Uterine leiomyomas are benign smooth-muscle tumors of extremely low malignant potential. Early work utilizing classical cytogenetics revealed that a subset of uterine leiomyomas harbor recurrent ...chromosomal rearrangements, such as translocations affecting the HMGA2 gene. Our understanding of the genetics of many tumor types has deepened remarkably with the emergence of next-generation sequencing technologies. Exome sequencing identified that the majority of leiomyomas display highly specific MED12 mutations. Further studies suggest that these MED12 hotspot mutations are also frequent in breast fibroadenomas, but not in other human tumors. Whole-genome sequencing showed that a subset of leiomyomas display complex chromosomal rearrangements resembling chromothripsis. These were formed in a single event of chromosomal breakage and random reassembly involving one or a limited number of chromosomes. Although most leiomyomas have been shown to arise independently, these studies also revealed that distinct nodules within a uterus may display identical genetic changes indicating a common clonal origin. A minority of leiomyomas were also found to display deletions within the COL4A5 - COL4A6 genes, leading to upregulation of the adjacent gene IRS4 . The findings derived from high-throughput sequencing combined with previous knowledge have led to an emerging molecular classification of leiomyomas, suggesting that there are several distinct pathogenic pathways involved in leiomyoma formation. The evidence points to at least 4 molecular subclasses: leiomyomas with MED12 mutation, FH inactivation, HMGA2 overexpression, and COL4A6-COL4A5 deletion. Elucidating the molecular pathogenesis of leiomyomas should be relevant for developing treatments for this very common disease.
Some leiomyomas have chromosomal rearrangements implicating chromothripsis, a process involving the formation of complex chromosomal rearrangements. In three instances, tumors obtained from the same ...woman were documented to be clonally related.
Uterine leiomyomas are benign smooth-muscle tumors with an estimated prevalence of 77% among women of reproductive age in the United States
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and can cause a range of health problems.
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According to a nationwide analysis of 518,828 hysterectomies performed in 2005 in the United States, 282,291 of the patients who underwent the procedure (54%) had leiomyomas.
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Hormonal factors, family history, African ancestry, and obesity increase the risk of leiomyomas.
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Presentation with multiple tumors is typical (an estimated average is six to seven
1
). Whether leiomyosarcomas develop from leiomyomas or arise independently is not known. Uterine leiomyosarcoma is very rare,
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and it . . .
Uterine smooth muscle tumors range from benign leiomyomas to malignant leiomyosarcomas. Based on numerous molecular studies, leiomyomas and leiomyosarcomas mostly lack shared mutations and the ...majority of tumors are believed to develop through distinct mechanisms. To further characterize the molecular variability among uterine smooth muscle tumors, and simultaneously insinuate their potential malignant progression, we examined the frequency of known genetic leiomyoma driver alterations (MED12 mutations, HMGA2 overexpression, biallelic FH inactivation) in 65 conventional leiomyomas, 94 histopathological leiomyoma variants (18 leiomyomas with bizarre nuclei, 22 cellular, 29 highly cellular, and 25 mitotically active leiomyomas), and 51 leiomyosarcomas. Of the 210 tumors analyzed, 107 had mutations in one of the three driver genes. No tumor had more than one mutation confirming that all alterations are mutually exclusive. MED12 mutations were the most common alterations in conventional and mitotically active leiomyomas and leiomyosarcomas, while leiomyomas with bizarre nuclei were most often FH deficient and cellular tumors showed frequent HMGA2 overexpression. Highly cellular leiomyomas displayed the least amount of alterations leaving the majority of tumors with no known driver aberration. Our results indicate that based on the molecular background, histopathological leiomyoma subtypes do not only differ from conventional leiomyomas, but also from each other. The presence of leiomyoma driver alterations in nearly one third of leiomyosarcomas suggests that some tumors arise through leiomyoma precursor lesion or that these mutations provide growth advantage also to highly aggressive cancers. It is clinically relevant to understand the molecular background of various smooth muscle tumor subtypes, as it may lead to improved diagnosis and personalized treatments in the future.
Uterine leiomyomas are common benign smooth muscle tumors that impose a major burden on women’s health. Recent sequencing studies have revealed recurrent and mutually exclusive mutations in ...leiomyomas, suggesting the involvement of molecularly distinct pathways. In this study, we explored transcriptional differences among leiomyomas harboring different genetic drivers, including high mobility group AT-hook 2 (HMGA2) rearrangements, mediator complex subunit 12 (MED12) mutations, biallelic inactivation of fumarate hydratase (FH), and collagen, type IV, alpha 5 and collagen, type IV, alpha 6 (COL4A5-COL4A6) deletions. We also explored the transcriptional consequences of 7q22, 22q, and 1p deletions, aiming to identify possible target genes. We investigated 94 leiomyomas and 60 corresponding myometrial tissues using exon arrays, whole genome sequencing, and SNP arrays. This integrative approach revealed subtype-specific expression changes in key driver pathways, including Wnt/β-catenin, Prolactin, and insulin-like growth factor (IGF)1 signaling. Leiomyomas with HMGA2 aberrations displayed highly significant up-regulation of the proto-oncogene pleomorphic adenoma gene 1 (PLAG1), suggesting that HMGA2 promotes tumorigenesis through PLAG1 activation. This was supported by the identification of genetic PLAG1 alterations resulting in expression signatures as seen in leiomyomas with HMGA2 aberrations. RAD51 paralog B (RAD51B), the preferential translocation partner of HMGA2, was up-regulated in MED12 mutant lesions, suggesting a role for this gene in the genesis of leiomyomas. FH-deficient leiomyomas were uniquely characterized by activation of nuclear factor erythroid 2-related factor 2 (NRF2) target genes, supporting the hypothesis that accumulation of fumarate leads to activation of the oncogenic transcription factor NRF2. This study emphasizes the need for molecular stratification in leiomyoma research and possibly in clinical practice as well. Further research is needed to determine whether the candidate biomarkers presented herein can provide guidance for managing the millions of patients affected by these lesions.
Uterine leiomyosarcomas (ULMSs) are aggressive smooth muscle tumors associated with poor clinical outcome. Despite previous cytogenetic and molecular studies, their molecular background has remained ...elusive. To examine somatic variation in ULMS, we performed exome sequencing on 19 tumors. Altogether, 43 genes were mutated in at least two ULMSs. Most frequently mutated genes included tumor protein P53 (TP53; 6/19; 33%), alpha thalassemia/mental retardation syndrome X-linked (ATRX; 5/19; 26%), and mediator complex subunit 12 (MED12; 4/19; 21%). Unlike ATRX mutations, both TP53 and MED12 alterations have repeatedly been associated with ULMSs. All the observed ATRX alterations were either nonsense or frameshift mutations. ATRX protein levels were reliably analyzed by immunohistochemistry in altogether 44 ULMSs, and the majority of tumors (23/44; 52%) showed clearly reduced expression. Loss of ATRX expression has been associated with alternative lengthening of telomeres (ALT), and thus the telomere length was analyzed with telomere-specific fluorescence in situ hybridization. The ALT phenotype was confirmed in all ULMSs showing diminished ATRX expression. Exome data also revealed one nonsense mutation in death-domain associated protein (DAXX), another gene previously associated with ALT, and the tumor showed ALT positivity. In conclusion, exome sequencing revealed that TP53, ATRX, and MED12 are frequently mutated in ULMSs. ALT phenotype was commonly seen in tumors, indicating that ATR inhibitors, which were recently suggested as possible new drugs for ATRX-deficient tumors, could provide a potential novel therapeutic option for ULMS.
Background
Uterine leiomyomas (ULs) are the most common gynecologic tumors and affect 3 of every 4 women by the age of 50 years. The majority of ULs are classified as conventional tumors, whereas 10% ...represent various histopathological subtypes with features that mimic malignancy. These subtypes include cellular and mitotically active ULs and ULs with bizarre nuclei. Uterine leiomyosarcoma (ULMS), the malignant counterpart of UL, is an aggressive cancer with poor overall survival. The early diagnosis and preoperative differentiation of ULMS from UL are often challenging because their symptoms and morphology resemble one another. Recent studies have shown frequent loss of alpha‐thalassemia/mental retardation syndrome X‐linked (ATRX) or death domain–associated protein (DAXX) expression in ULMS, and this is often associated with an alternative lengthening of telomeres (ALT) phenotype.
Methods
To investigate ATRX and DAXX expression and the presence of ALT in UL subtypes, immunohistochemical and telomere‐specific fluorescence in situ hybridization analyses were performed. The study material consisted of 142 formalin‐fixed, paraffin‐embedded tissue samples representing various UL subtypes and 64 conventional ULs.
Results
A loss of ATRX or DAXX and/or ALT was detected in 6.3% of the histopathological UL subtype samples (9 of 142). Two patients whose ULs showed either ATRX loss or ALT were later diagnosed with a pulmonary smooth muscle tumor. Pulmonary tumors displayed molecular alterations found in the corresponding uterine tumors, which indicated metastasis to the lungs. All conventional ULs displayed normal ATRX, DAXX, and telomeres.
Conclusions
These results highlight the differences between conventional and histopathologically atypical ULs and indicate that some UL subtype tumors may harbor long‐term malignant potential.
A loss of alpha‐thalassemia/mental retardation syndrome X‐linked (ATRX)/death domain–associated protein (DAXX), alternative lengthening of telomeres, or both were found in 9/142 of uterine leiomyoma variant tumors. Two of these patients developed a pulmonary tumor, which indicated dissemination of the uterine tumor. Some variant uterine leiomyomas may harbor long‐term malignant potential.
Objective To assess whether the prognostic impact of conventional risk factors and ancillary biomarkers differs across the 2 largest ProMisE molecular subgroups of endometrial carcinoma (EC). Methods ...Direct sequencing of POLE exonuclease domain hot spots and immunohistochemistry for MLH1, PMS2, MSH2, MSH6 and p53 were performed on 745 unselected endometrioid ECs to identify mismatch repair deficient (MMR-D, n = 264) and no specific molecular profile (NSMP, n = 206) ECs. Molecular group-specific survival analyses and interaction analyses were performed to determine the prognostic relevance of clinicopathological factors and various biomarkers (L1 cell adhesion molecule, estrogen and progesterone receptor, beta-catenin, p16, E-cadherin, KRAS) within the subgroups. Results Molecular subgroup did not have an independent effect on disease-specific survival after adjustment for conventional risk factors (P = 0.101). High grade (G3) and p16 hyperexpression remained significant predictors of survival in NSMP. Stage II-IV, greater than or equal to50% myometrial invasion, lymphovascular space invasion and loss of E-cadherin were independent predictors in the MMR-D group. In the interaction analysis, molecular subclass significantly modified the prognostic effect of high grade and p16 hyperexpression, which showed a stronger negative effect on survival in NSMP as compared to MMR-D (P for interaction = 0.016 for grade and 0.033 for p16). Conclusions Grade of differentiation and p16 hyperexpression appear to have a stronger prognostic impact in NSMP as compared to MMR-D EC. While these results need to be confirmed in a larger study population, they indicate that differential impact of risk factors needs to be taken into account when developing new molecular class-integrated risk stratification algorithms for EC.
Approximately 15% of colorectal cancers exhibit microsatellite instability (MSI), which leads to accumulation of large numbers of small insertions and deletions (indels). Genes that provide growth ...advantage to cells via loss-of-function mutations in microsatellites are called MSI target genes. Several criteria to define these genes have been suggested, one of them being simple mutation frequency. Microsatellite mutation rate, however, depends on the length and nucleotide context of the microsatellite. Therefore, assessing the general impact of mismatch repair deficiency on the likelihood of mutation events is paramount when following this approach. To identify MSI target genes, we developed a statistical model for the somatic background indel mutation rate of microsatellites to assess mutation significance. Exome sequencing data of 24 MSI colorectal cancers revealed indels at 54 million mononucleotide microsatellites of three or more nucleotides in length. The top 105 microsatellites from 71 genes were further analyzed in 93 additional MSI colorectal cancers. Mutation significance and estimated clonality of mutations determined the most likely MSI target genes to be the aminoadipate-semialdehyde dehydrogenase
and the solute transporter
Our findings offer a systematic profiling of the somatic background mutation rate in protein-coding mononucleotide microsatellites, allowing a full cataloging of the true targets of MSI in colorectal cancer.
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Objective To determine the frequency of mediator complex subunit 12 (MED12) mutations in well-documented, prospectively collected, unselected series of sporadic uterine leiomyomas to better ...understand the contribution of MED12 mutations in leiomyoma genesis. Design Mutation analysis of two prospectively collected sample series. Setting Department of gynecology in university hospital and medical genetics research laboratory. Patient(s) 164 uterine leiomyomas from 28 patients (13 consecutive and 15 unselected patients) undergoing hysterectomy. Intervention(s) MED12 mutation screening by direct sequencing, and clinical data collection. Main Outcome Measure(s) MED12 mutation status and various clinical variables. Result(s) MED12 mutations were found in 73 (83.0%) of 88 and 65 (85.5%) of 76 of uterine leiomyomas from the consecutive and unselected patient series, respectively. Smaller tumor size and a larger number of tumors correlated with positive MED12 mutation status. Conclusion(s) The frequency of MED12 mutations in our prospectively collected uterine leiomyoma sets was higher than in previous works. This is in keeping with the concept that MED12 mutation-positive tumors tend to be smaller in size than MED12 mutation-negative tumors. The results highlight the central role of MED12 mutations in uterine leiomyoma genesis.
Up to 86% of uterine leiomyomas harbour somatic mutations in mediator complex subunit 12 (MED12). These mutations have been associated with conventional histology, smaller tumour size, and larger ...number of tumours within the uterus. Prior studies, with limited sample sizes, have failed to detect associations between other clinical features and MED12 mutations. Here, we prospectively collected 763 uterine leiomyomas and the corresponding normal myometrial tissue from 244 hysterectomy patients, recorded tumour characteristics, collected clinical data from medical records, and screened the tissue samples for MED12 mutations to assess potential associations between clinical variables and mutation status. Out of 763 leiomyomas, 599 (79%) harboured a MED12 mutation. In the analysis of tumour characteristics, positive MED12-mutation status was significantly associated with smaller tumour size, conventional histology, and subserous location, relative to intramural. In the analysis of clinical variables, the number of MED12-mutation-positive tumours showed an inverse association with parity, and the number of mutation-negative tumours showed a positive association with a history of pelvic inflammatory disease. This study confirmed the previously reported differences and discovered novel differentiating features for MED12-mutation-positive and -negative leiomyomas. These findings emphasise the relevance of specific driver mutations in genesis and presentation of uterine leiomyomas.
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