Cell-intrinsic PD-L1 signaling drives immunosuppression by myeloid-derived suppressor cells through IL-6/Jak/Stat3 in PD-L1-high lung cancer.

Some patients with non-small-cell lung cancer (NSCLC) benefit from immune checkpoint inhibitors (ICIs) despite programmed death-ligand 1 (PD-L1) expression. To address the mechanism of ICI resistance in PD-L1-positive NSCLC, we investigated the role of tumor-cell-intrinsic function of PD-L1 in interleukin (IL)-6-mediated immunosuppression. Cohorts of NSCLC patients treated with ICI and public datasets were analyzed. PD-L1-overexpressing and PD-L1-knockdown NSCLC cells were submitted to RNA-seq, in vitro analyses, chromatin immunoprecipitation-qPCR, CUT&Tag, and biochemical assays. Human myeloid-derived suppressor cells (MDSCs) sorted from peripheral blood mononuclear cells were co-cultured with NSCLC cells and then assessed for their immunosuppressive activity on T-cells. Mouse Lewis lung carcinoma (LLC) cells with PD-L1 overexpression or knockdown were subcutaneously injected into wild-type or PD-1-knockout C57BL/6 mice in the presence of IL-6 and/or PD-1 blockade. In the ICI cohort with RNA-seq data, the IL-6/Jak/Stat3 pathway was enriched, and IL-6 expression was higher in patients with PD-L1-high NSCLCs who did not respond to ICIs. In another cohort, a higher baseline serum IL-6 level was associated with poor clinical outcomes after ICI therapy. IL-6 expression and the IL-6/Jak/Stat3 pathway were enhanced in PD-L1-high NSCLCs in the ICI cohorts and The Cancer Genome Atlas analysis. IL-6 expression correlated positively with tumor-infiltrating MDSCs in NSCLCs. In NSCLC cells, PD-L1 activated Jak2/Stat3 signaling by binding to and inhibiting protein tyrosine phosphatase 1B. PD-L1 also bound to p-Stat3 in the nucleus, thus promoting the activity of p-Stat3 in the transcription of several cytokines (IL-6, TGF-β, TNF-α, IL-1β) and chemokines. PD-L1-overexpressing NSCLC cells enhanced the migration and immunosuppressive activity of human MDSCs in vitro, mediated by IL-6 and CXCL1. In both wild-type and PD-1-knockout mice, PD-L1-overexpressing LLC tumors were infiltrated by increased MDSCs with high immunosuppressive function, increased Tregs, and decreased granzyme B+ or IFNγ+ CD8 T-cells. These responses were mediated by IL-6 secreted from PD-L1-overexpressing tumor cells. Combined blockade of PD-1 and IL-6 was effective in tumor control and decreased MDSCs while increasing granzyme B+ or IFNγ+ CD8 T-cells. The tumor-cell-intrinsic function of PD-L1 drives immunosuppression and tumor progression through the PD-L1/Jak/Stat3/IL-6/MDSC axis. This pathway represents a potential therapeutic target to improve ICI efficacy in PD-L1-high NSCLC.

Jeong H ，Koh J ，Kim S ，Yim J ，Song SG ，Kim H ，Li Y ，Lee SH ，Chung YK ，Kim H ，Lee CH ，Kim HY ，Keam B ，Lee SH ，Chung DH ，Jeon YK ... -  《Journal for ImmunoTherapy of Cancer》

LKB1 dictates sensitivity to immunotherapy through Skp2-mediated ubiquitination of PD-L1 protein in non-small cell lung cancer.

Loss-of-function mutations of liver kinase B (LKB1, also termed as STK11 (serine/threonine kinase 11)) are frequently detected in patients with non-small cell lung cancer (NSCLC). The LKB1 mutant NSCLC was refractory to almost all the antitumor treatments, including programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) blockade therapy. Unfortunately, mechanisms underlying resistance to immunotherapy are not fully understood. In this study, we deciphered how LKB1 regulated sensitivity to anti-PD-1/PD-L1 immunotherapy. We investigated the mutational landscape of LKB1 mutant NSCLC in next generation sequencing (NGS) data sets. Expression of LKB1, PD-L1 and S-phase kinase-associated protein 2 (Skp2) in NSCLC samples were assessed by immunohistochemistry (IHC). The tumor microenvironment (TME) profiling of LKB1 wild type (WT) and mutant NSCLC was performed using fluorescent multiplex IHC. Mass spectrometry and enrichment analysis were used to identify LKB1 interacting proteins. Mechanistic pathways were explored by immunoblotting, ubiquitination assay, cycloheximide chase assay and immunoprecipitation assay. By using NGS data sets and histological approaches, we demonstrated that LKB1 status was positively associated with PD-L1 protein expression and conferred a T cell-enriched "hot" TME in NSCLC. Patients with good responses to anti-PD-1/PD-L1 immunotherapy possessed a high level of LKB1 and PD-L1. Skp2 emerged as the molecular hub connecting LKB1 and PD-L1, by which Skp2 catalyzed K63-linked polyubiquitination on K136 and K280 residues to stabilize PD-L1 protein. Inhibition of Skp2 expression by short hairpin RNA or its E3 ligase activity by compound #25 abrogated intact expression of PD-L1 in vitro and generated a T cell-excluded "cold" TME in vivo. Thus, the LKB1-Skp2-PD-L1 regulatory loop was crucial for retaining PD-L1 protein expression and manipulation of this pathway would be a feasible approach for TME remodeling. LKB1 and Skp2 are required for intact PD-L1 protein expression and TME remodeling in NSCLC. Inhibition of Skp2 resulted in a conversion from "hot" TME to "cold" TME and abrogated therapeutic outcomes of immunotherapy. Screening LKB1 and Skp2 status would be helpful to select recipients who may benefit from anti-PD-1/PD-L1 immunotherapy.

Lv L ，Miao Q ，Zhan S ，Chen P ，Liu W ，Lv J ，Yan W ，Wang D ，Liu H ，Yin J ，Feng J ，Song Y ，Ye M ，Lv T ... -  《Journal for ImmunoTherapy of Cancer》

PD-L1 and IFN-γ modulate Non-Small Cell Lung Cancer (NSCLC) cell plasticity associated to immune checkpoint inhibitor (ICI)-mediated hyperprogressive disease (HPD).

Non-Small Cell Lung Cancer (NSCLC) is the leading cause of cancer death worldwide. Although immune checkpoint inhibitors (ICIs) have shown remarkable clinical efficacy, they can also induce a paradoxical cancer acceleration, known as hyperprogressive disease (HPD), whose causative mechanisms are still unclear. This study investigated the mechanisms of ICI resistance in an HPD-NSCLC model. Two primary cell cultures were established from samples of a NSCLC patient, before ICI initiation ("baseline", NSCLC-B) and during HPD ("hyperprogression", NSCLC-H). The cell lines were phenotypically and molecularly characterized through immunofluorescence, Western Blotting and RNA-Seq analysis. To assess cell plasticity and aggressiveness, cellular growth patterns were evaluated both in vitro and in vivo through 2D and 3D cell growth assays and patient-derived xenografts establishment. In vitro investigations, including the evaluation of cell sensitivity to interferon-gamma (IFN-γ) and cell response to PD-L1 modulation, were conducted to explore the influence of these factors on cell plasticity regulation. NSCLC-H exhibited increased expression of specific CD44 isoforms and a more aggressive phenotype, including organoid formation ability, compared to NSCLC-B. Plastic changes in NSCLC-H were well described by a deep transcriptome shift, that also affected IFN-γ-related genes, including PD-L1. IFN-γ-mediated cell growth inhibition was compromised in both 2D-cultured NSCLC-B and NSCLC-H cells. Further, the cytokine induced a partial activation of both type I and type II IFN-pathway mediators, together with a striking increase in NSCLC-B growth in 3D cell culture systems. Finally, low IFN-γ doses and PD-L1 modulation both promoted plastic changes in NSCLC-B, increasing CD44 expression and its ability to produce spheres. Our findings identified plasticity as a relevant hallmark of ICI-mediated HPD by demonstrating that ICIs can modulate the IFN-γ and PD-L1 pathways, driving tumor cell plasticity and fueling HPD development.

Angelicola S ，Giunchi F ，Ruzzi F ，Frascino M ，Pitzalis M ，Scalambra L ，Semprini MS ，Pittino OM ，Cappello C ，Siracusa I ，Chillico IC ，Di Noia M ，Turato C ，De Siervi S ，Lescai F ，Ciavattini T ，Lopatriello G ，Bertoli L ，De Jonge H ，Iamele L ，Altimari A ，Gruppioni E ，Ardizzoni A ，Rossato M ，Gelsomino F ，Lollini PL ，Palladini A ... -  《Journal of Translational Medicine》

[High RNF7 expression enhances PD-1 resistance of non-small cell lung cancer cells by promoting CXCL1 expression and myeloid-derived suppressor cell recruitment via activating NF-κB signaling].

Zhong N ，Wang H ，Zhao W ，Sun Z ，Geng B ... -  《-》

Liposomal honokiol inhibits non-small cell lung cancer progression and enhances PD-1 blockade via suppressing M2 macrophages polarization.

Honokiol (HNK), a natural phenolic compound derived from Magnolia plants, exhibits therapeutic effects on various diseases, including cancer. The advent of immune checkpoint inhibitors (ICIs) has marked a breakthrough in non-small cell lung cancer (NSCLC) treatment. However, a significant subset of patients exhibits primary or acquired resistance to anti-PD-1/PD-L1 therapies, necessitating the development of novel combination strategies to enhance therapeutic efficacy and overcome resistance. This study aimed to explore the anti-tumor efficacy of liposomal honokiol (Lipo-HNK) and elucidate the synergistic effects of Lipo-HNK and ICIs on NSCLC. The effects of Lipo-HNK on cell proliferation and apoptosis were assessed in human lung cancer cell lines H460 and A549, and mouse Lewis lung cancer cell line (LL2). A murine lung cancer model was established by injecting LL2 cells via the tail vein to evaluate the therapeutic effects of Lipo-HNK and ICIs. Tumor microenvironment features were characterized using immunofluorescence and flow cytometry. Primary macrophages were extracted from mouse bone marrow for mechanistic studies. High-throughput sequencing and bioinformatics analyses of Lipo-HNK-treated macrophages were conducted to identify key signaling pathways, which were subsequently confirmed by Western blotting and inhibitor blockade. Lipo-HNK, with enhanced solubility and bioavailability, demonstrated potent cytotoxicity against NSCLC cell lines. In the murine lung cancer model, Lipo-HNK exhibited synergistic anti-cancer effects when combined with anti-PD-1 therapy. Immunofluorescence and flow cytometry analyses revealed that Lipo-HNK significantly reduced the infiltration of myeloid-derived suppressor cells (MDSCs) and M2 macrophages (CD206+). Macrophage depletion experiment showed the anti-tumor effects of Lipo-HNK was macrophage-dependent. M2 macrophages induced by tumor-conditioned medium (TCM) or interleukin-4 (IL-4) released immunosuppressive cytokines such as IL-10, Arg-1, and TGF-β. RNA sequencing analyses showed that Lipo-HNK effectively inhibited the PI3K/Akt signaling pathway, blocking macrophage polarization to the M2 type. Furthermore, the combination of Lipo-HNK and anti-PD-1 therapy led to increased CD8+ T-cell infiltration and activation, enhancing the overall anti-tumor immune response. This study validated the anti-tumor efficacy of Lipo-HNK against NSCLC. Lipo-HNK reduced the infiltration of MDSCs and M2 macrophages by inhibiting the PI3K/Akt pathway and enhanced the therapeutic effects of ICIs. These findings provide evidence and new insights into Lipo-HNK as a promising anti-cancer drug for NSCLC treatment, highlighting its potential to overcome resistance to current ICI therapies.

Cheng Y ，Han X ，Lai X ，Wei X ... -  《-》