Warner-Lambert/Parke-Davis Award lecture. Many tumors and many genes: genetics of uterine leiomyomata

No microsatellite instability using Bethesda panel and revised markers in uterine leiomyomas

Uterine leiomyomas are benign tumors of the uterus that arise clonally from smooth muscle cells of the myometrium and are very common reason for hysterectomy. The aim of this study was to evaluate microsatellite instability (MSI) in uterine leiomyomas using a set of MSI markers by Promega Corporation (Madison, WI, USA) and the Bethesda guideline. DNA was isolated from paired normal and tumoral tissues in 50 patients with uterine leiomyomas and MSI was analyzed by using seven microsatellite markers. Our result showed that microsatellite stability was found in all uterine leiomyomas. These data confirm the genetic status of uterine leiomyomas for the first time in Korean populations, and suggest that uterine leiomyomas have genetic stability in Korean.

Uterine leiomyoma is associated with a polymorphism in the interleukin 1-beta gene

PROBLEM

To investigate whether polymorphisms in the interleukin-1beta (IL-1beta) gene are associated with uterine leiomyoma.

METHOD OF STUDY

Case-control study in a collective of 131 patients and 280 controls. Genotyping of the IL-1beta-511 and IL-1beta-3954 polymorphism was performed by PCR amplification and subsequent RFLP analysis.

RESULTS

A significant difference in the allele frequencies of the IL-1beta-511 C<T polymorphism was found. Allele frequencies of the IL-1beta-511 C<T polymorphism were 70.6% (C allele) in the patient group and 57.1% in the control group [P < 0.0002; odds ratio (OR) 1.81; 95% confidence interval (CI): 1.32-2.47]. The genotype distributions showed also differences using a dominant genotype model (C/C vs. C/T+T/T; P < 0.0002; OR 2.73; 95% CI: 1.77-4.2). No difference was found in the IL-1beta-3954 polymorphism.

CONCLUSION

The IL-1beta-511 promoter polymorphism is related to an increased susceptibility to uterine leiomyoma, suggesting that this polymorphism does contribute to the development of this disease.

The genetic heterogeneity of uterine leiomyomata

Research investigating the genetics of UL has already been successful in gathering epidemiologic evidence for heritability, establishing the clonal and mosaic nature of these tumors, correlating genotypic and phenotypic characteristics, defining cytogenetic subgroups, and identifying specific genes involved in tumorigenesis. Although UL are known to be benign tumors, the impact they have on the lives of so many women can only be described as "malignant". For this reason, continuing the quest to ascertain the genes, functions, and mechanisms integral to UL development is absolutely imperative. Genetic tests for personalized medical management of women with fibroids is at the threshold for providing the most appropriate treatments (Fig. 3), and combined with developing less invasive therapies portends a brighter future for a major health problem for women.

Diagnostic Imaging of Myomas

As treatment options become less invasive and more sophisticated it is imperative that benign myomas be distinguished from potential malignant conditions without falter. The radiologic-pathologic correlations have been integral to our ability to characterize and to localize uterine leiomyomas with accuracy. TVUS remains the standard assessment tool. Its usefulness may be enhanced by SHG or transabdominal ultrasound in certain circumstances; however, it falls short in its ability to map multiple myomas or those in large volume uteri. MRI has become ultrasound's complement and far exceeds ultrasound's technical limitations in precise fibroid mapping and characterization.

Reduced expression of early growth response-1 gene in leiomyoma as identified by mRNA differential display

OBJECTIVES

Despite being the most common pelvic tumor in women, little is known about the molecular basis of uterine leiomyoma growth. The purpose of this study was to (1) identify genes important for leiomyogenesis by comparing gene expression in leiomyoma and normal myometrium and (2) examine the expression level of selected genes on a larger panel of leiomyomas.

METHODS

The technique of mRNA differential display (DD) was used to perform a larger survey of gene expression in leiomyoma by comparing it to matched normal myometrium. Transcripts differentially expressed in leiomyoma were sequenced and further analyzed. Selected differentially expressed transcripts were used as probes on RNA blots of 20 pairs of leiomyomas and their matched myometria to evaluate their expression. The level of expression was analyzed by densitometry.

RESULTS

From 80 differentially expressed transcripts picked by DD, 30 were sequenced and compared to GenBank data. Selected transcripts were analyzed for mRNA levels on a panel of 20 pairs of leiomyomas and matched normal myometria. One transcript that matches the early response gene EGR1 was found to be dramatically reduced (9.2 times on average) in leiomyomas. The reduction was present in 100% of the tumors.

CONCLUSIONS

mRNA differential display is a valid method for finding differences in gene expression between leiomyoma and normal myometrium. The consistency and level of EGR1 mRNA reduction in leiomyoma is an indication that this gene may play a role in the origin or growth of leiomyoma.

Lessons from pregnancy and parturition: uterine leiomyomas result from discordant differentiation and dedifferentiation responses in smooth muscle cells

Leiomyomas, benign smooth muscle tumors of the uterus, are the most common gynecological neoplasm in women. Studies with human tissues and primary cultures have revealed little about the development of leiomyomas, although several genes have been shown to be differentially expressed in leiomyomas compared to matched normal myometrium. We propose that uterine smooth muscle tumor cells mimic a differentiated myometrial cell of pregnancy, and are associated with a hypersensitivity to sex steroid hormones, preventing the cells from responding to normal apoptotic or dedifferentiation signals which would return the cells to a nongravid phenotype. Support of this hypothesis is derived from experimental studies in female Eker rats which develop uterine leiomyoma with many similarities to the human disease. Members of the steroid receptor superfamily as well as the binding partners and co-regulators necessary for transactivation and gene transcription, may be involved in the altered pathway of cellular differentiation and regulation observed in uterine leiomyomas.

Molecular cytogenetic analysis of uterine leiomyoma and leiomyosarcoma by comparative genomic hybridization

Uterine leiomyomata are among the most common of human neoplasms and are associated with abnormal uterine bleeding, infertility, and abdominal pain. Uterine leiomyosarcomata are presumed to be the malignant counterpart to uterine leiomyomata and are very rare. Transformation of uterine leiomyoma (ULM) into uterine leiomyosarcoma (ULMS) is yet to be conclusively confirmed, and each type of tumor may represent a distinct genetic entity. We used comparative genomic hybridization (CGH) to evaluate DNA sequence copy-number changes in 12 specimens of ULM and 8 of ULMS. CGH analysis of ULM demonstrated chromosomal imbalances in 8 of 12 (66. 7%) specimens. The most frequent ULM gains were observed at 9q34 (a novel finding) and on chromosome 19. Other ULM imbalances included gains and losses of chromosome 1p, losses on 7q, and gains on 12q. All ULMS specimens demonstrated chromosomal aberrations. Chromosome 1 imbalances were very prominent. The most frequent losses were detected on 14q and 22q. Losses on 14q are rarely seen in other types of leiomyo-sarcoma and may be a distinctive feature of ULMS. Gains on chromosomes 8, 17, and X were observed in half the cases and were accompanied by high-level amplification. Other chromosome arms overrepresented included 12q and 19p. The absence of specific anomalies common to all ULM and ULMS argues against their being benign-malignant counterparts.

Contribution of molecular genetic data to the classification of sarcomas

Many sarcomas are characterized by specific recurrent chromosomal translocations which provide powerful diagnostic tumor markers. Since 1992, the genes involved by almost all of these translocations have been cloned, inaugurating a new era in the study of sarcomas. At the biological level, these chromosomal translocations produce highly specific gene fusions, usually encoding aberrant chimeric transcription factors. Clinically, the correlation of these translocation-derived genetic markers and discrete histopathologic entities has been remarkable. Fusion gene detection has confirmed and refined the nosology of several sarcoma groups. The overall effect has been to strengthen certain pathological concepts rather than to revolutionize. The focus of this brief review is the recent impact that the cytogenetic and molecular detection of these translocations has had on sarcoma diagnosis and classification.

Current aspects of the pathology of soft tissue sarcomas

In soft tissue sarcomas, advances in pathological techniques, including immunohistochemistry, cytogenetics, and molecular genetics, have improved diagnostic accuracy, confirmed or clarified interrelationships between tumor subtypes, and revealed mechanisms of tumorigenesis. Many sarcomas are associated with abnormalities of tumor-suppressor genes, and several types have been found to have specific chromosomal translocations. These data and correlative clinicopathologic studies, although confirming many traditional pathological views, enable refinement or reassessment of terminology and classification of some small round cell, spindle cell, pleomorphic, and lipogenic tumors. New factors are emerging for prediction of tumor behavior, which might ultimately relate to therapy once a wider range of treatment options becomes available. This article reviews these current aspects of sarcoma pathology.