Fig. 1

circPPFIA1 is downregulated in liver metastatic colorectal cancer. A Transwell invasion and migration assays were carried out to examine the invasive and migratory abilities of KM12C and KM12L4 cells. Metastatic potential was determined by counting the number of invaded and migrated cells, and the representative images are shown. B Liver metastasis was examined through in vivo intrasplenic injection. At four weeks post-injection, the optical and MRI images were obtained. The degree of liver metastasis (n = 5) was calculated by giving scores in arbitrary units (0–3). C Volcano plot illustrating differentially expressed circRNAs in KM12C versus KM12L4. Blue and red dots represent circPPFIA1-L and -S, respectively. D Expression level of circPPFIA1-L and -S in KM12C and KM12L4 cells. E Schematic illustration and detailed information of circPPFIA1-L and -S. F, G Expression levels of circPPFIA1-L, -S, and linear PPFIA1 mRNA were determined by RT-qPCR (F) and semi-qPCR (G). H, I The levels of circPPFIA1-L and -S in primary and liver metastatic colon cancer tissues were determined by RT-qPCR (H) and semi-qPCR (I). Statistical significance was calculated from three independent experiments using the Student’s t-test (*p < 0.05). All data represent mean ± standard deviation (SD)