Fibroids display an anti-angiogenic gene expression profile when compared with adjacent myometrium

Abstract

The aetiology of uterine fibroids remains unknown, despite causing significant gynaecological morbidity. Fibroids have a reduced microvascular density when compared with adjacent myometrial tissue. The aim of this study was to identify genes with differential expression between fibroid and adjacent normal myometrium, particularly genes with a role in angiogenesis. Total RNA was extracted from fibroid/myometrium pairs from 12 hysterectomy specimens, and used to perform 24 cDNA microarrays. There were 10,500 genes screened on each microarray for differential expression. Analysis of expression data was carried out using multiple t-tests, as well as a novel class prediction algorithm (GeneRaVE). The differential gene expression of selected genes was confirmed by quantitative 'real time' RT-PCR. Selected genes with a role in angiogenesis were further analysed for expression in isolated cell populations of endothelial cells (fibroid and myometrium) and smooth muscle cells (fibroid and myometrium), to see if their expression was confined to particular cell types. Twenty-five genes with differential gene expression between fibroid and myometrium were identified. Insulin-like growth factor-2, endothelin A receptor, connective tissue growth factor (CTGF), cysteine-rich angiogenic inducer 61 (CYR61) and collagen 4alpha2 (COL4A2) were confirmed by RT-PCR. CTGF and CYR61, both angiogenesis promoters, were reduced in expression relative to myometrium. COL4A2, the precursor for an angiogenesis inhibitor, canstatin, was increased relative to myometrium. These three genes display an anti-angiogenic expression profile in fibroids relative to myometrium. These findings may explain the reduced microvascular density seen in fibroids relative to myometrium.

Expression of insulin-like growth factors (IGFs) and IGF signaling: molecular complexity in uterine leiomyomas

“…Over-expression of IGF-2 in fibroids has been identified in many independent global gene profiling analyses (15)(16)(17)(18)(19)(20)(21). Insulin-like growth factor-2 is one of a few growth factors identified by global transcription profiling as up-regulated, and the level of its over-expression is generally in the range of a two-to threefold increase in fibroids compared with matched myometrium (5).…”

“…The mitogenic role of IGF-1 in fibroid growth has been reported both in vitro and in vivo (10)(11)(12). As a potent mitogenic factor (13), IGF-2 was reported to be overexpressed in fibroids in 1990 (14), and recent global gene transcription profiling analyses have supported the speculation that it is one of few genes constantly over-expressed in fibroids (15)(16)(17)(18)(19)(20)(21). However, the function and regulation (22)(23)(24) of IGF-2 in fibroids are largely unknown.…”

SPARC-like1 mRNA is overexpressed in human uterine leiomyoma

“…Weston et al found that these fibroids have an anti-angiogenic expression profile (6), which may explain the reduced microvascular density observed in fibroids relative to the myometrium. Furthermore, a review of gene expression data revealed concordant changes in the genes regulating retinoid synthesis, insulin-like growth factor metabolism, transforming growth factor signaling and extracellular matrix formation (7).…”

Early growth response gene-1 plays a pivotal role in down-regulation of a cohort of genes in uterine leiomyoma

“…Gene array studies have been conducted to clarify the alteration of gene expression profiles in uterine leiomyoma and have identified numerous genes for which expression is up-or down-regulated compared with levels in normal myometrium (Tsibris et al 2002, Catherino et al 2003, Chegini et al 2003, Skubitz & Skubitz 2003, Wang et al 2003, Weston et al 2003, Hoffman et al 2004, Quade et al 2004. Although the total number of genes analyzed in each array has varied, 5-358 genes per study have been identified as down-regulated in leiomyoma, greatly exceeding the number of up-regulated genes in eight out of nine independent array-based studies (Tsibris et al 2002, Ahn et al 2003, Catherino et al 2003, Chegini et al 2003, Skubitz & Skubitz 2003, Wang et al 2003, Weston et al 2003, Quade et al 2004, Arslan et al 2005.…”

“…Although the total number of genes analyzed in each array has varied, 5-358 genes per study have been identified as down-regulated in leiomyoma, greatly exceeding the number of up-regulated genes in eight out of nine independent array-based studies (Tsibris et al 2002, Ahn et al 2003, Catherino et al 2003, Chegini et al 2003, Skubitz & Skubitz 2003, Wang et al 2003, Weston et al 2003, Quade et al 2004, Arslan et al 2005. Downregulated genes would play an important role in leiomyoma phenotype, similar to or more important than up-regulated genes.…”