Urinary Biomarkers and Overactive Bladder Symptoms Before and After Prolapse Surgery.

IMPORTANCE: Women with pelvic organ prolapse (POP) have increased prevalence of overactive bladder (OAB) and the evaluation of urinary biomarkers associated with OAB in the setting of POP is limited. OBJECTIVE: The objective is to determine whether associations exist between urinary biomarkers measured before POP surgery with postoperative OAB symptoms. STUDY DESIGN: In this prospective cohort study, women with anterior and/or apical POP beyond the hymen undergoing POP surgery were assessed using the OAB Questionnaire Short Form (OAB-q SF) and the Urogenital Distress Inventory 6 (UDI-6) preoperatively and 3 months postoperatively. A first morning voided urine specimen was collected preoperatively and 3 months postoperatively. Urinary biomarkers for inflammation, neuroinflammation, and tissue remodeling were measured. Univariate generalized linear models measured the relationship between biomarkers and symptoms. Between- and within-cohort assessments were made using 2-sample paired and unpaired t tests, respectively. RESULTS: Seventy-seven participants with OAB (n = 67, 87.0%) and without OAB (n = 10, 13.0%) were enrolled. Seventy-four participants (96%) completed 3-month follow up. The OAB-q SF and UDI-6 scores significantly improved between preoperative and postoperative measures. Preoperative urinary biomarkers did not demonstrate significant correlations with postoperative OAB-q SF or UDI-6 scores. No significant differences were measured in preoperative biomarkers between patients with and without OAB or when comparing preoperative and postoperative biomarkers in patients with OAB. CONCLUSIONS: Urinary biomarkers for tissue remodeling, inflammation, and neuroinflammation were not significantly correlated with OAB symptoms in a population of patients with OAB and POP.

A Case of Persistent Human Pegivirus Infection in Two Separate Pregnancies of a Woman.

Human pegivirus (HPgV) is best known for persistent, presumably non-pathogenic, infection and a propensity to co-infect with human immunodeficiency virus or hepatitis C virus. However, unique attributes, such as the increased risk of malignancy or immune modulation, have been recently recognized for HPgV. We have identified a unique case of a woman with high levels HPgV infection in two pregnancies, which occurred 4 years apart and without evidence of human immunodeficiency virus or hepatitis C virus infection. The second pregnancy was complicated by congenital heart disease. A high level of HPgV infection was detected in the maternal blood from different trimesters by RT-PCR and identified as HPgV type 1 genotype 2 in both pregnancies. In the second pregnancy, the decidua and intervillous tissue of the placenta were positive for HPgV by PCR but not the chorion or cord blood (from both pregnancies), suggesting no vertical transmission despite high levels of viremia. The HPgV genome sequence was remarkably conserved over the 4 years. Using VirScan, sera antibodies for HPgV were detected in the first trimester of both pregnancies. We observed the same anti-HPgV antibodies against the non-structural NS5 protein in both pregnancies, suggesting a similar non-E2 protein humoral immune response over time. To the best of our knowledge, this is the first report of persistent HPgV infection involving placental tissues with no clear indication of vertical transmission. Our results reveal a more elaborate viral-host interaction than previously reported, expand our knowledge about tropism, and opens avenues for exploring the replication sites of this virus.

Umbilical Cord Blood Leptin and IL-6 in the Presence of Maternal Diabetes or Chorioamnionitis.

Diabetes during pregnancy is associated with elevated maternal insulin, leptin and IL-6. Within the placenta, IL-6 can further stimulate leptin production. Despite structural similarities and shared roles in inflammation, leptin and IL-6 have contrasting effects on neurodevelopment, and the relative importance of maternal diabetes or chorioamnionitis on fetal hormone exposure has not been defined. We hypothesized that there would be a positive correlation between IL-6 and leptin with progressively increased levels in pregnancies complicated by maternal diabetes and chorioamnionitis. To test this hypothesis, cord blood samples were obtained from 104 term infants, including 47 exposed to maternal diabetes. Leptin, insulin, and IL-6 were quantified by multiplex assay. Factors independently associated with hormone levels were identified by univariate and multivariate linear regression. Unlike IL-6, leptin and insulin were significantly increased by maternal diabetes. Maternal BMI and birth weight were independent predictors of leptin and insulin with birth weight the strongest predictor of leptin. Clinically diagnosed chorioamnionitis and neonatal sepsis were associated with increased IL-6 but not leptin. Among appropriate for gestational age infants without sepsis, IL-6 and leptin were strongly correlated (R=0.6, P<0.001). In summary, maternal diabetes and birth weight are associated with leptin while chorioamnionitis is associated with IL-6. The constraint of the positive association between leptin and IL-6 to infants without sepsis suggests that the term infant and placenta may have a limited capacity to increase cord blood levels of the neuroprotective hormone leptin in the presence of increased cord blood levels of the potential neurotoxin IL-6.

Advantages of Tyrosine Kinase Anti-Angiogenic Cediranib over Bevacizumab: Cell Cycle Abrogation and Synergy with Chemotherapy.

Angiogenesis plays a crucial role in tumor development and metastasis. Both bevacizumab and cediranib have demonstrated activity as single anti-angiogenic agents in endometrial cancer, though subsequent studies of bevacizumab combined with chemotherapy failed to improve outcomes compared to chemotherapy alone. Our objective was to compare the efficacy of cediranib and bevacizumab in endometrial cancer models. The cellular effects of bevacizumab and cediranib were examined in endometrial cancer cell lines using extracellular signal-related kinase (ERK) phosphorylation, ligand shedding, cell viability, and cell cycle progression as readouts. Cellular viability was also tested in eight patient-derived organoid models of endometrial cancer. Finally, we performed a phosphoproteomic array of 875 phosphoproteins to define the signaling changes related to bevacizumab versus cediranib. Cediranib but not bevacizumab blocked ligand-mediated ERK activation in endometrial cancer cells. In both cell lines and patient-derived organoids, neither bevacizumab nor cediranib alone had a notable effect on cell viability. Cediranib but not bevacizumab promoted marked cell death when combined with chemotherapy. Cell cycle analysis demonstrated an accumulation in mitosis after treatment with cediranib + chemotherapy, consistent with the abrogation of the G2/M checkpoint and subsequent mitotic catastrophe. Molecular analysis of key controllers of the G2/M cell cycle checkpoint confirmed its abrogation. Phosphoproteomic analysis revealed that bevacizumab and cediranib had both similar and unique effects on cell signaling that underlie their shared versus individual actions as anti-angiogenic agents. An anti-angiogenic tyrosine kinase inhibitor such as cediranib has the potential to be superior to bevacizumab in combination with chemotherapy.

Prevalence and Distribution of Electronic Cigarette Use Before and During Pregnancy Among Women in 38 States of the United States.

INTRODUCTION: To examine the prevalence and the changing pattern of e-cigarette use from preconception to pregnancy. AIMS AND METHODS: This is a cross-sectional study using data from the multi-site Pregnancy Risk Assessment Monitoring System in the United States, 2016-2017. All participating mothers with information on e-cigarette use before and during pregnancy were included. Self-reported information about e-cigarette use were assessed using questionnaires. Weighted prevalences of e-cigarette use before and during pregnancy were calculated. Multivariable logistic regressions were used to examine the association between various demographic characteristics and e-cigarette use before or during pregnancy. RESULTS: This study included 69 508 pregnant women from 38 states in the United States. The weighted prevalence of e-cigarette use before pregnancy and during the last 3 months of pregnancy was 3.6% (95% confidence interval [CI] 3.4%-3.9%) and 1.1% (0.9%-1.2%), respectively. The prevalence varied across states, ranging from 1.3% to 8.3% for e-cigarette use before pregnancy and from 0.1% to 3.4% for e-cigarette use during the last 3 months of pregnancy. Among women who used e-cigarettes before pregnancy, 24.4% (21.7%-27.1%) continued to use e-cigarettes during pregnancy. Among women who used e-cigarettes during pregnancy, 62.3% (56.5%-68.0%) were dual users. In multivariable analyses, cigarette smoking was most strongly associated with e-cigarette use. The adjusted odds ratio comparing smokers with nonsmokers before pregnancy was 11.10 (95% CI 9.34-13.20) for e-cigarette use before pregnancy and 6.72 (95% CI 4.38-10.31) for e-cigarette use during pregnancy. CONCLUSIONS: Using data from 38 states in the United States, we showed geographical variations in the prevalence of e-cigarette use before and during pregnancy. Among women who used e-cigarettes before pregnancy, a quarter of them continued to use e-cigarettes during pregnancy. Conventional cigarette use is a strong risk factor for e-cigarette use before and during pregnancy. The prevalence of e-cigarette use needs to be monitored continuously. IMPLICATIONS: This study provides important information to understand the status and changing patterns of e-cigarette use in pregnant women in the United States. Among pregnant women in 38 states in the United States, 3.6% of them used e-cigarettes during the 3 months before pregnancy and 1.1% used them during the last 3 months of pregnancy. The prevalence varied across states. A quarter of women who used e-cigarettes before pregnancy continued to use e-cigarettes during pregnancy. Cigarette smoking is the strongest predictor of e-cigarette use. Future research about health effects of e-cigarette use during pregnancy is in urgent need.

Manipulating CD4+ T Cell Pathways to Prevent Preeclampsia.

Preeclampsia (PreE) is a placental disorder characterized by hypertension (HTN), proteinuria, and oxidative stress. Individuals with PreE and their children are at an increased risk of serious short- and long-term complications, such as cardiovascular disease, end-organ failure, HTN, neurodevelopmental disorders, and more. Currently, delivery is the only cure for PreE, which remains a leading cause of morbidity and mortality among pregnant individuals and neonates. There is evidence that an imbalance favoring a pro-inflammatory CD4+ T cell milieu is associated with the inadequate spiral artery remodeling and subsequent oxidative stress that prime PreE's clinical symptoms. Immunomodulatory therapies targeting CD4+ T cell mechanisms have been investigated for other immune-mediated inflammatory diseases, and the application of these prevention tactics to PreE is promising, as we review here. These immunomodulatory therapies may, among other things, decrease tumor necrosis factor alpha (TNF-α), cytolytic natural killer cells, reduce pro-inflammatory cytokine production [e.g. interleukin (IL)-17 and IL-6], stimulate regulatory T cells (Tregs), inhibit type 1 and 17 T helper cells, prevent inappropriate dendritic cell maturation, and induce anti-inflammatory cytokine action [e.g. IL-10, Interferon gamma (IFN-γ)]. We review therapies including neutralizing monoclonal antibodies against TNF-α, IL-17, IL-6, and CD28; statins; 17-hydroxyprogesterone caproate, a synthetic hormone; adoptive exogenous Treg therapy; and endothelin-1 pathway inhibitors. Rebalancing the maternal inflammatory milieu may allow for proper spiral artery invasion, placentation, and maternal tolerance of foreign fetal/paternal antigens, thereby combatting early PreE pathogenesis.

Aggregation of Human Mesenchymal Stromal Cells Eliminates Their Ability to Suppress Human T Cells.

Mesenchymal stromal cells (MSCs) are administered locally to treat sites of inflammation. Local delivery is known to cause MSCs to aggregate into "spheroids," which alters gene expression and phenotype. While adherent MSCs are highly efficient in their inhibition of T cells, whether or not this property is altered upon MSC aggregation has not been thoroughly determined. In this study, we discovered that aggregation of MSCs into spheroids causes them to lose their T cell-suppressive abilities. Interestingly, adding budesonide, a topical glucocorticoid steroid, alongside spheroids partially restored MSC suppression of T cell proliferation. Through a series of inhibition and add-back studies, we determined budesonide acts synergistically with spheroid MSC-produced PGE2 to suppress T cell proliferation through the PGE2 receptors EP2 and EP4. These findings highlight critical differences between adherent and spheroid MSC interactions with human immune cells that have significant translational consequences. In addition, we uncovered a mechanism through which spheroid MSC suppression of T cells can be partly restored. By understanding the phenotypic changes that occur upon MSC aggregation and the impact of MSC drug interactions, improved immunosuppressive MSC therapies for localized delivery can be designed.

Nature vs. Nurture: Defining the Effects of Mesenchymal Stromal Cell Isolation and Culture Conditions on Resiliency to Palmitate Challenge.

As MSC products move from early development to clinical translation, culture conditions shift from xeno- to xeno-free systems. However, the impact of isolation and culture-expansion methods on the long-term resiliency of MSCs within challenging transplant environments is not fully understood. Recent work in our lab has shown that palmitate, a saturated fatty acid elevated in the serum of patients with obesity, causes MSCs to convert from an immunosuppressive to an immunostimulatory state at moderate to high physiological levels. This demonstrated that metabolically-diseased environments, like obesity, alter the immunomodulatory efficacy of healthy donor MSCs. In addition, it highlighted the need to test MSC efficacy not only in ideal conditions, but within challenging metabolic environments. To determine how the choice of xeno- vs. xeno-free media during isolation and expansion would affect future immunosuppressive function, umbilical cord explants from seven donors were subdivided and cultured within xeno- (fetal bovine serum, FBS) or xeno-free (human platelet lysate, PLT) medias, creating 14 distinct MSC preparations. After isolation and primary expansion, umbilical cord MSCs (ucMSC) were evaluated according to the ISCT minimal criteria for MSCs. Following baseline characterization, ucMSC were exposed to physiological doses of palmitate and analyzed for metabolic health, apoptotic induction, and immunomodulatory potency in co-cultures with stimulated human peripheral blood mononuclear cells. The paired experimental design (each ucMSC donor grown in two distinct culture environments) allowed us to delineate the contribution of inherent (nature) vs. environmentally-driven (nurture) donor characteristics to the phenotypic response of ucMSC during palmitate exposure. Culturing MSCs in PLT-media led to more consistent growth characteristics during the isolation and expansion for all donors, resulting in faster doubling times and higher cell yields compared to FBS. Upon palmitate challenge, PLT-ucMSCs showed a higher susceptibility to palmitate-induced metabolic disturbance, but less susceptibility to palmitate-induced apoptosis. Most striking however, was that the PLT-ucMSCs resisted the conversion to an immunostimulatory phenotype better than their FBS counterparts. Interestingly, examining MSC suppression of PBMC proliferation at physiologic doses of palmitate magnified the differences between donors, highlighting the utility of evaluating MSC products in stress-based assays that reflect the challenges MSCs may encounter post-transplantation.

Cullin-5, a ubiquitin ligase scaffold protein, is significantly underexpressed in endometrial adenocarcinomas and is a target of miR-182.

Altered expression of cullin-5 (CUL5), a member of the cullin-RING E3 ubiquitin ligase family, has been implicated in a number of types of cancers including breast, cervical and hepatocellular cancers. In the present study, we found that CUL5 expression was significantly decreased in both endometrioid and serous endometrial adenocarcinomas with the more aggressive serous type displaying a higher reduction (-4.3-fold) than the less aggressive endometrioid type (-2.9-fold). Overexpression of CUL5 mRNA and protein in Ishikawa H endometrial cancer cells resulted in decreased cell proliferation and in a reduction in CUL5-RING E3 ligase downstream clients JAK2 and FAS-L. Finally, we demonstrated for the first time that CUL5 is a direct target of miR-182 that we previously showed to be significantly overexpressed in endometrial adenocarcinomas and we provided evidence that increased miR-182 expression is, at least in part, a result of demethylation of its upstream promoter. These data suggest a cascade in which miR-182 expression is epigenetically increased leading to decreased CUL5 expression and increased cellular proliferation. The final step in the cascade may be operating through a decrease in ubiquitination of pro-growth CUL5 ubiquitin ligase clients. This cascade offers a series of potential interventional steps involving epigenetic modification, miRNA and/or gene targeting and ubiquitination.

Dopaminergic Toxin 1-Methyl-4-Phenylpyridinium, Proteins α-Synuclein and Glia Maturation Factor Activate Mast Cells and Release Inflammatory Mediators.

Parkinson's disease (PD) is characterized by the presence of Lewy bodies and degeneration of dopaminergic neurons. 1-methyl-4-phenylpyridinium (MPP+), a metabolite of neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and Lewy body component α-synuclein activates glia in PD pathogenesis. Mast cells and glia maturation factor (GMF) are implicated in neuroinflammatory conditions including Multiple Sclerosis. However, the role of mast cells in PD is not yet known. We have analyzed the effect of recombinant GMF, MPP+, α-synuclein and interleukin-33 (IL-33) on mouse bone marrow-derived cultured mast cells (BMMCs), human umbilical cord blood-derived cultured mast cells (hCBMCs) and mouse brain-derived cultured astrocytes by quantifying cytokines/chemokines released using ELISA or by detecting the expression of co-stimulatory molecules CD40 and CD40L by flow cytometry. GMF significantly released chemokine (C-C motif) ligand 2 (CCL2) from BMMCs but its release was reduced in BMMCs from GMF knockout mice. GMF, α-synuclein and MPP+ released IL-1ß, ß-hexosaminidase from BMMCs, and IL-8 from hCBMCs. GMF released CCL5, and IL-33- induced the expression of GMF from hCBMCs. Novel GMF expression was detected in hCBMCs and BMMCs by immunocytochemistry. GMF released tumor necrosis factor-alpha (TNF-α) from mouse astrocytes, and this release was greater in BMMC- astrocyte coculture than in individual cultures. Flow cytometry results showed increased IL-33 expression by GMF and MPP+, and GMF-induced CD40 expression in astrocytes. Proinflammatory mediator release by GMF, MPP+ and α-synuclein, as well as GMF expression by mast cells indicate a potential therapeutic target for neurodegenerative diseases including PD.

FSH receptor (FSHR) expression in human extragonadal reproductive tissues and the developing placenta, and the impact of its deletion on pregnancy in mice.

Expression and function of the follicle-stimulating hormone receptor (FSHR) in females were long thought to be limited to the ovary. Here, however, we identify extragonadal FSHR in both the human female reproductive tract and the placenta, and test its physiological relevance in mice. We show that in nonpregnant women FSHR is present on: endothelial cells of blood vessels in the endometrium, myometrium, and cervix; endometrial glands of the proliferative and secretory endometrium; cervical glands and the cervical stroma; and (at low levels) stromal cells and muscle fibers of the myometrium. In pregnant women, placental FSHR was detected as early as 8-10 wk of gestation and continued through term. It was expressed on: endothelial cells in fetal portions of the placenta and the umbilical cord; epithelial cells of the amnion; decidualized cells surrounding the maternal arteries in the maternal decidua; and the stromal cells and muscle fibers of the myometrium, with particularly strong expression at term. These findings suggest that FSHR expression is upregulated during decidualization and upregulated in myometrium as a function of pregnancy. The presence of FSHR in the placental vasculature suggests a role in placental angiogenesis. Analysis of genetically modified mice in which Fshr is lacking in fetal portions of the placenta revealed adverse effects on fetoplacental development. Our data further demonstrate FSHB and CGA mRNAs in placenta and uterus, consistent with potential local sources of FSH. Collectively, our data suggest heretofore unappreciated roles of extragonadal FSHR in female reproductive physiology.

Vasopressin in preeclampsia: a novel very early human pregnancy biomarker and clinically relevant mouse model.

Preeclampsia, a cardiovascular disorder of late pregnancy, is characterized as a low-renin hypertensive state relative to normotensive pregnancy. Because other nonpregnant low-renin hypertensive disorders often exhibit and are occasionally dependent on elevated arginine vasopressin (AVP) secretion, we hypothesized a possible use for plasma AVP measurements in the prediction of preeclampsia. Copeptin is an inert prosegment of AVP that is secreted in a 1:1 molar ratio and exhibits a substantially longer biological half-life compared with AVP, rendering it a clinically useful biomarker of AVP secretion. Copeptin was measured throughout pregnancy in maternal plasma from preeclamptic and control women. Maternal plasma copeptin was significantly higher throughout preeclamptic pregnancies versus control pregnancies. While controlling for clinically significant confounders (age, body mass index, chronic essential hypertension, twin gestation, diabetes mellitus, and history of preeclampsia) using multivariate regression, the association of higher copeptin concentration and the development of preeclampsia remained significant. Receiver operating characteristic analyses reveal that as early as the sixth week of gestation, elevated maternal plasma copeptin concentration is a highly significant predictor of preeclampsia throughout pregnancy. Finally, chronic infusion of AVP during pregnancy (24 ng per hour) is sufficient to phenocopy preeclampsia in C57BL/6J mice, causing pregnancy-specific hypertension, renal glomerular endotheliosis, proteinuria, and intrauterine growth restriction. These data implicate AVP release as a novel predictive biomarker for preeclampsia very early in pregnancy, identify chronic AVP infusion as a novel and clinically relevant model of preeclampsia in mice, and are consistent with a potential causative role for AVP in preeclampsia in humans.

"Collection of a lifetime: a practical approach to developing a longitudinal collection of women's healthcare biological samples".

OBJECTIVE: The objective is to develop a biorepository of samples that represent all stages of a women's life. Importantly, our goal is to collect longitudinal physical specimens as well as the associated short and long-term clinical information. STUDY DESIGN: The Women's Health Tissue Repository was established to encompass four tissue banks: Well Women Tissue Bank, Reproductive Endocrinology and Infertility Tissue Bank, Maternal Fetal Tissue Bank, and the long-established Gynecologic Malignancies Tissue Bank. Based on their health status, women being seen in Women's Health at the University of Iowa are recruited to contribute samples and grant access to their electronic medical record to the biorepository. Samples are coded, processed, and stored for use by investigators. RESULTS: The Maternal Fetal Tissue Bank was the first expansion of our department's biobanking efforts. Approximately 75% of the women approached consent to participate in the Maternal Fetal Tissue Bank. Enrollment has steadily increased. Samples have been used for over 20 projects in the first 3 years and are critical to 7 funded grants and 3 patent applications. CONCLUSION: Patient samples with corresponding clinical data are initially important to women's health research. Our model demonstrates that many research projects by faculty, fellows, and residents have benefited from the existence of the Women's Health Tissue Repository. While challenging to achieve, longitudinal sampling allows for the greatest opportunity to study normal and pathological changes throughout all phases of a women's life, including pregnancy. This bank facilitates and accelerates the development of novel research, technologies, and possible therapeutic options in women's health. The establishment of more longitudinal biorepositories based on our model would enhance women's health research.

Placenta-specific protein 1: a potential key to many oncofetal-placental OB/GYN research questions.

Placenta-specific protein 1 (PLAC1) is a secreted protein found in trophoblasts. Several reports implicate a central role for PLAC1 in establishment and maintenance of the placenta. In addition to placentae PLAC1 is expressed in a variety of solids including breast, endometrial, and ovarian cancers. In order to show that PLAC1 is potentially relevant to a number of research questions in OB/GYN, we report on PLAC1 expression in a selected panel that includes two choriocarcinoma cell lines, normal placental tissues, and endometrial and ovarian tumors. We report for the first time that PLAC1 is also expressed in human fetal tissues. PLAC1 is transcriptionally heterogeneous with one promoter (P1) generating two transcripts with alternately spliced 5' UTRs and the other promoter (P2) generating a third transcript. Placental tissues favor P2 transcripts, while P1 is favored in most of the other cells. Mechanisms determining multiple PLAC1 transcripts and promoter preferences are as yet unknown, but it is clear that this protein is likely to be important in a variety of phenomena relevant to both gynecologic oncology and maternal-fetal medicine.

From molecules to medicine: a future cure for preeclampsia?

In the United States, preeclampsia (PreE) affects 5-7% of all pregnancies, yet represents 15% of all maternal-fetal morbidity and mortality. PreE causes fetal growth restriction, oligohydramnios, fetal death, and maternal seizures, stroke, cerebrovascular hemorrhage and death. It has immediate and potentially long-term effects on both the fetus and mother. To date, the molecular pathogenesis of PreE is largely unknown. Multiple pathways, including dysfunctional angiogenesis, inappropriate placentation, oxidative stress and an altered immunological milieu have been proposed as key players in the development of PreE. In addition, genetic factors in all of these pathways are essential components in the etiology of this disease. This review introduces the clinical presentation of PreE and its particular disease phenotype that has prompted some of the molecular investigations of its etiology. Evidence of the many molecular pathways involved in the pathogenesis of PreE, as well as the therapeutic investigations targeting these pathways, is presented.

Loss of MLL PHD finger 3 is necessary for MLL-ENL-induced hematopoietic stem cell immortalization.

Reciprocal chromosomal translocations at the MLL gene locus result in expression of novel fusion proteins, such as MLL-ENL, associated with leukemia. The three PHD finger cassette, one of the highly conserved domains in MLL, is absent in all fusion proteins. This domain has been shown to interact with Cyp33, a cyclophilin which enhances the recruitment of histone deacetylases (HDAC) to the MLL repression domain and mediates HOX gene repression. Insertion of the third PHD finger of MLL into MLL-ENL allows the recruitment of Cyp33 and, subsequently, HDAC1 to the fusion protein. Furthermore, expression of the fusion protein with the PHD finger insertion mediates the down-regulation of the HOXC8 gene expression in a Cyp33-dependent manner. Finally, the addition of the PHD finger domain or the third PHD finger alone into MLL-ENL blocks the hematopoietic stem cell immortalization potential of the fusion protein in serial plating colony assays. Insertion of only the first and second PHD fingers has no such effect. These data support the hypothesis that the binding of Cyp33 to the MLL third PHD finger switches the MLL function from transactivation to repression. In the immortalizing MLL fusion protein, the loss of the PHD fingers, in combination with the gain of the activation domain of ENL or of other partner proteins, makes the fusion protein a constitutive transactivator. This leads to constitutive overexpression of MLL target genes that block stem cell commitment and promote stem cell renewal, probably the first step in MLL-related leukemogenesis.

Bromodomain and histone acetyltransferase domain specificities control mixed lineage leukemia phenotype.

A critical unanswered question about mixed lineage leukemia (MLL) is how specific MLL fusion partners control leukemia phenotype. The MLL-cyclic AMP-responsive element binding protein-binding protein (CBP) fusion requires both the CBP bromodomain and histone acetyltransferase (HAT) domain for transformation and causes acute myelogenous leukemia (AML), often preceded by a myelodysplastic phase. We did domain-swapping experiments to define whether unique specificities of these CBP domains drive this specific MLL phenotype. Within MLL-CBP, we replaced the CBP bromodomain or HAT domain with P300/CBP-associated factor (P/CAF) or TAF(II)250 bromodomains or the P/CAF or GCN5 HAT domains. HAT, but not bromodomain, substitutions conferred enhanced proliferative capacity in vitro but lacked expression of myeloid cell surface markers normally seen with MLL-CBP. Mice reconstituted with domain-swapped hematopoietic progenitors developed different disease from those with MLL-CBP. This included development of lymphoid disease and lower frequency of the myelodysplastic phase in those mice developing AML. We conclude that both the CBP bromodomain and HAT domain play different but critical roles in determining the phenotype of MLL-CBP leukemia. Our results support an important role for MLL partner genes in determining the leukemia phenotype besides their necessity in leukemogenesis. Here, we find that subtleties in MLL fusion protein domain specificity direct cells toward a specific disease phenotype.

The MLL fusion gene, MLL-AF4, regulates cyclin-dependent kinase inhibitor CDKN1B (p27kip1) expression.

MLL, involved in many chromosomal translocations associated with acute myeloid and lymphoid leukemia, has >50 known partner genes with which it is able to form in-frame fusions. Characterizing important downstream target genes of MLL and of MLL fusion proteins may provide rational therapeutic strategies for the treatment of MLL-associated leukemia. We explored downstream target genes of the most prevalent MLL fusion protein, MLL-AF4. To this end, we developed inducible MLL-AF4 fusion cell lines in different backgrounds. Overexpression of MLL-AF4 does not lead to increased proliferation in either cell line, but rather, cell growth was slowed compared with similar cell lines inducibly expressing truncated MLL. We found that in the MLL-AF4-induced cell lines, the expression of the cyclin-dependent kinase inhibitor gene CDKN1B was dramatically changed at both the RNA and protein (p27kip1) levels. In contrast, the expression levels of CDKN1A (p21) and CDKN2A (p16) were unchanged. To explore whether CDKN1B might be a direct target of MLL and of MLL-AF4, we used chromatin immunoprecipitation (ChIP) assays and luciferase reporter gene assays. MLL-AF4 binds to the CDKN1B promoter in vivo and regulates CDKN1B promoter activity. Further, we confirmed CDKN1B promoter binding by ChIP in MLL-AF4 as well as in MLL-AF9 leukemia cell lines. Our results suggest that CDKN1B is a downstream target of MLL and of MLL-AF4, and that, depending on the background cell type, MLL-AF4 inhibits or activates CDKN1B expression. This finding may have implications in terms of leukemia stem cell resistance to chemotherapy in MLL-AF4 leukemias.