Archana Laknaur

Silencing Med12 Gene Reduces Proliferation of Human Leiomyoma Cells Mediated via Wnt/β-Catenin Signaling Pathway.

Uterine fibroids, or leiomyoma, are the most common benign tumors in women of reproductive age. In this work, the effect of silencing the mediator complex subunit 12 (Med12) gene in human uterine fibroid cells was evaluated. The role of Med12 in the modulation of Wnt/β-catenin and cell proliferation-associated signaling was evaluated in human uterine fibroid cells. Med12 was silenced in the immortalized human uterine fibroid cell line (HuLM) using a lentivirus-based Med12 gene-specific RNA interference strategy. HuLM cells were infected with lentiviruses carrying Med12-specific short hairpin RNA (shRNA) sequences or a nonfunctional shRNA scrambled control with green fluorescence protein. Stable cells that expressed low levels of Med12 protein were characterized. Wnt/β-catenin signaling, sex steroid receptor signaling, cell cycle-associated, and fibrosis-associated proteins were measured. Med12 knockdown cells showed significantly (P < 0.05) reduced levels of Wnt4 and β-catenin proteins as well as cell proliferation, as compared with scrambled control cells. Med12 knockdown cells also showed reduced levels of cell cycle-associated cyclin D1, Cdk1, and Cdk2 proteins as well as reduced activation of p-extracellular signal-regulated kinase, p-protein kinase B, and transforming growth factor (TGF)-β signaling pathways as compared with scrambled control cells. Moreover, TGF-β-regulated fibrosis-related proteins such as fibronectin, collagen type 1, and plasminogen activator inhibitor-1 were significantly (P < 0.05) reduced in Med12 knockdown cells as compared with scrambled control cells. Together, these results suggest that Med12 plays a key role in the regulation of HuLM cell proliferation through the modulation of Wnt/β-catenin, cell cycle-associated, and fibrosis-associated protein expression.

The Polycomb Group Protein EZH2 Impairs DNA Damage Repair Gene Expression in Human Uterine Fibroids

ABSTRACT Uterine fibroids are benign, smooth muscle tumors that occur in approximately 70%–80% of women by age 50 yr. The cellular and molecular mechanism(s) by which uterine fibroids (UFs) develop are not fully understood. Accumulating evidence demonstrates that several genetic abnormalities, including deletions, rearrangements, translocations, as well as mutations, have been found in UFs. These genetic anomalies suggest that low DNA damage repair capacity may be involved in UF formation. The objective of this study was to determine whether expression levels of DNA damage repair-related genes were altered, and how they were regulated in the pathogenesis of UFs. Expression levels of DNA repair-related genes RAD51 and BRCA1 were deregulated in fibroid tissues as compared to adjacent myometrial tissues. Expression levels of chromatin protein enhancer of zeste homolog 2 (EZH2) were higher in a subset of fibroids as compared to adjacent myometrial tissues by both immunohistochemistry and Western blot analysis. Treatment with an inhibitor of EZH2 markedly increased expression levels of RAD51 and BRCA1 in fibroid cells and inhibited cell proliferation paired with cell cycle arrest. Restoring the expression of RAD51 and BRCA1 by treatment with EZH2 inhibitor was dependent on reducing the enrichment of trimethylation of histone 3 lysine 27 epigenetic mark in their promoter regions. This study reveals the important role of EZH2-regulated DNA damage-repair genes via histone methylation in fibroid biology, and may provide novel therapeutic targets for the medical treatment of women with symptomatic UFs.

Identification of Polycomb Group Protein EZH2-Mediated DNA Mismatch Repair Gene MSH2 in Human Uterine Fibroids.

Uterine fibroids (UFs) are benign smooth muscle neoplasms affecting up to 70% of reproductive age women. Treatment of symptomatic UFs places a significant economic burden on the US health-care system. Several specific genetic abnormalities have been described as etiologic factors of UFs, suggesting that a low DNA damage repair capacity may be involved in the formation of UF. In this study, we used human fibroid and adjacent myometrial tissues, as well as an in vitro cell culture model, to evaluate the expression of MutS homolog 2 (MSH2), which encodes a protein belongs to the mismatch repair system. In addition, we deciphered the mechanism by which polycomb repressive complex 2 protein, EZH2, deregulates MSH2 in UFs. The RNA expression analysis demonstrated the deregulation of MSH2 expression in UF tissues in comparison to its adjacent myometrium. Notably, protein levels of MSH2 were upregulated in 90% of fibroid tissues (9 of 10) as compared to matched adjacent myometrial tissues. Human fibroid primary cells treated with 3-deazaneplanocin A (DZNep), chemical inhibitor of EZH2, exhibited a significant increase in MSH2 expression (P < .05). Overexpression of EZH2 using an adenoviral vector approach significantly downregulated the expression of MSH2 (P < .05). Chromatin immunoprecipitation assay demonstrated that enrichment of H3K27me3 in promoter regions of MSH2 was significantly decreased in DZNep-treated fibroid cells as compared to vehicle control. These data suggest that EZH2-H3K27me3 regulatory mechanism dynamically changes the expression levels of DNA mismatch repair gene MSH2, through epigenetic mark H3K27me3. MSH2 may be considered as a marker for early detection of UFs.

Altered expression of histone deacetylases, inflammatory cytokines and contractile-associated factors in uterine myometrium of Long Evans rats gestationally exposed to benzo[a]pyrene

Etiology of preterm birth (PTB) is multifactorial; therefore, decreasing the incidence of PTB is a major challenge in the field of obstetrics. Epidemiological studies have reported an association between toxicants and PTB. However, there are no studies on the role of benzo[a]pyrene (BaP), an environmental toxicant, in the incidence of PTB. We first assessed the effects of BaP (150 and 300 µg kg–1 body weight) dosed via gavage from day 14 to 17 of pregnancy on gestation length in Long Evans rats. We further assessed the histopathology of the uterus, expression of inflammatory cytokines, contractile‐associated factors, histone deacetylases (HDACs) and NFқB‐p65 in myometrium collected on day 22 postpartum versus vehicle‐treated controls. In our study, rats exposed to BaP delivered prematurely (P < 0.05) compared to control. Hematoxylin and eosin staining of uterus showed squamous metaplasia, glandular and stromal hyperplasia in BaP‐exposed rats versus control. The concentrations of BaP metabolites measured by high‐pressure liquid chromatography were higher in uterine myometrium of BaP‐exposed rats while they were undetectable in controls. Quantitative real‐time polymerase chain reaction showed significant increases in mRNA expression of interleukin‐1β and ‐8, tumor necrosis factor‐α, connexin 43, cyclo‐oxygenase‐2 and prostaglandin F2α receptor as compared to controls (P < 0.05). Western blot analysis revealed that BaP exposure caused decreases in class I HDACs 1 and 3 and increases in class II HDAC 5, cyclo‐oxygenase‐2 and nuclear translocation of NFκB‐p65 relative to controls. Our results suggest that gestational exposure to BaP increases incidence of PTB through epigenetic changes that causes increases in the expression of contractile‐associated factors through the NFκB pathway. Copyright

Defective expression of ATG4D abrogates autophagy and promotes growth in human uterine fibroids

Uterine fibroids (UF) are the most common pelvic tumors in women of reproductive-age and they usually cause heavy menstrual bleeding, pain and infertility. Autophagy is a collection of processes that enables the cells to digest and recycle their cytoplasmic contents, such as toxic protein aggregates, defunct or disused organelles and invading microorganisms. Dysregulation in autophagy process were described in neoplasms; however, the contribution of autophagy to the pathogenesis of UF remains unknown. In this study, we demonstrate that autophagy is deregulated in human UF as evidenced by significant accumulation of autophagosome in human UF cells compared to normal myometrium cells. Analysis of the autophagy markers revealed an enhanced initiation of the autophagy in UF tissues compared to their adjacent myometrial tissues (MyoF). However, autophagosome maturation and flux was blocked in UF tissues, as marked by accumulation of LC3-B and P62 protein. This block was associated with defective expression of autophagy-related protein 4 (ATG4) in the UF tissues compared to MyoF in ~90% of patient samples. Silencing of ATG4D in normal human myometrial cells resulted in defective autophagy flux, enhanced cell proliferation and increased extracellular matrix production, which phenocopy UF cell line. This study indicates that impairment of autophagy flux secondary to defective expression of ATG4D expression is a new mechanistic aberration that contributes to UF pathogenesis. Targeting autophagy pathway could provide novel medical therapeutic approach for non-surgical treatment of UF.

Effects of Benzo(a)pyrene During Pregnancy

INTRODUCTION: Preterm birth is significantly higher in African Americans. They also have higher lifelong exposure to environmental toxins like benzo(a)pyrene, which has been reported to affect fetal growth. Initial studies from our laboratory showed that rats treated with benzo(a)pyrene deliver preterm. In addition, superarray suggested that benzo(a)pyrene regulates histone deacetylases in myometrium of treated rats. Because histone deacetylases have been reported to play a role in inflammation, we measured the histone deacetylases and contractile-associated factors in myometrium of rats treated with benzo(a)pyrene in this study. METHODS: Pregnant Long Evan rats were gavaged 150, 300, and 600 micrograms benzo(a)pyrene from day 14 to day 17 of pregnancy and euthanized after delivery. The uterus was dissected, endometrium removed, and myometrium was subjected to Western blot analysis using histone deacetylase, connexin 43, and cyclooxygenase-2 antibodies. RESULTS: Western blot analysis performed to assess the epigenetic changes demonstrated a significant (P<.05) decrease in histone deacetylase 1, 3, and 4 but not in 2, 5, and 6 in myometrium obtained from rats treated with benzo(a)pyrene. Western analysis of inflammatory marker, cyclooxygenase-2, and contractile-associated protein connexin 43 showed a significant (P<.05) decrease in myometrium of rats treated with benzo(a)pyrene compared with the control rats. CONCLUSIONS: Our results suggest that: 1) exposure to benzo(a)pyrene during pregnancy increases inflammatory and contractile proteins through downregulation of histone deacetylases; and 2) exposure to environmental toxins is a risk factor to preterm birth. However, additional studies are needed to assess the effects of histone deacetylase inhibitors as a therapeutic strategy to inhibit the deleterious effects of benzo(a)pyrene on pregnancy and fetal growth.