Global and gene specific DNA methylation in breast cancer cells was not affected during epithelial-to-mesenchymal transition in vitro

Abstract

Epithelial-to-mesenchymal transition (EMT) significantly affects the risk of metastasising in breast cancer. Plasticity and reversibility of EMT suggest that epigenetic mechanisms could be the key drivers of these processes, but little is known about the dynamics of EMT-related epigenetic alterations. We hypothesised that EMT, mediated by autocrine and paracrine signals, will be accompanied by changes in DNA methylation profiles. Therefore, conditioned medium from adipose tissue-derived mesenchymal stromal cells was used for induction of EMT in human breast cancer SK-BR-3 cell line. EMT-related morphological alterations and changes in gene expression of EMT-associated markers were assessed. To reverse EMT, 20 nm size gold nanoparticles (AuNPs) synthesized by the citrate reduction method were applied. Finally, DNA methylation of LINE-1 sequences and promoter methylation of TIMP3, ADAM23 and BRMS1 genes were quantitatively evaluated by pyrosequencing. Despite the presence of EMT-associated morphological and gene expression changes in tumour cells, EMT induced by adipose tissue-derived mesenchymal stromal cells had almost no effect on LINE-1 and gene-specific DNA methylation patterns of TIMP3, ADAM23 and BRMS1 genes. Although treatment for 24, 48 or 72 hours with 20 nm AuNPs at a concentration of 3 µg/ml slightly decreased gene expression of EMT-associated markers in SK-BR-3 cells, it did not alter global or gene-specific DNA methylation. Our results suggest that changes in DNA methylation are not detectable in vitro in early phases of EMT. Previously published positive findings could represent rather the sustained presence of potent EMT-inducing signals or the synergistic effect of various epigenetic mechanisms. Treatment with AuNPs slightly attenuated EMT, and their therapeutic potential needs to be further investigated.

A review on the epigenetics modifications to nanomaterials in humans and animals: Novel epigenetic regulator

“…As reported previously, human em-bryonic kidney (HEK293) cells exposed to high levels of AuNPs (100 µg/mL) for three days exhibited a considerable lowering in global DNA methylation (Sooklert et al, 2019). On the contrary, AuNPs had no considerable effects on DNA demethylating activity in numerous studied cell lines, for example, MRC5 fetal fibroblasts (Ng et al, 2011), human breast cancer cells (SK-BR-3; Smolkova et al, 2016), as well as HepG2 hepatic cancer cells (Brzóska et al, 2019). These disturbances of the impacts of AgNPs on global DNA methylation might be associated with the type of cell line, level of NMs, experimental conditions, duration of exposure, and synthesis of nanomaterial (such as chemical or biogenic methods).…”

Detection of Breast Cancer Cells Using Acoustics Aptasensor Specific to HER2 Receptors

“…Smolkova at al. [29] verified the toxicity of 20 nm AuNPs in the culture medium on SK-BR-3 breast cancer cells. Cells were exposed to four different concentrations of AuNPs (0.8 µg/mL, 4 µg/mL, 21 µg/mL and 28 µg/mL) for 2, 24 and 48 h. The results of this study confirmed the cytotoxic effect of AuNPs already at 4 μg/mL.…”

Genome-wide DNA methylome and transcriptome changes induced by inorganic nanoparticles in human kidney cells after chronic exposure

“…For example, a correlation between an increase in global DNA methylation and the expression of DNA methyltransferases was observed in normal human fibroblasts but not melanoma A375 cells after 24 h exposure to AuNPs (Patil et al 2019 ). In contrast, no change in global DNA methylation was found in HaCaT and HEK293 cells (Sooklert et al 2019 ), human breast SK-BR-3 cells (Smolkova et al 2016 ), or human hepatoma HepG2 cells (Brzóska et al 2019 ) after the short-term exposure to AuNPs. In our study, we identified 102 genes differentially methylated; promoter methylation was present in 48 of them, including 11 TFs.…”