DNA methyltransferase inhibitors influence on the DIRAS3 and STAT3 expression and in vitro migration of ovarian and breast cancer cells.

OBJECTIVES: Downregulation of DIRAS3 (DIRAS family, GTP-binding Ras-like 3) is related to ovarian and breast cancer progression. A possible mechanism that silences this gene is the promoter region DNA methylation. The potential reversibility of this epigenetic mechanism makes it more attractive candidate for new mode of cancer treatment. DIRAS3 regulates cell cycle, tumor dormancy and inhibits cancer cell growth and motility, all of which may indirectly depend on interaction with STAT3 (Signal Transducer and Activator of Transcription 3) classified as a potential oncogene. The restoration of DIRAS3 expression could inhibit cell proliferation and invasiveness. MATERIAL AND METHODS: Human ovarian carcinoma cell line (A2780) and human breast cancer cell line (MCF7) were exposed to two DNA methyltransferase inhibitors (DNMTi): decitabine (5-aza-2'-deoxycytidine) [25 µM and 12.5 µM] and RG108 [150 µM and 100 µM]. In vitro migration changes of cancer cells were examined with wound healing assay. After 7 days of DNMTi treatment cells were harvested and DNA and RNA was isolated. The methylation status of the promoter sequences of DIRAS3 and STAT3 genes was determined using methylation specific PCR (MS-PCR). Level of target genes' expression was quantified using quantitative reverse transcription PCR (QRT-PCR). RESULTS AND CONCLUSIONS: The in vitro wound healing assay showed changes in the migration rate of both adherent cell lines after DNMTi treatment compared to the untreated cells. Relative balance between methylated and unmethylated variants of DIRAS3 after MS-PCR was shifted towards unmethylated version after DNMTi treatment in A2780 cells. Statistically significant dose dependent effect of decitabine and RG108 on DIRAS3 expression in A2780 cells was observed.

[Silencing of the STAT3 gene expression activity and cancer cells metastatic potential at in vitro studies]. / Wyciszanie aktywnosci ekspresyjnej genu STAT3, a potencjal metastatyczny komórek nowotworowych w badaniach in vitro.

INTRODUCTION: The STAT proteins are the mediators in the signal transduction in between extracellular environment and nucleus. Based on its own activity STATs regulate expression of genes involved in normal and pathological cellular processes. Constitutive STAT3 activation, the results of different cytokines inductions, has been shown in many primary human cancers. STAT3, as an oncogenic protein, plays an important role in the regulation of autonomous properties of cancer cells. MATERIAL AND METHODS: In this study the effectiveness of the STAT3 gene expression activity silencing with RNA interference method was assessed. pSUPER.neo shRNA coding expression vector: shRNA-STAT3 and control vectors: shRNA-SCR, and pGFP were used. Effects of silencing of the examined gene was described as the phenotype changes of modulated HeLa (CCL-2) cancer cell line. To characterize modulated cancer cells phenotype changes two methods were applied: Wound Healing Assay and the stimulation to the apoptosis with anisomycin. RESULTS: According to control cells, the silencing of the STAT3 gene expression activity reduced the mobility of modulated cells as well after 24 as after 48 hours after modulation. Also, after anisomycin stimulation the increasing in apoptotic modulated cell death was seen. CONCLUSIONS: The inhibition of the activity of the STAT3 gene decreases HeLa cell migration, moreover the blocked STAT3 ability to the antyapoptotic gene expression activation leads to the increased susceptibility to apoptotic cell death.