Modulation of the ETV6::RUNX1 Gene Fusion Prevalence in Newborns by Corticosteroid Use During Pregnancy

Abstract

ETV6::RUNX1-positive pediatric acute lymphoblastic leukemia frequently has a prenatal origin and follows a two-hit model: a first somatic alteration leads to the formation of the oncogenic fusion gene ETV6::RUNX1 and the generation of a preleukemic clone in utero. Secondary hits after birth are necessary to convert the preleukemic clone into clinically overt leukemia. However, prenatal factors triggering the first hit have not yet been determined. Here, we explore the influence of maternal factors during pregnancy on the prevalence of the ETV6::RUNX1 fusion. To this end, we employed a nested interventional cohort study (IMPACT-BCN trial), including 1221 pregnancies (randomized into usual care, a Mediterranean diet, or mindfulness-based stress reduction) and determined the prevalence of the fusion gene in the DNA of cord blood samples at delivery (n = 741) using the state-of-the-art GIPFEL (genomic inverse PCR for exploration of ligated breakpoints) technique. A total of 6.5% (n = 48 of 741) of healthy newborns tested positive for ETV6::RUNX1. Our multiple regression analyses showed a trend toward lower ETV6::RUNX1 prevalence in offspring of the high-adherence intervention groups. Strikingly, corticosteroid use for lung maturation during pregnancy was significantly associated with ETV6::RUNX1 (adjusted OR 3.9, 95% CI 1.6-9.8) in 39 neonates, particularly if applied before 26 weeks of gestation (OR 7.7, 95% CI 1.08-50) or if betamethasone (OR 4.0, 95% CI 1.4-11.3) was used. Prenatal exposure to corticosteroids within a critical time window may therefore increase the risk of developing ETV6::RUNX1+ preleukemic clones and potentially leukemia after birth. Taken together, this study indicates that ETV6::RUNX1 preleukemia prevalence may be modulated and potentially prevented.

Keywords: ETV6::RUNX1; childhood leukemia; cord blood; corticosteroids; prenatal.

Figure 1

Study design depicting the study population, the intervention arms, and performed laboratory and statistical analyses. In the nested interventional cohort study (IMPACT-BCN trial).

Figure 2

High adherence to a Mediterranean diet and stress reduction interventions, as well as exogenous glucocorticoid application, is associated with a lower prevalence of the ETV6::RUNX1 fusion as determined by the GIPFEL method. (A) The bar graphs present the percentage of ETV6::RUNX1 fusions considering only participants with high adherence to the interventions showing a non-significant trend toward lower prevalence (stress reduction (OR = 0.8, p = 0.683) and mediterranean diet (OR = 0.7, p = 0.482)). (B) The bar graph presents the prevalence of ETV6::RUNX1 in newborns whose mothers received exogenous corticosteroids during pregnancy (n = 39 in total; ETV6::RUNX1+ n = 7 of 48; ETV6::RUNX1− n = 32 of 693; OR = 3.5, p = 0.005).

Figure 3

Glucocorticoids can inhibit DNA topoisomerase II (Topo II) activity, potentially by downregulating its expression or modifying its access to DNA through chromatin remodeling. Reduced Topo II activity compromises its role in resolving DNA supercoiling, untangling chromatids, and repairing double-strand breaks (DSBs). One proposed mechanism for leukemia-causing chromosomal translocations entails chromosomal breakage by DNA topoisomerase II and recombination of DNA free ends from different chromosomes through DNA repair. Topo II inhibition increases the risk of chromosomal translocations, such as those involving the MLL gene rearrangements on chromosome 11q23, a hallmark of de novo acute leukemia development. Similarly, dysregulated Topo II activity has been linked to secondary leukemias, particularly therapy-related acute myeloid leukemia (t-AML) [42].

Figure 4

Potential impact of glucocorticoids on fetal prenatal and early postnatal development, as well as ALL therapy. (A) Endogenous glucocorticoid (cortisol) levels may increase due to prenatal stress perception during the second trimester. However, only a limited amount of endogenous GC crosses the placental barrier as they serve as a good substrate for the placental 11β-HSD2 enzyme, getting inactivated. Hence, exogenous GCs, such as betamethasone, may be administered to promote fetal lung maturation. These GCs, being steroid compounds, can easily cross the placenta and bind to the glucocorticoid receptor (GR) with a higher affinity compared to endogenous ones. Particularly, betamethasone shows a higher affinity for GR than other GCs. Upon binding, GR translocates to the nucleus, where it acts as either a transcriptional activator or repressor of target genes. Fetal exposure to high levels of GCs, whether from elevated maternal stress or medical treatment, may promote myeloid hematopoiesis and bone marrow or bone erythropoiesis by shifting hematopoietic stem cell (HSC) differentiation toward common myeloid progenitors (CMP) rather than common lymphoid progenitors (CLP). Additionally, GCs can influence bone marrow stromal cells, such as osteoblasts, which release soluble factors that regulate HSC differentiation and proliferation. Such changes in hematopoiesis may correlate with compromised humoral (B cell-derived) immune responses and perinatal neutrophil (Neu) function. GC excess in the thymus acts as a potent inducer of immature double-positive (DP) thymocyte apoptosis, as GCs are, in addition, locally produced here toward the end of the pregnancy, subsequently accelerating the maturation of double-negative (DN) thymocytes to occupy the available niche. By inhibiting T-cell receptor signaling (TCR) or autoimmune regulator (AIRE)-mediated autoantigen transcription, glucocorticoids may mitigate the apoptosis event, allowing autoreactive CD4 and CD8 single-positive (SP) T cells to circulate. Prenatal GC exposure also programs CD4 T helper (Th) cells toward a Th2 response. Furthermore, prenatal glucocorticoids may increase postnatal HPA axis activity, resulting in elevated levels of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP). This hyperactivity can enhance both innate and adaptive immune responses, potentially leading to monocyte (Mo), macrophage, and dendritic cell (DC) tolerance to pathogens or excessive mast cell degranulation. These prenatal adaptations in immune function may increase the risk of infections, asthma, and other immune-related disorders in later life. (B) Exogenous GC, in contrast to endogenous GC, can bypass the placental and fetal 11ẞ-HSD2 enzyme, and promote fetal lung maturation and preterm survival rate. (C) Increased plasma cortisol levels resulting from excess GC-induced perturbations to the hypothalamus–pituitary–adrenal axis may directly eliminate pre-leukemic cells and suppress leukemia-promoting Th1-cytokine responses. (D) Mechanisms of action of glucocorticoid in ALL therapy. Glucocorticoid-mediated apoptosis is thought to be induced via the mitochondrial pathway through caspase activation.