Inhibition of osteosarcoma by European Mistletoe derived val-miR218

In recent years, there has been a growing interest in the therapeutic potential of plant-derived miRNAs, which have been considered new bioactive ingredients in medicinal plants. Viscum album L., commonly used as an adjuvant cancer therapy in central Europe, contains a large number of miRNAs associated with human diseases such as cancer, cardiovascular diseases, and neurological disorders. This study aimed to investigate whether mistletoe miRNAs, specifically val-miR218, exert anti-cancer activity against osteosarcoma.

The anti-cancer effects of miRNAs from V. album L. were evaluated. The targets of val-miR218 were identified by RNA-seq. The mRNA and protein expression of the targets was confirmed by RT-qPCR and western blot analyses. The interaction between the val-miR218 and miRNA recognition elements (MREs) was validated by the dual-luciferase assay. The inhibitory effect of val-miR218 against osteosarcoma was investigated in vivo.

Among these abundant miRNAs in V. album L., val-miR218 showed high potential anti-cancer effects against osteosarcoma. To clarify its molecular mechanism of action, we sequenced val-miR218 associated RNAs and their down-regulated RNAs. As a result, 61 genes were considered the direct targets of val-miR218. Interestingly, these targets were related to essential cellular functions such as cell cycle, DNA replication, and cell morphology, suggesting that val-miR218 significantly inhibited cell growth and arrested osteosarcoma cells in G0/G1 phase by influencing basic cell activities. Mistletoe extracellular vesicles offered val-miR218 adequate protection and facilitated the uptake of val-miR281 by human cells. Moreover, val-miR218 showed significant anti-tumor effects in vivo.

This study demonstrated the significant potential of val-miR218 regarding proliferation inhibition in various tumor cell lines in vitro and for osteosarcoma in vivo. Due to the increasing problems during chemotherapy, new therapeutic approaches are becoming more critical. The significant anti-cancer effects of medicinal plants derived miRNAs indicate a promising therapeutic strategy for treating cancer.