The role of exosomal inhibitors in epigenetic regülation

DNA methylation is one of the main mechanisms of epigenetic gene regulation and the most well-known epigenetic marks. This epigenetic modification is catalyzed by DNA methyltransferases (DNMTs) and are divided into two groups based on their functions; maintenance DNMT (DNMT1) and de novo DNMTs (DNMT 3A and DNMT3B). Aberration of DNA methylation occurs frequently in prostate cancer and has been associated with increased DNMT enzyme expression. Exosomes are one of the key mechanisms in cell-cell communication and play an important role in not only tumor progression but also non-mutational epigenetic reprogramming in recipient cells. In the light of this information, we aimed to determine, firstly whether DNA methyltransferase enzymes are among the exosomal cargo molecules derived from prostate cancer cells at transcripsional and translational levels, secondly how exosomal DNMTs affect the expression of DNMTs in recipient cells, and finally the effect of spesific exosome inhibitors on the expression of DNMTs. The expression of DNMTs (DNMT1, DNMT3A and DNMT3B) were analyzed by qPCR in exosome, recipient cells with/without treatment with an exosome inhibitor (GW4869).Protein expression was determined by immunoblotting. Exosome was isolated using exosome isolation reagent. For the first time, we show that DNMT mRNAs (DNMT1, DNMT3A, DNMT3B) were involved among exosomal cargo molecules in prostate cancer-derive exosomes. Thereafter, we observed an increase in DNMT mRNA levels, especially DNMT3A, in PC3 cells treated with exosomes derived from PC3 cells depending on concentration and time. Finally, we determined that in a dose-independent manner, the specific exosome inhibitor GW4869 decreased the expression of DNMTs in PC3 cells containing exosomes at the transcriptional level. However, we observed that GW4869 significantly diminished the expression of DNMT mRNAs in both PC3 cells containing exosomes and non exosome. Our findings showed that prostate cancer derive exosome containing DNMT mRNAs may contribute to the reprogramming of DNA methylation in the recipient cells and we also suggest that exosome inhibitors can be used as new DNMT inhibitors. Further studies are needed to support our results.