Deletion 7q in uterine leiomyoma: fluorescence in situ hybridization characterization on primary cytogenetic preparations

Molecular and Cellular Insights into the Development of Uterine Fibroids

Uterine leiomyomas represent the most common benign gynecologic tumor. These hormone-dependent smooth-muscle formations occur with an estimated prevalence of ~70% among women of reproductive age and cause symptoms including pain, abnormal uterine bleeding, infertility, and recurrent abortion. Despite the prevalence and public health impact of uterine leiomyomas, available treatments remain limited. Among the potential causes of leiomyomas, early hormonal exposure during periods of development may result in developmental reprogramming via epigenetic changes that persist in adulthood, leading to disease onset or progression. Recent developments in unbiased high-throughput sequencing technology enable powerful approaches to detect driver mutations, yielding new insights into the genomic instability of leiomyomas. Current data also suggest that each leiomyoma originates from the clonal expansion of a single transformed somatic stem cell of the myometrium. In this review, we propose an integrated cellular and molecular view of the origins of leiomyomas, as well as paradigm-shifting studies that will lead to better understanding and the future development of non-surgical treatments for these highly frequent tumors.

Identification of CUX1 as the recurrent chromosomal band 7q22 target gene in human uterine leiomyoma

Uterine leiomyomas are benign solid tumors of mesenchymal origin which occur with an estimated incidence of up to 77% of all women of reproductive age. The majority of these tumors remains symptomless, but in about a quarter of cases they cause leiomyoma-associated symptoms including chronic pelvic pain, menorrhagia-induced anemia, and impaired fertility. As a consequence, they are the most common indication for pre-menopausal hysterectomy in the USA and Japan and annually translate into a multibillion dollar healthcare problem. Approximately 40% of these neoplasms present with recurring structural cytogenetic anomalies, including del(7)(q22), t(12;14)(q15;q24), t(1;2)(p36;p24), and anomalies affecting 6p21 and/or 10q22. Using positional cloning strategies, we and others previously identified HMGA1, HMGA2, RAD51L1, MORF, and, more recently, NCOA1 as primary target (fusion) genes associated with tumor initiation in four of these distinct cytogenetic subgroups. Despite the fact that the del(7)(q22) subgroup is the largest among leiomyomas, and was first described more than twenty years ago, the 7q22 leiomyoma target gene still awaits unequivocal identification. We here describe a positional cloning effort from two independent uterine leiomyomas, containing respectively a pericentric and a paracentric chromosomal inversion, both affecting band 7q22. We found that both chromosomal inversions target the cut-like homeobox 1 (CUX1) gene on chromosomal band 7q22.1 in a way which is functionally equivalent to the more frequently observed del(7q) cases, and which is compatible with a mono-allelic knock-out scenario, similar as was previously described for the cytogenetic subgroup showing chromosome 14q involvement.

Cytogenetic aberrations and the development of uterine leiomyomata

This study was conducted to define the cytogenetically critical regions of uterine leiomyomata, hoping to demonstrate the presence of possible genes involved in their evolution. It was carried out on 25 randomly selected uterine leiomyoma specimens obtained from 16 patients during hysterectomy or myomectomy operations. Successful tissue culture and karyotyping were performed in 19 specimens. There was no correlation between patient age, gravidity, or presenting symptom and the presence of chromosomal abnormality. A significant correlation was found between short culture turnaround time and the occurrence of chromosomal abnormality. Abnormal clonal karyotypes were present in 6 specimens, non-clonal abnormalities in 4 specimens and normal karyotypes were found in 9 specimens. Myomas with cross section >4 cm showed an increased incidence of abnormal karyotypes and a statistically significant higher incidence of clonal abnormalities. On the other hand, submucous myomas presented fewer clonal abnormalities than did intramural or subserosal myomas. Clonal chromosomal abnormalities involved 5 different chromosomes (2, 7, 8, 12, 22), which indicate genetic heterogeneity of such benign tumors and the need of molecular cytogenetic studies or molecular studies to characterize possible candidate genes at specific chromosomal breakpoints.

Analysis of Allelic Loss as an Adjuvant Tool in Evaluation of Malignancy in Uterine Smooth Muscle Tumors

Uterine smooth muscle tumors of uncertain malignant potential (STUMPs) are difficult both from the diagnostic and patient management standpoint because they cannot be classified as benign or malignant by conventional histologic criteria. This study's aim was to determine the diagnostic utility of allelic imbalance (AI) analysis in uterine smooth muscle tumors. Using microdissection and genotyping, we tested 5 leiomyomas, 6 STUMPs, and 10 leiomyosarcomas with follow-up for AI across a panel of seven tumor suppressor genes (p16, p21, p53, VHL, XRCC3, RB, and NM-23). None of the 6 patients with STUMP experienced recurrent disease, whereas 8 of the 10 patients diagnosed with leiomyosarcoma died of disease at follow-up. The mean frequency of allelic loss (FAL) for leiomyomas (18%) was not significantly different from that of STUMPs (21%) (P = 1), whereas leiomyosarcomas displayed a significantly higher FAL (52%) than both leiomyomas (P = 0.001) and STUMPs (P = 0.002). Loss of NM-23, a reported tumor metastasis suppressor gene, was found only in leiomyosarcomas (5 of 9, or 56%), and 4 of 5 (80%) of these were the only cases that demonstrated distant metastases (P = 0.04). Additionally, an FAL of >50% correlated with both NM-23 loss (P = 0.008) and distant metastatic disease (P = 0.04). In conclusion, leiomyomas and STUMPs displayed similar mean FALs and all were clinically benign, whereas uterine leiomyosarcomas had significantly higher frequencies of allelic loss than both leiomyomas and STUMPs. Molecular profiling may thus provide a valuable tool in assessment of malignancy in uterine smooth muscle tumors. Additionally, NM-23 is a promising candidate gene for determination of metastatic potential in these tumors.

Cumulative dosage effect of a RAD51L1/HMGA2 fusion and RAD51L1 loss in a case of pseudo-Meigs' syndrome

Uterine leiomyoma presenting with ascites and pleural fluid is referred to as pseudo-Meigs' syndrome. It is unclear whether common uterine leiomyomas and uterine leiomyomas causing pseudo-Meigs' syndrome are cytogenetically related or whether functionally different primary pathogenetic triggers are responsible for the differences in tumor phenotype. In this study, we investigated the possible involvement of RAD51LI and HMGA2 (formerly known as HMGIC) in initiation and/or progression of a huge uterine leiomyoma presenting as pseudo-Meigs' syndrome. The detailed cytogenetic and FISH analysis revealed the presence of two subclones with a complex karyotype, 46,XX,t(2;12)(q31;q21),ins(14;12)(q23-24;q15q21).ish del(12)(q15q15) (LL12NC01-142H1-,LL12NC01-27E12-),der(12)t(2;12)(LL12NC01-142H1+,LL12NC01-27E12-),der(14)ins(14;12)(q22;q15q15) (LL12NC01-142H1+,LL12NC01-27E12+,RAD51LI+), der(14)ins(14;12)(q23-q24;q15q21) (LL12NC01-142H1-, LL12NC01-27E12+) [20]/46,idem,del(14)(q21q24).ish(RAD51LI-) [6], indicating intragenic HMGA2 rearrangement and loss of one of the RAD51LI alleles in a derivative subclone with chromosome 14 deletion. Furthermore, RACE and RT-PCR analysis of the tumor cells did not reveal abnormal HMGA2 or RAD51LI transcripts. Additionally, the cellular subclone with intrachromosomal 14q21-q24/RAD51LI deletion showed an in vitro growth advantage over the subclone without the deletion. This observation supports a model in which accumulation of two independent mutations-a classical structural rearrangement involving HMGA2 and RAD51L1, in combination with a loss of the second RAD51L1 allele-might play a major role in the development of pseudo-Meigs' syndrome.

Localization of a gene (MCUL1) for multiple cutaneous leiomyomata and uterine fibroids to chromosome 1q42.3-q43

Dominant transmission of multiple uterine and cutaneous smooth-muscle tumors is seen in the disorder multiple leiomyomatosis (ML). We undertook a genomewide screen of 11 families segregating ML and found evidence for linkage to chromosome 1q42.3-q43 (maximum multipoint LOD score 5.40). Haplotype construction and analysis of recombinations permitted the minimal interval containing the locus, which we have designated "MCUL1," to be refined to an approximately 14-cM region flanked by markers D1S517 and D1S2842. Allelic-loss studies of tumors indicated that MCUL1 may act as a tumor suppressor. Identification of MCUL1 should have wide interest, since this gene may harbor low-penetrance variants predisposing to the common form of uterine fibroids and/or may undergo somatic mutation in sporadic leiomyomata.