Uterine leiomyoma in the Eker rat: a unique model for important diseases of women

Eker rats carry a defect in the Tsc-2 tumor suppressor gene and female Eker rats develop uterine leiomyoma with a high frequency. The presentation, response to hormones and molecular alterations in these mesenchymal smooth muscle tumors, closely resembles their cognate human disease. Female rats and tumor-derived cell lines from Eker rat leiomyomas (ELT lines) have been developed as an in vivo/in vitro model system for preclinical studies to identify novel therapeutic agents for this disease and for studying disease pathogenesis. In addition to serving as a model for uterine leiomyoma, Eker rats have proven valuable for studying lymphangioleiomyomatosis, a related proliferative smooth muscle disease of women.     

Uterine leiomyomas: mechanisms of tumorigenesis

Uterine leiomyomas, also called fibroids, are the most common reproductive tract neoplasm and the leading indication for hysterectomy in premenopausal women. The discovery and development of medicinal therapies for uterine leiomyoma have been hampered by a lack of understanding regarding the etiology and molecular mechanisms underlying the development of these lesions. Although the estrogen responsiveness of uterine leiomyoma is well established, the impact of environmental estrogens and their contribution to the development of these tumors is currently unknown. The Eker rat model of uterine leiomyoma has proven useful for addressing these issues and understanding the pathophysiology of this disease. The Eker rat is the only animal model that develops spontaneous uterine leiomyomas, and these tumors share many characteristics with those found in humans. The availability of tumor-derived cell lines from these rats has made this a valuable in vitro/in vivo model system for experimental studies to investigate molecular mechanisms of disease and to design interventional and preventative strategies for this clinically relevant tumor.     

Expression profile of tuberin and some potential tumorigenic factors in 60 patients with uterine leiomyomata.

Human uterine leiomyomata are the most common tumors in women of reproductive age. The pathogenesis of leiomyomata remains unknown. An animal model of Eker rats with deleted tuberous sclerosis complex gene 2 (tuberin) shows increased incidence of leiomyomata. The role of tuberin in human leiomyomata is unknown. In this study, we designed a tissue microarray with tissue cores of leiomyomata and the matched myometrium from 60 hysterectomy specimens. We examined the expression of tuberin and tuberous sclerosis complex gene 1 product hamartin, proteins of the insulin-signaling pathway, steroid receptors and some of their cofactors, and human mobility group gene A2 by immunohistochemistry. We found that nearly half of the cases displayed either reduction or loss of tuberin in leiomyomata compared with matched normal myometrium. No change of hamartin was noted. Furthermore, a significant reduction of glucocorticoid receptor was found in leiomyomata with reduced tuberin. The proteins insulin like growth factor 1, insulin-like growth factor receptor beta, AKT kinase, and phosphatidylinositol 3-kinase were upregulated. Nearly half of leiomyomata show upregulation of human mobility group gene A2, along with the steroid receptor cofactors. Our findings suggest that there are two broad groups of uterine leiomyomata. One group is associated with an alteration of tuberin and glucocorticoid receptor. The other group is associated with upregulation of human mobility group gene A2 and steroid receptor cofactors.     

Bilateral massive ovarian leiomyomata in a young woman: a case report with review of the literature.

We report a case of ovarian leiomyomata, bilateral and massive, in a 21-yr-old woman. Primary leiomyoma of the ovary is a very rare tumor and is usually small, unilateral, and concomitant with uterine leiomyomata. To our knowledge, this is the first report in the English literature of bilateral ovarian leiomyomata. We document the smooth muscle origin of the tumors with immunohistochemical studies that show appropriate staining with antibodies to vimentin, muscle specific actin, desmin, smooth muscle actin, and collagen type IV. The available literature is reviewed. The characteristics of both typical and atypical ovarian leiomyoma and theories of its origin are discussed.     

Human atherosclerotic plaque cells and leiomyoma cells. Comparison of in vitro growth characteristics.

Cells derived from human atherosclerotic plaques and from arterial media were compared with cells obtained from human leiomyomata and myometrium with respect to growth behavior in long-term cell culture. None of numerous variations in culture media, including alterations of serum concentration and source, improved the rate of cell multiplication or in vitro longevity. Both uterine cell types, but neither arterial cell type, multiplied after tissue dissociation with enzymes (elastase, collagenase, hyaluronidase). The replicative life-span of each of eight samples of arterial plaque cells was equal to or less than that of the corresponding medial cells. A similar relationship was observed for eight paired sets of leiomyoma and myometrial cells. The results indicate that, under the conditions of culture in vitro, cells of a bona fide smooth muscle tumor have a finite replicative life-span and smooth muscle cells of atherosclerotic plaques behave in a similar manner.     

Lipid-rich residual bodies in human myometrium: qualitative observations.

Uterine leiomyomata and histologically normal myometrium were examined by light and electron microscopy. All myometrial samples contained smooth muscle cells with distinctive cytoplasmic inclusions located at the nuclear poles. These were seen in only one case in routine paraffin wax sections, where they appeared as clear vacuoles, but they were more obvious in epoxy resin sections stained with toluidine blue. Staining with Oil Red O and for acid phosphatase was positive at the site of the vacuoles. In ultrathin sections, these structures possessed a single membrane and contained abundant lipid droplets, with a sparse, coarsely granular matrix. They were designated as lipid-rich residual bodies. Such organelles were all but absent from leiomyomata. Lipid-rich residual bodies with the features described here have not been studied in detail before in smooth muscle cells of the human myometrium. The possibility that they arise from the cyclical stimulation of lipid synthesis by ovarian hormones is discussed.     

246例子宫平滑肌肿瘤临床病理分析

目的:探讨子宫平滑肌肿瘤临床病理特征.方法:对246例子宫平滑肌肿瘤的临床病理资料进行回顾性分析.结果:子宫平滑肌肿瘤发病高峰年龄为40～50岁,可伴内膜增生或腺肌病,同时与卵巢、宫颈多种良恶性病变并存.246例子宫平滑肌肿瘤中,91.4%为普通型良性平滑肌瘤;6.9%为平滑肌瘤特殊组织学类型;0.8%为平滑肌肉瘤;0...     

Mesometrial smooth muscle as an origin of female retroperitoneal (pelvic) leiomyomas

Retroperitoneal (pelvic) leiomyomas have recently come to be recognized as distinctive lesions. Retroperitoneal leiomyomas occur almost exclusively in women, and past studies on these invariably emphasized a striking similarity between their histological features, with those of uterine leiomyoma, whereas their origin remains unknown. In this study, we took notice of mesometrial smooth muscle, which has been little known either clinically or pathologically, as a possible origin of tumor. Anatomically, the mesometrial smooth muscle was an accumulation of thin bundles (approximately 1 mm in thickness) that ran parallel to the oviduct. It was connected broadly with the lateral wall of the uterine body and ended in the pelvic floor. The mesometrial smooth muscle was present just beneath the serosal surface of the anterior aspect of the mesometrium and continuously transited from the smooth muscle bundles of the outer layer of the uterine myometrium. The muscle cells were immunopositive for smooth muscle cell markers and estrogen/progesterone receptors. In all of the six female retroperitoneal leiomyomas examined, hormone receptor-positive nontumorous smooth muscle layers were present in the periphery of the tumors, seemingly representing the mesometrial smooth muscles. In conclusion, we believe most retroperitoneal (pelvic) leiomyomas in females arise from the mesometrial smooth muscle.     

The growth arrest-specific gene CCN5 is deficient in human leiomyomas and inhibits the proliferation and motility of cultured human uterine smooth muscle cells

Uterine fibroids (leiomyomas) are a major women's health problem. Currently, the standard for treatment remains hysterectomy, since no other treatment modalities can reduce both symptoms and recurrence. As leiomyomas are benign neoplasias of smooth muscle cells, we sought to understand the regulation of uterine smooth muscle cell mitogenesis by CCN5, a growth arrest-specific gene in vascular smooth muscle cells which is induced and maintained by heparin treatment. Using autologous human myometrial and leiomyoma smooth muscle cells, we demonstrate that the proliferation and motility of both cell types are inhibited by the overexpression of CCN5. Surprisingly, we show that even though CCN5 is induced by heparin in vascular smooth muscle cells, treatment with heparin does not induce CCN5 expression in human uterine smooth muscle cells. Furthermore, we examine CCN5 mRNA expression in 10 autologous pairs of human myometrial and leiomyoma tissues and determine that CCN5 is down-regulated in 100% of the leiomyoma tissues analysed when compared to their normal myometrial counterparts. Thus, our data strongly suggest that CCN5 may exert an important function in maintaining the normal uterine phenotype and that loss of the anti-proliferative protein CCN5 from normal myometrium may account, at least in part, for tumorigenesis.     

Progesterone, estradiol and their receptors in leiomyomata and the adjacent normal myometria of black Kenyan women

The contents of progesterone and oestrogen, and their respective receptors in uterine leiomyomata and adjacent normal myometrial tissue in indigenous black women in Kenya were studied. A random selection of twenty women undergoing hysterectomy for uterine fibroids at Kenyatta National Hospital was used for the studies. The myometria contained higher levels of E(2 ) (181% : P < 0.001); and P(4 ) (240.6 % : P < 0.001); as compared to the leiomyomata. On the other hand uterine leiomyomata contained significantly higher levels of ER (147.6% : P < 0.001); and PR (178.7% : P < 0.001 ); than normal myometria. These findings differ slightly from those reported in black women in developed countries, but support the proposal that manipulation of sex steroids may be useful in the treatment and management of uterine leiomyomata.     

Cell proliferation and apoptosis in human uterine leiomyomas and myometria

To determine the role of cell proliferation and apoptosis in uterine leiomyoma growth, we studied protein expression of two major regulatory proteins of apoptosis -- Bcl-2 (anti-apoptotic) and Bax (pro-apoptotic) -- and two endogenous markers of cell replication - proliferating cell nuclear antigen (PCNA) and Ki-67 - in tumors and matched myometrium from premenopausal women. Conventional mitotic indices also were determined, and all proliferation data were correlated to tumor size. In situ end-labeling of fragmented DNA and routine histology were used to assess apoptosis. Our results showed that the apoptosis-regulating proteins (Bcl-2 and Bax) were expressed in the cytoplasm of the leiomyoma and myometrial smooth muscle cells throughout the menstrual cycle. Bax expression differed from Bcl-2 in that it also was found in the cytoplasm of vascular smooth muscle cells of the myometria and tumors. Both tumors and myometrial samples expressed 26-kDa and 21-kDa proteins that reacted with antibodies directed towards Bcl-2 and Bax, respectively. Apoptosis was not a prominent feature of uterine leiomyomas or myometrium. PCNA- and Ki-67-labeling and mitotic counts were significantly ( P<0.05) higher in leiomyomas than in matched myometrial samples. Proliferative activity was variable for individual tumors of the same patient and independent of tumor size. Our results suggest that altered apoptosis by overexpression of Bcl-2 or by decreased expression of Bax does not appear to be a major factor in uterine leiomyoma growth. We conclude that increased cell proliferation is the most significant contributor to growth and that the proliferative state is autonomous for each tumor in a given patient and is independent of tumor size.     

Heparin inhibits the motility and proliferation of human myometrial and leiomyoma smooth muscle cells

Uterine fibroids (leiomyomas) are a major women's health problem. Currently, the standard for treatment remains hysterectomy, because no other treatment modalities can reduce both symptoms and recurrence. As leiomyomas are a hyperproliferation of smooth muscle cells, we sought to understand the regulation of uterine smooth muscle cell mitogenesis by the glycosaminoglycan heparin, which has been extensively studied as an anti-proliferative molecule in vascular smooth muscle cells. Using matched pairs of human myometrial and leiomyoma smooth muscle cells from the same uterus, we demonstrate that the proliferation and motility of both cell types are inhibited by heparin. We report that the decrease in cell number seen in the presence of heparin is not because of cell death. Interestingly, there is significant patient-to-patient variability in the proliferation response but not in the motility response to heparin. Furthermore, nonanticoagulant and anticoagulant heparin were equally effective at inhibiting leiomyoma and myometrial smooth muscle cell proliferation. These results warrant further investigation into the possibility that heparin might be useful in the treatment of uterine fibroids.     

Molecular and cytogenetic characterization of plexiform leiomyomata provide further evidence for genetic heterogeneity underlying uterine fibroids

The plexiform variant of uterine leiomyomata (UL) is named for its ribbons or nests of smooth muscle cells that have a rounded, epithelioid shape caused by their entrapment in abundant extracellular matrix. Plexiform UL are currently classified as epithelioid smooth muscle tumors alongside the less predictable, "true" epithelioid tumors (ie, leiomyoblastomas). Karyotypes of six plexiform UL cases were studied, and their abnormalities were found to differ from those of leiomyoblastomas. Analyses using real-time polymerase chain reaction, immunohistochemistry, and fluorescence in situ hybridization demonstrated elevated mRNA and protein levels of the architectural factor HMGA2 and, in some cases, increased DNA copy number. Four of these plexiform UL were profiled with Affymetrix human U133 plus 2.0 expression arrays. Cluster analysis using genes previously shown to discriminate benign and malignant uterine smooth muscle tissues revealed that the plexiform tumors form an isolated group in the benign branch. This is in contrast to an earlier finding in which another variant, cellular UL characterized by loss of a portion of the short arm of chromosome 1, clustered with malignant leiomyosarcomas. These results provide additional evidence of genetic heterogeneity underlying UL of various histological types. We further suggest that plexiform UL should be classified among tumors with extensive hyalinization rather than with "true" epithelioid smooth muscle neoplasms.     

An immunohistochemical analysis of stathmin 1 expression in uterine smooth muscle tumors: differential expression in leiomyosarcomas and leiomyomas

The oncogenic phosphatidylinositol 3-kinase-AKT-mammlian target of rapamycin pathway (PI3K-AKT-mTOR) pathway is known to be activated in uterine smooth muscle tumors, and Stathmin 1 (STMN1) expression has been identified as a marker of PI3K-AKT-mTOR pathway activation. We hypothesized that STMN1 may have some diagnostic utility and explored how well STMN1 expression correlated with histologic classifications of uterine smooth muscle tumors into benign and malignant groupings. 84 smooth muscle tumors were assessed for STMN1 expression by immunohistochemistry. These included spindle cell leiomyosarcoma (n = 32), conventional spindle cell leiomyomas (n = 30), atypical (symplastic) leiomyoma (n = 5), cellular leiomyoma (n = 7), smooth muscle tumor of uncertain malignant potential (n = 4), mitotically active leiomyomas (n = 2), benign metastasizing leiomyoma (n = 3), and cotyledonoid dissecting leiomyoma (n = 1). All spindle cell leiomyosarcomas were positive (32/32 positive; 100%) as compared with conventional leiomyomata (11/30; 37%) (P < 0.0001). The average immunohistochemical score (0-12+, reflective of intensity and extent) for leiomyosarcomas was 8.7 (± 1.43) whereas the conventional leiomyomata average score was 1.6 (± 1.07) (P < 0.0001). This difference in scores was reflected in the patterns of expression: leiomyosarcomas were predominantly strongly and diffusely positive whereas leiomyomata were predominantly weakly, albeit diffusely positive when expression was present. The sensitivity of STMN1 expression for leiomyosarcomas was 100%. However, the specificity was found to be only 55% (CI = 43-68%). The negative and positive predictive values for leiomyosarcomas were 100% and 52% respectively. The odds ratio (OR) for any STMN1 expression in predicting a spindle cell leiomyosarcoma diagnosis from this dataset was highly significant (OR = 144, P = 0.0006). Thirteen non-smooth muscle tumors that involved the uterus all showed at least focal STMN1 immunoreactivity. In summary, STMN1 is a highly sensitive marker for leiomyosarcoma but is suboptimally specific for diagnostic purposes. The 100% negative predictive value for leiomyosarcoma may offer some diagnostic utility in a small sample, since the absence of STMN1 immunoreactivity in a putative leiomyosarcoma is a strong argument against this diagnostic possibility.