Fig. 1

circAKT3 expression is increased in CDDP-resistant GC cells and tissues. a Validated expression of 10 circRNAs in the tissues from 44 GC patients using RT-qPCR. b Expression levels of circAKT3 in CDDP-resistant and their matched sensitive parental cell lines (SGC7901CDDP, BGC823CDDP, SGC7901 and BGC823) normalized to GAPDH expression. c The existence of circAKT3 was validated by Sanger sequencing. The red arrow shows the “head-to-tail” splicing sites of circAKT3. d The existence of circAKT3 was validated in SGC7901CDDP and BGC823CDDP cell lines by RT-PCR. Divergent primers amplified circAKT3 in cDNA but not in genomic DNA (gDNA). GAPDH served as a negative control. e RNA from SGC7901CDDP and BGC823CDDP cells was treated with or without RNase R for RT-qPCR. The relative levels of circAKT3 and AKT3 mRNA were normalized to the values measured in the mock-treated cells. f Levels of small nucleolar RNA (U6, as a positive control for the nuclear fraction), GAPDH (positive control for cytoplasmic fraction), AKT3 mRNA and circRNAs from the nuclear and cytoplasmic fractions of SGC7901CDDP cells. g RNA stability of circular and linear transcripts of AKT3 and of 18S rRNA in SGC7901CDDP cells. h Representative images of RNA FISH of circAKT3 expression in SGC7901CDDP cells, which show that circAKT3 is predominantly localized to the cytoplasm. Nuclei were stained with DAPI. Scale bar, 10 μm. The results are presented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001