Supplementary Material for: Circular RNA hsa_circ_0068252 functions in cisplatin resistance and immune response via miR-1304-5p/PD-L1 axis in non-small cell lung cancer

Background: Research suggests that circRNAs play important roles in non-small cell lung cancer (NSCLC). The function of hsa_circ_0068252 in NSCLC, especially in cisplatin (DDP) resistance and the mechanisms, was explored in this study. Methods: NSCLC patient samples and two NSCLC cell lines along with corresponding DDP-resistant cell lines were used. Expression levels of circ_0068252 was detected. SiRNA for circ_0068252 and inhibitor for miRNA were used in all functional analysis. A co-culture system of NSCLC cells with CD8+ T cells was used. The cellular location of circ_0068252 was detected and its target miRNA was predicted and verified. Finally, the mechanism responsible for circ_0068252 function on PD-L1 was analyzed using luciferase reporter assay in the two DDP-resistant cell lines, as well as in the co-culture system. The cytotoxicity of T cells was detected by lactate dehydrogenase (LDH) assay. Results: Our findings revealed that high level of circ_0068252 was correlated with poor prognosis of NSCLC and DDP resistance. Knockdown of circ_0068252 could promote the sensitivity of DDP-resistant NSCLC cells to DDP. Moreover, knockdown of circ_0068252 could regulate the immune micro-environment which was mediated via CD8+ T cells. Finally, circ_0068252 could up-regulate PD-L1 expression by adsorbing miR-1304-5p. Conclusion: The circ_0068252/miR-1304-5p/PD-L1 signal axis participates in the regulation of DDP resistance and immune escape of NSCLC cells. Our results suggest that circ_0068252 may be a potential diagnostic marker and therapeutic target for DDP-resistant NSCLC.