Mechanistic Insights of Anti-Immune Evasion by Nobiletin through Regulating miR-197/STAT3/PD-L1 Signaling in Non-Small Cell Lung Cancer (NSCLC) Cells

Abstract

Tumor immune escape is a common process in the tumorigenesis of non-small cell lung cancer (NSCLC) cells where programmed death ligand-1 (PD-L1) expression, playing a vital role in immunosuppression activity. Additionally, epidermal growth factor receptor (EGFR) phosphorylation activates Janus kinase-2 (JAK2) and signal transduction, thus activating transcription 3 (STAT3) to results in the regulation of PD-L1 expression. Chemotherapy with commercially available drugs against NSCLC has struggled in the prospect of adverse effects. Nobiletin is a natural flavonoid isolated from the citrus peel that exhibits anti-cancer activity. Here, we demonstrated the role of nobiletin in evasion of immunosuppression in NSCLC cells by Western blotting and real-time polymerase chain reaction methods for molecular signaling analysis supported by gene silencing and specific inhibitors. From the results, we found that nobiletin inhibited PD-L1 expression through EGFR/JAK2/STAT3 signaling. We also demonstrated that nobiletin exhibited p53-independent PD-L1 suppression, and that miR-197 regulates the expression of STAT3 and PD-L1, thereby enhancing anti-tumor immunity. Further, we evaluated the combination ability of nobiletin with an anti-PD-1 monoclonal antibody in NSCLC co-culture with peripheral blood mononuclear cells. Similarly, we found that nobiletin assisted the induction of PD-1/PD-L1 blockade, which is a key factor for the immune escape mechanism. Altogether, we propose nobiletin as a modulator of tumor microenvironment for cancer immunotherapy.

Integrating HPLC-Q-TOF-MS/MS, network pharmacology and experimental validation to decipher the chemical substances and mechanism of modified Gui-shao-liu-jun-zi decoction against gastric cancer

“… 64 Nobiletin inhibited PD-L1 expression to reduce anti-immune evasion through the inhibition of the EGFR/JAK2/STAT3 signaling pathway. 65 …”

Antioxidant Properties and Aldehyde Reactivity of PD-L1 Targeted Aryl-Pyrazolone Anticancer Agents

“…We consider that the development of a PD-L1 inhibitor with marked antioxidant properties can be beneficial. It has been shown that antioxidants can enhance the efficacy of immunotherapy via different mechanisms: (i) via a down-regulation of PD-L1 expression in cancer cells, as observed with the antioxidant natural products such as cardamonin, nobiletin, sesamin and hesperetin [ 40 , 41 , 42 , 43 ], (ii) via an upregulation of major histocompatibility complex and surface activation molecules in dendritic cells, as reported with the antioxidant polysaccharide fucoidan [ 44 ], (iii) via the stimulation of TET2 enzyme leading to an increased intratumoral infiltration of T cells and the expression of cytokines and chemokines, as found recently with the prototypical antioxidant ascorbic acid [ 45 ], or (iv) via other mechanisms implicating the HIF1α/STAT3 pathway for example [ 46 ]. Ascorbic acid (vitamin C) has been shown to empower cancer immunotherapy through its pro-oxidant potential, based on its capacity to modulate epigenetic factors and to regulate expression of different cytokines involved in the immune response [ 47 , 48 ].…”

MicroRNAs as regulators of immune checkpoints in cancer immunotherapy: targeting PD-1/PD-L1 and CTLA-4 pathways

“…It effectively inhibits the expression of PD-L1 by targeting the EGFR/JAK2/STAT3 signaling pathway in NSCLC. Nobiletin demonstrates p53-independent suppression of PD-L1 and miR-197 is identified as a regulator of STAT3 and PD-L1 expression [ 233 ].…”