RGMb impacts partial epithelial-mesenchymal transition and BMP2-Induced ID mRNA expression independent of PD-L2 in nonsmall cell lung cancer cells.

PD-1/PD-ligand-axis immunotherapy-mediated activation of T-cells for cancer cell elimination is a promising treatment of nonsmall cell lung cancer (NSCLC). However, the effect of immunotherapy on intracellular signaling pathways in cancer cells still needs further delineation. Repulsive Guidance Molecule b (RGMb), a regulator of Bone Morphogenetic Proteins (BMPs) signaling, interacts with the PD-ligand, PD-L2, at cancer cell membranes. Accordingly, a clarification of the functions of RGMb and its relation to PD-L2 might provide insight into NSCLC cell signaling responses to PD-1/PD-ligand-axis immunotherapy. In this study, the functions of RGMb and PD-L2 were examined using the two NSCLC cell lines HCC827 and A549. CRISPR/Cas9 was used to decrease the expression of RGMb and PD-L2, while lentiviral vectors were used to increase their expression. Downstream effects were examined by RT-qPCR and immunoassays. Ectopic expression of RGMb impacted BMP2-induced expression of ID1 and ID2 messenger RNA (mRNA) independently of PD-L2, while RGMb depletion by CRISPR/Cas9 did not affect the BMP2-mediated induction of ID1, ID2, and ID3 mRNA. However, depletion of RGMb resulted in a partial epithelial-mesenchymal transition (EMT) gene expression profile in HCC827 cells, which was not mimicked by PD-L2 depletion. The results show that RGMb is a coregulator of BMP signaling and hence, ID mRNA expression and that RGMb can control the EMT balance in NSCLC cells. However, RGMb appears to exert these functions independently of PD-L2, and accordingly, the PD-1/PD-ligand axis for immune surveillance in NSCLC cells.

PD-L1 and PD-L2 immune checkpoint protein induction by type III interferon in non-small cell lung cancer cells.

INTRODUCTION: Despite the clinical success of PD-1/PD-1-ligand immunotherapy in non-small cell lung cancer (NSCLC), the appearance of primary and acquired therapy resistance is a major challenge reflecting that the mechanisms regulating the expression of the PD-1-ligands PD-L1 and PD-L2 are not fully explored. Type I and II interferons (IFNs) induce PD-L1 and PD-L2 expression. Here, we examined if PD-L1 and PD-L2 expression also can be induced by type III IFN, IFN-λ, which is peculiarly important for airway epithelial surfaces. METHODS: In silico mRNA expression analysis of PD-L1 (CD274), PD-L2 (PDCD1LG2), and IFN- λ signaling signature genes in NSCLC tumors and cell lines was performed using RNA sequencing expression data from TCGA, OncoSG, and DepMap portals. IFN-λ-mediated induction of PD-L1 and PD-L2 expression in NSCLC cell lines was examined by real-time quantitative polymerase chain reaction and flow cytometry. RESULTS: IFNL genes encoding IFN- λ variants are expressed in the majority of NSCLC tumors and cell lines along with the IFNLR1 and IL10R2 genes encoding the IFN-λ receptor subunits. The expression of PD-L1 and PD-L2 mRNA is higher in NSCLC tumors with IFNL mRNA expression compared to tumors without IFNL expression. In the NSCLC cell line HCC827, stimulation with IFN-λ induced both an increase in PD-L1 and PD-L2 mRNA expression and cell surface abundance of the corresponding proteins. In the NSCLC cell line A427, displaying a low basal expression of PD-L1 and PD-L2 mRNA and corresponding proteins, stimulation with IFN-λ resulted in an induction of the former. CONCLUSION: The type III IFN, IFN- λ, is capable of inducing PD-L1 and PD-L2 expression, at least in some NSCLC cells, and this regulation will need acknowledgment in the development of new diagnostic procedures, such as gene expression signature profiles, to improve PD-1/PD-1-ligand immunotherapy in NSCLC.

An Extended PD-L2 Cytoplasmic Domain Results From Alternative Splicing in NSCLC Cells.

Antibody-based immunotherapy targeting the interaction between programmed cell death 1 (PD-1) and its ligand PD-L1 has shown impressive clinical outcomes in various cancer types, including nonsmall cell lung cancer (NSCLC). However, regulatory mechanisms in this immune checkpoint pathway still needs clarification. PD-L2 is structurally homologous to PD-L1 and is a second PD-1 ligand. Alternative mRNA splicing from the CD274 and PDCD1LG2 genes holds the potential to generate PD-L1 and PD-L2 isoforms, respectively, with novel functionality in regulation of the PD-1 immune checkpoint pathway. Here, we describe alternative splicing in NSCLC cells potentially generating eight different PD-L2 isoforms from the PDCD1LG2 gene. Extension of exon 6 by four nucleotides is the most prominent alternative splicing event and results in PD-L2 isoform V with a cytoplasmic domain containing a 10 amino acid extension. On average 13% of the PDCD1LG2 transcripts in NSCLC cell lines and 22% of the transcripts in NSCLC tumor biopsies encode PD-L2 isoform V. PD-L2 isoform V localizes to the cell surface membrane but less efficiently than the canonical PD-L2 isoform I. The cytoplasmic domains of PD-1 ligands can affect immune checkpoint pathways by conferring membrane localization and protein stability and thereby represent alternative targets for immunotherapy. In addition, cytoplasmic domains are involved in intracellular signalling cascades in cancer cells. The presented observations of different cytoplasmic domains of PD-L2 will be important in the future delineation of the PD-1 immune checkpoint pathway.

PD-L1 and PD-L2 expression correlated genes in non-small-cell lung cancer.

BACKGROUND: Programmed cell death ligand-1 (PD-L1) and ligand-2 (PD-L2) interaction with programmed cell death protein-1 (PD-1) represent an immune-inhibiting checkpoint mediating immune evasion and is, accordingly, an important target for blockade-based immunotherapy in cancer. In non-small-cell lung cancer (NSCLC), improved understanding of PD-1 checkpoint blockade-responsive biology and identification of biomarkers for prediction of a clinical response to immunotherapy is warranted. Thus, in the present study, we systematically described PD-L1 and PD-L2 expression correlated genes in NSCLC. METHODS: We performed comparative retrospective analyses to identify PD-L1 and PD-L2 mRNA expression correlated genes in NSCLC. For this, we examined available datasets from the cancer cell line encyclopedia (CCLE) project lung non-small-cell (Lung_NSC) and the cancer genome atlas (TCGA) projects lung adenocarcinoma (LUAD) and squamous cell carcinoma (LUSC). RESULTS: Analysis of the CCLE dataset Lung_NSC identified expression correlation between PD-L1 and PD-L2. Moreover, we identified expression correlation between 489 genes and PD-L1, 191 genes and PD-L2, and 111 genes for both. PD-L1 and PD-L2 also expression correlated in TCGA datasets LUAD and LUSC. In LUAD, we identified expression correlation between 257 genes and PD-L1, 914 genes and PD-L2, and 211 genes for both. In LUSC, we identified expression correlation between 26 genes and PD-L1, 326 genes and PD-L2, and 13 genes for both. Only a few genes expression correlated with PD-L1 and PD-L2 across the CCLE and TCGA datasets. Expression of Interferon signaling-involved genes converged in particular with the expression correlated genes for PD-L1 in Lung_NSC, for PD-L2 in LUSC, and for both PD-L1 and PD-L2 in LUAD. In LUSC, PD-L1, and to a lesser extent PD-L2, expression correlated with chromosome 9p24 localized genes, indicating a chromosome 9p24 topologically associated domain as an important driver of in particular LUSC PD-L1 expression. Expression correlation analyses of the PD-L1 and PD-L2 receptors programmed cell death protein-1 (PD-1), Cluster of differentiation 80 (CD80), and Repulsive guidance molecule B (RGMB) showed that PD-1 and CD80 expression correlated with both PD-L1 and PD-L2 in LUAD. CD80 expression correlated with PD-L2 in LUSC. CONCLUSIONS: We present gene signatures associated with PD-L1 and PD-L2 mRNA expression in NSCLC which could possess importance in relation to understand PD-1 checkpoint blockade-responsive biology and development of gene signature based biomarkers for predicting clinical responses to immunotherapy.

Changes in first trimester fetal CYP1A1 and AHRR DNA methylation and mRNA expression in response to exposure to maternal cigarette smoking.

Prenatal exposure to maternal cigarette smoking increases the risk of intrauterine growth retardation, adverse pregnancy outcomes, and diseases later in life. Exposure can result in postnatal global and gene-specific DNA methylation changes, with the latter well documented for the CYP1A1 and AHRR genes involved in the detoxification of xenobiotic substances. This study assessed the impact of exposure to maternal smoking on first trimester fetal CYP1A1 and AHRR mRNA expression and DNA methylation for CpG-sites displaying maternal smoking during pregnancy-mediated methylation changes at birth. The analyses included first trimester (6-12 weeks) placentas (N=39) and livers (N=43). For AHRR, exposure to maternal smoking was associated with increased DNA methylation in the placentas of female fetuses; mRNA expression, however, was unchanged. While exposure to maternal smoking was not associated with AHRR DNA methylation changes in fetal livers; mRNA expression was increased. For CYP1A1, exposure to maternal smoking was not associated with fetal DNA methylation changes whereas mRNA expression increased in placentas and male fetal livers. These results show that first trimester exposure to maternal smoking is associated with CYP1A1 and AHRR DNA methylation and mRNA expression changes. However, the results also indicate that maternal smoking during pregnancy-mediated postnatal CYP1A1 and AHRR DNA methylation changes are not imprinted during the first trimester.

Assessment of global DNA methylation in the first trimester fetal tissues exposed to maternal cigarette smoking.

AIMS: Maternal cigarette smoking during pregnancy increases the risk of negative health consequences for the exposed child. Epigenetic mechanisms constitute a likely link between the prenatal exposure to maternal cigarette smoking and the increased risk in later life for diverse pathologies. Maternal smoking induces gene-specific DNA methylation alterations as well as global DNA hypermethylation in the term placentas and hypomethylation in the cord blood. Early pregnancy represents a developmental time where the fetal epigenome is remodeled and accordingly can be expected to be highly prone to exposures with an epigenetic impact. We have assessed the influence of maternal cigarette smoking during the first trimester for fetal global DNA methylation. METHODS AND RESULTS: We analyzed the human fetal intestines and livers as well as the placentas from the first trimester pregnancies. Global DNA methylation levels were quantified with ELISA using a methylcytosine antibody as well as with the bisulfite pyrosequencing of surrogate markers for global methylation status, LINE-1, and AluYb8. We identified gender-specific differences in global DNA methylation levels, but no significant DNA methylation changes in exposure responses to the first trimester maternal cigarette smoking. CONCLUSIONS: Acknowledging that only examining subsets of global DNA methylation markers and fetal sample availability represents possible limitations for the analyses, our presented results indicate that the first trimester maternal cigarette smoking is not manifested in immediate aberrations of fetal global DNA methylation.