Breast cancer is the most common in women worldwide, with some 5-10% of all cases due to inherited mutations of BRCA1 and BRCA2 genes. Obesity, hormone therapy and use of alcohol are possible causes and over-expression of leptin in adipose tissue may also play a role. Normally surgery, radiation therapy and chemotherapy allow a good prognosis where screening measures are in place. New hope in treatment measures include adjuvant therapy, neoadjuvant therapy, and introduction of mono-clonal antibodies and enzyme inhibitors.

No abstract

Pregnancy complications are a major cause of fetal and maternal morbidity and mortality in humans. The majority of pregnancy complications initiate due to abnormal placental development and function. During the last decade, the role of microRNAs (miRNAs) in regulating placental and fetal development has become evident. Dysregulation of miRNAs in the placenta not only affects placental development and function, but these miRNAs can also be exported to both maternal and fetal compartments and affect maternal physiology and fetal growth and development. Due to their differential expression in the placenta and maternal circulation during pregnancy complications, miRNAs can be used as diagnostic biomarkers. However, the differential expression of a miRNA in the placenta may not always be reflected in maternal circulation, which makes it difficult to find a reliable biomarker for placental dysfunction. In this review, we provide an overview of differentially expressed miRNAs in the placenta and/or maternal circulation during preeclampsia (PE) and intrauterine growth restriction (IUGR), which can potentially serve as biomarkers for prediction or diagnosis of pregnancy complications. Using different bioinformatics tools, we also identified potential target genes of miRNAs associated with PE and IUGR, and the role of miRNA-mRNA networks in the regulation of important signaling pathways and biological processes.

Chorionic Somatomammotropin (CSH) is one of the most abundantly produced placental hormones, yet its exact function remains elusive. Near-term (135 dGA), CSH RNA interference (RNAi) results in two distinct phenotypes: 1) pregnancies with intrauterine growth restriction (IUGR), and 2) pregnancies with normal fetal and placental weights. Here we report the physiological changes in CSH RNAi pregnancies without IUGR. The trophectoderm of hatched blastocysts (9 dGA) were infected with lentiviral-constructs expressing either a scrambled control (Control RNAi) or CSH-specific shRNA (CSH RNAi), prior to transfer into synchronized recipient ewes. At 126 dGA, Control RNAi (n = 6) and CSH RNAi (n = 6) pregnancies were fitted with maternal and fetal catheters. Uterine and umbilical blood flows were measured at 132 dGA and nutrient uptakes were calculated by the Fick principle. Control RNAi and CSH RNAi pregnancies were compared by analysis of variance, and significance was set at P ≤ 0.05. Absolute (ml/min) and relative (ml/min/kg fetus) uterine blood flows were reduced (P ≤ 0.05) in CSH RNAi pregnancies, but umbilical flows were not impacted. The uterine artery-to-vein glucose gradient (mmol/l) was significantly (P ≤ 0.05) increased. The uteroplacental glucose uptake (μmol/min/kg placenta) was increased (P ≤ 0.05), whereas umbilical glucose uptake (μmol/min/kg fetus) was reduced. Our results demonstrate that CSH RNAi has significant physiological ramifications, even in the absence of IUGR, and comparing CSH RNAi pregnancies exhibiting both IUGR and non-IUGR phenotypes may help determine the direct effects of CSH and its potential impact on fetal development.

The chromatin associated transcription factor HMGA2 is a downstream target of let-7 miRNAs and binds to chromatin to regulate gene expression. Inhibition of let-7 miRNAs by RNA binding proteins LIN28A and LIN28B is necessary during early embryogenesis to ensure stable expression of HMGA2. In addition to LIN28, HMGA2 is regulated by a BRCA1/ZNF350/CtIP repressor complex. In normal tissues, the BRCA1/ZNF350/CtIP complex binds to the HMGA2 promoter to prevent transcription. However, in many cancers the oncomiR miR-182 targets BRCA1, preventing BRCA1 translation and allowing for increased HMGA2. Little is known about the regulation of HMGA2 during early placental development therefore we hypothesized that both LIN28 and BRCA1 can regulate HMGA2 in placental cells. Using siRNA and CRISPR gene editing techniques, we found that knockdowns of both LIN28A and LIN28B increase HMGA2 levels in ACH-3P cells. These cells also demonstrated deficiencies in cell differentiation, seemingly differentiating solely towards the syncytiotrophoblast sublineage, secreting higher amounts of hCG and displaying upregulated ERVW-1. Additionally, we found that a knockout of both LIN28A and LIN28B caused a significant increase of miR-182 and a decrease in BRCA1 allowing HMGA2 mRNA levels to increase and protein levels to remain the same. Using chromatin immunoprecipitation, we saw binding of the BRCA1 repressor complex to HMGA2. We also saw a decrease in binding to HMGA2's promoter in the LIN28A/B knockout cells. These findings suggest a novel role for BRCA1 during early human placental development.

Abnormal placental development is one of the main etiological factors for intrauterine growth restriction (IUGR). Here, we show that LIN28A and LIN28B are significantly lower and lethal‐7 (let‐7) microRNAs (miRNAs) significantly higher in term human IUGR vs. normal placentas. We hypothesize that let‐7 miRNAs regulate genes with known importance for human placental development [high‐mobility group AT‐hook 1 (HMGA1), transcriptional regulator Myc‐like (c‐myc), vascular endothelial growth factor A (VEGF‐A), and Wnt family member 1 (WNT1)] by targeting the AT‐rich interacting domain (ARID)‐3B complex. ACH‐3P cells with LIN28A and LIN28B knockout (DKOs) significantly increased let‐7 miRNAs, leading to significantly decreased ARID3A, ARID3B, and lysine demethylase 4C (KDM4C). Similarly, Sw.71 cells overexpressing LIN28A and LIN28B (DKIs) significantly decreased let‐7 miRNAs, leading to significantly increased ARID3A, ARID3B, and KDM4C. In ACH‐3P cells, ARID3A, ARID3B, and KDM4C make a triprotein complex [triprotein complex comprising ARID3A, ARID3B, and KDM4C (ARID3B‐complex)] that binds the promoter regions of HMGA1, c‐MYC, VEGF‐A, and WNT1. ARID3B knockout in ACH‐3P cells disrupted the ARID3B‐complex, leading to a significant decrease in HMGA1, c‐MYC, VEGF‐A, and WNT1. DKOs had a significant reduction, whereas DKIs had a significant increase in HMGA1, c‐MYC, VEGF‐A, and WNT1, potentially due to regulation by the ARID3B‐complex. This is the first study showing regulation of let‐7 targets in immortalized human trophoblast cells by the ARID3B‐complex.—Ali, A., Anthony, R. V., Bouma, G. J., Winger, Q. A. LIN28‐let‐7 axis regulates genes in immortalized human trophoblast cells by targeting the ARID3B‐complex. FASEB J. 33, 12348–12363 (2019). http://www.fasebj.org

Placental disorders are a major cause of pregnancy loss in humans, and 40–60% of embryos are lost between fertilization and birth. Successful embryo implantation and placental development requires rapid proliferation, invasion, and migration of trophoblast cells. In recent years, microRNAs (miRNAs) have emerged as key regulators of molecular pathways involved in trophoblast function. A miRNA binds its target mRNA in the 3ʹ-untranslated region (3ʹ-UTR), causing its degradation or translational repression. Lethal-7 (let-7) miRNAs induce cell differentiation and reduce cell proliferation by targeting proliferation-associated genes. The oncoprotein LIN28 represses the biogenesis of mature let-7 miRNAs. Proliferating cells have high LIN28 and low let-7 miRNAs, whereas differentiating cells have low LIN28 and high let-7 miRNAs. In placenta, low LIN28 and high let-7 miRNAs can lead to reduced proliferation of trophoblast cells, resulting in abnormal placental development. In trophoblast cells, let-7 miRNAs reduce the expression of proliferation factors either directly by binding their mRNA in 3ʹ-UTR or indirectly by targeting the AT-rich interaction domain (ARID)3B complex, a transcription-activating complex comprised of ARID3A, ARID3B, and histone demethylase 4C (KDM4C). In this review, we discuss regulation of trophoblast function by miRNAs, focusing on the role of LIN28-let-7-ARID3B pathway in placental development.

Intrauterine growth restriction (IUGR) occurs in 15–20% of pig neonates and poses huge economic losses to the pig industry. IUGR piglets have reduced skeletal muscle growth, which may persist after birth. Prenatal muscle growth is regulated by complex molecular pathways that are not well understood. MicroRNAs (miRNAs) have emerged as the main regulators of vital pathways and biological processes in the body. This study was designed to identify miRNA–mRNA networks regulating prenatal skeletal muscle development in pigs. We performed an integrative miRNA–mRNA transcriptomic analysis in longissimus dorsi muscle from IUGR fetuses and appropriate for gestational age (AGA) fetuses at 63 days post conception. Our data showed that 47 miRNAs and 3257 mRNAs were significantly upregulated, and six miRNAs and 477 mRNAs were significantly downregulated in IUGR compared to AGA fetuses. Moreover, 47 upregulated miRNAs were negatively correlated and can potentially target 326 downregulated genes, whereas six downregulated miRNAs were negatively correlated and can potentially target 1291 upregulated genes. These miRNA–mRNA networks showed enrichment in biological processes and pathways critical for fetal growth, development, and metabolism. The miRNA–mRNA networks identified in this study can potentially serve as indicators of prenatal fetal growth and development as well as postnatal carcass quality.