Fig. 1

circRNA expression profiles in MSS/pMMR CRC and characterization of circPHLPP2. a Heatmap of circRNA expression in MSS/pMMR CRC tumor tissues resistant (n = 10) or responsive (n = 8) to anti‑PD‑1 therapy. b Heatmap of circRNA expression in MSS/pMMR CRC tumor tissues (n = 18) and paired adjacent normal tissues (n = 18), cut off is Log2 (Fold change) > 1 or < − 1, P value < 0.05. c A Venn diagram illustrating the overlapping circRNAs that are up-regulated in tissues resistant to anti-PD-1 therapy and in colorectal cancer tissues. d Relative expression of circPHLPP2 in tissues resistant (n = 20) and responsive to anti‑PD‑1 therapy (n = 47) detected by RT-qPCR. e Relative expression of circPHLPP2 in primary CRC tissues and paired adjacent normal tissues measured by RT-qPCR (n = 67). f Kaplan–Meier analysis of overall survival in CRC patients with different circPHLPP2 expression levels (n = 67, log-rank test). g Schematic illustration of circPHLPP2 formation. h The backsplice junction site of circPHLPP2 was identified by Sanger sequencing. i The existence of circPHLPP2 was validated in HCT116 and MC38 cell lines by RT-qPCR and gel electrophoresis. j The relative RNA levels of circPHLPP2 and mPHLPP2 in reverse transcription experiments using Random hexamers or oligo (dT)₁₈ primers. k Resistance of circPHLPP2 and mPHLPP2 to digestion with RNase R was detected by RT-qPCR. l RNA abundance of circPHLPP2 and mPHLPP2 treated with Actinomycin D (2 µg/ml) was detected by RT-qPCR. m The intracellular localization of circPHLPP2 was detected by RNA cytoplasm/ nucleus fractionation assay. n The intracellular localization of circPHLPP2 was detected by FISH in HCT116 cells. Nuclei were stained with DAPI. Data in d, e, j and k were calculated by Student’s t test. Data in l were calculated by two‑way ANOVA test. **P < 0.01, ***P < 0.001, ****P < 0.0001