This study confirmed the previously reported differences and discovered novel differentiating features for MED12-mutation-positive and -negative leiomyomas.
However, G>A transitions of nucleotides c.130 or c.131 correlate with a significantly larger size of the fibroids compared to other MED12 mutations thus explaining the high prevalence of the former mutations among clinically detectable fibroids.
Unsupervised clustering of results from DNA methylation analyses segregates normal myometrium from fibroids and further segregates the fibroids into subtypes characterized by MED12 mutation or activation of either HMGA2 or HMGA1 expression.
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.
MED12-negative leiomyomas contain copy number alterations involving the Mediator complex subunits such as MED8, MED18, CDK8, and long intergenic nonprotein coding RNA340 (CASC15), which may affect the Mediator architecture and/or its transcriptional activity.
The recent discovery of somatic mutations involving mediator subunit complex 12 (MED12) or high-mobility group AT-hook 2 (HMGA2) in the majority of fibroids and the links to their pathophysiology were also significant advances.
On the basis of this finding, we suggest that the MED12 status stratifies the ULs into two mutually exclusive pathways of leiomyoma genesis, one with IGF-2 overexpression and the other with no IGF-2 activation.
Our study defined the proteome of uterine fibroids and identified that increased ECM protein expression, in particular periostin, is a hallmark of uterine fibroids regardless of MED12 mutation status.
Here, we observed that overexpression of HMGA2 mRNA in tumors measured by quantitative PCR and compared to myometrium is a common phenomenon in fibroids and is frequently associated with MED12 mutations.
MED12 mutations were equally distributed among karyotypically normal and abnormal uterine leiomyomas and were identified in leiomyomas from both black and white American women.
An unsupervised hierarchical clustering analysis revealed two main clusters with one of them (26 of 42 UL) showing an enrichment of MED12 mutated cases (18 of 26 UL).
Whereas 70.0% (14/20) HMGA2-mutated fibroids made their appearance as solitary nodules, 85.5% (153/179) MED12-mutated fibroids occurred as multiple nodules as a rule of independent clonal origin, as reflected by different MED12 mutations.
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.
Our study suggests that the MED12 mutations play unique roles in the pathogenesis of uterine leiomyomas and mutated MED12 could be therapeutically targeted in uterine leiomyomas.
To better define this relationship, we collected ULM with MED12 (n = 25), HMGA2 (n = 15), and FH (n = 27) mutations and examined the sex steroid hormone, cell cycle, and AKT pathway genes by immunohistochemistry.
We identified a minimal cyclin C-CDK8 activation domain on MED12 spanning amino acids 15 through 80 that includes all recorded UF-linked mutations in MED12, suggesting that disruption of Mediator kinase activity is a principal biochemical defect arising from these pathogenic alterations.
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.
In order to elucidate molecular and genetic mechanisms responsible for the increased prevalence and morbidity associated with UL in black women, clinical, pathologic, cytogenetic, and select molecular profiling (MED12 mutation analysis) of 75 self-reported black women undergoing surgical treatment for UL was performed.
Recently, we discovered through exome sequencing that as many as 70% of uterine leiomyomas harbour specific mutations in exon 2 of mediator complex subunit 12 (MED12).