lymphoma in rheumatoid arthritis (RA) patients treated with methotrexate (MTX), an increasing number of reports of this association continue to appear. We describe two cases, review the cases in the world's literature, and summarize their important characteristics. Possible oncogenic mechanisms are discussed. Most lymphoproliferation cases presented here have features of immunosuppression-associated lymphoma. The immunosuppressed state is attributable to a combination of factors, such as RA itself and the actions of MTX. The risk factors for RA patients to develop lymphoma while on MTX include severe disease, intense immunosuppression, genetic predisposition, and an increased frequency of latent infection with prooncogenic viruses such as Epstein-Barr virus (EBV). The spontaneous remission of lymphomas in eight RA patients after MTX was stopped highlights the likely causative role of the drug in the development of these malignancies. If the clinical situation permits, a period of observation for spontaneous remission after MTX is stopped is advisable. The physicians caring for RA patients on MTX should maintain a high surveillance for signs and symptoms suggestive of lymphoma.

Hematologic malignancies and the use of methotrexate in rheumatoid arthritis: a retrospective study

PURPOSE

To evaluate the relationship between use of methotrexate in rheumatoid arthritis patients and development of hematologic malignancies.

PATIENTS AND METHODS

We retrospectively analyzed all patients registered at the Mayo Clinic from 1976 through 1992 with rheumatoid arthritis (n = 16,263) cross-indexed with patients registered during the same period with a hematologic malignancy (n = 21,270). Adult patients were selected who had rheumatoid arthritis, were treated with a disease-modifying antirheumatic drug, and subsequently developed a hematologic malignancy.

RESULTS

Thirty-nine patients met the selection criteria. Twelve of them had been given methotrexate. The characteristics of those who received methotrexate, including the type of hematologic malignancy, did not differ from those of patients who received other disease-modifying antirheumatic drugs.

CONCLUSIONS

Hematologic malignancies are uncommon in patients with rheumatoid arthritis treated with disease-modifying antirheumatic drugs, including methotrexate. There does not appear to be a relationship between the peak or cumulative dose or the duration of methotrexate therapy and the subsequent development of hematologic malignancy. The histologic types of hematologic malignancy seen in the methotrexate-treated patients did not differ from those of patients treated with other disease-modifying antirheumatic drugs.

Methotrexate and reproduction in men: case report and recommendations

Methotrexate has been used in the treatment of recalcitrant psoriasis for more than 35 years. We examined the significance of impaired spermatogenesis in a young man undergoing methotrexate treatment for severe psoriasis with associated arthritis. A medical geneticist was consulted and a review of the literature was performed. Genetic abnormalities that could lead to mutagenesis include chromosomal abnormalities and single-gene mutations. These aspects are considered and recommendations are made for counseling men undergoing methotrexate therapy so that risks and options can be considered.

Decrease in deoxyribonucleotide triphosphate pools and induction of alkaline-labile sites in mouse bone marrow cells by multiple treatments with methotrexate

Methotrexate (MTX), an inhibitor of dihydrofolate reductase (DHFR), slightly induced micronuclei in bone marrow and peripheral blood cells, and this induction was enhanced by multiple treatments with the drug. Furthermore, we have suggested that the multiple-dose effect on the induction of micronuclei by MTX might be explained by intracellular accumulation of the drug, resulting in an enhancement of DHFR inhibition. An imbalance or decrease in the deoxyribonucleotide (dNTP) pool would be generated by this enzyme inhibition. Therefore, we attempted to determine the level of the dNTP pool in mouse bone marrow cells. The levels of three dNTPs (dTTP, dATP, dGTP) as determined by HPLC were only 1/10-1/40 of the levels previously found in mammalian cell lines, but dCTP levels could not be determined precisely because they approached the limits of detectability. The levels of dTTP, dATP and dGTP in mouse bone marrow cells 3 h after four injections of MTX (4 mg/kg/day) decreased to 21.2%, 47.0% and 38.1%, respectively, of those in the control group. The level of dTTP 3 h after four injections of 100 mg/kg of the drug decreased to almost 0%. The results of alkaline elution assays suggested that alkaline-labile sites were generated in mouse bone marrow cells 6 h after four injections of MTX (4 mg/kg). These findings suggest that the multiple-dose effects of MTX on micronucleus induction in mouse bone marrow cells may be explained by the decrease in the dNTP pool and subsequent generation of alkaline-labile sites (possibly apurinic/apyrimidinic sites).

In vitro micronucleus bioassay of human peripheral lymphocytes for adriamycin in the presence of cyclophosphamide and urines of patients administered anticancer drugs

The aim of this study was to develop an in vitro human peripheral lymphocyte micronucleus bioassay involving phytohemagglutinin stimulant for urines containing adriamycin (ADR) and cyclophosphamide (CP). In vitro studies with defined concentrations of ADR, CP, and fresh urine showed that mitotic indices and micronuclei counts/1,000 cells had to be log (X + 1) transformed to be able to use parametric statistics and that a specific micronucleus assay for ADR in the presence of CP and urine for 5-15 ng ADR/mL had been developed. Whereas CP alone could be detected between 196-522 micrograms/mL, this effect was abolished in the presence of 15 ng ADR/mL. Interdonor variabilities relative to ADR sensitivity and CP linear dynamic range were marked, but intradonor variability was small. The MN bioassay tolerated < 10% urine. Results for urines from nine patients receiving antineoplastic drugs (CP, all; ADR, 3; 5-fluorouracil, 3; methotrexate, 3; vincristine, 4; procarbazine, 1; and megestrol acetate, 1) showed that only 1/3 patients given ADR were detected, and two others not given ADR were positive. All frozen urines from the 12 control subjects and the nine patients exhibited depressed mitotic index, with, however, no control patient urines inducing increased micronuclei. Two patients had urines of undefined genotoxic potential since undepressed mitotic indices were not attainable by dilution. The effects of combination chemotherapy in addition to freezing and storage influences were complex. More research is required to be able to interpret the results.

Mechanism of induction of micronuclei and chromosome aberrations in mouse bone marrow by multiple treatments of methotrexate

Methotrexate (MTX), an inhibitor of dihydrofolate reductase (DHFR), slightly induced micronuclei and this induction of micronuclei was enhanced by multiple treatments with the drug (Yamamoto et al., 1981; Hayashi et al., 1984; CSGMT/JEM.MMS, 1990). More micronuclei and chromosomal aberrations in mouse bone marrow cells were induced by multiple than by single treatment. The MTX level in mouse plasma and bone marrow showed little (or no) differences between single and quadruple treatments several hours after the injection(s). On the other hand, the DHFR activity in bone marrow cells 3 h after one and four injections was decreased to approximately 38 and 0%, respectively, of that in non-treated mice. Furthermore, the intracellular MTX level in the bone marrow cells (but not in total bone marrow) after four injections was about 10-fold higher than that after one injection. The amount of MTX bound to protein 3 h after four injections, as assayed by gel filtration (Sephadex G-25), was approximately 8-fold greater than after one injection. Therefore, the multiple-dose effects of MTX on the induction of micronuclei and chromosomal aberrations may be explained by the intracellular accumulation of MTX resulting in an enhancement of enzyme inhibition.

Cytogenetic effects of dacarbazine on mouse bone marrow cells in vivo

The mutagenicity of dacarbazine was assayed in an in vivo test utilizing mouse bone marrow cells. The dose rates used in the experiments were computed according to the standard surface area of the mouse and were proportional to the human dose rate. These were 0.27, 0.44 and 0.60 mg/30 g body weight, each given twice daily at an interval of not less than 6 h. The duration of drug treatment was 24, 48 and 72 h. This alkylating agent proved to be mitodepressive and produced a 3-fold reduction in the mitotic index. The drug also induced chromosome anomalies mainly in the form of chromatid gaps and breaks. These anomalies were proportional to dose rate and duration of drug treatment.

Methotrexate: assessment of in vivo clastogenicity and carcinogenicity

The genotoxic and oncogenic potentials of methotrexate were studied in Sprague-Dawley rats. The rats received 0.1, 0.2, or 0.4 mg/kg of methotrexate as dietary admixtures on a 5 days on, 9 days off, regimen for 23 months. In the females of the high-dose group, there was a significant increase in mortality starting at 18 months. Significant increases in the number of rats with focal pulmonary interstitial fibrosis were seen in both sexes at the high-dose level. At the mid- and high-dose levels of both sexes, there was a significantly increased number of rats with myeloid and erythroid bone marrow hypoplasia. There was no evidence of either early onset or increased incidence of any tumor type in the treatment groups. Therefore, it is concluded that methotrexate does not have oncogenic potential. Also, at terminal sacrifice, bone marrow cells were harvested from selected animals on the last day of the 5-day dosing cycle and cytogenetic evaluation was performed. No significant increase in chromosomal aberrations was seen in any dose group relative to the control group. This observation further substantiates the absence of oncogenic potential due to methotrexate in rats.

The incorporation of deoxyuridine monophosphate into DNA increases the sister-chromatid exchange yield

The effect of a treatment with 5-fluoro-2'-deoxyuridine (FdUrd) in combination with 2'-deoxyuridine (dUrd) on cell proliferation, incorporation of DNA precursors into DNA and sister-chromatid exchanges (SCEs) has been analyzed in Allium cepa meristem cells. FdUrd in the range 10(-9)-5 X 10(-7) M produced a dose- and time-dependent decrease in the amount of cells in mitosis. This inhibitory effect could be reversed by 70-80% in short-term (6 h) experiments, by exogenously supplied dUrd at a concentration of 10(-4) M. However, at the highest FdUrd dose tested (10(-7) M), 10(-4) M dUrd could not reverse the FdUrd effect in long-term experiments (20 h, about one cell cycle interval), as shown by analyzing the kinetics of synchronous cell populations. DNA extracted from cells pulsed with [6-3H]dUrd in the presence of FdUrd and 6-amino-uracil (6-AU), an inhibitor of uracil-DNA glycosylase, contained a small amount of label (at least 3% of the total radioactivity incorporated into DNA) in the form of [6-3H]dUMP. Thus, we conclude that, under our experimental conditions, exogenously supplied dUrd may be metabolized intracellularly to 2'-deoxyuridine triphosphate (dUTP) and that this deoxynucleotide may eventually be mis-incorporated into DNA. As far as the formation of SCEs is concerned, analysis of second division chromosomes showed that 2'-deoxyuridine monophosphate (dUMP) residues present in newly-synthesized DNA strands are probably not relevant to SCE formation. However, by analyzing SCE levels in third division chromosomes of cells treated with FdUrd and dUrd during their second cycle, we have scored a 6-fold increase in the reciprocal SCE level which demonstrates that the replication of a dUMP-containing DNA template leads to a higher SCE yield.

Cyclophosphamide-induced cytogenetic effects in mouse bone marrow and spleen cells in in vivo and in vivo/in vitro assays

Sister chromatid exchange (SCE) and chromosomal aberration studies have been used to monitor human populations for genotoxic exposure to chemical substances. These monitoring techniques involve collection of blood and/or bone marrow from the exposed subjects and culturing cells for one or two cell cycles with various treatments in culture. The results obtained from such in vivo/in vitro studies may lead to an over- or underestimation of the damage that could occur in vivo. In the present study, which uses a mouse model, the in vivo/in vitro cytogenetic assays (SCEs and chromosomal aberrations) have been compared with similar in vivo systems in bone marrow and spleen cells treated with various doses of cyclophosphamide (CPA). The results indicate a significant difference in CPA-induced cytogenetic endpoints between in vivo and in vivo/in vitro conditions in both organs. However, linear relationships were found between CPA dose and cytogenetic end point analyzed under both conditions. Based on these results it appears that the in vivo/in vitro assay is a useful technique for indicating potential in vivo damage of chemicals.

A two-parameter flow cytometry protocol for the detection and characterization of the clastogenic, cytostatic and cytotoxic activities of chemicals

Cultured, freshly-isolated rat fibroblasts were exposed in vitro to vincristine sulphate (VC), amethopterin (AM), bleomycin (BL), benomyl (BE) and practolol (PR). Cells treated for 5 h were subjected 24 h later to a two-parameter (DNA/protein) flow cytometry analysis. The fluorochromes used were sulphorhodamin 101 and DAPI. From DNA and protein histograms, alterations in cell-cycle kinetics, variations in the amount of DNA in individual G1-phase cells and the enhancement of or increased variation in the protein content of the exposed cells were determined. Each of the 5 chemicals induced a specific dose-dependent pattern of changes in the DNA and protein histograms. DNA dispersion was enhanced with VC, AM, BL and BE but not with PR. The cell cycle was blocked in the G2 phase with VC, at early S phase with amethopterin and, depending on the dose, at the G1 or G2 phase with bleomycin or at the S phase or G2 phase with benomyl. Practolol inhibited cells slightly in the S phase at the highest exposure level. Protein analysis allows cytotoxic activity (loss of proteins) or induced unbalanced growth (protein accumulation) of test compounds to be recognized. The results obtained imply that the proposed two-parameter DNA/protein analysis by flow cytometry is a suitable method for prospective testing of chemicals for their induction of structural or numerical chromosome aberrations. Simultaneously, a broad range of cytotoxic, cytostatic and cell-cycle perturbing activities of the test agents can be recognized.

Comparative in vivo and in vitro sister chromatid exchange studies in Chinese hamster bone marrow and spleen cells

The sister chromatid exchange (SCE) assay in bone marrow and spleen cells of Chinese hamsters was used to evaluate the differences between in vivo and in vivo/in vitro (exposure of animals to chemical followed by culturing of cells) conditions. Cyclophosphamide, a mutagenic carcinogen, caused dose-related SCEs both in vivo and in vivo/in vitro. In the in vivo group, both bone marrow and spleen cells showed approximately a five-fold increase in SCEs over controls following 40 mg cyclophosphamide/kg treatment. The same dose, under in vivo/in vitro conditions, caused about three- and six-fold increases in SCEs over controls in bone marrow and spleen cells, respectively. While the extent of cyclophosphamide-induced SCEs (after subtraction of baseline level) in bone marrow is approximately the same under both conditions, the response was significantly higher in spleen cells in vivo/in vitro than in vivo. Under in vitro conditions, treatment of bone marrow and spleen primary cell cultures with a direct acting mutagen, trinitrofluorenone, caused significant dose-related increases in SCEs in both cell types in an equivalent manner. The replicative indices under these experimental conditions remained almost the same. Thus, this study indicates the potential usefulness of Chinese hamster bone marrow and spleen cells for in vivo and in vitro comparative studies with the same tissue to better assess the genotoxic hazard of chemicals.

Occupational exposure to anticancer drug--potential and real hazards

Many anticancer agents have been shown to be mutagenic, teratogenic and carcinogenic in experimental systems and second malignancies are known to be associated with several specific therapeutic treatments. Anticancer agents thus represent a class of occupational carcinogens, the handling of which should involve no unnecessary exposure. The available methodologies to detect possible exposures from ambient air and from biological samples are discussed, and the published data on results are reviewed. Analytical methods are available for the detection of most frequently used anticancer drugs from all groups, i.e., alkylating agents, mitotic inhibitors, antimetabolites and antibiotics. The ambient samples taken from sites of admixture of cytostatics have often shown detectable, but low concentrations of anticancer agents. Urine samples from patients under chemotherapy as well as from personnel handling the drugs occupationally in hospitals have been analyzed both chemically and for excreted mutagenicity. Both cisplatin and cyclophosphamide have been detected in the urine of patients; furthermore, cyclophosphamide was observed in the urine of nurses who formulate and deliver this drug. Urinary mutagenicity assays have given both positive and negative results in various groups of nursing and pharmacy personnel. Cytogenetic methods have, likewise, been applied for monitoring purposes. Most of the available data concerns chromosome aberrations (CA) or sister-chromatid exchanges (SCE) induced in peripheral blood lymphocytes of patients under chemotherapy. A few studies on groups occupationally exposed to anticancer drugs have given positive results, but also negative reports have appeared for these same cytogenetic parameters. No studies are as yet available on the possible carcinogenic effects of occupational handling of anticancer drugs. Two recent case-referent studies among hospital personnel have pointed to slightly increased risks of disorders in pregnancy outcome; one of the studies has shown an excess of spontaneous abortions and other malformations in children of females with a history of work with anticancer agents.

A possible role for deoxyribonucleotide pool imbalances in carcinogenesis

Thymine nucleotide pool alterations, produced by attack on non-DNA primary targets, induce a variety of chromosome and chromatid aberrations. Specifically, in lower eukaryotes, thymidylate deprivation and excess are recombinagenic and dTMP depletion also produces DNA strand breakage. In higher eukaryotes, imbalances in thymine nucleotide pools provoke chromosome breaks and rearrangements, and inhibition of thymidylate biosynthesis causes morphological and oncogenic transformation in vitro. Thus, chromosomal rearrangements induced by dTMP deprivation may be the critical changes that lead to oncogenic transformation in response to thymine nucleotide depletion.

Chromosome aberrations induced in patients treated with chemotherapeutic drugs and irradiation for acute lymphatic leukemia

Chromosome analyses were carried out in lymphocytes of ten children with ALL, prior to and during combined therapy with antineoplastic drugs and cranial irradiation. Chromosome preparations from group I (four patients) were analysed by conventional staining. For group II (six patients) the FPG technique (fluorescence plus Giemsa) was applied after BrdU treatment of cultures and cells were scored exclusively in first division. A significant clastogenic effect could not be detected in samples collected during or after chemotherapy for either group. After cranial irradiation of those patients in group II. linear dose-effect relationships for dicentric plus ring chromosomes, and for excess acentrics, could be demonstrated after correction for the relative amount of irradiated volume.

No increase in second tumors after cytotoxic chemotherapy for gestational trophoblastic tumors

We investigated the incidence of second tumors after cytotoxic chemotherapy in 457 long-term survivors treated for choriocarcinoma or an invasive mole between 1958 and 1978. Treatment was given according to regular intermittent schedules and over a mean period of four months, with no maintenance. Methotrexate was given to all but two patients, and 261 (57 per cent) also received other cytotoxic drugs, most commonly dactinomycin, vincristine, cyclophosphamide, mercaptopurine, and 6-azauridine. After a mean period of 7.8 years since the beginning of treatment and a total of 3522 patient-years of risk, second neoplasms had developed in only two women (acute leukemia in one and carcinoma of the breast in the other). This figure is less than the number of cases of cancer that would have been expected (3.5) in this group and suggests that the use of methotrexate as chemotherapy for choriocarcinoma is not carcinogenic in the medium term.

Characterization of a new chromosomal marker for acute lymphoblastic leukemia from a long-term cell line

A bone marrow aspirate from a child with acute lymphoblastic leukemia (ALL) at first relapse was used to establish cell line # 697. The cultured line and marrow aspirates taken at initial diagnosis and first relapse were examined and compared. Similarities in all patterns evaluated confirmed the leukemic origin of the line. Morphologically, the cells were typically lymphoblastic. Cytochemically, they were slightly acid phosphatase-positive and negative for peroxidase, ASD chloroacetate esterase, and nonspecific esterase. Immunologically, they were found positive for common-ALL antigen (CALLA), Ia-associated antigen, terminal deoxynucleotidyl transferase (TdT), and cytoplasmic IgM (cIgM) and slightly positive for surface IgM (sIgM). Testing for Epstein-Barr virus (EBV) capsid antigen was also positive. Cytogenetic evaluations performed on initial, relapse, and cell line specimens each revealed the presence of a pseudodiploid cell line characterized by a consistent marker chromosome. GTG-, QFQ-, and RF-banding identified the marker as being derived from a translocation involving chromosomes #7 and #19: t(7;19) (q11;q13). Iso 7q, -5, -9, and +2 were also found in significant association with the marker and were viewed as demonstrating continued karyotypic evolution within the cell line. From these data, cell line #697 has been classified as a leukemic line of B-cell lineage in a transitional stage between pre-B and mature B cells.