Supplementary MaterialsSUPPLEMENTAL MATERIAL 41419_2018_485_MOESM1_ESM. and promoted proliferation via acting as a GSK2110183 analog 1 sponge of microRNA-217. Further, exosomal circRNA_100284 was upregulated in the sera of people exposed to arsenite. Thus, exosomes derived from transformed L-02 cells transferred circRNA_100284 to surrounding cells, which induced an accelerated cell cycle and promoted proliferation of normal liver cells and led to the malignant transformation of the non-transformed cells. The findings support the concept that exosomal circRNAs are involved in cellCcell communication during carcinogenesis induced by arsenite. Introduction Arsenic is a naturally existing, GSK2110183 analog 1 toxic metalloid that is often a contaminant in drinking water, and there can be harmful effects from arsenic even when levels are below the drinking water standard. Long-term exposure to arsenic is associated with lung, bladder, and skin cancer, and with noncancerous disorders such as cardiovascular disease, diabetes, and skin lesions1,2. Carcinogenesis induced by arsenic is related to genetic variants3,4, oxidative DNA damage5, and DNA methylation6. Inorganic arsenic affects various signaling pathways7 and stimulates cell proliferation by increasing the population of cells in the S phase of the cell cycle8. However, the molecular mechanisms remain unclear. Noncoding RNAs (ncRNAs) are not translated into protein. Abundant and functionally active types of noncoding RNAs include transfer RNAs (tRNAs), ribosomal RNAs (rRNAs), small RNAs such as microRNAs (miRNAs), and long ncRNAs (lncRNAs). Chronic exposure to arsenite causes abnormal expression of various ncRNAs, including miR-21;9 miR-143;10 and the lncRNA MALAT111. Circular RNA (circRNA), unlike the better-known linear RNA, has a covalently closed, continuous loop, with the 3 and 5 ends joined together. For humans, thousands of circRNAs have been identified by use of p(A)-without RNase R RNA-seq data12. Several circRNAs serve as biomarkers in the development of hepatocellular carcinomas and regulate gene expression by acting as miRNA sponges13,14. By use of a circRNA microarray, we found, in a previous study, that, in arsenite-transformed HaCaT cells, circRNA_100284 showed the greatest upregulation and was involved in the arsenite-accelerated cell cycle of human keratinocytes in the process of carcinogenesis15. In the tumor microenvironment, crosstalk ERK1 of malignant cells with nonmalignant cells is essential for tumor progression16. Exosomes, with diameters of 30C100?nm, are cell-derived vesicles that are present in many, and perhaps all, eukaryotic fluids, including blood, and urine, and in the culture medium of cells17,18. Exosomes carry messenger RNAs (mRNAs), miRNAs19, and double-stranded DNA20. Exosomes are involved in cell-to-cell signaling and may influence processes in normal cells because they can merge with and release their contents into cells that are distant from their cell of origin. GSK2110183 analog 1 For example, as shown in our previous studies, RNAs shuttled from one cell to another, known as exosomal shuttle RNAs, can affect protein production in normal cells21,22. In exosomes, circRNAs are enriched and stable23, and, in KRAS mutant colon cancer cells, circRNAs can be transferred into exosomes24. However, the functions of exosomal circRNAs remain GSK2110183 analog 1 undefined. In the present study, we investigated the influence of arsenic-transformed L-02 cells on the cell cycle and cell proliferation of normal liver cells. Chronic exposure to arsenite elevated circRNA_100284 levels, which were involved in the malignant transformation of normal L-02 cells. circRNA_100284 was contained in exosomes released by transformed cells and could be transferred into normal cells, and exosomal circRNA_100284 regulated the cell cycle and stimulated cell proliferation of normal liver cells by interacting with miRNA-217 (miR-217). These findings contribute to an understanding of the processes involved in carcinogenesis caused by arsenite. Materials and methods Cell culture and reagents L-02 cells, GSK2110183 analog 1 a line of normal human liver cells, were obtained from the Shanghai Institute of Cell Biology, Chinese Academy of Sciences (Shanghai, China) and were maintained in 5% CO2 at 37?C in RPMI-1640 medium supplemented with 10% fetal bovine serum (FBS,.