Mediator Subunit Med28 Is Essential for Mouse Peri-Implantation Development and Pluripotency

The multi-subunit mammalian Mediator complex acts as an integrator of transcriptional regulation by RNA Polymerase II, and has emerged as a master coordinator of development and cell fate determination. We previously identified the Mediator subunit, MED28, as a cytosolic binding partner of merlin, the Neurofibromatosis 2 (NF2) tumor suppressor, and thus MED28 is distinct in having a cytosolic role as an NF2 interacting protein as well as a nuclear role as a Mediator complex subunit. Although limited in vitro studies have been performed on MED28, its in vivo function remains unknown. Employing a knockout mouse model, we describe for the first time the requirement for Med28 in the developing mouse embryo. Med28-deficiency causes peri-implantation lethality resulting from the loss of pluripotency of the inner cell mass accompanied by reduced expression of key pluripotency transcription factors Oct4 and Nanog. Further, overexpression of Med28 in mouse embryonic fibroblasts enhances the efficiency of their reprogramming to pluripotency. Cre-mediated inactivation of Med28 in induced pluripotent stem cells shows that Med28 is required for their survival. Intriguingly, heterozygous loss of Med28 results in differentiation of induced pluripotent stem cells into extraembryonic trophectoderm and primitive endoderm lineages. Our findings document the essential role of Med28 in the developing embryo as well as in acquisition and maintenance of pluripotency during reprogramming.

Genomic landscapes of breast fibroepithelial tumors

Breast fibroepithelial tumors comprise a heterogeneous spectrum of pathological entities, from benign fibroadenomas to malignant phyllodes tumors. Although MED12 mutations have been frequently found in fibroadenomas and phyllodes tumors, the landscapes of genetic alterations across the fibroepithelial tumor spectrum remain unclear. Here, by performing exome sequencing of 22 phyllodes tumors followed by targeted sequencing of 100 breast fibroepithelial tumors, we observed three distinct somatic mutation patterns. First, we frequently observed MED12 and RARA mutations in both fibroadenomas and phyllodes tumors, emphasizing the importance of these mutations in fibroepithelial tumorigenesis. Second, phyllodes tumors exhibited mutations in FLNA, SETD2 and KMT2D, suggesting a role in driving phyllodes tumor development. Third, borderline and malignant phyllodes tumors harbored additional mutations in cancer-associated genes. RARA mutations exhibited clustering in the portion of the gene encoding the ligand-binding domain, functionally suppressed RARA-mediated transcriptional activation and enhanced RARA interactions with transcriptional co-repressors. This study provides insights into the molecular pathogenesis of breast fibroepithelial tumors, with potential clinical implications.

Role of vitamin D in uterine fibroid biology

OBJECTIVE

To provide a detailed summary of current scientific knowledge on uterine fibroids (leiomyomas) in vitro and in in vivo animal models, as well as to postulate the potential role of vitamin D3 as an effective, inexpensive, safe, long-term treatment option for uterine fibroids.

DESIGN

PubMed search articles were used to identify the most relevant studies on uterine fibroids, as well as effects of vitamin D3 on uterine fibroid cells and fibroid tumor growth in in vivo animal models.

SETTING

University research laboratory.

PATIENT(S)

Not applicable.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Not applicable.

RESULT(S)

Despite numerous publications available on uterine fibroids, information about the role that vitamin D3 plays in the regulation of uterine fibroids is limited. Most of the recent vitamin D3-related studies on uterine fibroids were published from our group. Recent studies have demonstrated that vitamin D deficiency plays a significant role in the development of uterine fibroids. Our recent studies have demonstrated that vitamin D3 reduces leiomyoma cell proliferation in vitro and leiomyoma tumor growth in in vivo animal models. These results postulate the potential role of vitamin D3 for an effective, safe, nonsurgical medical treatment option for uterine fibroids.

CONCLUSION(S)

This article reviews human and animal studies and uncovers new possibilities for understanding the vitamin D-based therapeutic option for an effective, safe, long-term treatment of uterine fibroids. On the basis of these results, a clinical trial with vitamin D3 or a hypocalcemic analog, paricalcitol, may be warranted for nonsurgical medical treatment of uterine fibroids.

Systematic analysis of gene expression pattern in has-miR-197 over-expressed human uterine leiomyoma cells

INTRODUCTION

Our previous study showed that the expression of miR-197 in leiomyoma was down-regulated compared with myometrium. Further, miR-197 has been identified to affect uterine leiomyoma cell proliferation, apoptosis, and metastasis ability, though the responsible molecular mechanism has not been well elucidated. In this study, we sought to determine the expression patterns of miR-197 targeted genes and to explore their potential functions, participating Pathways and the networks that are involved in the biological behavior of human uterine leiomyoma.

METHODS

After transfection of human uterine leiomyoma cells with miR-197, we confirmed the expression level of miR-197 using quantitative real-time PCR (qRT-PCR), and we detected the gene expression profiles after miR-197 over-expression through DNA microarray analysis. Further, we performed GO and Pathway analysis. The dominantly dys-regulated genes, which were up- or down-regulated by more than 10-fold, compared with parental cells, were confirmed using qRT-PCR technology.

RESULT

Compared with the control group, miR-197 was up-regulated by 30-fold after miR-197 lentiviral transfection. The microarray data showed that 872 genes were dys-regulated by more than 2-fold in human uterine leiomyoma cells after miR-197 overexpression, including 537 up-regulated and 335 down-regulated genes. The GO analysis indicated that the dys-regulated genes were primarily involved in response to stimuli, multicellular organ processes, and the signaling of biological progression. Further, Pathway analysis data showed that these genes participated in regulating several signaling Pathways, including the JAK/STAT signaling Pathway, the Toll-like receptor signaling Pathway, and cytokine-cytokine receptor interaction. The qRT-PCR results confirmed that 17 of the 66 selected genes, which were up- or down-regulated more than 10-fold by miR-197, were consistent with the microarray results, including tumorigenesis-related genes, such as DRT7, SLC549, SFMBT2, FLJ37956, FBLN2, C10orf35, HOXD12, CACNG7, and LOC100134279.

CONCLUSION

Our study explored gene expression patterns after miR-197 overexpression and confirmed 17 dominantly dys-regulated genes, which could expand the insights into the function of miR-197 and the molecular mechanisms during the development and progression of uterine leiomyomas. This study might afford new clues for understanding the pathogenesis of uterine leiomyomas, and it could likely provide a unique method for diagnosing or predicting prognosis in the clinical treatment of leiomyoma.

Mutational analysis of MED12 exon 2 in a spectrum of fibroepithelial tumours of the breast: implications for pathogenesis and histogenesis

AIMS

Fibroadenomas (FAs) and phyllodes tumours (PTs) are fibroepithelial tumours. Mutations in MED12 exon 2 have been reported in FAs. This study investigated the MED12 mutations in a spectrum of fibroepithelial tumours.

METHODS AND RESULTS

Using direct sequencing, we analysed MED12 exon 2 mutations on 121 samples, including PTs and FAs and variants. We found MED12 mutations in 71.4% of PTs. No significant difference in the mutation frequency was observed between benign, borderline and malignant PTs, and a general lack of correlation existed between mutations and pathological factors associated with PT grading. The mutation patterns were similar between PTs and FAs, with codon 44 being involved most frequently. MED12 mutations were identified in 47.1, 52.6 and 50.0% of complex FAs, juvenile FAs and tubular adenomas (TAs), respectively, and the frequency and mutation patterns were similar between these FA variants and usual FAs.

CONCLUSIONS

The high frequency and similar patterns of MED12 mutations in FAs and various grades of PTs implies that the MED12 mutation is a common and early pathological event in these fibroepithelial tumours. The similar frequency and patterns of the MED12 mutation between FAs and variants suggests that FA variants are bona fide FAs, with identical pathogenesis involving MED12 mutations.

Fine mapping of the uterine leiomyoma locus on 1q43 close to a lncRNA in the RGS7-FH interval

Mutations in fumarate hydratase (FH) on chromosome 1q43 cause a rare cancer syndrome, hereditary leiomyomatosis and renal cell cancer (HLRCC), but are rare in nonsyndromic and common uterine leiomyoma (UL) or fibroids. Studies suggested that variants in FH or in a linked gene may also predispose to UL. We re-sequenced 2.3 Mb of DNA spanning FH in 96 UL cases and controls from the multiethnic NIEHS-uterine fibroid study, and in 18 HLRCC-associated UL probands from European families then selected 221 informative SNPs for follow-up genotyping. We report promising susceptibility associations with UL peaking at rs78220092 (P=7.0×10(-5)) in the RGS7-FH interval in African Americans. In race-combined analyses and in meta-analyses (n=916), we identified promising associations with risk peaking upstream of a non-protein coding RNA (lncRNA) locus located in the RGS7-FH interval closer to RGS7, and associations with tumor size peaking in the distal phospholipase D family, member 5 (PLD5) gene at rs2654879 (P=1.7×10(-4)). We corroborated previously reported FH mutations in nine out of the 18 HLRCC-associated UL cases and identified two missense mutations in FH in only two nonsyndromic UL cases and one control. Our fine association mapping and integration of existing gene profiling data showing upregulated expression of the lncRNA and downregulation of PLD5 in fibroids, as compared to matched myometrium, suggest a potential role of this genomic region in UL pathogenesis. While the identified variations at 1q43 represent a potential risk locus for UL, future replication analyses are required to substantiate our observation.

Med12 gain-of-function mutation causes leiomyomas and genomic instability

Uterine leiomyomas are benign tumors that can cause pain, bleeding, and infertility in some women. Mediator complex subunit 12 (MED12) exon 2 variants are associated with uterine leiomyomas; however, the causality of MED12 variants, their genetic mode of action, and their role in genomic instability have not been established. Here, we generated a mouse model that conditionally expresses a Med12 missense variant (c.131G>A) in the uterus and demonstrated that this alteration alone promotes uterine leiomyoma formation and hyperplasia in both WT mice and animals harboring a uterine mesenchymal cell-specific Med12 deletion. Compared with WT animals, expression of Med12 c.131G>A in conditional Med12-KO mice resulted in earlier onset of leiomyoma lesions that were also greater in size. Moreover, leiomyomatous, Med12 c.131G>A variant-expressing uteri developed chromosomal rearrangements. Together, our results show that the common human leiomyoma-associated MED12 variant can cause leiomyomas in mice via a gain of function that drives genomic instability, which is frequently observed in human leiomyomas.

Mediator kinase module and human tumorigenesis

Mediator is a conserved multi-subunit signal processor through which regulatory informatiosn conveyed by gene-specific transcription factors is transduced to RNA Polymerase II (Pol II). In humans, MED13, MED12, CDK8 and Cyclin C (CycC) comprise a four-subunit "kinase" module that exists in variable association with a 26-subunit Mediator core. Genetic and biochemical studies have established the Mediator kinase module as a major ingress of developmental and oncogenic signaling through Mediator, and much of its function in signal-dependent gene regulation derives from its resident CDK8 kinase activity. For example, CDK8-targeted substrate phosphorylation impacts transcription factor half-life, Pol II activity and chromatin chemistry and functional status. Recent structural and biochemical studies have revealed a precise network of physical and functional subunit interactions required for proper kinase module activity. Accordingly, pathologic change in this activity through altered expression or mutation of constituent kinase module subunits can have profound consequences for altered signaling and tumor formation. Herein, we review the structural organization, biological function and oncogenic potential of the Mediator kinase module. We focus principally on tumor-associated alterations in kinase module subunits for which mechanistic relationships as opposed to strictly correlative associations are established. These considerations point to an emerging picture of the Mediator kinase module as an oncogenic unit, one in which pathogenic activation/deactivation through component change drives tumor formation through perturbation of signal-dependent gene regulation. It follows that therapeutic strategies to combat CDK8-driven tumors will involve targeted modulation of CDK8 activity or pharmacologic manipulation of dysregulated CDK8-dependent signaling pathways.

Evaluation of GWAS candidate susceptibility loci for uterine leiomyoma in the multi-ethnic NIEHS uterine fibroid study

We evaluated the association of 56 candidate SNPs identified in two published genome-wide association studies (GWAS) of uterine leiomyoma (UL), or fibroids, with the risk and tumor size in the multi-ethnic uterine fibroid study (NIEHS-UFS). The selected SNPs were genotyped in 916 premenopausal women of African American (AA) and European American (EA) descents and their association with the outcomes was evaluated in race-stratified models and in meta-analysis of risk in NIEHS-UFS and discovery and replication GWAS in the Japanese population. We report moderate associations of variant rs4954368 in THSD7B (thrombospondin, type I, domain containing 7B) with tumor size in pooled analysis of AA and EA samples (P = 0.004), and at TNRC6B (trinucleotide repeat containing 6B) variants rs138039 and rs139909 in EA (P = 0.001 and 0.008, respectively). The most significant associations with risk in meta-analysis were observed at TNRC6B variants rs739182 (P = 3.7 × 10(-10)) and rs2072858 (P = 1.1 × 10(-9)) and were stronger than those reported in the discovery GWAS (P = 2.01 × 10(-8) and 2.58 × 10(-8), respectively). The present study failed to replicate the associations reported for CCDC57 and FASN in a discovery GWAS in populations of European descent. Consistent with previous replication studies in the Right From the Start Study (RFTS) and the BioVU DNA repository, we provide independent evidence for association of TNRC6B with both risk and size of UL. The present study is the first to report a replicated association of THSD7B with UL, albeit with tumor size and not with risk.

Epidemiological and genetic clues for molecular mechanisms involved in uterine leiomyoma development and growth

BACKGROUND

Uterine leiomyomas (fibroids) are highly prevalent benign smooth muscle tumors of the uterus. In the USA, the lifetime risk for women developing uterine leiomyomas is estimated as up to 75%. Except for hysterectomy, most therapies or treatments often provide only partial or temporary relief and are not successful in every patient. There is a clear racial disparity in the disease; African-American women are estimated to be three times more likely to develop uterine leiomyomas and generally develop more severe symptoms. There is also familial clustering between first-degree relatives and twins, and multiple inherited syndromes in which fibroid development occurs. Leiomyomas have been described as clonal and hormonally regulated, but despite the healthcare burden imposed by the disease, the etiology of uterine leiomyomas remains largely unknown. The mechanisms involved in their growth are also essentially unknown, which has contributed to the slow progress in development of effective treatment options.

METHODS

A comprehensive PubMed search for and critical assessment of articles related to the epidemiological, biological and genetic clues for uterine leiomyoma development was performed. The individual functions of some of the best candidate genes are explained to provide more insight into their biological function and to interconnect and organize genes and pathways in one overarching figure that represents the current state of knowledge about uterine leiomyoma development and growth.

RESULTS

In this review, the widely recognized roles of estrogen and progesterone in uterine leiomyoma pathobiology on the basis of clinical and experimental data are presented. This is followed by fundamental aspects and concepts including the possible cellular origin of uterine fibroids. The central themes in the subsequent parts are cytogenetic aberrations in leiomyomas and the racial/ethnic disparities in uterine fibroid biology. Then, the attributes of various in vitro and in vivo, human syndrome, rodent xenograft, naturally mutant, and genetically modified models used to study possible molecular mechanisms of leiomyoma development and growth are described. Particular emphasis is placed on known links to fibrosis, hypertrophy, and hyperplasia and genes that are potentially important in these processes.

CONCLUSIONS

Menstrual cycle-related injury and repair and coinciding hormonal cycling appears to affect myometrial stem cells that, at a certain stage of fibroid development, often obtain cytogenetic aberrations and mutations of Mediator complex subunit 12 (MED12). Mammalian target of rapamycin (mTOR), a master regulator of proliferation, is activated in many of these tumors, possibly by mechanisms that are similar to some human fibrosis syndromes and/or by mutation of upstream tumor suppressor genes. Animal models of the disease support some of these dysregulated pathways in fibroid etiology or pathogenesis, but none are definitive. All of this suggests that there are likely several key mechanisms involved in the disease that, in addition to increasing the complexity of uterine fibroid pathobiology, offer possible approaches for patient-specific therapies. A final model that incorporates many of these reported mechanisms is presented with a discussion of their implications for leiomyoma clinical practice.

MED12 is frequently mutated in breast phyllodes tumours: a study of 112 cases

AIM

To determine the frequency of MED12 mutations in a series of 112 breast phyllodes tumours, and to correlate the findings with clinicopathological parameters and survival outcomes.

METHODS

Phyllodes tumours from the Department of Pathology, Singapore General Hospital, were classified into benign, borderline and malignant categories. Genomic DNA from formalin-fixed paraffin-embedded phyllodes tumours was extracted, purified and subjected to ultra-deep-targeted amplicon sequencing across exon 2 of the MED12 gene. Sequencing was performed on the Illumina MiSeq next-generation sequencing platform and bioinformatics analysis applied. Appropriate statistical analyses were carried out.

RESULTS

There were 66 benign, 32 borderline and 14 malignant tumours, with 43 (65.1%), 21 (65.6%) and 6 (42.8%) disclosing MED12 mutations (missense, splice site, indel), respectively. For 97 cases with available follow-up, there were 10 (10.3%) recurrences. Patients with phyllodes tumours that harboured MED12 mutations experienced improved disease-free survivals, with higher recurrence likelihood in those without MED12 mutations (HR 9.99, 95% CIs 1.55 to 64.42, p=0.015).

CONCLUSIONS

Similar to fibroadenomas, phyllodes tumours show a high frequency of MED12 mutations, affirming the close biological relationship between these fibroepithelial neoplasms.

MED12 somatic mutations in fibroadenomas and phyllodes tumours of the breast

AIMS

Somatic mutations in exon 2 of the mediator complex subunit 12 (MED12) gene have been identified in 60% of breast fibroadenomas (FAs). The aim of this study was to define whether phyllodes tumours (PTs) would harbour MED12 somatic mutations in a way akin to FAs.

METHODS AND RESULTS

A collection of 73 fibroepithelial tumours (including 26 FAs, 25 benign PTs, nine borderline PTs and 13 malignant PTs) from 64 patients was retrieved from the authors' institution. Sections from formalin-fixed paraffin-embedded (FFPE) blocks were microdissected to ensure an enrichment in neoplastic stromal elements of >70%. DNA samples extracted from tumour and matched normal tissues were subjected to Sanger sequencing of exon 2 of the MED12 gene. MED12 exon 2 somatic mutations, including 28 somatic single nucleotide variants and 19 insertions and deletions, were found in 65%, 88%, 78% and 8% of FAs, benign PTs, borderline PTs and malignant PTs, respectively. Malignant PTs harboured MED12 exon 2 somatic mutations significantly less frequently than FAs, benign and borderline PTs.

CONCLUSIONS

Although MED12 exon 2 somatic mutations probably constitute the driver genetic event of most FAs, benign and borderline PTs, our results suggest that the majority of malignant PTs may be driven by other genetic/epigenetic alterations.

Clonally related uterine leiomyomas are common and display branched tumor evolution

Uterine leiomyomas are extremely frequent benign smooth muscle tumors often presenting as multiple concurrent lesions and causing symptoms such as abnormal menstrual bleeding, abdominal pain and infertility. While most leiomyomas are believed to arise independently, a few studies have encountered separate lesions harboring identical genetic changes, suggesting a common clonal origin. To investigate the frequency of clonally related leiomyomas, genome-wide tools need to be utilized, and thus little is known about this phenomenon. Using MED12 sequencing and SNP arrays, we searched for clonally related uterine leiomyomas in a set of 103 tumors from 14 consecutive patients who entered hysterectomy owing to symptomatic lesions. Whole-genome sequencing was also utilized to study the genomic architecture of clonally related tumors. This revealed four patients to have two or more tumors that were clonally related, all of which lacked MED12 mutations. Furthermore, some tumors were composed of genetically distinct subclones, indicating a nonlinear, branched model of tumor evolution. DEPDC5 was discovered as a novel tumor suppressor gene playing a role in the progression of uterine leiomyomas. Perhaps counterintuitively—considering Knudson's two-hit hypothesis—a large shared deletion was followed by different truncating DEPDC5 mutations in four clonally related leiomyomas. This study provides insight into the intratumor heterogeneity of these tumors and suggests that a shared clonal origin is a common feature of leiomyomas that do not carry an MED12 mutation. These observations also offer one explanation to the common occurrence of multiple concurrent lesions.

Clinical practice. Uterine fibroids

A 47-year-old black woman has heavy menstrual bleeding and iron-deficiency anemia.She reports nocturia and urinary frequency. A colonoscopy is negative. Ultrasonography shows a modestly enlarged uterus with three uterine fibroids. She is not planning to become pregnant. How should this case be evaluated and managed?

MED12 mutation in patients with hysteromyoma

Mediator Complex Subunit 12 (MED12) is a subunit of the mediator complex, which is believed to regulate global, as well as gene-specific, transcription. It has been reported that MED12 is mutated at high frequency in hysteromyoma. Recent studies have also shown that MED12 presents with different mutation frequencies in hysteromyoma patients of different populations. However, there are few studies with regard to the MED12 gene mutation in hysteromyoma patients in the Chinese Han population. In the present study, the MED12 mutations of 171 patients with hysteromyoma were analyzed; the results showed that 93 patients exhibited different MED12 mutations, including 131G→T, 131G→A, 130G→A, 146C→T, 130G→A, 130G→C, 128A→C, 130G→T, 127Ins27, 118_132Del15, 117_134Del18, 131_148Del18 and 141_165Del15. The mutation frequency was similar to that found in individuals of African descent or individuals of other non-Caucasian ethnicities, and lower than that in the Finnish or North American populations. Further analysis of 141 patients whose hysteromyoma was measured showed that the mutation frequency of MED12 in patients with large hysteromyomas was significantly lower than that in those with small hysteromyomas. These results suggested that MED12 mutation was important in the development of hysteromyomas in the Chinese Han population and that the size of the hysteromyoma may negatively correlate with the mutation frequency of MED12. This study supplemented current information on MED12 mutations in different races and may aid in developing personalized diagnoses for patients with hysteromyoma in the future.

Signaling Pathways in Leiomyoma: Understanding Pathobiology and Implications for Therapy

Uterine leiomyomas are the most common tumors of the female genital tract, affecting 50% to 70% of females by the age of 50. Despite their prevalence and enormous medical and economic impact, no effective medical treatment is currently available. This is, in part, due to the poor understanding of their underlying pathobiology. Although they are thought to start as a clonal proliferation of a single myometrial smooth muscle cell, these early cytogenetic alterations are considered insufficient for tumor development and additional complex signaling pathway alterations are crucial. These include steroids, growth factors, transforming growth factor-beta (TGF-β)/Smad; wingless-type (Wnt)/β-catenin, retinoic acid, vitamin D, and peroxisome proliferator-activated receptor γ (PPARγ). An important finding is that several of these pathways converge in a summative way. For example, mitogen-activated protein kinase (MAPK) and Akt pathways seem to act as signal integrators, incorporating input from several signaling pathways, including growth factors, estrogen and vitamin D. This underlines the multifactorial origin and complex nature of these tumors. In this review, we aim to dissect these pathways and discuss their interconnections, aberrations and role in leiomyoma pathobiology. We also aim to identify potential targets for development of novel therapeutics.

MED12 exon 2 mutations in phyllodes tumors of the breast

Exon 2 of MED12, a subunit of the transcriptional mediator complex, has been frequently mutated in uterine leiomyomas and breast fibroadenomas; however, it has been rarely mutated in other tumors. Although the mutations were also found in uterine leiomyosarcomas, the frequency was significantly lower than in uterine leiomyomas. Here, we examined the MED12 mutation in phyllodes tumors, another biphasic tumor with epithelial and stromal components related to breast fibroadenomas. Mutations in MED12 exon 2 were analyzed in nine fibroadenomas and eleven phyllodes tumors via Sanger sequencing. A panel of cancer- and sarcoma-related genes was also analyzed using Ion Torrent next-generation sequencing. Six mutations in fibroadenomas, including those previously reported (6/9, 67%), and five mutations in phyllodes tumors (5/11, 45%) were observed. Three mutations in the phyllodes tumors were missense mutations at Gly44, which is common in uterine leiomyomas and breast fibroadenomas. In addition, two deletion mutations (in-frame c.133_144del12 and loss of splice acceptor c.100-68_137del106) were observed in the phyllodes tumors. No other recurrent mutation was observed with next-generation sequencing. Frequent mutations in MED12 exon 2 in the phyllodes tumors suggest that it may share genetic etiology with uterine leiomyoma, a subgroup of uterine leiomyosarcomas and breast fibroadenoma.

Frequent MED12 mutations in phyllodes tumours of the breast

BACKGROUND

Phyllodes tumours are rare fibroepithelial tumours of the breast, that include benign, borderline, and malignant lesions. Although the molecular basis of phyllodes tumours largely remains unknown, a recent exome study identified MED12 mutations as a sole recurrent genetic alteration in fibroadenoma, a common benign fibroepithelial tumour that shares some histological features with the phyllodes tumour.

METHODS

Forty-six phyllodes tumours and 58 fibroadenomas of the breast were analysed for MED12 mutations by using Sanger sequencing.

RESULTS

MED12 mutations were identified in 37 out of the 46 phyllodes tumours (80%). The prevalence of MED12 mutations was similar among benign (15/18, 83%), borderline (12/15, 80%), and malignant tumours (10/13, 77%). MED12 mutations were also identified in 36 of the 58 fibroadenomas (62%). The mutations were frequent among intracanalicular-type (24/32, 75%) and complex-type lesions (4/6, 67%), but were significantly less common among the pericanalicular-type lesions (8/20, 40%). A microdissection-based analysis showed that MED12 mutations were confined to the stromal components in both phyllodes tumours and fibroadenomas.

CONCLUSIONS

MED12 mutations were frequent among the phyllodes tumours of the breast, regardless of the tumour grade. Phyllodes tumours and fibroadenomas share, at least in part, a common genetic background.

Human uterine leiomyoma stem/progenitor cells expressing CD34 and CD49b initiate tumors in vivo

CONTEXT

Uterine leiomyoma is the most common benign tumor in reproductive-age women. Using a dye-exclusion technique, we previously identified a side population of leiomyoma cells exhibiting stem cell characteristics. However, unless mixed with mature myometrial cells, these leiomyoma side population cells did not survive or grow well in vitro or in vivo.

OBJECTIVE

The objective of this study was to identify cell surface markers to isolate leiomyoma stem/progenitor cells.

DESIGN

Real-time PCR screening was used to identify cell surface markers preferentially expressed in leiomyoma side population cells. In vitro colony-formation assay and in vivo tumor-regeneration assay were used to demonstrate functions of leiomyoma stem/progenitor cells.

RESULTS

We found significantly elevated CD49b and CD34 gene expression in side population cells compared with main population cells. Leiomyoma cells were sorted into three populations based on the expression of CD34 and CD49b: CD34(+)/CD49b(+), CD34(+)/CD49b(-), and CD34(-)/CD49b(-) cells, with the majority of the side population cells residing in the CD34(+)/CD49b(+) fraction. Of these populations, CD34(+)/CD49b(+) cells expressed the lowest levels of estrogen receptor-α, progesterone receptor, and α-smooth muscle actin, but the highest levels of KLF4, NANOG, SOX2, and OCT4, confirming their more undifferentiated status. The stemness of CD34(+)/CD49b(+) cells was also demonstrated by their strongest in vitro colony-formation capacity and in vivo tumor-regeneration ability.

CONCLUSIONS

CD34 and CD49b are cell surface markers that can be used to enrich a subpopulation of leiomyoma cells possessing stem/progenitor cell properties; this technique will accelerate efforts to develop new therapies for uterine leiomyoma.

Leiomyosarcoma with alternative lengthening of telomeres is associated with aggressive histologic features, loss of ATRX expression, and poor clinical outcome

Leiomyosarcoma is an aggressive soft tissue sarcoma with poor patient survival. Recently, it was shown that 53% to 62% of leiomyosarcomas use the alternative lengthening of telomeres (ALT) as their telomere maintenance mechanism. The molecular basis of this mechanism has not been elucidated. Studies of pancreatic neuroendocrine tumor have suggested that the inactivation of either α-thalassemia/mental retardation syndrome X-linked (ATRX) or death domain-associated (DAXX) protein is associated with the ALT phenotype. In this study, we sought to determine the clinicopathologic features of leiomyosarcoma with the ALT phenotype and the possible relationship between this phenotype and ATRX/DAXX expression. Telomerase reverse transcriptase gene (TERT) promoter mutation analysis was also performed. Ninety-two leiomyosarcomas derived from the uterus, retroperitoneum/intra-abdomen, and various other sites were analyzed. Telomere-specific fluorescence in situ hybridization revealed that 59% (51/86) of leiomyosarcomas had the ALT phenotype. Loss of ATRX expression was observed in 33% of the tumors (30/92), and all but 2 ATRX-deficient tumors were ALT positive. Both the ALT phenotype and loss of ATRX expression were associated with epithelioid/pleomorphic cell morphology, tumor necrosis, and poor differentiation. None of the 92 cases lost DAXX expression. No TERT promoter mutation was detected (n=39). For survival analysis, poor differentiation, high FNCLCC grade, tumor size, and ALT phenotype were correlated with poor overall survival in univariate analysis. Tumor size and ALT phenotype remained independent prognostic factors in multivariate analysis. We concluded that the ALT phenotype in the leiomyosarcoma is associated with aggressive histologic features, loss of ATRX expression, and poor clinical outcome.

High-resolution melting analysis of MED12 mutations in uterine leiomyomas in Chinese patients

OBJECTIVES

Somatic mutations in mediator complex subunit 12 (MED12) have emerged as a critical genetic change in the development of uterine leiomyomas. Studies, however, have focused largely on cohorts consisting of Caucasian patients. In this study, uterine leiomyomas from Chinese patients were examined for MED12 mutations. In addition, polymerase chain reaction (PCR)-based high-resolution melting analysis (HRMA) was compared with direct sequencing as a potentially more sensitive method for the detection of MED12 mutations.

METHODS

Tissue samples with the pathologies of uterine leiomyoma (n=181) and other endometrial diseases (n=157) were collected from Chinese patients at the Taizhou People's Hospital and Taizhou Polytechnic College (Taizhou City, China). Genomic DNA was prepared from all samples. Both PCR-based HRMA and PCR-based direct sequencing were used to detect MED12 mutations.

RESULTS

PCR-based HRMA and direct sequencing revealed MED12 mutations in 95/181 (52.5%) and 93/181 (51.4%) uterine leiomyomas, respectively. Nearly half of these mutations (46/93) were found in a single codon, codon 131. The coincidence rate between the two methods was 98.9% (179/181) so that no statistically significant difference was evident in the application of the methodologies (χ(2)=0.011, p=0.916). In addition, MED12 mutations were identified in 1/157 (4.17%) case of other endometrial pathologies by both methods.

CONCLUSIONS

MED12 mutations were closely associated with the development of uterine leiomyomas, as opposed to other uterine pathologies in Chinese patients, and PCR-based HRMA was found to be a reliable method for the detection of MED12 mutations.

The Mediator complex: a central integrator of transcription

The RNA polymerase II (Pol II) enzyme transcribes all protein-coding and most non-coding RNA genes and is globally regulated by Mediator - a large, conformationally flexible protein complex with a variable subunit composition (for example, a four-subunit cyclin-dependent kinase 8 module can reversibly associate with it). These biochemical characteristics are fundamentally important for Mediator's ability to control various processes that are important for transcription, including the organization of chromatin architecture and the regulation of Pol II pre-initiation, initiation, re-initiation, pausing and elongation. Although Mediator exists in all eukaryotes, a variety of Mediator functions seem to be specific to metazoans, which is indicative of more diverse regulatory requirements.

Novel KAT6B-KANSL1 fusion gene identified by RNA sequencing in retroperitoneal leiomyoma with t(10;17)(q22;q21)

Retroperitoneal leiomyoma is a rare type of benign smooth muscle tumor almost exclusively found in women and with histopathological features similar to uterine leiomyomas. The pathogenesis of retroperitoneal leiomyoma is unclear and next to nothing is known about the cytogenetics and molecular genetics of the tumor. Here we present the first cytogenetically analyzed retroperitoneal leiomyoma. It had a t(10;17)(q22;q21) as the sole chromosomal abnormality. Using RNA-Sequencing and the ‘grep’ command to search the fastq files of the sequence data we found that the translocation resulted in fusion of the genes KAT6B (10q22) with KANSL1 (17q21). RT-PCR together with direct (Sanger) sequencing verified the presence of a KAT6B-KANSL1 fusion transcript. No reciprocal KANSL1-KAT6B transcript was amplified suggesting that it was either absent or unexpressed. The KAT6B-KANSL1 fusion transcript consists of exons 1 to 3 of KAT6B and exons 11 to 15 of KANSL1, is 3667 bp long, has a 1398 bp long open reading frame, and codes for a 466 amino acid residue protein. The corresponding KAT6B-KANSL1 protein contains the NEMM domain (including the linker histone H1/H5, domain H15) of KAT6B and the PEHE domain of KANSL1. The function of the fusion protein might be regulation of transcription with an affinity for chromatin (linker histone H1/H5) and interaction with the HAT domain of KAT8 (PEHE domain). The tumor expressed HMGA2 and HMGA1 even though 12q14-15 and 6p looked normal by G-banding analysis. The tumor also expressed MED12 in the absence of exon 2 mutations. Overall, the data show that the examined retroperitoneal leiomyoma resembles a subset of uterine leiomyomas in terms of histology and genetics.

Endometriosis, leiomyoma and adenomyosis: the risk of gynecologic malignancy

The aim of this review article was to evaluate the relationship and the possible etiological mechanisms between endometriosis, leiomyoma (LM) and adenomyosis and gynecological cancers, such as ovarian and endometrial cancer and leiomyosarcoma (LMS). MEDLINE was searched for all articles written in the English literature from July 1966 to May 2013. Reports were collected systematically and all the references were also reviewed. Malignant transformation of gynecologic benign diseases such as endometriosis, adenomyosis and LM to ovarian and endometrial cancer remains unclear. Hormonal factors, inflammation, familial predisposition, genetic alterations, growth factors, diet, altered immune system, environmental factors and oxidative stress may be causative factors in carcinogenesis. Early menarche, low parity, late menopause and infertility have also been implicated in the pathogenesis of these cancers. Ovarian cancers and endometriosis have been shown to have common genetic alterations such as loss of heterozygosity (LOH), PTEN, p53, ARID1A mutations. MicroRNAs have also been implicated in malignant transformation. Inflammation releases proinflammatory cytokines, and activates tumor associated macrophages (TAMS) and nuclear factor kappa b (NF-KB) signaling pathways that promote genetic mutations and carcinogenesis. MED12 mutations in LM and smooth muscle tumors of undetermined malignant potential (STUMP) may contribute to malignant transformation to LMS. A hyperestrogenic state may be shared in common with pathogenesis of adenomyosis, LM and endometrial cancer. However, the effect of these benign gynecologic diseases on endometrial cancer should be studied in detail. This review study indicates that endometriosis, LM, adenomyosis may be associated with increased risk of gynecological cancers such as endometrial and ovarian cancers. The patients who have these gynecological benign diseases should be counseled about the future risks of developing cancer. Further studies are needed to investigate the relationship between STUMPs, LMS and LM and characteristics and outcome endometrial carcinoma in adenomyotic patients.

Next-Gen Sequencing Exposes Frequent MED12 Mutations and Actionable Therapeutic Targets in Phyllodes Tumors

Phyllodes tumors are rare fibroepithelial tumors with variable clinical behavior accounting for a small subset of all breast neoplasms, yet little is known about the genetic alterations that drive tumor initiation and/or progression. Here, targeted next-generation sequencing (NGS) was used to identify somatic alterations in formalin-fixed paraffin-embedded (FFPE) patient specimens from malignant, borderline, and benign cases. NGS revealed mutations in mediator complex subunit 12 (MED12) affecting the G44 hotspot residue in the majority (67%) of cases spanning all three histologic grades. In addition, loss-of-function mutations in p53 (TP53) as well as deleterious mutations in the tumor suppressors retinoblastoma (RB1) and neurofibromin 1 (NF1) were identified exclusively in malignant tumors. High-level copy-number alterations (CNA) were nearly exclusively confined to malignant tumors, including potentially clinically actionable gene amplifications in IGF1R and EGFR. Taken together, this study defines the genomic landscape underlying phyllodes tumor development, suggests potential molecular correlates to histologic grade, expands the spectrum of human tumors with frequent recurrent MED12 mutations, and identifies IGF1R and EGFR as potential therapeutic targets in malignant cases.

IMPLICATIONS

Integrated genomic sequencing and mutational profiling provides insight into the molecular origin of phyllodes tumors and indicates potential druggable targets in malignant disease. Visual Overview: http://mcr.aacrjournals.org/content/early/2015/04/02/1541-7786.MCR-14-0578/F1.large.jpg.

Overexpression of the truncated form of High Mobility Group A proteins (HMGA2) in human myometrial cells induces leiomyoma-like tissue formation

The pathogenesis of uterine leiomyomas, the most common benign tumor in women, is still unknown. This lack of basic knowledge limits the development of novel non-invasive therapies. Our group has previously demonstrated that leiomyoma side population (SP) cells are present in tumor lesions and act like putative tumor-initiating stem cells in human leiomyoma. Moreover, accumulated evidence demonstrates that these benign tumors of mesenchymal origin are characterized by rearrangements of the High Mobility Group A proteins (HMGA). In this work, we tested the hypothesis that leiomyoma development may be due to overexpression of HMGA2 (encoding high mobility group AT-hook2) in myometrial stem cells using in vitro and in vivo approaches. Our work demonstrates that the truncated/short form of HMGA2 induces myometrial cell transformation toward putative tumor-initiating leiomyoma cells and opens up new possibilities to understand the origin of leiomyomas and the development of new therapeutic approaches.

Quantitative proteome profiling of human myoma and myometrium tissue reveals kinase expression signatures with potential for therapeutic intervention

Uterine leiomyomas are benign tumors affecting a large proportion of the female population. Despite the very high prevalence, the molecular basis for understanding the onset and development of the disease are still poorly understood. In this study, we profiled the proteomes and kinomes of leiomyoma as well as myometrium samples from patients to a depth of >7000 proteins including 200 kinases. Statistical analysis identified a number of molecular signatures distinguishing healthy from diseased tissue. Among these, nine kinases (ADCK4, CDK5, CSNK2B, DDR1, EPHB1, MAP2K2, PRKCB, PRKG1, and RPS6KA5) representing a number of cellular signaling pathways showed particularly strong discrimination potential. Preliminary statistical analysis by receiver operator characteristics plots revealed very good performance for individual kinases (area under the curve, AUC of 0.70-0.94) as well as binary combinations thereof (AUC 0.70-1.00) that might be used to assess the activity of signaling pathways in myomas. Of note, the receptor tyrosine kinase DDR1 holds future potential as a drug target owing to its strong links to collagen signaling and the excessive formation of extracellular matrix typical for leiomyomas in humans.

Cytogenetically normal uterine leiomyomas without MED12-mutations - a source to identify unknown mechanisms of the development of uterine smooth muscle tumors

Background

Recent findings on genetic changes in uterine leiomyomas suggest these benign tumors being a heterogeneous group of diseases in terms of molecular pathogenesis with those showing karyotype alterations as well as those characterized only by cytogenetically invisible mutations of mediator subcomplex 12 (MED12). Herein, five uterine leiomyomas (UL) with an apparently normal karyotype that lacked MED12-mutations were investigated by copy number variation arrays along with their matching myometrium to search for small genomic imbalances.

Results

Of five tumors one showed chromothripsis-like phenomena with numerous gains and losses of small segments mainly clustered to five chromosomal regions i.e. 2p14-2pter, 2q33.1-2q37.3, 5q31.3-5qter,11q14.1-11qter, and 18p11.21-18q2.3. Apparently, these cells had escaped detection by classical cytogenetics. Histologically, the tumor presented as a cellular leiomyoma with extended hyalinization. Of the remaining four tumors, one had a small intragenic deletion of the HMGA2 gene that was lacking in the corresponding myometrium. The other three tumors did not show relevant copy number alterations at all.

Conclusions

Overall, the results suggest that leiomyomas with an apparently normal karyotype based on classical cytogenetics and lacking MED12 mutations represent a heterogeneous group of diseases. While the HMGA2 deletion detected in one of the tumors likely represents the driver mutation and, due to its size, has escaped detection by classical cytogenetics, the extended genomic imbalances detected in one of the other cases cannot be overlooked by this method suggesting an inability of the affected cells to divide in vitro. Of particular interest in that case is the occurrence of so-called “chromothripsis” or “firestorms” without involvement of the loci of common chromosomal rearrangements in UL, as e.g. 12q14 ~ 15 and 6p21. While chromothripsis was initially described as a hallmark of malignancy, the etiology and significance of this phenomenon in benign tumors still remain obscure. In uterine smooth muscle tumors, these changes per se do not indicate malignancy.

Follow-up to genome-wide linkage and admixture mapping studies implicates components of the extracellular matrix in susceptibility to and size of uterine fibroids

OBJECTIVE

To conduct a follow-up association mapping to independent genome-wide linkage and admixture mapping studies of uterine leiomyoma.

DESIGN

Case-control, cross-sectional study.

SETTING

Not applicable.

PATIENT(S)

A total of 1,045 premenopausal North American participants in the National Institute of Environmental Health Sciences Uterine Fibroid Study.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

We genotyped 2,772 single-nucleotide polymorphisms from candidate genes located in peaks of linkage (2q37, 3p21, 5p13, 10p11, 11p15, 12q14, and 17q25) or admixture linkage disequilibrium (2q37, 4p16.1, and 10q26) mapping and reported to have regulated expression in uterine fibroids.

RESULT(S)

We report significant associations of variant members of the collagen gene family with risk and tumor size, including missense variants in COL6A3 and COL13A, with replications in African American and European American study groups. Furthermore, the cell-matrix Rho GTPase-encoding ARHGAP26 gene, and MAN1C1, a gene encoding a Golgi mannosidase involved in the maturation of procollagens, emerged as new candidate uterine leiomyoma genes affecting both risk and tumor size.

CONCLUSION(S)

Our data converge onto a possible model of uterine leiomyoma pathogenesis resulting from altered regulation, maintenance, and/or renewal of the extracellular matrix.

Tissue-specific stem cells in the myometrium and tumor-initiating cells in leiomyoma

Tissue-specific (or somatic) stem cells constitute a subset of cells residing in normal adult tissues. By undergoing asymmetric division, they retain their ability to self-renew while producing daughter cells that go on to differentiate and play a role in tissue regeneration and repair. The human uterus consists primarily of endometrium and myometrium (the smooth muscle layer) that rapidly enlarges through its tremendous regenerative and remodeling capacity to accommodate the developing fetus. Such uterine enlargement and remodeling can take place repeatedly and cyclically over the course of a woman's reproductive life. These unique properties of the uterus suggest the existence of endometrial and myometrial stem cell systems. In addition, like somatic cells, tumor stem cells or tumor-initiating cells, a subset of cells within a tumor, retain the ability to reconstitute tumors. Uterine smooth muscle cells are thought to be the origin of leiomyomas that are the most common type of gynecologic tumor. Recent work has identified, isolated, and characterized putative stem/progenitor cells in the myometrium and in leiomyomas. Here, we review current studies of myometrial and leiomyoma stem/progenitor cells and provide a new paradigm for understanding myometrial physiology and pathology and how these cells might contribute to uterine remodeling during pregnancy and the formation of leiomyomas. The role of the WNT/CTNNB1 pathway in the pathogenesis of leiomyoma is also discussed.

5-Hydroxymethylcytosine promotes proliferation of human uterine leiomyoma: a biological link to a new epigenetic modification in benign tumors

CONTEXT

Uterine leiomyoma, or fibroids, represent the most common benign tumors of the female reproductive tract. A newly discovered epigenetic modification, 5-hydroxymethylation (5-hmC), and its regulators, the TET (Ten Eleven Translocation) enzymes, were implicated in the pathology of malignant tumors; however, their roles in benign tumors, including uterine fibroids, remain unknown.

OBJECTIVE

To determine the role of 5-hmC and TET proteins in the pathogenesis of leiomyoma using human uterine leiomyoma and normal matched myometrial tissues and primary cells.

DESIGN

5-hmC levels were determined by ELISA and immunofluorescent staining in matched myometrial and leiomyoma tissues. TET expression was analyzed by quantitative RT-PCR and immunoblotting. TET1 or TET3 were silenced or inhibited by small interfering RNA or 2-hydroxyglutarate to study their effects on 5-hmC content and cell proliferation.

RESULTS

We demonstrated significantly higher 5-hmC levels in the genomic DNA of leiomyoma tissue compared to normal myometrial tissue. The increase in 5-hmC levels was associated with the up-regulation of TET1 or TET3 mRNA and protein expression in leiomyoma tissue. TET1 or TET3 knockdown significantly reduced 5-hmC levels in leiomyoma cells and decreased cell proliferation. Treatment with 2-hydroxyglutarate, a competitive TET enzyme inhibitor, significantly decreased both 5-hmC content and cell proliferation of leiomyoma cells.

CONCLUSION

An epigenetic imbalance in the 5-hmC content of leiomyoma tissue, caused by up-regulation of the TET1 and TET3 enzymes, might lead to discovery of new therapeutic targets in leiomyoma.

Minimally invasive surgical techniques versus open myomectomy for uterine fibroids

BACKGROUND

Fibroids are common benign tumours arising in the uterus. Myomectomy is the surgical treatment of choice for women with symptomatic fibroids who prefer or want uterine conservation. Myomectomy can be performed by conventional laparotomy, by mini-laparotomy or by minimal access techniques such as hysteroscopy and laparoscopy.

OBJECTIVES

To determine the benefits and harms of laparoscopic or hysteroscopic myomectomy compared with open myomectomy.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (inception to July 2014), the Menstrual Disorders and Subfertility Group (MDSG) Specialised Register of Controlled Trials (inception to July 2014), MEDLINE(R) (inception to July 2014), EMBASE (inception to July 2014), PsycINFO (inception to July 2014) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (inception to July 2014) to identify relevant randomised controlled trials (RCTs). We also searched trial registers and references from selected relevant trials and review articles. We applied no language restriction in these searches.

SELECTION CRITERIA

All published and unpublished randomised controlled trials comparing myomectomy via laparotomy, mini-laparotomy or laparoscopically assisted mini-laparotomy versus laparoscopy or hysteroscopy in premenopausal women with uterine fibroids diagnosed by clinical and ultrasound examination were included in the meta-analysis.

DATA COLLECTION AND ANALYSIS

We conducted study selection and extracted data in duplicate. Primary outcomes were postoperative pain, reported in six studies, and in-hospital adverse events, reported in eight studies. Secondary outcomes included length of hospital stay, reported in four studies, operating time, reported in eight studies and recurrence of fibroids, reported in three studies. Each of the other secondary outcomes-improvement in menstrual symptoms, change in quality of life, repeat myomectomy and hysterectomy at a later date-was reported in a single study. Odds ratios (ORs), mean differences (MDs) and 95% confidence intervals (CIs) were calculated and data combined using the fixed-effect model. The quality of evidence was assessed using Grades of Recommendation, Assessment, Development and Evaluation (GRADE) methods.

MAIN RESULTS

We found 23 potentially relevant trials, of which nine were eligible for inclusion in this review. The nine trials included in our meta-analysis had a total of 808 women. The overall risk of bias of included studies was low, as most studies properly reported their methods.Postoperative pain: Postoperative pain was measured on a visual analogue scale (VAS), with zero meaning 'no pain at all' and 10 signifying 'pain as bad as it could be.' Postoperative pain was significantly less, as determined by subjectively assessed pain score at six hours (MD -2.40, 95% CI -2.88 to -1.92, one study, 148 women, moderate-quality evidence) and 48 hours postoperatively (MD -1.90, 95% CI -2.80 to -1.00, two studies, 80 women, I² = 0%, moderate-quality evidence) in the laparoscopic myomectomy group compared with the open myomectomy group. This means that among women undergoing laparoscopic myomectomy, mean pain score at six hours and 48 hours would be likely to range from about three points lower to one point lower on a VAS zero-to-10 scale. No significant difference in postoperative pain score was noted between the laparoscopic and open myomectomy groups at 24 hours (MD -0.29, 95% CI -0.7 to 0.12, four studies, 232 women, I² = 43%, moderate-quality evidence). The overall quality of these findings is moderate; therefore further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.In-hospital adverse events: No evidence suggested a difference in unscheduled return to theatre (OR 3.04, 95% CI 0.12 to 75.86, two studies, 188 women, I² = 0%, low-quality evidence) and laparoconversion (OR 1.11, 95% CI 0.44 to 2.83, eight studies, 756 women, I² = 53%, moderate-quality evidence) when open myomectomy was compared with laparoscopic myomectomy. Only one study including 148 women reported injury to pelvic organs (no events were described in other studies), and no significant difference was noted between laparoscopic myomectomy and laparoscopically assisted mini-laparotomy myomectomy (OR 3.04, 95% CI 0.12 to 75.86). Significantly lower risk of postoperative fever was observed in the laparoscopic myomectomy group compared with groups treated with all types of open myomectomy (OR 0.44, 95% CI 0.26 to 0.77, I² = 0%, six studies, 635 women). This indicates that among women undergoing laparoscopic myomectomy, the risk of postoperative fever is 50% lower than among those treated with open surgery. No studies reported immediate hysterectomy, uterine rupture, thromboembolism or mortality. Six studies including 549 women reported haemoglobin drop, but these studies were not pooled because of extreme heterogeneity (I² = 97%) and therefore could not be included in the analysis.

AUTHORS' CONCLUSIONS

Laparoscopic myomectomy is a procedure associated with less subjectively reported postoperative pain, lower postoperative fever and shorter hospital stay compared with all types of open myomectomy. No evidence suggested a difference in recurrence risk between laparoscopic and open myomectomy. More studies are needed to assess rates of uterine rupture, occurrence of thromboembolism, need for repeat myomectomy and hysterectomy at a later stage.

Novel MED12 gene somatic mutations in women from the Southern United States with symptomatic uterine fibroids

Although somatic mutations in exon 2 of the mediator complex subunit 12 (MED12) gene have been reported previously in uterine fibroids in women from Finland, South Africa, and North America, the status of these mutations was not reported in the Southern United States women. The aim of this study is to determine the MED12 somatic mutations in uterine fibroids of women from Southern Unites States, which will help to better understand the contribution of MED12 mutations in fibroid tumor biology. Herein, we determined the frequency of MED12 gene exon 2 somatic mutations in 143 fibroid tumors from a total of 135 women from the Southern United States and in 50 samples of the adjacent myometrium using PCR amplification and Sanger sequencing. We observed that the MED12 gene is mutated in 64.33 % (92/143) of uterine fibroid cases in the exon 2 (including deletion mutations). These mutations include 107T > G (4.3 %), 130G > C (2.8 %), 130G > A (7.0 %), 130G > T (2.8 %), 131G > C (2.1 %), 131G > A (20.2 %), and 131G > T (2.1 %). Interestingly, we identified four novel mutations in these patients: 107 T > C (12.8 %), 105A > T (2.1 %), 122T > A (2.1 %), and 92T > A (2.1 %). As expected, we did not observe any mutations in the normal myometrium. Moreover, we found a higher rate of deletion mutations (17.5 %, 25/143) in the above fibroid tumors. Our results clearly demonstrate that the MED12 gene exon 2 is frequently mutated in human uterine fibroids in Southern United States women. These results highlight the molecular pathogenesis of human uterine fibroids with the central role of MED12 somatic mutations.

Molecular analyses of 6 different types of uterine smooth muscle tumors: Emphasis in atypical leiomyoma

BACKGROUND

Uterine smooth muscle tumors (USMTs) constitute a group of histologic, genetic, and clinical heterogeneous tumors that include at least 6 major histologically defined tumor types: leiomyoma (ULM), mitotically active leiomyoma (MALM), cellular leiomyoma (CLM), atypical leiomyoma (ALM), uncertain malignant potential (STUMP), and leiomyosarcoma (LMS). Apart from ULM and LMS, the nature of these variants is not well defined.

METHODS

A total of 167 cases of different USMT variants were collected, reviewed, and diagnostically confirmed based on the World Health Organization and Stanford schemes. These included 38 cases of LMS, 18 cases of STUMP, 42 cases of ALM, 22 cases of CLM, 7 cases of MALM, and 40 cases of ULM. Molecular analysis included selected microRNAs (miRNAs), oncogenes, and tumor suppressors that are highly relevant to USMT.

RESULTS

Overall, 49% (17/35) of LMS cases and 7% (1/14) of STUMP cases died due to their USMT, but no deaths were attributed to ALM. miRNA profiling revealed that ALM and LMS shared similar miRNA signatures. P53 mutations and PTEN deletions were significantly higher in LMS, ALM, and STUMP compared with other USMT variants (P < .01). In contrast, MED12 mutations were extremely common in ULM and MALM (> 74%) but were significantly less common (< 15%) in CLM, ALM, STUMP, and LMS (P < .01).

CONCLUSION

Six types of USMT have different gene mutation fingerprints. ALM shares many molecular alterations with LMS. Our findings suggest that ALM may be a precursor lesion of LMS or have similar genetic changes during its early stage.

A role for versican in the development of leiomyosarcoma

Leiomyosarcoma (LMS) is a mesenchymal cancer that occurs throughout the body. Although LMS is easily recognized histopathologically, the cause of the disease remains unknown. Versican, an extracellular matrix proteoglycan, increases in LMS. Microarray analyses of 80 LMSs and 24 leiomyomas showed a significant elevated expression of versican in human LMS versus benign leiomyomas. To explore the importance of versican in this smooth muscle cell tumor, we used versican-directed siRNA to knock down versican expression in a LMS human cell line, SK-LMS-1. Decreased versican expression was accompanied by slower rates of LMS cell proliferation and migration, increased adhesion, and decreased accumulation of the extracellular matrix macromolecule hyaluronan. Addition of purified versican to cells expressing versican siRNA restored cell proliferation to the level of LMS controls, increased the pericellular coat and the retention of hyaluronan, and decreased cell adhesion in a dose-dependent manner. The presence of versican was not only synergistic with hyaluronan in increasing cell proliferation, but the depletion of versican decreased hyaluronan synthase expression and decreased the retention of hyaluronan. When LMS cells stably expressing versican siRNA were injected into nude mice, the resulting tumors displayed significantly less versican and hyaluronan staining, had lower volumes, and had reduced levels of mitosis as compared with controls. Collectively, these results suggest a role for using versican as a point of control in the management and treatment of LMS.

Enhancer alterations in cancer: a source for a cell identity crisis

Enhancers are selectively utilized to orchestrate gene expression programs that first govern pluripotency and then proceed to highly specialized programs required for the process of cellular differentiation. Whereas gene-proximal promoters are typically active across numerous cell types, distal enhancer activation is cell-type-specific and central to cell fate determination, thereby accounting for cell identity. Recent studies have highlighted the diversity of enhancer usage, cataloguing millions of such elements in the human genome. The disruption of enhancer activity, through genetic or epigenetic alterations, can impact cell-type-specific functions, resulting in a wide range of pathologies. In cancer, these alterations can promote a 'cell identity crisis', in which enhancers associated with oncogenes and multipotentiality are activated, while those promoting cell fate commitment are inactivated. Overall, these alterations favor an undifferentiated cellular phenotype. Here, we review the current knowledge regarding the role of enhancers in normal cell function, and discuss how genetic and epigenetic changes in enhancer elements potentiate oncogenesis. In addition, we discuss how understanding the mechanisms regulating enhancer activity can inform therapeutic opportunities in cancer cells and highlight key challenges that remain in understanding enhancer biology as it relates to oncology.

Molecular pathways and targets in prostate cancer

Prostate cancer co-opts a unique set of cellular pathways in its initiation and progression. The heterogeneity of prostate cancers is evident at earlier stages, and has led to rigorous efforts to stratify the localized prostate cancers, so that progression to advanced stages could be predicted based upon salient features of the early disease. The deregulated androgen receptor signaling is undeniably most important in the progression of the majority of prostate tumors. It is perhaps because of the primacy of the androgen receptor governed transcriptional program in prostate epithelium cells that once this program is corrupted, the consequences of the ensuing changes in activity are pleotropic and could contribute to malignancy in multiple ways. Following localized surgical and radiation therapies, 20-40% of patients will relapse and progress, and will be treated with androgen deprivation therapies. The successful development of the new agents that inhibit androgen signaling has changed the progression free survival in hormone resistant disease, but this has not changed the almost ubiquitous development of truly resistant phenotypes in advanced prostate cancer. This review summarizes the current understanding of the molecular pathways involved in localized and metastatic prostate cancer, with an emphasis on the clinical implications of the new knowledge.

Ovarian steroids, stem cells and uterine leiomyoma: therapeutic implications

BACKGROUND

Uterine leiomyoma is the most common benign tumor in women and is thought to arise from the clonal expansion of a single myometrial smooth muscle cell transformed by a cellular insult. Leiomyomas cause a variety of symptoms, including abnormal uterine bleeding, pelvic pain, bladder or bowel dysfunction, and recurrent pregnancy loss, and are the most common indication for hysterectomy in the USA. A slow rate of cell proliferation, combined with the production of copious amounts of extracellular matrix, accounts for tumor expansion. A common salient feature of leiomyomas is their responsiveness to steroid hormones, thus providing an opportunity for intervention.

METHODS

A comprehensive search of PUBMED was conducted to identify peer-reviewed literature published since 1980 pertinent to the roles of steroid hormones and somatic stem cells in leiomyoma, including literature on therapeutics that target steroid hormone action in leiomyoma. Reviewed articles were restricted to English language only. Studies in both animals and humans were reviewed for the manuscript.

RESULTS

Estrogen stimulates the growth of leiomyomas, which are exposed to this hormone not only through ovarian steroidogenesis, but also through local conversion of androgens by aromatase within the tumors themselves. The primary action of estrogen, together with its receptor estrogen receptor α (ERα), is likely mediated via induction of progesterone receptor (PR) expression, thereby allowing leiomyoma responsiveness to progesterone. Progesterone has been shown to stimulate the growth of leiomyoma through a set of key genes that regulate both apoptosis and proliferation. Given these findings, aromatase inhibitors and antiprogestins have been developed for the treatment of leiomyoma, but neither treatment results in complete regression of leiomyoma, and tumors recur after treatment is stopped. Recently, distinct cell populations were discovered in leiomyomas; a small population showed stem-progenitor cell properties, and was found to be essential for ovarian steroid-dependent growth of leiomyomas. Interestingly, these stem-progenitor cells were deficient in ERα and PR and instead relied on the strikingly higher levels of these receptors in surrounding differentiated cells to mediate estrogen and progesterone action via paracrine signaling.

CONCLUSIONS

It has been well established that estrogen and progesterone are involved in the proliferation and maintenance of uterine leiomyoma, and the majority of medical treatments currently available for leiomyoma work by inhibiting steroid hormone production or action. A pitfall of these therapeutics is that they decrease leiomyoma size, but do not completely eradicate them, and tumors tend to regrow once treatment is stopped. The recent discovery of stem cells and their paracrine interactions with more differentiated cell populations within leiomyoma has the potential to provide the missing link between developing therapeutics that temper leiomyoma growth and those that eradicate them.

Hyperplasia and fibrosis in mice with conditional loss of the TSC2 tumor suppressor in Müllerian duct mesenchyme-derived myometria

Uterine leiomyomata are the most common tumors found in the female reproductive tract. Despite the high prevalence and associated morbidities of these benign tumors, little is known about the molecular basis of uterine leiomyoma development and progression. Loss of the Tuberous Sclerosis 2 (TSC2) tumor suppressor has been proposed as a mechanism important for the etiology of uterine leiomyomata based on the Eker rat model. However, conflicting evidence showing increased TSC2 expression has been reported in human uterine leiomyomata, suggesting that TSC2 might not be involved in the pathogenesis of this disorder. We have produced mice with conditional deletion of the Tsc2 gene in the myometria to determine whether loss of TSC2 leads to leiomyoma development in murine uteri. Myometrial hyperplasia and increased collagen deposition was observed in Tsc2(cKO) mice compared with control mice, but no leiomyomata were detected by post-natal week 24. Increased signaling activity of mammalian target of rapamycin complex 1, which is normally repressed by TSC2, was also detected in the myometria of Tsc2(cKO) mice. Treatment of the mutant mice with rapamycin significantly inhibited myometrial expansion, but treatment with the progesterone receptor modulator, mifepristone, did not. The ovaries of the Tsc2(cKO) mice appeared normal, but half the mice were infertile and most of the other half became infertile after a single litter, which was likely due to oviductal blockage. Our study shows that although TSC2 loss alone does not lead to leiomyoma development, it does lead to myometrial hyperplasia and fibrosis.