The effects of the prolonged Cd exposure on gene expression changes in in Uterine Leiomyoma Cells [cancer progression]

The heavy metal Cadmium (Cd), a widespread environmental contaminant, poses serious hazards to human health, and is considered a metallohormone and carcinogen. In women with uterine fibroids, there is a significant association between blood Cd levels and fibroid tumor size. The aim of this study was to determine if benign uterine fibroid cells could be malignantly transformed in vitro by continuous Cd exposure, and if so, explore a molecular mechanism by which this could occur. We found when fibroid cells were exposed to 10 µM CdCl2 for 8 weeks, a robust and fast-growing Cd- Resistant Leiomyoma (CR-LM) culture was established. The CR-LM cells showed the ability to form viable colonies in soft agar, increased glycogen aggregates, enhanced cell motility, a higher percentage of cells in G2/M phase, and increased expression of the proliferation marker Ki-67. NanoString analysis showed downregulation of genes encoding for ECM components, such as collagens, fibronectins, laminins, and SLRP family proteins; whereas, genes involved in ECM degradation (MMP1, MMP3 and MMP10) were significantly upregulated. A volcano plot showed that the direction of expression changes of the top differentially genes favored cancer progression. Functional analysis by IPA predicted a significant inhibition of TGFβ signaling, leading to enhanced proliferation and attenuated fibrosis. Prolonged Cd exposure altered phenotypic characteristics and dysregulated genes in fibroid cells predicative of progression towards a cancer phenotype. Therefore, continuous Cd exposures changes the phenotype of benign fibroid cells in vitro and could possibly pose a health risk for women with uterine fibroids. A human uterine leiomyoma cell line immortalized via retroviral transfection of telomerase (ht-UtLM) was generated by our laboratory. For 8-week Cd-exposure experiment, the ht-UtLM cultures were maintained continuously in ht-UtLM culture medium supplemented with 10 μM CdCl2 for 8 weeks. The culture medium was replaced with fresh medium with 10 μM CdCl2 every 3 days. Passage-matched control ht-UtLM cultures were run concurrently with Cd exposed cells. All cultures were kept in a standard tissue culture incubator at 37°C with 5% CO2.