Methotrexate-resistant form of dihydrofolate reductase protects transgenic murine embryos from teratogenic effects of methotrexate

Improvements in Clinical Trials Information Will Improve the Reproductive Health and Fertility of Cancer Patients

There are a number of barriers that result in cancer patients not being referred for oncofertility care, which include knowledge about reproductive risks of antineoplastic agents. Without this information, clinicians do not always make recommendations for oncofertility care. The objective of this study was to describe the level of reproductive information and recommendations that clinicians have available in clinical trial protocols regarding oncofertility management and follow-up, and the information that patients may receive in clinical trials patient information sheets or consent forms. A literature review of the 71 antineoplastic drugs included in the 68 clinical trial protocols showed that 68% of the antineoplastic drugs had gonadotoxic animal data, 32% had gonadotoxic human data, 83% had teratogenic animal data, and 32% had teratogenic human data. When the clinical trial protocols were reviewed, only 22% of the protocols reported the teratogenic risks and 32% of the protocols reported the gonadotoxic risk. Only 56% of phase 3 protocols had gonadotoxic information and 13% of phase 3 protocols had teratogenic information. Nine percent of the protocols provided fertility preservation recommendations and 4% provided reproductive information in the follow-up and survivorship period. Twenty-six percent had a section in the clinical trials protocol, which identified oncofertility information easily. When gonadotoxic and teratogenic effects of treatment were known, they were not consistently included in the clinical trial protocols and the lack of data for new drugs was not reported. Very few protocols gave recommendations for oncofertility management and follow-up following the completion of cancer treatment. The research team proposes a number of recommendations that should be required for clinicians and pharmaceutical companies developing new trials.

Safety of conventional systemic therapies for psoriasis on reproductive potential and outcomes

The effects of conventional systemic therapies for psoriasis on pregnancy outcomes, lactation, male fertility and mutagenicity are common concerns in the clinical setting. There is relatively little evidence to guide clinician and patient. In this study, we review the safety profile of the commonly used conventional systemic therapies used for psoriasis in individuals of reproductive potential. Safety data are derived from large-scale registries, adverse-event reporting databases, clinical trials and case reports. We assess the effect of each therapy on adverse pregnancy outcomes, including congenital malformations, and lactation with maternal administration. We also assess the effect of the therapies on male fertility and potential mutagenicity with paternal administration. We provide applicable guidance to inform clinician and patient before and after conception.

Teratogen update: methotrexate

Methotrexate and aminopterin are folic acid antagonists that inhibit dihydrofolate reductase, resulting in a block in the synthesis of thymidine and inhibition of DNA synthesis. Methotrexate has been used for the treatment of malignancy, rheumatic disorders, and psoriasis and termination of intrauterine pregnancy. Recently, methotrexate has become a standard treatment for ectopic pregnancy. The misdiagnosis of an intrauterine pregnancy as an ectopic pregnancy can result in exposure of a continuing pregnancy to dose levels of methotrexate of 50 mg/m(2) (maternal body surface area). Experimental animal studies have associated methotrexate therapy with embryo death in mice, rats, rabbits, and monkeys. Structural malformations have been most consistently produced in rabbits at a maternal dose level of 19.2 mg/kg. Abnormalities in rabbits include hydrocephalus, microphthalmia, cleft lip and palate, micrognathia, dysplastic sacral and caudal vertebrate, phocomelia, hemimelia, syndactyly, and ectrodactyly. Based on human case reports of methotrexate exposure during pregnancy, a methotrexate embryopathy has been described that includes growth deficiency, microcephaly, hypoplasia of skull bones, wide fontanels, coronal or lambdoidal craniosynostosis, upswept frontal scalp hair, broad nasal bridge, shallow supraorbital ridges, prominent eyes, low-set ears, maxillary hypoplasia, epicanthal folds, short limbs, talipes, hypodactyly, and syndactyly. This syndrome may be associated with exposures between 6 and 8 weeks after conception and dose levels of 10 mg/week or greater. More recent case reports of methotrexate exposure for the misdiagnosis of ectopic pregnancy involve treatment before 6 weeks after conception and have raised the suggestion of a distinct syndrome due to such early exposures. Tetralogy of Fallot and perhaps other neural crest cell-related abnormalities may be features of this early syndrome. A disproportionality analysis of methotrexate and aminopterin case reports and series provides support for pulmonary atresia, craniosynostosis, and limb deficiencies as reported more often than expected in methotrexate-exposed children. Denominator-based data will be welcome to better define elements of a methotrexate embryopathy and possibly to distinguish an early exposure syndrome from anomalies traditionally associated with methotrexate exposure.

A role for Drosophila in understanding drug-induced cytotoxicity and teratogenesis

Drosophila research has been and continues to be an essential tool for many aspects of biological scientific research and has provided insight into numerous genetic, biochemical, and behavioral processes. As well, due to the remarkable conservation of gene function between Drosophila and humans, and the easy ability to manipulate these genes in a whole organism, Drosophila research has proven critical for studying human disease and the physiological response to chemical reagents. Methotrexate, a widely prescribed pharmaceutical which inhibits dihydrofolate reductase and therefore folate metabolism, is known to cause teratogenic effects in human fetuses. Recently, there has been resurgence in the use of methotrexate for inflammatory diseases and ectopic or unwanted pregnancies thus, increasing the need to fully understand the cytotoxicity of this pharmaceutical. Concerns have been raised over the ethics of studying teratogenic drugs like methotrexate in mammalian systems and thus, we have proposed a Drosophila model. We have shown that exposure of female Drosophila to methotrexate results in progeny with developmental abnormalities. We have also shown that methotrexate exposure changes the abundance of many fundamental cellular transcripts. Expression of a dihydrofolate reductase with a reduced affinity for methotrexate can not only prevent much of the abnormal transcript profile but the teratogenesis seen after drug treatment. In the future, such studies may generate useful tools for mammalian antifolate "rescue" therapies.

Transgenic rescue of methotrexate-induced teratogenicity in Drosophila melanogaster

The folic acid analog methotrexate (MTX), a competitive inhibitor of dihydrofolate reductase (DHFR), is used to treat a variety of cancers and autoimmune disorders. However, MTX also causes a wide range of toxic effects in healthy cells and is an established teratogen. Efforts to "rescue" the defects caused by MTX by administering a folate analog or by transgenic expression of a DHFR with an altered affinity for MTX have been attempted in a variety of mammals but limited protection was conferred. As a result, our understanding of the effect of MTX at the molecular genetic level remains incomplete and, in addition, continued mammalian sacrifice is not ideal. Due to the similarity of teratogenic effects produced by MTX in Drosophila melanogaster these insects were transformed with DHFR alleles to determine if rescue could be achieved. The resulting "MTX-resistant" flies were subsequently used to investigate changes in gene expression in response to MTX using semiquantitative reverse transcription PCR. The majority (12/14) of key transcripts that were affected in MTX-exposed females including transcripts involved in cell cycle, defense response, and transport were "rescued" in the "MTX-resistant" transgenic flies. These studies illustrate the utility of this invertebrate model for the investigation of molecular effects of MTX-induced teratogenicity, MTX-resistant DHFRs for gene therapy techniques, and teratogenic protection.

Involvement of NF-κB in the response of embryonic cells to Methotrexate

The involvement of NF-kappaB in the regulation of the apoptotic process was demonstrated previously, however, its exact role has not been established yet. In order to unravel mechanisms underlying teratogen-induced cell death, we tried in our present study to assess the involvement of the p65 subunit of NF-kappaB in the response of mouse embryonic fibroblasts (MEFs) to the anti-cancer drug methotrexate (MTX), using p65 knockout MEFs (p65(-/-)). Indeed, this cell line was found to be more susceptible to the exposure to MTX, demonstrated by more profound changes in cell survival, cell cycle, proliferation and the percentage of apoptotic or necrotic cells, as compared to wild type (WT) MEFs. Also, a different pattern of intracellular localization of p65 in WT cells as well as IkappaBalpha and Bax in both cell lines was detected in response to MTX. Altogether, our results implicate the p65 subunit of NF-kappaB to play an important role in the response of embryonic cells to MTX.

The effects of methotrexate on Drosophila development, female fecundity, and gene expression

Methotrexate (MTX), a synthetic folate analog, is a tight-binding inhibitor of dihydrofolate reductase (DHFR), a key enzyme for the biosynthesis of purines, thymidylate, and several amino acids. As a consequence, MTX decreases titres of reduced folates, interferes with DNA synthesis, and results in the arrest of rapidly proliferating cells, making it a drug of choice for the treatment of a variety of cancers and auto-immune disorders. MTX is also a known teratogen in all higher animals tested, but there is little information about the effects of this drug on invertebrates. Here we show that MTX has little effect on the survival of Drosophila melanogaster adult flies, but severely diminishes female fecundity. Reduced oviposition, coupled with aberrant egg morphologies, resulted in near sterility of MTX-treated females. Rare surviving progeny showed developmental abnormalities including larval tumors, and bristle, wing, eye, and leg defects. To determine if these phenotypes could be attributed solely to DHFR inhibition, microarray analysis was undertaken and included MTX-treated females, ovaries, and cell line samples. Genes encoding transcripts that were perturbed by the drug were verified using quantitative real-time RT-PCR. Many of these genes were involved in cell cycle regulation, signal transduction, transport, defense response, transcription, or various aspects of metabolism. These studies show that MTX treatment has multiple targets and, in addition, provides a new invertebrate model for the study of teratogenesis.

Cyclophosphamide, methotrexate, and cytarabine embropathy: is apoptosis the common pathway?

BACKGROUND

Cyclophosphamide (CP) is an alkylating agent primarily used for the treatment of autoimmune disease and cancer. The purpose of this article is two-fold: first, to indicate that CP is a recognized human teratogen based on the features seen in a child prenatally exposed to this agent, as well as features seen in the previously reported cases; second, to suggest a common pathway to explain the similarity in the pattern of malformation seen in infants prenatally exposed to CP, in infants prenatally exposed to methotrexate (MTX), and in infants prenatally exposed to cytosine arabinoside (CA).

METHODS

Case report and review of the literature of an infant prenatally exposed to CP during the first trimester with a specific pattern of malformation. Features are compared to seven previous reports.

RESULTS

A common pattern of malformation is delineated including growth deficiency, hypoplasia of the calvarial and facial bones, and oligodactyly.

CONCLUSIONS

The finding of a similar pattern of malformation among eight infants prenatally exposed to CP suggests that CP is a human teratogen. MTX and CA produce similar patterns of malformation in prenatally exposed infants despite very different pharmocologic profiles and metabolism. We speculate that the phenotype is a consequence of apoptosis in certain cells which are susceptible to the effects of the teratogen at specific stages of development.

Expression and activity of the DNA repair enzyme uracil DNA glycosylase during organogenesis in the rat conceptus and following methotrexate exposure in vitro

Uracil incorporation into DNA occurs under conditions that limit thymidine biosynthesis; uracil is removed by two isoforms of uracil DNA glycosylase (UNG; EC 3.2.2.3), UNG1 and UNG2. We hypothesize that UNG is important in protecting the mid-organogenesis stage [gestational day (GD) 10-12] rat conceptus against conditions that limit thymidine biosynthesis. Transcripts for both UNG isoforms were expressed highly in the yolk sac and embryo, increasing over 400% in the embryo between GD11 and 12. GD10 and 11 yolk sacs showed the highest levels of putatively active UNG2 protein, with little UNG1 protein. Moderate levels of UNG2 and UNG1 proteins were found in the embryo on GDs 10 through 12; no significant increase in either protein occurred on GD12. UNG activity was higher in yolk sac than embryo on GDs 10 and 11, mirroring protein levels. Exposure to the teratogen methotrexate (MTX) leads to nucleotide pool imbalance, uracil incorporation into DNA, and genotoxic stress-induced cell death. Concentration-dependent decreases in developmental growth parameters, decreased yolk sac vasculature, and malformations such as kinked tail and retarded limb development were observed in embryos exposed to MTX (0.5, 2.5, or 5 microM). UNG transcripts were elevated 30-40% in both yolk sac and embryo after a 6-hr culture with 0.5 microM MTX; however, protein expression and activity were unaffected. Thus, MTX exposure caused malformations but did not modify UNG protein expression or activity, indicating an inability to increase the removal of MTX-induced genotoxic damage. Furthermore, UNG expression was developmental stage- and tissue-specific; the discrepancy between transcript and protein levels suggests post-transcriptional regulation.