Background Non-small cell lung cancer (NSCLC) cells derived intracellular and extracellular programmed cell death ligand 1 (PD-L1) promoted cancer progression and drug resistance, and facilitated tumor immune evasion. However, the detailed molecular mechanisms are still largely unknown. In the present study, we aimed to explore the role of circular RNA circ-CPA4/let-7 miRNA/PD-L1 axis in the regulation of NSCLC progression, drug resistance and tumor immune microenvironment. Methods Real-Time qPCR and Western Blot analysis were conducted to examine gene expressions at transcriptional and translated levels, respectively. The regulatory mechanisms of circ-CPA4, let-7 miRNA and PD-L1 were validated by dual-luciferase reporter gene system and RNA pull-down assay. Cell growth and apoptosis were determined by CCK-8 assay, colony formation assay and Annexin V-FITC/PI double staining assay. Cell mobility was evaluated by transwell assay. Results Circ-CPA4 and PD-L1 were high-expressed, while let-7 miRNA was low-expressed in NSCLC cells and cancer tissues compared to the human bronchial epithelial (HBE) cells and their paired clinical normal adjacent tissues, respectively. Besides, knock-down of circ-CPA4 inhibited cell growth, mobility and epithelial-mesenchymal transition (EMT), and promoted cell death in NSCLC cells by downregulating PD-L1 through serving as a RNA sponge for let-7 miRNA. In addition, the NSCLC cells derived PD-L1-containing exosomes promoted cell stemness and increased resistance of NSCLC cells to cisplatin. Notably, by co-culturing the NSCLC cells with CD8 + T cells isolated from human peripheral blood mononuclear cells (hPBMCs) in a transwell co-culturing system, we found that NSCLC cells inactivated CD8 + T cells in a secreted PD-L1-dependent manner. Further results suggested that circ-CPA4 also positively regulated exosomal PD-L1, and the NSCLC cells with circ-CPA4 ablation re-activated CD8 + T cells in the co-culturing system. Conclusion Taken together, circ-CPA4 regulated cell growth, mobility, stemness and drug resistance in NSCLC cells and inactivated CD8 + T cells in the tumor immune microenvironment through let-7 miRNA/PD-L1 axis.

More efficient drug delivery system and formulation with less adverse effects are needed for the clinical application of broad-spectrum antineoplastic agent doxorubicin (DOX). Here we obtained outer-membrane vesicles (OMVs), a nano-sized proteoliposomes naturally released by Gram-negative bacteria, from attenuated Klebsiella pneumonia and prepared doxorubicin-loaded O0MVs (DOX-OMV). Confocal microscopy and in vivo distribution study observed that DOX encapsulated in OMVs was efficiently transported into NSCLC A549 cells. DOX-OMV resulted in intensive cytotoxic effects and cell apoptosis in vitro as evident from MTT assay, Western blotting and flow cytometry due to the rapid cellular uptake of DOX. In A549 tumor-bearing BALB/c nude mice, DOX-OMV presented a substantial tumor growth inhibition with favorable tolerability and pharmacokinetic profile, and TUNEL assay and H&E staining displayed extensive apoptotic cells and necrosis in tumor tissues. More importantly, OMVs’ appropriate immunogenicity enabled the recruitment of macrophages in tumor microenvironment which might synergize with their cargo DOX in vivo . Our results suggest that OMVs can not only function as biological nanocarriers for chemotherapeutic agents but also elicit suitable immune responses, thus having a great potential for the tumor chemoimmunotherapy.

Lung cancer has been proved to be one of the most common kinds of cancers around the globe. Meanwhile, as the predominant type of lung cancer, lung adenocarcinoma (LUAD) has received increasing attention in cancer research. Long noncoding RNAs (lncRNAs) are known to be associated with oncogenesis and progression of various cancers. However, many lncRNAs have not been thoroughly detected in LUAD. In this study, through bioinformatics analysis we found that zinc finger protein multitype 2 antisense RNA 1 (ZFPM2‐AS1) was associated with poor prognosis of LUAD patients. Also, ZFPM2‐AS1 was detected to be overexpressed in LUAD tissues and cells. Furthermore, ZFPM2‐AS1 could promote the proliferation of LUAD cells. Next, miR‐18b‐5p was found to bind with and negatively regulated by ZFPM2‐AS1. VMA21, target gene of miR‐18b‐5p, could bind with and be negatively regulated by miR‐18b‐5p. More importantly, both ZFPM2‐AS1 and VMA21 were found to be attached to the RNA‐induced silencing complex constructed from miR‐18b‐5p and Ago2. Also, ZFPM2‐AS1 could regulate the expression of VMA21. Therefore, ZFPM2‐AS1 were confirmed to regulate VMA21 by competitively binding with miR‐18b‐5p. Finally, rescue assays confirmed that ZFPM2‐AS1 could regulate LUAD cell proliferation via miR‐18b‐5p/VMA21 axis.