Immunoglobulin-like transcript 4 promotes tumor progression and metastasis and up-regulates VEGF-C expression via ERK signaling pathway in non-small cell lung cancer

LILRB2 inhibition enhances radiation sensitivity in non-small cell lung cancer by attenuating radiation-induced senescence

Radiotherapy (RT) in non-small cell lung cancer (NSCLC) triggers cellular senescence, complicating tumor microenvironments and affecting treatment outcomes. This study examines the role of lymphocyte immunoglobulin-like receptor B2 (LILRB2) in modulating RT-induced senescence and radiosensitivity in NSCLC. Through methodologies including irradiation, lentivirus transfection, and various molecular assays, we assessed LILRB2's expression and its impact on cellular senescence levels and tumor cell behaviors. Our findings reveal that RT upregulates LILRB2, facilitating senescence and a senescence-associated secretory phenotype (SASP), which in turn enhances tumor proliferation and resistance to radiation. Importantly, LILRB2 silencing attenuates these effects by inhibiting the JAK2/STAT3 pathway, significantly increasing radiosensitivity in NSCLC models. Clinical data correlate high LILRB2 expression with reduced RT response and poorer prognosis, suggesting LILRB2's pivotal role in RT-induced senescence and its potential as a therapeutic target to improve NSCLC radiosensitivity.

ILT4 facilitates angiogenesis in non-small cell lung cancer

Antiangiogenic therapy targeting VEGF-A has become the standard of first-line therapy for non-small cell lung cancer (NSCLC). However, its clinical response rate is still less than 50%, and most patients eventually develop resistance, even when using combination therapy with chemotherapy. The major cause of resistance is the activation of complex bypass signals that induce angiogenesis and tumor progression. Therefore, exploring novel proangiogenic mechanisms and developing promising targets for combination therapy are crucial for improving the efficacy of antiangiogenic therapy. Immunoglobulin-like transcript (ILT) 4 is a classic immunosuppressive molecule that inhibits myeloid cell activation. Recent studies have shown that tumor cell-derived ILT4 drives tumor progression via the induction of malignant biologies and creation of an immunosuppressive microenvironment. However, whether and how ILT4 participates in NSCLC angiogenesis remain elusive. Herein, we found that enriched ILT4 in NSCLC is positively correlated with high microvessel density, advanced disease, and poor overall survival. Tumor cell-derived ILT4 induced angiogenesis both in vitro and in vivo and tumor progression and metastasis in vivo. Mechanistically, ILT4 was upregulated by its ligand angiopoietin-like protein 2 (ANGPTL2). Their interaction subsequently activated the ERK1/2 signaling pathway to increase the secretion of the proangiogenic factors VEGF-A and MMP-9, which are responsible for NSCLC angiogenesis. Our study explored a novel mechanism for ILT4-induced tumor progression and provided a potential target for antiangiogenic therapy in NSCLC.

Dexamethasone promotes renal fibrosis by upregulating ILT4 expression in myeloid-derived suppressor cells

Studies have shown that adoptive transfer of myeloid-derived suppressor cells (MDSCs) can alleviate various inflammatory diseases, including glomerulonephritis, but the long-term effects of the transferred MDSCs are still unclear. In addition, although glucocorticoids exert immunosuppressive effects on inflammatory diseases by inducing the expansion of MDSCs, the impact of glucocorticoids on the immunosuppressive function of MDSCs and their molecular mechanisms are unclear. In this study, we found that adoptive transfer of MDSCs to doxorubicin-induced focal segmental glomerulosclerosis (FSGS) mice for eight consecutive weeks led to an increase in serum creatinine and proteinuria and aggravation of renal interstitial fibrosis. Similarly, 8 weeks of high-dose dexamethasone administration exacerbated renal interstitial injury and interstitial fibrosis in doxorubicin-induced mice, manifested as an increase in serum creatinine and proteinuria, collagen deposition and α-SMA expression. On this basis, we found that dexamethasone could enhance MDSC expression and secretion of the fibrosis-related cytokines TGF-β and IL-10. Mechanistically, we revealed that dexamethasone promotes the expression of immunoglobulin-like transcription factor 4 (ILT4), which enhances the T-cell inhibitory function of MDSCs and promotes the activation of STAT6, thereby strengthening the expression and secretion of TGF-β and IL-10. Knocking down ILT4 alleviated renal fibrosis caused by adoptive transfer of MDSCs. Therefore, our findings demonstrate that the role and mechanism of dexamethasone mediate the expression and secretion of TGF-β and IL-10 in MDSCs by promoting the expression of ILT4, thereby leading to renal fibrosis.

Analysis of HLA-G 14 bp Insertion/Deletion Polymorphism and HLA-G, ILT2 and ILT4 Expression in Head and Neck Squamous Cell Carcinoma Patients

HLA-G is the checkpoint molecule involved in the suppression of the immune response. Increased expression of HLA-G and its ILTs receptors have been correlated with tumor progression in various cancer types. In head and neck squamous cell carcinoma (HNSCC) tumors, the effect of HLA-G, ILT2 and ILT4 expression on cancer development has to be explained. The 34 HNSCC patients and 98 controls were genotyped for the HLA-G 14 bp ins/del polymorphism. In HNSCC lesions, HLA-G, ILT2 and ILT4 mRNA expression was analysed using real-time PCR. The association between HLA-G, ILT2 and ILT4 mRNA expression and clinical variables (age at onset, TNM staging system and p16 positivity) was also evaluated. No genetic association between the HLA-G 14 bp ins/del and HNSCC risk was detected (p > 0.05). However, in the non-metastatic HNSCC group, a significantly higher HLA-G mRNA expression was noted in tumors in the T4 stage compared to those in the T1 and T2 stages (p = 0.0289). ILT2 mRNA expression was significantly increased in non-metastatic vs. metastatic tumors (p = 0.0269). Furthermore, a significantly higher ILT4 mRNA expression was noted in tumors in the T1+T2 stage compared to those in the T3 stage (p = 0.0495). Our results suggest that the HLA-G molecule creates an immunological microenvironment involved in HNSCC development.

Leukocyte immunoglobulin-like receptor B2 overexpression as a promising therapeutic target and noninvasive screening biomarker for colorectal cancer

BACKGROUND

Colorectal cancer (CRC) has become the second most deadly malignancy in the world, and the exploration of screening markers and precise therapeutic targets is urgent. Our previous research identified leukocyte immunoglobulin-like receptor B2 (LILRB2) protein as a characteristic protein of CRC, but the association between LILRB2 expression and clinicopathological features, the internal mechanism related to CRC progression, and screening diagnostic efficacy are not clear. Therefore, we hypothesized that LILRB2 is significantly highly expressed in CRC tissues, correlated with advanced stage and a poor prognosis, and could be used as a therapeutic target and potential screening biomarker for CRC.

AIM

To explore whether LILRB2 can be used as a potential therapeutic target and noninvasive screening biomarker for CRC.

METHODS

Patients who underwent radical surgery for CRC at China-Japan Friendship Hospital between February 2021 and October 2022 were included. Cancer and paracancerous tissues were collected to verify LILRB2 expression, and the association between LILRB2 expression and clinicopathological features was analysed. Serum was collected from CRC patients, adenoma patients and healthy controls during the same period to assess the diagnostic value of LILRB2 as a noninvasive screening biomarker, and its diagnostic value was further compared with that of the traditional markers carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9).

RESULTS

A total of 58 CRC patients were included, and LILRB2 protein was significantly overexpressed in cancer tissues compared with paracancerous tissues (P < 0.001). Angiopoietin-like protein 2 (ANGPTL2) protein, as the ligand of LILRB2, was synergistically overexpressed in CRC tissues (P < 0.001), and overexpression of LILRB2 and ANGPTL2 protein was significantly correlated with poor to moderate differentiation, vascular involvement, lymph node metastasis, distant metastasis, advanced tumor-node-metastasis stage and a poor prognosis (P < 0.05), which suggested that LILRB2 and ANGPTL2 are closely associated with CRC progression. In addition, serum LILRB2 concentrations increased stepwise in healthy individuals, adenoma patients and CRC patients with statistically significant differences. The sensitivity of serum LILRB2 for the diagnosis of CRC was 89.74%, the specificity was 88.89%, the area under the curve was 0.95, and the diagnostic efficacy was better than that of conventional CEA and CA19-9.

CONCLUSION

LILRB2 protein can be used as a potential novel therapeutic target and noninvasive screening biomarker for CRC, which is beneficial for early screening and precise treatment.

ILT4 reprograms glucose metabolism to promote tumor progression in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive and poorly treated subtype of breast cancer. Identifying novel drivers and mechanisms for tumor progression is essential for precise targeted therapy of TNBC. Immunoglobulin-like transcript 4 (ILT4; also known as LILRB2) is a classic myeloid suppressor for their activation and immune response. Our recent results found that ILT4 is also highly expressed in lung cancer cells, where it has a role in promoting immune evasion and thus tumor formation. However, the expression and function of ILT4 in breast cancer remains elusive. Here, using our patient cohort and public database analysis, we found that TNBC displayed the most abundant ILT4 expression among all breast cancer subtypes. Functionally, enriched ILT4 promoted TNBC cell proliferation, migration and invasion in vitro, as well as tumor growth and metastasis in vivo. Further mechanistic analysis revealed that ILT4 reprogrammed aerobic glycolysis of tumor cells via AKT-mTOR signaling-mediated glucose transporter 3 (GLUT3; also known as SLC2A3) and pyruvate kinase muscle 2 (PKM2, an isoform encoded by PKM) overexpression. ILT4 inhibition in TNBC reduced tumor progression and GLUT3 and PKM2 expression in vivo. Our study identified a novel driver for TNBC progression and proposed a promising strategy to combat TNBC by targeting ILT4.

HLA-G expression in transitional bladder carcinoma. Relationship with tumor invasion level and patient survival: Experience in a public hospital in Argentina

Transitional carcinoma (TC) is the most common neoplasm of the bladder (80%). The immune checkpoint (IC) Human leukocyte antigen G (HLA-G) expression has been demonstrated within numerous types of cancer and correlates with the degree of malignancy. This study aims for HLA-G expression in the bladder TC in a public hospital in Argentina linking its malignancy grade with the survival of the patients. We study thirty TC samples, in which we determine the invasion level and the HLA-G expression by immunohistochemistry. From all analyzed cases, 23 correspond to high-grade TC, of whom 91% presented HLA-G immunostaining and 83% compromised the muscularis propria layer of the bladder. Four patients in this group have not exceeded 5 years of survival. This data confirms that HLA-G expression in the bladder TC is associated with greater aggressiveness. Therefore, adding this immunostaining to the immunohistochemical panel used in the routine diagnosis of this neoplasm would be very useful.

Comprehensive analysis of LILR family genes expression and tumour-infiltrating immune cells in early-stage pancreatic ductal adenocarcinoma

Leucocyte immunoglobulin-like receptors (LILRs) are closely related to tumourigenesis, but their clinical value in early-stage pancreatic ductal adenocarcinoma (PDAC) after pancreaticoduodenectomy remains unknown. Kaplan-Meier and Cox proportional hazards regression models is used to investigate the association between LILR expression and prognosis in tumour biopsies and peripheral blood mononuclear cells. Risk score was calculated for each patient based on the prognostic model. DAVID, STRING, GeneMANIA, and GSEA were used to conduct pathway and functional analyses. The CIBERSORT algorithm is used to analyse tumour-infiltrating immune cells. Survival analysis showed that high levels of LILRA4 (p = 0.006) and LILRB4 (p = 0.04) were significantly associated with better overall survival. High levels of LILRA2 (p = 0.008) and LILRB4 (p = 0.038) were significantly associated with better relapse-free survival. JAK-STAT signalling pathway, regulation of T cell activation, regulation of the immune effector process, and tumour necrosis factor superfamily cytokine production were involved in molecular mechanisms that affected poor prognoses in the high-risk group in GSEA. CIBERSORT demonstrated that the high-risk group had significantly higher infiltrating fraction of memory-activated CD4 T cells and activated NK cells and lower fraction of resting dendritic cells and neutrophils. LILRB4 plays crucial roles in affecting the clinical outcomes of early-stage PDAC.

HLA and tumour immunology: immune escape, immunotherapy and immune-related adverse events

PURPOSE

As molecules responsible for presenting antigens to T lymphocytes, leukocytes antigens (HLAs) play a vital role in cancer immunology. This review aims to provide current understanding of HLAs in tumour immunology.

METHODS

Perspectives on how HLA alterations may contribute to the immune escape of cancer cells and resistance to immunotherapy, and potential methods to overcome HLA defects were summarized. In addition, we discussed the potential association between HLA and immune-related adverse events (irAEs), which has not been reviewed elsewhere.

RESULTS

Downregulation, loss of heterogeneity and entire loss of HLAs are responsible for the immune escape of tumour cells. The strategies to overcome the HLA defects can be effective therapies of cancer. Compared with classical HLA-I, non-classical HLA-I molecules, such as HLA-E and HLA-G, appear to be more reliable predictors of prognosis, as they tend to play immunosuppressive roles in antitumor response. Relative diversified or high expression of classical HLA-I are potential predictors of favourable response of immunotherapy. Certain HLA types may be associated to enhanced affinity to self-antigen-mimicked tumour-antigens, thus may positively correlated to irAEs triggered by checkpoint inhibitors.

CONCLUSIONS

Further studies exploring the relationship between HLAs and cancer may not only lead to the development of novel therapies but also bring about better management of irAEs.

Tumor-derived Immunoglobulin-like transcript 4 facilitates angiogenesis of colorectal cancer

Current anti-angiogenic therapies have changed the paradigm of treating colorectal cancer (CRC) patients with advanced diseases. However, the clinical response rate is still low at less than 10% due largely to complex angiogenic factors released by tumor cells. Exploring novel mechanisms of tumor angiogenesis and identifying alternative targets for combination therapies are therefore essential to effective inhibition of tumor vascularization and CRC development. Immunoglobulin-like transcript 4 (ILT4), initially identified as a suppressor of myeloid cell activity, is enriched in solid tumor cells. ILT4 favors tumor progression by inducing tumor malignant biologies as well as an immunosuppressive microenvironment. However, whether and how tumor-derived ILT4 orchestrates tumor angiogenesis is still undetermined. Here we found that tumor-derived ILT4 was positively correlated with microvessel density in CRC tissues. ILT4 induced the migration and tube formation of HUVECs in vitro and angiogenesis in vivo. Mechanistically, the activation of MAPK/ERK signaling and subsequent up-regulation of vascular endothelial growth factor-A (VEGF-A) and fibroblast growth factor 1 (FGF-1) were responsible for ILT4-induced angiogenesis and tumor progression. Importantly, ILT4 inhibition suppressed tumor angiogenesis and enhanced the efficacy of Bevacizumab treatment in CRC. Our study has identified a novel mechanism for ILT4-mediated tumor progression, which signals a new therapeutic target and alternative combination strategies to combat CRC.

The Role of Leukocyte Immunoglobulin-Like Receptors Focusing on the Therapeutic Implications of the Subfamily B2

The leukocyte immunoglobulin (Ig)-like receptors (LILRs) are constituted by five inhibitory subpopulations (LILRB1-5) and six stimulatory subpopulations (LILRA1-6). The LILR populations substantially reside in immune cells, especially myeloid cells, functioning as a regulator in immunosuppressive and immunostimulatory responses, during which the nonclassical major histocompatibility complex (MHC) class I molecules are widely involved. In addition, LILRs are also distributed in certain tumor cells, implicated in the malignancy progression. Collectively, the suppressive Ig-like LILRB2 is relatively well-studied to date. Herein, we summarized the whole family of LILRs and their biologic function in various diseases upon ligation to the critical ligands, therefore providing more information on their potential roles in these pathological processes and giving the clinical significance of strategies targeting LILRs.

Analysis of the expression and prognosis for leukocyte immunoglobulin-like receptor subfamily B in human liver cancer

Background

Leukocyte immunoglobulin-like receptor subfamily B (LILRB), including 5 subtypes, is a group of inhibitory receptors in the immune system. The LILRB family is known to be involved in the tumor progression of various cancer types, especially liver cancer. However, the expression patterns and prognostic values of LILRB family members in liver cancer tissues remain unclear.

Methods

We used the Oncomine database, GEPIA database, Kaplan–Meier Plotter, Timer, and TISIDB to assess the expression and prognostic value of the LILRB family in liver cancer patients. We also verified the expression of the LILRB family in tumor tissues and tumor-free liver tissues at the protein level by using immunohistochemistry. The STRING website was used to explore the interaction between the LILRB family and their related genes. The DAVID database was used to perform the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Flow cytometry was used to assess the infiltrated NK cells in liver cancer tissues.

Results

Our study revealed that the mRNA expression of LILRB1, LILRB2, LILRB3, and LILRB5 was downregulated, while compared with normal tissues, the mRNA expression of LILRB4 was upregulated in liver cancer tissues. Survival analysis revealed that LILRB2 and LILRB5 mRNA expression levels were significantly positively associated with overall survival (OS) and disease-free survival (DSS) and that the mRNA expression of all LILRB family members was significantly positively correlated with recurrence-free survival (RFS) and progression-free survival (PFS). Next, we further found that the mRNA expression of all LILRB family members was significantly associated with the infiltration of B cells, CD8⁺ T cells, CD4⁺ T cells, macrophages, neutrophils, and dendritic cells in liver cancer. Finally, GO and KEGG analyses found that the LILRB family and its related genes were involved in antigen processing and presentation and natural killer cell-mediated cytotoxicity pathways.

Conclusions

Our study suggested that LILRB family expression was associated with the prognosis of liver cancer patients and infiltrated immune cells. The LILRB family might be involved in antigen processing and presentation and natural killer cell-mediated cytotoxicity pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02562-w.

ILT4 in Colorectal Cancer Cells Induces Suppressive T Cell Contexture and Disease Progression

Purpose

Immune checkpoint blockade (ICB) therapy shows little or no clinical benefit in most colorectal cancer (CRC) patients, due to the immunosuppressive T cell contexture in the tumor microenvironment (TME). Immunoglobulin-like transcript (ILT) 4 is an immunosuppressive molecule in myeloid cells. ILT4 is enriched in solid tumor cells, facilitating their proliferation, invasion, and metastasis. However, the regulatory role of ILT4 in T cell immunity of CRC is still undetermined. Here, we aimed to explore how tumor cell-derived ILT4 orchestrates T cell infiltration, subset distribution, and function in CRC.

Methods

A total of 145 paraffin-embedded cancer tissues and the corresponding clinicopathological information were collected from CRC patients. Immunohistochemical (IHC) staining and public database analyses determined the correlation of ILT4 expression with different T cell subset densities, IFN-γ levels, and patient outcomes. Paired Ig-like receptor B (PIR-B, ILT4 mouse ortholog)-overexpressing/-downregulated MC38 cells were subcutaneously injected into C57BL/6 mice as a CRC transplantation model. The frequencies, subsets, and IFN-γ levels of T cells in mouse blood and spleens were determined using flow cytometry and immunohistochemistry, respectively.

Results

High ILT4 expression in CRC cells was associated with decreased T cell infiltration, disease progression, and poor patient survival. T cell subset analyses indicated that ILT4-high patients showed reduced CD8⁺ T cell but elevated FOXP3⁺ regulatory T (Treg) cell frequencies in the TME. High ILT4 levels predicted lower IFN-γ production by tumor-infiltrating lymphocytes (TILs), especially by CD8⁺T cells in human CRC tissues. Moreover, PIR-B overexpression accelerated MC38 growth in mice, decreased CD3⁺/CD8⁺/IFN-γ⁺ T cell densities, and elevated Treg infiltration in the TME, blood, and spleens. PIR-B knockdown had the opposite effects.

Conclusion

ILT4 in CRC cells induced immunosuppressive T cell subset infiltration and impaired IFN-γ production in TILs, suggesting that ILT4 might be a potential immunotherapeutic target and prognostic biomarker.

Prognostic Significance of Immune Checkpoints HLA-G/ILT-2/4 and PD-L1 in Colorectal Cancer

Immune checkpoint inhibitors (ICIs) have become a promising area of research for cancer treatment. In addition to the well-known ICIs targeting PD-1/PD-L1, HLA-G/ILT-2/-4 is relatively new immune checkpoint that has been evaluated in early clinical trials in patients with advanced solid tumors. In this study, the expression of HLA-G (n=157), ILT-2/4 (n=82), and PD-L1 (n=70) in epithelial cell adhesion molecule (EpCAM)-positive colorectal cancer (CRC) cells was analyzed by multicolor flow cytometry, and the prognostic significance of these molecules was evaluated. In EpCAM⁺ CRC cells, the median percentages of HLA-G, ILT-2, ILT-4, and PD-L1 were 14.90%, 67.70%, 8.55% and 80.30%, respectively. In addition, a positive correlation was observed between them (all p<0.001). Higher levels of these immune checkpoint proteins are associated with lymph node metastasis. In addition to the AJCC stage (p=0.001), Kaplan-Meier survival analysis showed that higher levels of HLA-G (p=0.041), ILT-2 (p=0.060), ILT-4 (p<0.001), PD-L1 (p=0.012), HLA-GILT4 (p<0.001) and ILT-2ILT-4 (p<0.001) were significantly associated with shorter survival of CRC patients. When CRC patients were stratified by early and advanced AJCC stages, HLA-G levels were only related to the survival among CRC patients with early disease stage (p=0.024), while ILT-4 levels were significant for both CRC patients with early (p=0.001) and advanced (p=0.020) disease stages. Multivariate cox regression analysis revealed that advanced AJCC stage (HR=2.435; p=0.005) and higher ILT-4 levels (HR=2.198; p=0.063) were independent risk factors for poor outcomes in patients with CRC. In summary, among the immune checkpoints, HLA-G/ILT-2/4 and PD-L1, ILT-4 is the most significant prognostic indicator of CRC. This finding indicated that a combination of immunotherapy strategies, such as ILT-4 blockade, could improve the clinical outcomes in patients with cancer. Moreover, multicolor flow cytometry can be employed as a reliable and efficient, alternative to immunohistochemistry, for evaluating the immune checkpoint proteins expressed in tumor lesions.

Tumor-derived ILT4 induces T cell senescence and suppresses tumor immunity

BACKGROUND

Current immunotherapies including checkpoint blockade therapy have limited success rates in certain types of cancers. Identification of alternative checkpoint molecules for the development of effective strategies for tumor immunotherapy is urgently needed. Immunoglobulin-like transcript 4 (ILT4) is an immunosuppressive molecule expressed in both myeloid innate cells and malignant tumor cells. However, the role of tumor-derived ILT4 in regulating cancer biology and tumor immunity remains unclear.

METHODS

ILT4 expression in tumor cells and patient samples was determined by real-time PCR, flow cytometry, and immunohistochemistry. T cell senescence induced by tumor was evaluated using multiple markers and assays. Moreover, metabolic enzyme and signaling molecule expression and lipid droplets in tumor cells were determined using real-time PCR, western blot and oil red O staining, respectively. Loss-of-function and gain-of-function strategies were used to identify the causative role of ILT4 in tumor-induced T cell senescence. In addition, breast cancer and melanoma mouse tumor models were performed to demonstrate the role of ILT4 as a checkpoint molecule for tumor immunotherapy.

RESULTS

We reported that ILT4 is highly expressed in human tumor cells and tissues, which is negatively associated with clinical outcomes. Furthermore, tumor-derived ILT4/PIR-B (ILT4 ortholog in mouse) is directly involved in induction of cell senescence in naïve/effector T cells mediated by tumor cells in vitro and in vivo. Mechanistically, ILT4/PIR-B increases fatty acid synthesis and lipid accumulation in tumor cells via activation of MAPK ERK1/2 signaling, resulting in promotion of tumor growth and progression, and induction of effector T cell senescence. In addition, blocking tumor-derived PIR-B can reprogram tumor metabolism, prevent senescence development in tumor-specific T cells, and enhance antitumor immunity in both breast cancer and melanoma mouse models.

CONCLUSIONS

These studies identify a novel mechanism responsible for ILT4-mediated immune suppression in the tumor microenvironment, and prove a novel concept of ILT4 as a critical checkpoint molecule for tumor immunotherapy.

ILT4 inhibition prevents TAM- and dysfunctional T cell-mediated immunosuppression and enhances the efficacy of anti-PD-L1 therapy in NSCLC with EGFR activation

Rationale: Immune checkpoint inhibitors (ICIs) against the PD-1/PD-L1 pathway showed limited success in non-small cell lung cancer (NSCLC) patients, especially in those with activating epidermal growth factor receptor (EGFR) mutations. Elucidation of the mechanisms underlying EGFR-mediated tumor immune escape and the development of effective immune therapeutics are urgently needed. Immunoglobulin-like transcript (ILT) 4, a crucial immunosuppressive molecule initially identified in myeloid cells, is enriched in solid tumor cells and promotes the malignant behavior of NSCLC. However, the upstream regulation of ILT4 overexpression and its function in tumor immunity of NSCLC with EGFR activation remains unclear. Methods: ILT4 expression and EGFR phosphorylation in human NSCLC tissues and cell lines were analyzed using immunohistochemistry (IHC), real-time PCR, Western blotting, immunofluorescence, and flow cytometry. The molecular signaling for EGFR-regulated ILT4 expression was investigated using mRNA microarray and The Cancer Genome Atlas (TCGA) database analyses and then confirmed by Western blotting. The regulation of tumor cell proliferation and apoptosis by ILT4 was examined by CCK8 proliferation and apoptosis assays. The impact of ILT4 and PD-L1 on tumor-associated macrophage (TAM) recruitment and polarization was evaluated using Transwell migration assay, flow cytometry, enzyme linked immunosorbent assay (ELISA) and real-time PCR, while their impact on T cell survival and cytotoxicity was analyzed by CFSE proliferation assay, apoptotic assay, flow cytometry, ELISA and cytolytic assay. Tumor immunotherapy models targeting at paired Ig-like receptor B (PIR-B, an ortholog of ILT4 in mouse)/ILT4 and/or PD-L1 were established in C57BL/6 mice inoculated with stable EGFR- overexpressing Lewis lung carcinoma (LLC) cells and in humanized NSG mice inoculated with EGFR mutant, gefitinib-resistant PC9 (PC9-GR) or EGFR-overexpressing wild type H1299 cells. PIR-B and ILT4 inhibition was implemented by infection of specific knockdown lentivirus and PD-L1 was blocked using human/mouse neutralizing antibodies. The tumor growth model was established in NSG mice injected with PIR-B-downregulated LLC cells to evaluate the effect of PIR-B on tumor proliferation. The frequencies and phenotypes of macrophages and T cells in mouse spleens and blood were detected by flow cytometry while those in tumor tissues were determined by IHC and immunofluorescence. Results: We found that ILT4 expression in tumor cells was positively correlated with EGFR phosphorylation in human NSCLC tissues. Using NSCLC cell lines, we demonstrated that ILT4 was upregulated by both tyrosine kinase mutation-induced and epidermal growth factor (EGF)-dependent EGFR activation and subsequent AKT/ERK1/2 phosphorylation. Overexpressed ILT4 in EGFR-activated tumor cells induced TAM recruitment and M2-like polarization, which impaired T cell function. ILT4 also directly inhibited T cell proliferation, cytotoxicity, and IFN-γ expression and secretion. In EGFR-activated cell lines in vitro and in wild-type EGFR-activated C57BL/6 and humanized NSG immunotherapy models in vivo, either ILT4 (PIR-B) or PD-L1 inhibition enhanced anti-tumor immunity and suppressed tumor progression by counteracting TAM- and dysfunctional T cell- induced immuno-suppressive TME; the combined inhibition of both molecules showed the most dramatic tumor retraction. Surprisingly, in EGFR mutant, TKI resistant humanized NSG immunotherapy model, ILT4 inhibition alone rather than in combination with a PD-L1 inhibitor suppressed tumor growth and immune evasion. Conclusions: ILT4 was induced by activation of EGFR-AKT and ERK1/2 signaling in NSCLC cells. Overexpressed ILT4 suppressed tumor immunity by recruiting M2-like TAMs and impairing T cell response, while ILT4 inhibition prevented immunosuppression and tumor promotion. Furthermore, ILT4 inhibition enhanced the efficacy of PD-L1 inhibitor in EGFR wild-type but not in EGFR mutant NSCLC. Our study identified novel mechanisms for EGFR-mediated tumor immune escape, and provided promising immunotherapeutic strategies for patients with EGFR-activated NSCLC.

The Molecular and Functional Characteristics of HLA-G and the Interaction with Its Receptors: Where to Intervene for Cancer Immunotherapy?

Human leukocyte antigen G (HLA-G) mediates maternal-fetal immune tolerance. It is also considered an immune checkpoint in cancer since it may mediate immune evasion and thus promote tumor growth. HLA-G is, therefore, a potential target for immunotherapy. However, existing monoclonal antibodies directed against HLA-G lack sufficient specificity and are not suitable for immune checkpoint inhibition in a clinical setting. For this reason, it is essential that alternative approaches are explored to block the interaction between HLA-G and its receptors. In this review, we discuss the structure and peptide presentation of HLA-G, and its interaction with the receptors Ig-like transcript (ILT) 2, ILT4, and Killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4). Based on our findings, we propose three alternative strategies to block the interaction between HLA-G and its receptors in cancer immunotherapy: (1) prevention of HLA-G dimerization, (2) targeting the peptide-binding groove of HLA-G, and (3) targeting the HLA-G receptors. These strategies should be an important focus of future studies that aim to develop immune checkpoint inhibitors to block the interaction between HLA-G and its receptors for the treatment of cancer.

HLA-G Neo-Expression on Tumors

HLA-G is known to modulate the immune system activity in tissues where physiological immune-tolerance is necessary (i.e., maternal-fetal interface, thymus, and cornea). However, the frequent neo-expression of HLA-G in many cancer types has been previously and extensively described and is correlated with a bad prognosis. Despite being an MHC class I molecule, HLA-G is highly present in tumor context and shows unique characteristics of tissue restriction of a Tumor Associated Antigen (TAA), and potent immunosuppressive activity of an Immune CheckPoint (ICP). Consequently, HLA-G appears to be an excellent molecular target for immunotherapy. Although the relevance of HLA-G in cancer incidence and development has been proven in numerous tumors, its neo-expression pattern is still difficult to determine. Indeed, the estimation of HLA-G's actual expression in tumor tissue is limited, particularly concerning the presence and percentage of the new non-canonical isoforms, for which detection antibodies are scarce or inexistent. Here, we summarize the current knowledge about HLA-G neo-expression and implication in various tumor types, pointing out the need for the development of new tools to analyze in-depth the HLA-G neo-expression patterns, opening the way for the generation of new monoclonal antibodies and cell-based immunotherapies.

The immune-checkpoint HLA-G/ILT4 is involved in the regulation of VEGF expression in clear cell renal cell carcinoma

Background

Clear cell renal cell carcinoma (ccRCC), the most aggressive renal cancer, is characterized by early lymph node metastases and bad prognosis. Most therapies targeting advanced or metastatic ccRCC are based, as first-line treatment, on the administration of the vascular endothelial growth factor (VEGF) neutralizing antibody termed Bevacizumab. Despite proven benefits, the expected results were not obtained for the majority of patients. The possibility that an intricate interplay between angiogenesis and immune-checkpoints might exist lead us to evaluate tumor angiogenesis, by means of VEGF expression together with the immune checkpoint HLA-G/ILT4.

Methods

Tumor specimens were obtained from patients from two separate cohorts: One from “Evita Pueblo” Hospital from Berazategui, (Buenos Aires, Argentina) and the second includes patients surgically operated at the Urology Department of Saint-Louis Hospital (Paris, France) with a confirmed ccRCC diagnosis. Immunohistochemistry was performed with specific antibodies directed against HLA-G, VEGF-A, VEGF-C, D240, CD34, ILT4 and Ca-IX. In addition, gene expression levels were measured in a cell line derived from a ccRCC patient by semi-quantitative RT-PCR.

Results

Our results show that the highly vascularized tumors of ccRCC patients express high levels of VEGF and the immune-checkpoint HLA-G. In addition, ILT4, one of the HLA-G receptors, was detected on macrophages surrounding tumor cells, suggesting the generation of an immune-tolerant microenvironment that might favor tumorigenesis. Notably, RT-qPCR analysis provided the first evidence on the transcriptional relationship between HLA-G/ILT4 and the VEGF family. Namely, in the presence of HLA-G or ILT4, the levels of VEGF-A are diminished whereas those of VEGF-C are increased.

Conclusions

In an effort to find new therapeutic molecules and fight against metastasis dissemination associated with the poor survival rates of ccRCC patients, these findings provide the rationale for co-targeting angiogenesis and the immune checkpoint HLA-G.

Overexpressed immunoglobulin-like transcript (ILT) 4 in lung adenocarcinoma is correlated with immunosuppressive T cell subset infiltration and poor patient outcomes

Background

The poor response to current PD-1/PD-L1 inhibitors in lung cancer patients requires development of novel immunotargets. Immunoglobulin-like transcript (ILT)4 is an immunosuppressive molecule mainly expressed in myeloid innate cells. Recent studies showed that ILT4 was highly expressed in multiple malignant cells and regulated tumor biologies including proliferation, invasion and metastasis. However, the immunomodulatory role of tumor cell-derived ILT4 is unclear. Here we aimed to analyze the correlation of tumor cell ILT4 expression with T cell infiltration and subset distribution, illustrate ILT4-regulated immunosuppressive microenvironment, and raise tumor cell-derived ILT4 as a novel immunotherapeutic target and prognostic biomarker for lung adenocarcinoma (LUAD) patients.

Methods

We collected the tissue samples and corresponding clinicopathological data from 216 primary LUAD patients. Using immunohistochemical staining and public database analyses we investigated the relationship between ILT4 expression and different T cell subset density as well as patient outcomes.

Results

Enriched ILT4 expression in tumor cells of LUAD tissues indicated reduced T cell infiltration in the tumor microenvironment (TME), advanced diseases and poor patient overall survival (OS). Further T cell subset analyses revealed that ILT4 expression was correlated with decreased CD8⁺T cell and increased Treg frequency in both cancer nest and stroma, but not with altered CD4⁺T cell frequency. High ILT4 level combined with low CD8⁺T cell/high Treg density predicted markedly poorer clinical outcomes compared with any of these biomarkers alone.

Conclusions

Tumor cell-derived ILT4 is correlated with immunosuppressive T cell subset infiltration and poor clinical outcomes, and might be a potential immunotherapeutic target and prognostic biomarker for LUAD patients. Combined ILT4 expression and CD8⁺ T cell/Treg frequency in tumor infiltrating lymphocytes (TILs) are stronger predictors for patient outcomes.

Comprehensive landscape of immune-checkpoints uncovered in clear cell renal cell carcinoma reveals new and emerging therapeutic targets

Clear cell renal cell carcinoma (ccRCC) constitutes the most common renal cell carcinoma subtype and has long been recognized as an immunogenic cancer. As such, significant attention has been directed toward optimizing immune-checkpoints (IC)-based therapies. Despite proven benefits, a substantial number of patients remain unresponsive to treatment, suggesting that yet unreported, immunosuppressive mechanisms coexist within tumors and their microenvironment. Here, we comprehensively analyzed and ranked forty-four immune-checkpoints expressed in ccRCC on the basis of in-depth analysis of RNAseq data collected from the TCGA database and advanced statistical methods designed to obtain the group of checkpoints that best discriminates tumor from healthy tissues. Immunohistochemistry and flow cytometry confirmed and enlarged the bioinformatics results. In particular, by using the recursive feature elimination method, we show that HLA-G, B7H3, PDL-1 and ILT2 are the most relevant genes that characterize ccRCC. Notably, ILT2 expression was detected for the first time on tumor cells. The levels of other ligand-receptor pairs such as CD70:CD27; 4-1BB:4-1BBL; CD40:CD40L; CD86:CTLA4; MHC-II:Lag3; CD200:CD200R; CD244:CD48 were also found highly expressed in tumors compared to adjacent non-tumor tissues. Collectively, our approach provides a comprehensible classification of forty-four IC expressed in ccRCC, some of which were never reported before to be co-expressed in ccRCC. In addition, the algorithms used allowed identifying the most relevant group that best discriminates tumor from healthy tissues. The data can potentially assist on the choice of valuable immune-therapy targets which hold potential for the development of more effective anti-tumor treatments.

Functions of Immune Checkpoint Molecules Beyond Immune Evasion

Immune checkpoint molecules, including inhibitory and stimulatory immune checkpoint molecules, are defined as ligand-receptor pairs that exert inhibitory or stimulatory effects on immune responses. Most of the immune checkpoint molecules that have been described so far are expressed on cells of the adaptive immune system, particularly on T cells, and of the innate immune system. They are crucial for maintaining the self-tolerance and modulating the length and magnitude of immune responses of effectors in different tissues to minimize the tissue damage. More and more evidences have shown that inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor types. Although the main function of tumor cell-associated immune checkpoint molecules is considered to mediate the immune evasion, it has been reported that the immune checkpoint molecules expressed on tumor cells also play important roles in the maintenance of many malignant behaviors, including self-renewal, epithelial-mesenchymal transition, metastasis, drug resistance, anti-apoptosis, angiogenesis, or enhanced energy metabolisms. In this section, we mainly focus on delineating the roles of the tumor cell-associated immune checkpoint molecules beyond immune evasion, such as PD-L1, PD-1, B7-H3, B7-H4, LILRB1, LILRB2, TIM3, CD47, CD137, and CD70.

Cyclosporine A sensitizes lung cancer cells to crizotinib through inhibition of the Ca2+/calcineurin/Erk pathway

Background

Crizotinib has potent anti-tumor activity in patients with advanced MET-amplified non-small cell lung cancer (NSCLC). However, the therapeutic effect is still not satisfying. Thus, developing approaches that improve the efficacy of crizotinib remains a significant challenge.

Methods

MET-amplified NSCLC cell lines were treated with crizotinib and cyclosporine A (CsA). Cell viability was determined by MTS assay. The changes of apoptosis, cell cycle and calcineurin-Erk pathways were assessed by western blot. Xenograft mouse model, primary human NSCLC cells and hollow fiber assays were utilized to confirm the effects of CsA.

Findings

We demonstrated that CsA significantly increased the anti-tumor effect of crizotinib on multiple MET-amplified NSCLC cells in vitro and in vivo. Mechanistically, crizotinib treatment led to the activation of Ca²⁺-calcineurin (CaN)-Kinase suppressor of Ras 2 (KSR2) signaling, resulting in Erk1/2 activation and enhanced survival of cancer cells. CsA effectively blocked CaN-KSR2-Erk1/2 signaling, promoting crizotinib-induced apoptosis and G2/M arrest. Similarly, pharmacologic or genetic inhibition of Erk1/2 also enhanced crizotinib-induced growth inhibition in vitro. Xenograft studies further confirmed that CsA or Erk1/2 inhibitor PD98059 enhanced the anti-cancer activity of crizotinib through inhibition of CaN-Erk1/2 axis. The results were also validated by primary human NSCLC cells in vitro and hollow fiber assays in vivo.

Interpretation

This study provides preclinical evidences that combination therapy of CsA and crizotinib is a promising approach for targeted treatment of MET-amplified lung cancer patients.

Fund

This work was supported by the National Natural Science Foundation of China, the Key Projects of Natural Foundation of Zhejiang Province, the Ten thousand plan youth talent support program of Zhejiang Province, the Zhejiang Natural Sciences Foundation Grant, and the Zhejiang medical innovative discipline construction project-2016.

Expression of ILT3 predicts poor prognosis and is inversely associated with infiltration of CD45RO+ T cells in patients with colorectal cancer

Immunoglobulin like transcript 3 (ILT3) was previously identified as an inhibitory receptor to induce T cell anergy in tranplantation, autoimmunity and allergy. Here we aimed to investigate the expression of ILT3 in colorectal cancer, analyze the association between ILT3 expression and clinicopathological variables and prognosis, and evaluate the correlation between the expression of ILT3 and CD45RO+ T cells density. Expression of ILT3 was identified on the cell membrane and/or in the cytoplasm. High expression ILT3 was identified in 55 of 85 (64.7%) tumor specimens, which was significantly higher than that in the adjacent normal tissues(5/30) (P < 0.001). High ILT3 expression was significantly associated with positive lymph node metastasis (N1-2; P = 0.03), advanced disease (stage III-IV; P = 0.03), and reduced OS in patients. The ILT3 expression level was an independent prognostic factor (P = 0.004) and inversely correlated with the number of CD45RO+ T cells (P = 0.019). In the present study, high ILT3 expression was observed in colorectal cancer and inversely associated with CD45RO+ T cells density and prognosis, suggesting that ILT3 played an important role in tumor progression by possible influence on CD45RO+ T cells in the tumor microenvironment.

Intratumor heterogeneity of immune checkpoints in primary renal cell cancer: Focus on HLA-G/ILT2/ILT4

The establishment and maintenance of anti-tumor immune responses are the objectives of cancer immunotherapy. Despite recent promising advances, the effectiveness of these approaches has been limited by the multiple immunosuppressive mechanisms developed by tumors (checkpoint). The aim of the present study was to demonstrate intratumor heterogeneity at the levels of immune escape strategies and tumor-host relationships. We focused on well-known checkpoints such as PD1/PDL1 and on a new checkpoint involving HLA-G and its receptors ILT2/ILT4. A prospective study was performed on 19 renal-cell carcinoma patients that were included during hospitalization for surgical tumor resection. Different areas of the tumor were collected for each patient and subjected to both immunohistochemical and flow cytometry analysis. Immune cells from peripheral blood were concomitantly analyzed for each patient. Our results show the heterogeneous expression of PD1/PDL1 and HLA-G/ILT in the various areas of the same tumor. Intratumor heterogeneity was found both at tumor cell and infiltrating immune cell levels. From a clinical point of view, this work highlights the functional redundancies of checkpoints and the need to adapt personalized poly-immunotherapy.

SCARA5 plays a critical role in the progression and metastasis of breast cancer by inactivating the ERK1/2, STAT3, and AKT signaling pathways

Scavenger receptor class A member 5 (SCARA5) is a candidate anti-oncogene in several malignancies. However, whether SCARA5 is a suppressor gene in breast cancer and its role in breast cancer cell growth and metastasis remain to be determined. Here, we investigated the biological functions of SCARA5 in the progression and metastasis of breast cancer and explored the underlying mechanisms. A total of 65 breast cancer patients and three cell lines (ZR-75-30, MCF-7, and MDA-MB-231) were analyzed in the study. RT-qPCR, western blotting, and immunohistochemistry were used to detect mRNA and protein expression, and lymphatic vessel density (LVD) and microvessel density (MVD). MTT, colony formation, TUNEL assays, invasion assays and Transwell assays, and flow cytometric analyses were used to evaluate the effect of SCARA5 on breast cancer cells. SCARA5 was significantly downregulated in breast cancer tissues and cells and significantly correlated with tumor size, histological grade, lymph node metastasis, pTNM stage, VEGF-A, VEGF-C, LVD, and MVD. SCARA5 overexpression significantly suppressed cell proliferation, colony formation, invasion, and migration, and induced G0/G1 arrest and apoptosis of ZR-75-30 cells. SCARA5 decreased the phosphorylation of ERK1/2, AKT, and STAT3, and downregulated downstream signaling effectors, including MMP-2, 3, and 9, VEGF-A, VEGF-C, Bax, Cyclin B1, Cyclin D1, and Cyclin E1, and upregulated E-cadherin, Bcl-2, and caspase 3. SCARA5 is associated with multiple signaling pathways and plays a critical role in the progression and metastasis of breast cancer. The present results provide the first evidence that SCARA5 inhibits lymphangiogenesis by downregulating VEGF-C, thereby inhibiting breast cancer lymphatic metastasis.

IL-17A promotes the proliferation of human nasopharyngeal carcinoma cells through p300-mediated Akt1 acetylation

Interleukin (IL)-17A is a T helper (Th)17 cell-secreted cytokine that is able to induce various inflammatory responses. There is emerging evidence that IL-17A is generated in the cancer microenvironment of human nasopharyngeal carcinoma (NPC). However, the role of IL-17A in NPC remains unclear. Thus, the present study aimed to examine the direct influence of IL-17A stimulation on the proliferation of human NPC cells and identify the underlying molecular mechanisms. Furthermore, E1A binding protein p300 (p300)-mediated AKT serine/threonine kinase 1 (Akt1) acetylation and its role in regulating the proliferation of NPC cells was investigated. The results of the current study demonstrated that IL-17A stimulation in vitro increased the proliferation of human NPC cells. Furthermore, Akt1 acetylation was identified to be enhanced in human NPC cells induced by IL-17A. Additionally, p300 induction was demonstrated to be required for Akt1 acetylation in human NPC cells following exposure to IL-17A. Functionally, p300-mediated Akt1 acetylation contributed to the proliferation of human NPC cells stimulated by IL-17A. In conclusion, the results of the present demonstrate a novel activity of IL-17A that promotes human NPC cell proliferation via p300-mediated Akt1 acetylation. This may provide a potential strategy for the treatment of patients with NPC through the inhibition of IL-17A or its receptors.

Methylation-mediated loss of SFRP2 enhances invasiveness of non-small cell lung cancer cells

The malignancy of non-small cell lung cancer (NSCLC) largely results from its invasive manner. Secreted frizzled-related proteins (SFRPs) have been recently found to suppress the invasiveness of some cancers. On the other hand, the methylation of SFRPs increases protein degradation to reduce the activity of SFRPs, resulting in increased tumor cell invasion and cancer metastasis. However, the role of SFRPs in the invasion of NSCLC has not been reported. Here we analyzed the regulation of SFRPs in NSCLC cells and its effects on cell invasion. We found that SFRP2 mRNA was significantly decreased and methylation of SFRP2 gene was significantly increased in NSCLC tissue, compared to the paired adjacent nontumor tissue. Moreover, SFRP2 expression was significantly decreased in NSCLC cell lines. In NSCLC cell lines, the SFRP2 expression would be restored by the demethylation of SFRP2 gene with 5'-aza-deoxycytidine in NSCLC cell lines, at the levels of both mRNA and protein. Thus, the cell invasion would be suppressed. Furthermore, the demethylation of SFRP2 gene appeared to inhibit Zinc Finger E-Box Binding Homeobox 1 (ZEB1) and matrix metallopeptidase 9 (MMP9), two key factors that enhance NSCLC cell invasion. Thus, SFRP2 may inhibit NSCLC invasion by suppressing ZEB1 and MMP9, while its methylation promotes NSCLC invasion.

Total saponins of panaxnotoginseng promotes lymphangiogenesis by activation VEGF-C expression of lymphatic endothelial cells

ETHNOPHARMACOLOGICAL RELEVANCE

Lymphatic system plays an important role in maintaining the fluid homeostasis and normal immune responses, anatomic or functional obstruction of which leads to lymphedema, and treatments for therapeutic lymphangiogenesis are efficiency for secondary lymphedema. Total saponins of panaxnotoginseng (PNS) are a mixture isolated from Panaxnotoginseng (Burkill) F.H.Chen, which has been used as traditional Chinese medicine in China for treatment of cardio- and cerebro-vascular diseases. The aim of this study was to determine the effect and mechanism of PNS on lymphangiogenesis.

METHODS

The Tg (fli1: egfp; gata1: dsred) transgenic zebrafish embryos were treated with different concentrations of PNS (10, 50, 100μM) for 48h with or without the 6h pretreatment of the 30μM Vascular endothelial growth factors receptor (VEGFR)-3 kinase inhibitor, followed with morphological observation and lympangiogenesis of thoracic duct assessment. The effect of PNS on cell viability, migration, tube formation and Vascular endothelial growth factors (VEGF)-C mRNA and protein expression of lymphatic endothelial cells (LECs) were determined. The role of phosphatidylinositol-3 (PI-3)-kinase (PI3K), extracellular signal-regulated kinase (ERK)1/2 pathways, c-Jun N-terminal kinase (JNK) and P38 mitogen activated protein kinases (MAPK) signaling in PNS-induced VEGF-C expression of LECs by using pharmacological agents to block each signal.

RESULTS

PNS promotes lymphangiogenesis of thoracic duct in zebrafish with or without VEGFR3 Kinase inhibitor pre-impairment. PNS promotes proliferation, migration and tube formation of LECs. The tube formation induced by PNS could be blocked by VEGFR3 Kinase inhibitor. PNS induce VEGF-C expression of LEC, which could be blocked by ERK1/2, PI3K and P38MAPK signaling inhibitors.

CONCLUSION

PNS activates lymphangiogenesis both in vivo and in vitro by up-regulating VEGF-C expression and activation of ERK1/2, PI3K and P38MAPK signaling. These findings provide a novel insight into the role of PNS in lymphangiogenesis and suggest that it might be an attractive and suitable therapeutic agent for treating secondary lymphedema or other lymphatic system impairment related disease.

Co-expression of ILT4/HLA-G in human non-small cell lung cancer correlates with poor prognosis and ILT4-HLA-G interaction activates ERK signaling

Non-small cell lung cancer (NSCLC) is the most common malignant tumor in the world, of which prognosis is generally poor due to insufficient mechanistic understanding. To explore the molecular pathogenesis of NSCLC, the co-expression of immunoglobulin-like transcript 4 (ILT4) and its ligand human leukocyte antigen G (HLA-G) in NSCLC tissues and cells were investigated. Here, we detected the expression of ILT4 and HLA-G in 81 tumor specimens from primary NSCLC patients, and we found that co-expression of ILT4/HLA-G was significantly associated with regional lymph node involvement, advanced stages, and the overall survival of patients. In NSCLC cell lines, HLA-G expression increased/decreased accordingly when ILT4 was up-/down-regulated, and ILT4 expression increased in a concentration-dependent manner via the stimulation of HLA-G fusion protein. Interestingly, HLA-G fusion protein could also up-regulate the phospho-ERK1/2 expression, which means the activation of extracellular signal-regulated kinase (ERK) signaling. All in all, our results indicate that the ILT4-HLA-G interaction might play an important role in NSCLC progression. Identification of ILT4 and HLA-G expression may provide an indicator to predict prognosis and guide prevention and treatment of NSCLC.