Gene fusion involving HMGIC is a frequent aberration in uterine leiomyomas

Keratin-Positive Giant Cell-Rich Tumor: A Review and Update

Keratin-positive giant cell-rich tumor (KPGCT) is an extremely rare and recently described mesenchymal neoplasm that occurs in both soft tissue and bone, frequently found in young women. It has locally recurrent potential if incompletely excised but low risk for metastasis. KPGCT is histologically similar to conventional giant cell tumors of soft tissue but shows the presence of keratin-positive mononuclear cells. Interestingly, KPGCT also shares some morphological features with xanthogranulomatous epithelial tumors. These two tumors have recently been shown to harbor an HMGA2-NCOR2 fusion, arguing in favor of a single entity. Surgery is the treatment of choice for localized KPGCT. Therapeutic options for advanced or metastatic disease are unknown. This review provides an overview of the current knowledge on the clinical presentation, pathogenesis, histopathology, and treatment of KPGCT. In addition, we will discuss the differential diagnosis of this emerging entity.

Sarcomas With RAD51B Fusions Are Associated With a Heterogeneous Phenotype

RAD51B-rearranged sarcomas are rare neoplasms that exhibit a heterogeneous morphology. To date, 6 cases have been reported, all involving the uterus, including 4 perivascular epithelioid cell tumors (PEComas) and 2 leiomyosarcomas (LMS). In this study, we describe the morphologic, immunohistochemical, and molecular features of 8 additional sarcomas with RAD51B rearrangement, including the first extrauterine example. All patients were women with a median age of 57 years at presentation. Seven tumors originated in the uterus, and one in the lower extremity soft tissue, with a median tumor size of 12 cm. Histologically, 4 tumors showed predominantly spindle cell morphology with eosinophilic fibrillary cytoplasm, with or without nuclear pleomorphism, whereas 2 tumors exhibited pleomorphic epithelioid cells, featuring clear to eosinophilic, granular cytoplasm. Two neoplasms exhibited undifferentiated cytomorphology, including one with uniform small blue round cells. All tumors showed high-grade cytologic atypia and high mitotic activity (median: 30/10 high-power fields), whereas coagulative necrosis was noted in 6 cases and lymphovascular invasion in 2. By immunohistochemistry, 2 showed myoid and melanocytic markers in keeping with PEComa, whereas 4 cases were only positive for smooth muscle markers consistent with LMS (including 3 myxoid). The remaining 2 cases had a nonspecific immunoprofile. Five cases tested by targeted RNA sequencing (Archer FusionPlex, Illumina TruSight) showed different fusion partners (HMGA2, PDDC1, and CEP170). RAD51B rearrangements were identified by FISH in the remaining 3 cases. Targeted DNA sequencing in 2 cases was negative for TSC gene alterations. Clinical outcome, available in 5 patients (median follow-up, 19 months), revealed 3 local recurrences, 2 lung metastases, and 4 deaths due to disease. Our results expand the spectrum of sarcomas with RAD51B fusions, demonstrating variable clinical presentations, morphologic spectrum, and fusion partners. These tumors have a predilection for a uterine location, with either LMS, PEComa, or undifferentiated phenotypes, and are associated with an aggressive clinical course.

Aggressive Angiomyxoma of the Lower Female Genital Tract in Pregnancy: A Review of the MITO Rare Tumors Group

Deep (aggressive) angiomyxoma of the lower genital tract is a rare malignancy affecting women of reproductive age. Being a hormone-sensitive tumor, its growth is particularly benefitted during pregnancy. Surgical excision with complete resection is indicated, even if a wait-and-see approach can be considered until delivery, to avoid destructive surgeries. The mode of delivery is to be evaluated based on the location and size of the neoplasm; vaginal delivery is not contraindicated, as long as the tumor does not obstruct the birth canal. Positive surgical margins are the most important prognostic factor for recurrence. Adjuvant therapy with gonadotropin-releasing hormone analogues may be proposed after pregnancy, in the case of non-radical surgery. Despite the high local relapse rate, the outcomes for mother and child are favorable. Since recurrences can occur after many years, the patient should be included in long-term follow-up.

A View on Uterine Leiomyoma Genesis through the Prism of Genetic, Epigenetic and Cellular Heterogeneity

Uterine leiomyomas (ULs), frequent benign tumours of the female reproductive tract, are associated with a range of symptoms and significant morbidity. Despite extensive research, there is no consensus on essential points of UL initiation and development. The main reason for this is a pronounced inter- and intratumoral heterogeneity resulting from diverse and complicated mechanisms underlying UL pathobiology. In this review, we comprehensively analyse risk and protective factors for UL development, UL cellular composition, hormonal and paracrine signalling, epigenetic regulation and genetic abnormalities. We conclude the need to carefully update the concept of UL genesis in light of the current data. Staying within the framework of the existing hypotheses, we introduce a possible timeline for UL development and the associated key events—from potential prerequisites to the beginning of UL formation and the onset of driver and passenger changes.

Neoplasia-associated Chromosome Translocations Resulting in Gene Truncation

Chromosomal translocations in cancer as well as benign neoplasias typically lead to the formation of fusion genes. Such genes may encode chimeric proteins when two protein-coding regions fuse in-frame, or they may result in deregulation of genes via promoter swapping or translocation of the gene into the vicinity of a highly active regulatory element. A less studied consequence of chromosomal translocations is the fusion of two breakpoint genes resulting in an out-of-frame chimera. The breaks then occur in one or both protein-coding regions forming a stop codon in the chimeric transcript shortly after the fusion point. Though the latter genetic events and mechanisms at first awoke little research interest, careful investigations have established them as neither rare nor inconsequential. In the present work, we review and discuss the truncation of genes in neoplastic cells resulting from chromosomal rearrangements, especially from seemingly balanced translocations.

Novel role of COX6c in the regulation of oxidative phosphorylation and diseases

Cytochrome c oxidase subunit VIc (COX6c) is one of the most important subunits of the terminal enzyme of the respiratory chain in mitochondria. Numerous studies have demonstrated that COX6c plays a critical role in the regulation of oxidative phosphorylation (OXPHOS) and energy production. The release of COX6c from the mitochondria may be a hallmark of the intrinsic apoptosis pathway. Moreover, The changes in COX6c expression are widespread in a variety of diseases and can be chosen as a potential biomarker for diagnosis and treatment. In light of its exclusive effects, we present the elaborate roles that COX6c plays in various diseases. In this review, we first introduced basic knowledge regarding COX6c and its functions in the OXPHOS and apoptosis pathways. Subsequently, we described the regulation of COX6c expression and activity in both positive and negative ways. Furthermore, we summarized the elaborate roles that COX6c plays in various diseases, including cardiovascular disease, kidney disease, brain injury, skeletal muscle injury, and tumors. This review highlights recent advances and provides a comprehensive summary of COX6c in the regulation of OXPHOS in multiple diseases and may be helpful for drug design and the prediction, diagnosis, treatment, and prognosis of diseases.

Cytoplasmic levels of high mobility group A2 determine survival prognoses in breast cancer patients

BACKGROUND

High mobility group A proteins are involved in chromatin remodeling, thereby influencing multiple fundamental biological processes. HMGA2 has been linked to oncogenic traits among a variety of malignancies.

OBJECTIVE

To determine the prognostic implications of subcellular distribution patterns of HMGA2 in breast cancer.

METHODS

Nuclear and cytoplasmic HMGA2 was evaluated in 342 breast cancer specimens and matched with clinico-pathological parameters.

RESULTS

Overall and cytoplasmic, but not nuclear, levels of HMGA2 correlated with better survival prognoses in our collective (hazard ratio (HR) 0.34, P = 0.001 and HR 0.34, P < 0.001, respectively). The protective effect of cytoplasmic HMGA2 persisted in the Luminal A and triple negative breast cancer subgroups. Evaluating Luminal A and B subgroups jointly, only cytoplasmic, but not overall or nuclear HMGA2 levels were associated with better survival (HR 0.42, 95% confidence interval 0.21, 0.86, P = 0.017), irrespective of tumor size and node status. The addition of HMGA2 overall and cytoplasmic scores strengthened the prognostic selectivity in a model of conventional breast cancer risk factors. No predictive significance with regard to endocrine or chemoendocrine therapies was observed.

CONCLUSION

Unexpectedly, we found a favorable survival probability upon overall levels of HMGA2 in our breast cancer collective, which was predominantly determined by the presence of HMGA2 in the cytoplasm.

High Mobility Group AT-Hook 2 (HMGA2) Oncogenicity in Mesenchymal and Epithelial Neoplasia

High mobility group AT-hook 2 (HMGA2) has been associated with increased cell proliferation and cell cycle dysregulation, leading to the ontogeny of varied tumor types and their metastatic potentials, a frequently used index of disease prognosis. In this review, we deepen our understanding of HMGA2 pathogenicity by exploring the mechanisms by which HMGA2 misexpression and ectopic expression induces mesenchymal and epithelial tumorigenesis respectively and distinguish the pathogenesis of benign from malignant mesenchymal tumors. Importantly, we highlight the regulatory role of let-7 microRNA family of tumor suppressors in determining HMGA2 misexpression events leading to tumor pathogenesis and focused on possible mechanisms by which HMGA2 could propagate lymphangioleiomyomatosis (LAM), benign mesenchymal tumors of the lungs. Lastly, we discuss potential therapeutic strategies for epithelial and mesenchymal tumorigenesis based on targeting the HMGA2 signaling pathway.

Genomic imbalances are involved in miR-30c and let-7a deregulation in ovarian tumors: implications for HMGA2 expression

The High-mobility group AT-hook 2 protein (HMGA2) is involved in different processes during tumorigenesis. High expression levels of HMGA2 are found in various types of cancer, with recent studies highlighting the important role of miRNAs in the regulation of HMGA2 expression. We report a study of 155 ovarian tumors (30 sex-cord stromal tumors, 22 borderline tumors, and 103 carcinomas) analyzed for HMGA2 expression as well as the expression of two miRNAs targeting this gene, let-7a and miR-30c. We also evaluated the expression of the fragile histidine triad (FHIT) and lin28 homologues (LIN28A/B) genes which are known to be an enhancer of miR-30c expression and a repressor of let-7a, respectively. HMGA2 was found expressed at high levels in most samples analyzed, with clear cell carcinomas as the only exception. let-7a and miR-30c were highly deregulated in all tumor types. LIN28A and FHIT were found overexpressed in all examined tumor types. The chromosomal imbalances that might lead to loss of the genes expressing let-7a and miR-30c could be evaluated on the basis of previously generated karyotypic and high resolution comparative genomic hybridization (CGH) data on 103 tumors. 76% of the samples with an imbalanced genome had at least one chromosomal aberration leading to a deletion of a miRNA cluster for let-7a and miR-30c. FISH using locus specific probes for these clusters validate the aberrations at the gene level. Our study shows that genomic imbalances are involved in miR-30c and let-7a deregulation. One can reasonably assume that dysregulation of these miRNAs is a cause leading to HMGA2 upregulation in ovarian tumors.

Molecular characterization of the t(4;12)(q27~28;q14~15) chromosomal rearrangement in lipoma

Lipomas are common benign soft tissue tumors whose genetic and cytogenetic features are well characterized. The karyotype is usually near- or pseudodiploid with characteristic structural chromosomal aberrations. The most common rearrangements target the high mobility group AT-hook 2 (HMGA2) gene in 12q14.3, with breakpoints occurring within or outside of the gene locus leading to deregulation of HMGA2. The most common fusion partner for HMGA2 in lipoma is lipoma-preferred partner (3q27), but also other genes frequently recombine with HMGA2. Furthermore, truncated HMGA2 transcripts are recurrently observed in lipomas. The present study describes 5 lipomas carrying the translocation t(4;12)(q27~28;q14~15) as the sole chromosomal anomaly, as well as 1 lipoma in which the three-way translocation t(1;4;12)(q21;q27~28;q14~15) was identified. Molecular analyses performed on 4 of these cases detected 4 truncated forms of HMGA2. In 3 tumors, the HMGA2 truncated transcripts included sequences originating from the chromosomal sub-band 4q28.1. Notably, in 2 of these cases, the fourth exon of HMGA2 was fused to transposable elements located in 4q28.1.

A novel truncated form of HMGA2 in tumors of the ovaries

Neoplasms of the ovary are the second most common tumor of the female reproductive system, and the most lethal of the gynecological malignancies. Ovarian tumors are divided into a copious number of different groups reflecting their different features. The present study analyzed 187 ovarian tumors (39 sex-cord stromal tumors, 22 borderline tumors and 126 carcinomas) for the expression of the high-mobility group AT-hook 2 (HMGA2) gene, for mutations in the isocitrate dehydrogenase (NADP(+)) 1, cytosolic (IDH1), isocitrate dehydrogenase (NADP(+)) 2, mitochondrial (IDH2) and telomerase reverse transcriptase (TERT) genes, and for methylation of the O⁶-methylguanine-DNA methyltransferase (MGMT) promoter. Reverse transcription-polymerase chain reaction analysis showed that HMGA2 was expressed in 74.5% of the samples (120/161). A truncated transcript of HMGA2 was identified in 11 cases. A novel truncated form of HMGA2 was found in 4 serous high-grade carcinomas. Only 4 tumors (4/185) showed the TERT C228T mutation. No IDH1 or IDH2 mutations were found. Methylation of the promoter of MGMT was found in 2 borderline tumors (2/185). HMGA2 was expressed, in its truncated and native form, in different ovarian tumors, even the less aggressive types, underscoring the general importance of this gene in ovarian tumorigenesis. Mutations involving TERT, as well as MGMT promoter methylation, are rare events in ovarian tumors.

HMGA2 expression pattern and TERT mutations in tumors of the vulva

Malignant tumors of the vulva account for only 5% of cancers of the female genital tract in the USA. The most frequent cancers of the vulva are squamous cell carcinoma (SCC) and malignant melanoma (MM). Little is known about the genetic aberrations carried by these tumors. We report a detailed study of 25 vulva tumors [22 SCC, 2 MM, 1 atypical squamous cell hyperplasia (AH)] analyzed for expression of the high-mobility group AT-hook family member genes HMGA2 and HMGA1, for mutations in the IDH1, IDH2 and TERT genes, and for methylation of the MGMT promoter. The RT-PCR and immunohistochemistry analyses showed that HMGA2 was expressed in the great majority of analyzed samples (20 out of 24; SCC as well as MM) but not in the normal controls. HMGA1, on the other hand, was expressed in both tumors and normal tissues. Five of the 24 tumors (all SCC) showed the C228T mutation in the TERT promoter. Our results showed that HMGA2 and TERT may be of importance in the genesis and/or the progression of tumors of the vulva.

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.

Inactivation of AKT induces cellular senescence in uterine leiomyoma

Uterine leiomyomas (fibroids) are a major public health problem. Current medical treatments with GnRH analogs do not provide long-term benefit. Thus, permanent shrinkage or inhibition of fibroid growth via medical means remains a challenge. The AKT pathway is a major growth and survival pathway for fibroids. We propose that AKT inhibition results in a transient regulation of specific mechanisms that ultimately drive cells into cellular senescence or cell death. In this study, we investigated specific mechanisms of AKT inhibition that resulted in senescence. We observed that administration of MK-2206, an allosteric AKT inhibitor, increased levels of reactive oxygen species, up-regulated the microRNA miR-182 and several senescence-associated genes (including p16, p53, p21, and β-galactosidase), and drove leiomyoma cells into stress-induced premature senescence (SIPS). Moreover, induction of SIPS was mediated by HMGA2, which colocalized to senescence-associated heterochromatin foci. This study provides a conceivable molecular mechanism of SIPS by AKT inhibition in fibroids.

Structural remodeling, trafficking and functions of glycosylphosphatidylinositol-anchored proteins

Glycosylphosphatidylinositol (GPI) is a glycolipid that is covalently attached to proteins as a post-translational modification. Such modification leads to the anchoring of the protein to the outer leaflet of the plasma membrane. Proteins that are decorated with GPIs have unique properties in terms of their physical nature. In particular, these proteins tend to accumulate in lipid rafts, which are critical for the functions and trafficking of GPI-anchored proteins (GPI-APs). Recent studies mainly using mutant cells revealed that various structural remodeling reactions occur to GPIs present in GPI-APs as they are transported from the endoplasmic reticulum to the cell surface. This review examines the recent progress describing the mechanisms of structural remodeling of mammalian GPI-anchors, such as inositol deacylation, glycan remodeling and fatty acid remodeling, with particular focus on their trafficking and functions, as well as the pathogenesis involving GPI-APs and their deficiency.

Value and limitation of immunohistochemical expression of HMGA2 in mesenchymal tumors: about a series of 1052 cases

The high mobility group A (HMGA2) gene encodes a protein that alters chromatin structure and regulates the transcription of many genes; it is implicated in both benign and malignant neoplasias, but its rearrangements are a feature of development of several mesenchymal tumors. Given its implication in these tumors and particularly adipocytic tumors, and the availability of antibodies usable on paraffin-embedded tissues, we evaluated the immunohistochemical expression of this gene in a series of 1052 mesenchymal tumors. The objective was to define the value and limitations of HMGA2 immunohistochemical expression for histotyping, and compare with molecular data reported in the literature. We thus analyzed 880 cases on tissue microarray and 182 cases on whole sections (211 adipocytic tumors, 628 sarcomas, 213 benign mesenchymal tumors, and 10 normal adipose tissues). A nuclear immunostaining was detected in 86% of conventional and intramuscular lipomas, in 86% of well-differentiated liposarcomas and in 67% of dedifferentiated liposarcomas, as opposed to 16% of other benign adipose tumors and to 15% of non-well-differentiated liposarcoma/dedifferentiated liposarcoma sarcomas. Among benign mesenchymal tumors and lesions, it was detected in 90% of nodular fasciitis and in 88% of benign fibrous histiocytomas with respective specificities of 85 and 100%, and in 90% of aggressive angiomyxoma, contrary to other vulvovaginal tumor types, which expressed HMGA2 only rarely. The normal adipose tissue was always negative for HMGA2. Although not specific, immunohistochemical detection of the HMGA2 protein is helpful for the distinction of normal adipose tissue from well-differentiated lesions, particularly on biopsy or on re-excision. It is less sensitive than MDM2/CDK4 for dedifferentiated liposarcomas diagnosis, but it appears more specific to distinguish dedifferentiated liposarcomas from other poorly differentiated sarcomas. Finally, and may be more importantly, HMGA2 is useful for the diagnosis of benign fibrous histiocytoma, nodular fasciitis and vulvovaginal benign mesenchymal tumors.

Antiproliferative effects by Let-7 repression of high-mobility group A2 in uterine leiomyoma

High-mobility group A2 (HMGA2) is commonly overexpressed in large leiomyomas. HMGA2 is an important regulator of cell growth, differentiation, apoptosis, and transformation. As a predicted target of Let-7 microRNAs (Let-7s), HMGA2 can be repressed by Let-7s in vitro. MicroRNA profiling analysis revealed that Let-7s were significantly dysregulated in uterine leiomyomas: high in small leiomyomas and lower in large leiomyomas. To evaluate whether Let-7 repression of HMGA2 plays a major role in leiomyomas, we analyzed the molecular relationship of HMGA2 and Let-7s, both in vitro and in vivo. We first characterized that exogenous Let-7 microRNAs could directly repress the dominant transcript of HMGA2, HMGA2a. This repression was also identified for two cryptic HMGA2 transcripts in primary leiomyoma cultures. Second, we found that the endogenous Let-7s were biologically active and played a major role in the regulation of HMGA2. Then, we illustrated that Let-7 repression of HMGA2 inhibited cellular proliferation. Finally, we examined the expression levels of Let-7c and HMGA2 in a large cohort of leiomyomas (n = 120), and we found high levels of Let-7 and low levels of HMGA2 in small leiomyomas, and low levels of Let-7 and high levels of HMGA2 in large leiomyomas. Our findings suggest that the Let-7-mediated repression of HMGA2 mechanism can be an important molecular event in leiomyoma growth.

Aggressive angiomyxoma with t(12;21) and HMGA2 rearrangement: report of a case and review of the literature

Conventional cytogenetic analysis of an aggressive angiomyxoma of the rectal wall of a 72-year-old woman revealed a translocation between the long arms of chromosomes 12 and 21, with the karyotype 46,XX,t(12;21)(q15;q21.1). Involvement of the HMGA2 gene locus (12q15) was confirmed by fluorescence in situ hybridization using an HMGA2 breakpoint flanking probe set performed on metaphase and interphase cells from an in situ culture of fresh lesional tissue. Karyotypic rearrangements of 12q13 approximately q15 are considered recurrent in aggressive angiomyxoma, although reported in only five previous cases. Translocation partner chromosome 21 is unique to the present case.

Identification and characterization of novel human transcripts embedded within HMGA2 in t(12;14)(q15;q24.1) uterine leiomyoma

The high mobility group A2 protein (HMGA2) has been implicated in the pathogenesis of mesenchymal tumors such as leiomyoma, lipoma and hamartoma. HMGA2 was pinpointed by mapping the breakpoints in the chromosomal translocations in 12q15, especially the t(12;14) that is commonly seen in uterine leiomyoma. It is generally assumed that altered expression of HMGA2 is an early event in the pathway to tumor formation. Here, we show evidence that three novel transcripts, A15, B6 and D12 are located within the HMGA2 gene itself and are transcribed from the opposite strand. These embedded transcripts are expressed at 6-20-fold higher levels in tumors compared to matched myometrium from the same patients. We estimate that the domain of increased expression extends 500kb on chromosome 12q15, and encompasses the majority of t(12;14) translocation breakpoints. However, a corresponding domain of consistently altered expression is not seen on chromosome 14 or outside of the chromosome 12 multiple aberration region. These data suggest that t(12;14) breakpoints contribute to the pathogenesis of uterine leiomyoma by interrupting a complex regulation of HMGA2 and other genes embedded within and around it. We also discovered a novel laminin receptor gene, transcribed from the opposite strand, within the promoter region of HMGA2. Although the roles for these embedded transcripts are still unknown, preliminary data suggest that they are members of the family of non-coding RNA and that they may play an important role in the pathology of uterine leiomyoma.

Extensive expression studies revealed a complex alternative splicing pattern of the HMGA2 gene

Chromosomal rearrangements of the HMGA2 locus belong to the most common aberrations in human benign tumors. HMGA2 rearrangements often result in chimeric genes expressing transcripts consisting of the first three exons of HMGA2 followed by ectopic sequences derived from intron 3 of that gene. RT-PCR-based expression studies of 4 of these HMGA2 transcripts revealed a co-expression with the "wild-type" HMGA2a in tumor samples as well as in normal tissues. Northern blot hybridizations of the lipoma cell line Li-14 revealed the expression of five additional HMGA2 transcripts consisting of exons 1 to 3 but not exons 4 to 5 besides the full-length HMGA2a transcript. In silico analyses have been performed showing a high homology to well-established consensus sequences for the 3' splice acceptor site, the branch site, and poly(A) signal. Thus, it is quite obvious that the HMGA2 transcripts described herein are alternative, not aberrant, splice-products of the HMGA2 gene. It is hypothesized that HMGA2-dependent tumorigenesis is caused by a disturbed equilibrium in the co-expression of the HMGA2 splice variants leading to aberrant cell proliferation and/or malignant transformation of cells.

Decreased expression of early growth response-1 and its role in uterine leiomyoma growth

Expression of early growth response (Egr)-1, a transcriptional factor implicated in growth regulation, is suppressed in several malignant tumors. The present study investigated the expression of Egr-1 and related genes in uterine leiomyoma and normal myometrium to determine possible contributions of Egr-1 to neoplastic growth in leiomyoma cells. Levels of Egr-1 transcripts were decreased in all leiomyomas (n = 20) to approximately 10% of levels in corresponding myometrium, where basal expression was high. Preoperative leuprorelin acetate therapy increased levels of Egr-1 mRNA in normal myometrium only. Northern blot analysis using additional sample sets (n = 5) revealed the full-length Egr-1 transcript. Western blot analysis (n = 5) confirmed decreased expression of Egr-1 protein. Southern blot analysis of the Egr-1 gene and microsatellite analysis of the chromosomal location at 5q31 (D5S414, D5S500, and D5S476) revealed neither DNA recombination nor loss of heterozygosity in leiomyomas. Moreover, Egr-1 retained identical responsiveness to phorbol 12-myristate 13-acetate in primary cultures derived from both leiomyoma and normal tissues. Electrophoretic mobility shift analysis revealed that phorbol 12-myristate 13-acetate-induced Egr-1 in leiomyoma cells retained DNA binding ability. Egr-1 thus appears functionally intact in leiomyoma cells. Finally, consistent with the role of Egr-1 in growth inhibition, transfection of Egr-1 expression vector into a myometrial cell line (KW) that expresses low levels of Egr-1 and displays rapid growth inhibited thymidine uptake in these cells. Egr-1 may display tumor-suppressing activity and offers a potential target for leiomyoma management.

Biallelic inactivation of fumarate hydratase (FH) occurs in nonsyndromic uterine leiomyomas but is rare in other tumors

Germline mutations in the fumarate hydratase (FH) gene at 1q43 predispose to dominantly inherited cutaneous and uterine leiomyomas, uterine leiomyosarcoma, and papillary renal cell cancer (HLRCC syndrome). To evaluate the role of FH inactivation in sporadic tumorigenesis, we analyzed a series of 299 malignant tumors representing 10 different malignant tumor types for FH mutations. Additionally, 153 uterine leiomyomas from 46 unselected individuals were subjected to and informative in loss of heterozygosity analysis at the FH locus, and the five (3.3%) tumors displaying loss of heterozygosity were subjected to FH mutation analysis. Although mutation search in the 299 malignant tumors was negative, somatic FH mutations were found in two nonsyndromic leiomyomas; a splice site change IVS4 + 3A>G, leading to deletion of exon four, and a missense mutation Ala196Thr. The occurrence of somatic mutations strongly suggests that FH is a true target of the 1q43 deletions. Although uterine leiomyomas are the most common tumors of women, specific inactivating somatic mutations contributing to the formation of nonsyndromic leiomyomas have not been reported previously. Taking into account the apparent risk of uterine leiomyosarcoma associated with FH germline mutations, the finding raises the possibility that also some nonsyndromic leiomyomas may have a genetic profile that is more prone to malignant degeneration. Our data also indicate that somatic FH mutations appear to be limited to tumor types observed in hereditary leiomyomatosis and renal cell cancer.

A functional genomic study to identify differential gene expression in the preterm and term human myometrium

The mechanisms that lead to the onset of human parturition are still unknown, although selected critical factors have been identified. To investigate the changes in myometrial gene expression associated with parturition, we used two macroarrays each containing 1176 different complementary human cDNA clones. Methods involving hierarchical clustering and conventional statistical analysis allowed us to generate a profile of genes expression at three stages of late pregnancy: preterm (29 wk amenorrhea); full term, not in labor (38 wk amenorrhea); and full term in labor (39 wk amenorrhea). Only 4% of the genes investigated were differentially expressed between the preterm and term groups (P < 0.05). These genes could be clustered as groups of either down-regulated or up-regulated transcripts. The changes in transcript abundance were particularly marked between the preterm and term stages of gestation, whereas the differences between term not in labor and term in labor were less pronounced. The parturition was characterized by a massive down-regulation of a large panel of developmental, cell adhesion molecule and proliferation-related genes, along with the up-regulation of inflammatory, contraction and apoptosis associated genes. We propose that the mechanisms of parturition consist primarily in the arrest of the processes of myometrial development, a step that might be essential to allow the uterus to recover appropriate contractile function before delivery.

Insights from gene arrays on the development and growth regulation of uterine leiomyomata

OBJECTIVE

To use microarray analysis as an unbiased approach to identify genes involved in the induction and growth of uterine leiomyomata.

DESIGN

Screen by arrays for up to 12,000 genes in leiomyoma (L) and control myometrium (M) from nine patients.

SETTING

University research laboratories.

PATIENT(S)

Nine patients in the follicular and luteal phases of the menstrual cycle.

INTERVENTION(S)

mRNA from L and M was converted to biotin-labeled cRNA and hybridized to cDNA oligonucleotide sequences on the arrays.

MAIN OUTCOME MEASURE(S)

Greater than two-fold change in gene expression between leiomyoma and matched myometrium.

RESULT(S)

Prominent among the 67 genes overexpressed in L relative to M were dlk or Pref-1, doublecortin, JM27, ionotropic glutamate receptor subunit 2, apolipoprotein E3, IGF2, semaphorin F, myelin proteolipid protein, MEST, frizzled, CRABP II, stromelysin-3, and TGFbeta3. The genes dlk, IGF2, and MEST are paternally expressed imprinted genes, and the others are involved in tissue differentiation and growth. Prominent among the 78 genes down-regulated in L relative to M were alcohol dehydrogenases 1alpha-gamma, tryptase, dermatopontin, thrombospondin, coxsackievirus receptor, nur77, and c-kit.

CONCLUSION(S)

Arrays offer large-scale screening of mRNA expression, which will help us differentiate between the genes and metabolic pathways necessary for leiomyoma growth and those regulating myometrial contractions.