Fig. 1

Discovery and characteristics of a new gemcitabine resistance-related circRNA in pancreatic cancer. A-B Two gemcitabine-resistant PDAC cell lines (PANC-1-GR, BxPC-3-GR) were established and confirmed using the IC50 and Cell viability C Volcano plots showing the up-regulated (red) and down-regulated (blue) circRNAs in PDAC from GSE79634, GSE69362 and circRNA-seq of PANC-1 (WT vs GR) (fold change > 2 or < 0.5, P < 0.05). D The Venn diagram shows the intersection of upregulated circRNA among the three results. E Schematic diagram of chromosomal location and formation of circ-MTHFD1L. F PCR detection of circ-MTHFD1L and linear transcript of MTHFD1L by divergent and convergent primers in cDNA and genomic DNA (gDNA). G Relative RNA level of circ-MTHFD1L and linear MTHFD1L treated with RNase R. H Relative RNA level of circ-MTHFD1L and linear MTHFD1L treated with actinomycin D at the indicated time. I The expression levels of circ-MTHFD1L in PADC cells (8988, AsPC-1, BxPC-3, PANC-1, SW1990) and normal human pancreatic duct epithelial (HPDE) were analyzed by qRT-PCR. J The expression levels of circ-MTHFD1L in tumor and matched non-tumor tissues from 96 gemcitabine-treated PADC patients were analyzed by qRT-PCR. K-L Kaplan-Meier survival analysis showed that PADC patients with low and high circ-MTHFD1L expression of overall survival and PFS. The median circ-MTHFD1L expression was used as the cutoff value. M Relative RNA level of circ-MTHFD1L in PFS < 10 months group and PFS ≥ 10 months group were analyzed by qRT-PCR. N Localization of circ-MTHFD1L (red) in PANC-1-GR cells and BxPC-3-GR cells using fluorescence in situ hybridization(FISH). Cell nuclei were counterstained with DAPI (blue). Scale bar, 50 μm. Data are shown as mean ± SD. *P < 0.05; ** P < 0.01; *** P < 0.001, between the indicated groups