Effects of in utero and lactational exposure to tamoxifen in SD rats

ESMO Expert Consensus Statements on the management of breast cancer during pregnancy (PrBC)

The management of breast cancer during pregnancy (PrBC) is a relatively rare indication and an area where no or little evidence is available since randomized controlled trials cannot be conducted. In general, advances related to breast cancer (BC) treatment outside pregnancy cannot always be translated to PrBC, because both the interests of the mother and of the unborn should be considered. Evidence remains limited and/or conflicting in some specific areas where the optimal approach remains controversial. In 2022, the European Society for Medical Oncology (ESMO) held a virtual consensus-building process on this topic to gain insights from a multidisciplinary group of experts and develop statements on controversial topics that cannot be adequately addressed in the current evidence-based ESMO Clinical Practice Guideline. The aim of this consensus-building process was to discuss controversial issues relating to the management of patients with PrBC. The virtual meeting included a multidisciplinary panel of 24 leading experts from 13 countries and was chaired by S. Loibl and F. Amant. All experts were allocated to one of four different working groups. Each working group covered a specific subject area with two chairs appointed: Planning, preparation and execution of the consensus process was conducted according to the ESMO standard operating procedures.

Can maternal exposure to tamoxifen compromise sperm and behavioural parameters of male rat offspring?

Tamoxifen, a selective non-steroidal estrogen receptor modulator, is the standard adjuvant endocrine treatment for breast cancer. Since information on the risk of using tamoxifen during pregnancy is still scarce, this study evaluated whether the in utero and lactational treatment with this drug could compromise reproductive and behavioural parameters in male offspring. Pregnant Wistar rats were exposed to three doses of tamoxifen (0.12; 0.6; 3 μg/kg), by gavage, from gestational day 15 to lactational day 20. Tamoxifen exposure did not alter the anogenital distance in the male offspring; however, there was a significant increase in the body weight in the 0.12 μg/kg dose and a decrease in the 0.6 μg/kg dose. The male offspring treated with the highest dose exhibited a delay in the onset of puberty, evidenced by an increase in the age of preputial separation. Regarding sperm parameters, there was an increase in the sperm count in the cauda epididymis in the intermediate and highest dose groups, in addition to an increase in the number of static sperm and a decrease in the progressive sperm in the same groups. Moreover, an increase in the number of hyperplasia of the epithelial clear cells was observed in the epididymis. In conclusion, the present study demonstrated that maternal exposure to tamoxifen compromised the installation of puberty of the male offspring and the maturation of the epididymis, affecting sperm storage and motility in the adult life.

Sites of Cre-recombinase activity in mouse lines targeting skeletal cells

The Cre/Lox system is a powerful tool in the biologist's toolbox, allowing loss-of-function and gain-of-function studies, as well as lineage tracing, through gene recombination in a tissue-specific and inducible manner. Evidence indicates, however, that Cre transgenic lines have a far more nuanced and broader pattern of Cre activity than initially thought, exhibiting "off-target" activity in tissues/cells other than the ones they were originally designed to target. With the goal of facilitating the comparison and selection of optimal Cre lines to be used for the study of gene function, we have summarized in a single manuscript the major sites and timing of Cre activity of the main Cre lines available to target bone mesenchymal stem cells, chondrocytes, osteoblasts, osteocytes, tenocytes, and osteoclasts, along with their reported sites of "off-target" Cre activity. We also discuss characteristics, advantages, and limitations of these Cre lines for users to avoid common risks related to overinterpretation or misinterpretation based on the assumption of strict cell-type specificity or unaccounted effect of the Cre transgene or Cre inducers. © 2021 American Society for Bone and Mineral Research (ASBMR).

Tamoxifen Exposure during Pregnancy: A Systematic Review and Three More Cases

Tamoxifen is frequently used as adjuvant treatment in premenopausal patients with hormone receptor-positive early breast cancer. According to guidelines, the use of nonhormonal barrier contraception is recommended during tamoxifen treatment and up to 3 months after its interruption prior to attempting conception. Nevertheless, when conception occurs inadvertently during tamoxifen treatment, the effects on the fetus and on the course of pregnancy are still not completely known. Here, we report 3 cases of young women who accidentally became pregnant while taking tamoxifen and perform a systematic review of the literature to provide more elements for better and clear multidisciplinary counselling of women facing this challenging situation.

Effects of in utero through lactational exposure to dicyclohexyl phthalate and p,p'-DDE in Sprague-Dawley rats

Anti-androgenic chemicals alter sexual differentiation by a variety of mechanisms, and the mechanisms between phthalate esters and p,p'-DDE are considered to be different. We performed an in utero through lactational exposure assay using dicyclohexyl phthalate and p,p'-DDE to investigate the sexual differentiation of these chemicals. Pregnant CD (SD) IGS rats were given dicyclohexyl phthalate or p,p'-DDE orally from gestational day (GD) 6 to postnatal day (PND) 20, and the endocrine-mediated effects in dams and their offspring were examined. The reproductive performance of offspring was also examined. The doses of dicyclohexyl phthalate were 0, 20, 100, and 500 mg/kg/day, and those of p,p'-DDE were 5, 15, and 50mg/kg/day. Using the dicyclohexyl phthalate, a dam in the 500 mg/kg group showed dystocia and died. The viability index of offspring on PND 4 decreased in the 500 mg/kg group. Prolonged preputial separation, reduced ano-genital distance, increased areolas/nipple retention, hypospadia, decreased ventral prostate and levator ani/bulbocavernosus muscle weights and decreased testicular germ cells were observed in male offspring in the 500 mg/kg group. In the assay using p,p'-DDE, decreased viability index of offspring on PND 21, prolonged preputial separation in male offspring and early vaginal opening in female offspring were observed in the 50mg/kg group. The copulation and fertility indices decreased in the reproductive performance of offspring in the 50mg/kg group. The endocrine-mediated effects were detected in offspring of dams given 100mg/kg dicyclohexyl phthalate, and in offspring of dams given 20mg/kg p,p'-DDE. Our results suggest that the in utero through lactational exposure assay is a useful method to detect endocrine-mediated effects and that further comparative study between this assay and two-generation reproductive test are necessary when this assay becomes one of the definitive tests.

The enhancement of the subacute repeat dose toxicity test OECD TG 407 for the detection of endocrine active chemicals: comparison with toxicity tests of longer duration

The OECD conventional 28-day repeat dose toxicity test (OECD TG 407) is widely employed in the initial hazard identification and characterization for commercial chemicals. The OECD has recently undertaken an international effort to "enhance" the conventional 28-day repeat dose toxicity test (OECD TG 407) in order to ensure that chemicals acting through (anti)estrogenic, (anti)androgenic, and (anti)thyroid mechanisms are identified. The enhancements include additional parameters based on the respective target organs from the male and female reproductive tracts, the thyroid, and circulating hormone levels. Ten chemicals with known endocrine modes of action and different potencies were administered using the "enhanced TG 407" test protocol to investigate the performance of this procedure. In the present evaluation, these "enhanced TG 407" protocol results, drawn from a report of the OECD validation studies, are compared to studies of the same or similar chemicals with longer and/or in utero exposures in order to evaluate the capability of the this "enhanced TG 407" in identifying the chemicals' mode of action. The major conclusions that can be drawn from these comparisons are: 1. The "enhanced TG 407" will reliably identify chemicals with a strong to moderate potential to act through endocrine modes of action on the gonads and the thyroid. In addition, this test method gives a first indication for the dose-related potency. 2. Substances with a low potency for an endocrine mode of action, i.e., having only marginal effects in the most comprehensive in vivo studies such as multi-generation studies, may not elicit clear endocrine-related effects in the "enhanced TG 407". In these cases, the primary or principal effects observed will be driven by other toxic actions of the test materials in the "enhanced TG 407". 3. It may be concluded from the present database that prolongation of exposure from 28 days up to 90 days is unlikely to improve the chance of detecting an endocrine-mediated effect 4. A number of higher tier studies with in utero and pubertal exposure show that prenatally exposed rats may be more sensitive to exposures to compounds with very low estrogenic or antiandrogenic potential in some cases than young adult rats as used in the "enhanced TG 407". 5. Overall, these comparisons support the use of the "enhanced TG407" for the detection of endocrine active chemicals. It is therefore recommended to fully accept the enhancements and include them in the test method for toxicological and regulatory use.

Evaluation of a two-generation reproduction toxicity study adding endpoints to detect endocrine disrupting activity using vinclozolin

A two-generation reproduction toxicity study in rats adding extra endpoints to detect endocrine disrupting activity was conducted using vinclozolin by dietary administration at 0, 40, 200, and 1000 ppm, for investigation of its utility. The extra endpoints included anogenital distance (AGD), nipple development, sexual maturation (vaginal opening and preputial separation), estrous cycle, spermatogenesis, sex organ weights, and blood hormone concentrations (thyroid and sex hormones). Hepatic drug-metabolizing enzyme activities were also measured. The results revealed changes due to vinclozolin in the AGD, nipple development, sexual maturation, sex organ weights, and blood sex hormone concentrations in males of both parental animals and offspring, even at the lowest dose of 40 ppm, confirmed by results for the classical endpoints of histopathological examination at 200 ppm and mating at 1000 ppm. The effects on parental males included increased pituitary and testis weights, and decreased epididymis weights at 1000 ppm in both generations, and decreased prostate and epididymis weights at 200 and 1000 ppm and seminal vesicle weights at 1000 ppm in F1 males. Histopathological examination revealed hypertrophy of the basophilic cells in the pituitary at these two doses, and diffuse hyperplasia of the testicular interstitial cells and atrophy of the seminal vesicle mucosa at 1000 ppm in F0 and F1 males. In addition, F1 males demonstrated decrease in prostate fluid at 200 and 1000 ppm. Blood hormone analysis revealed increases in LH, FSH, testosterone, and DHT in F0 and F1 males at 1000 ppm. General toxicological effects included suppressed body weight gain in F0 and F1 females and in F1 males, and reduced food consumption in F0 and F1 females at 1000 ppm. Histopathological examination revealed centrilobular hepatocellular hypertrophy in males at 200 and 1000 ppm and in females at 1000 ppm, increased lipid droplets in the adrenal zona fasciculata and zona glomerulosa in males at 200 and 1000 ppm and in females at 40 ppm and above, and hyperplasia of ovarian interstitial cells and vacuolation of lutein cells in females at 1000 ppm in both generations. Almost all the tissue changes were accompanied by changes in weights. Decreases in T3 and/or T4 were observed in both sexes and generations at 1000 ppm and in F0 females at 200 ppm. However, these were presumed to be secondary to induction of hepatic drug-metabolizing enzymes, activities being increased for a range of enzymes in both sexes and generations at 1000 ppm. Rise in BROD activity was the most prominent, suggesting that vinclozolin mainly induces CYP2B. As for effects on reproductive function, a marked decrease in the fertility index caused by male infertility was observed in F1 animals at 1000 ppm. However, no effects on spermatogenesis were seen in either F0 or F1 males. Since cleft prepuce and penile hypoplasia were observed in infertile males, it is probable that the cause of infertility in F1 males was related to morphological abnormalities in the external genitalia. Vinclozolin did not affect the estrous cycle, mating, fertility, pregnancy, parturition, or nursing behavior in either F0 or F1 females. In offspring, in addition to suppressed body weight gain in F1 males and females at 1000 ppm, neonatal toxicity caused by antiandrogen activity of vinclozolin was observed in F1 and F2 males. Effects included shortened AGD in F1 males at 1000 ppm and in F2 males at 200 and 1000 ppm, and nipple/areola remnants in F1 males at 200 and 1000 ppm and in F2 males at 40 ppm and above. In addition, decreased epididymis weights at weaning and morphological abnormalities of the external genitalia, including cleft prepuce, penile hypoplasia, and vaginal pouch, were seen in F1 and F2 males at 1000 ppm.

EVALUATION OF A TWO-GENERATION REPRODUCTION TOXICITY STUDY ADDING ENDOPOINTS TO DETECT ENDOCRINE DISRUPTING ACTIVITY USING LINDANE

A two-generation reproduction toxicity study in rats adding extra endpoints to detect endocrine disrupting activity was conducted using lindane by dietary administration at 0, 10, 60, and 300 ppm, for investigation of its utility. The extra endpoints included anogenital distance (AGD), nipple development, sexual maturation (vaginal opening and preputial separation), estrous cycle, spermatogenesis, sex organ weights, and blood hormone concentrations (thyroid and sex hormones). F1 offspring were examined for emotionality (open field test), motor coordination (rotarod test), as well as learning and memory (pole-climbing test). Hepatic drug-metabolizing enzyme activities were also measured. The results revealed general toxicological effects on parental animals, influence on reproductive function, and altered development of offspring; however, they did not demonstrate any distinct changes in the extra endpoints for detection of endocrine disrupting activity. Adult toxicity was observed in both F0 and F1 animals, including suppressed body weight gain and reduced food consumption in both sexes, and deaths of females at 300 ppm. Convulsions and irritability were observed during the perinatal period in pregnant F1 females given 300 ppm. Pathological examination revealed increased liver weights and centrilobular hepatocellular hypertrophy in both sexes and generations at 10 or 60 ppm and above; in addition, increased kidney weights and increased hyaline droplets in the proximal tubule epithelium, and basophilic renal tubules in males were noted at 10 ppm and above. Pituitary weights were decreased in F0 females and in F1 males and females and adrenal weights were increased in F1 males and females at 300 ppm; however, no histological changes were observed, and manifestations suggesting endocrine disrupting activity related to these changes were lacking. Hypertrophy of the thyroid follicular epithelium in F0 females at 300 ppm and in F1 males at 60 and 300 ppm, and decreases in T3 and/or T4 in both sexes and generations at 300 ppm were presumed to be secondary changes associated with the induction of hepatic drug-metabolizing enzymes. Blood hormone analysis revealed no changes in sex hormones attributable to lindane in males or females. Hepatic drug-metabolizing enzyme activities were increased dose-dependently from 10 ppm in both sexes and generations, with the rise in BROD activity being the most prominent. There were also increases in MROD, EROD, T-6beta-OH, and T4-UDP-GT activities (BROD >> EROD > MROD, T-6beta-OH, T4-UDP-GT). This suggests that while lindane most strongly induces CYP2B, it also upregulates a number of other drug metabolizing enzymes, such as CYP1A, CYP3A, and UDP-GT. As for effects on reproductive function, lack of maternal behavior, including lactation and retrieval behavior, and consequent total litter loss were observed in F1 dams at 300 ppm. There were no effects of lindane on the estrous cycle, spermatogenesis, mating, fertility, pregnancy, or parturition. Neonatal toxicity was observed in both sexes and generations, including suppressed body weight gain at 60 and 300 ppm, and decreased thymus and spleen weights without histological change at 300 ppm. The postnatal survival rate in F2 offspring was decreased due to lack of maternal behavior in dams at 300 ppm.