PD-L1 expression is associated with epithelial-mesenchymal transition in head and neck squamous cell carcinoma

Brusatol improves the efficacy of an anti-mouse-PD-1 antibody via inhibiting programmed cell death 1 ligand 1 expression in a murine head and neck squamous cell carcinoma model

OBJECTIVE

Combing PD-1/PD-L1 immune checkpoint inhibitors with natural products has exhibited better efficacy than monotherapy. Hence, the purpose of this research was to examine the anti-cancer effects of brusatol, a natural quassinoid-terpenoid derived from Brucea javanica, when used in conjunction with an anti-mouse-PD-1 antibody in a murine head and neck squamous cell carcinoma (HNSCC) model and elucidate underlying mechanisms.

DESIGN

A murine HNSCC model and an SCC-15 cell xenograft nude mouse model were established to investigate the anti-cancer effects of brusatol and anti-PD-1 antibody. Mechanistic studies were performed using immunohistochemistry. Cell proliferation, migration, colony formation, and invasion were evaluated by MTT, migration, colony formation, and transwell invasion assays. PD-L1 levels in oral squamous cell carcinoma (OSCC) cells were assessed through qRT-PCR, flow cytometry, and western blotting assays. The impact of brusatol on Jurkat T cell function was assessed by an OSCC/Jurkat co-culture assay.

RESULTS

Brusatol improved tumor suppression by anti-PD-1 antibody in HNSCC mouse models. Mechanistic studies revealed brusatol inhibited tumor cell growth and angiogenesis, induced apoptosis, increased T lymphocyte infiltration, and reduced PD-L1 expression in tumors. Furthermore, in vitro assays confirmed brusatol inhibited PD-L1 expression in OSCC cells and suppressed cell migration, colony formation, and invasion. Co-culture assays indicated that brusatol's PD-L1 inhibition enhanced Jurkat T cell-mediated OSCC cell death and reversed the inhibitory effect induced by OSCC cells.

CONCLUSIONS

Brusatol improves anti-PD-1 antibody efficacy by targeting PD-L1, suggesting its potential as an adjuvant in anti-PD-1 immunotherapy.

Epithelial-mesenchymal transition induced by tumor cell-intrinsic PD-L1 signaling predicts a poor response to immune checkpoint inhibitors in PD-L1-high lung cancer

BACKGROUND

We investigated the role of tumor cell-intrinsic PD-L1 signaling in the epithelial-mesenchymal transition (EMT) in non-small-cell lung cancer (NSCLC) and the role of EMT as a predictive biomarker for immune checkpoint inhibitor (ICI) therapy.

METHODS

PD-L1-overexpressing or PD-L1-knockdown NSCLC cells underwent RNA-seq and EMT phenotype assessment. Mouse lung cancer LLC cells were injected into nude mice. Two cohorts of patients with NSCLC undergoing ICI therapy were analyzed.

RESULTS

RNA-seq showed that EMT pathways were enriched in PD-L1-high NSCLC cells. EMT was enhanced by PD-L1 in NSCLC cells, which was mediated by transforming growth factor-β (TGFβ). PD-L1 promoted the activation of p38-MAPK by binding to and inhibiting the protein phosphatase PPM1B, thereby increasing the TGFβ production. Tumor growth and metastasis increased in nude mice injected with PD-L1-overexpressing LLC cells. In the ICI cohort, EMT signature was higher in patients with progressive disease than in those with responses, and EMT was significantly associated with poor survival in PD-L1-high NSCLC. In PD-L1-high NSCLC, EMT was associated with increased M2-macrophage and regulatory T-cell infiltrations and decreased cytotoxic T-cell infiltration.

CONCLUSIONS

Tumor cell-intrinsic PD-L1 function contributes to NSCLC progression by promoting EMT. EMT may predict an unfavorable outcome after ICI therapy in PD-L1-high NSCLC.

Impact of PIK3CA and cell cycle pathway genetic alterations on durvalumab efficacy in patients with head and neck squamous cell carcinoma: Post hoc analysis of TRIUMPH study

OBJECTIVES

This study aimed to investigate whether genetic alterations in PI3KCA and the cell cycle pathways influence the efficacy of durvalumab, an immune checkpoint inhibitor, in patients with head and neck squamous cell carcinoma (HNSCC) who had previously failed platinum-based treatment.

MATERIALS AND METHODS

We obtained data from a phase II umbrella trial of patients with HNSCC who failed platinum-based treatment (TRIUMPH, NCT03292250). Patients receiving durvalumab treatment comprised those with PIK3CA alterations (Group A), those with cell cycle pathway alterations such as CDKN2A (Group B), and those with no druggable genetic alterations (Group C). We analyzed the overall response rate (ORR), progression-free survival (PFS), and overall survival (OS) in each group and evaluated the potential predictive factors for durvalumab.

RESULTS

We analyzed the data of 87 patients: 18, 12, and 57 in groups A, B, and C, respectively. The ORRs were 27.8 %, 8.3 %, and 15.8 % in Groups A, B, and C, respectively (P = 0.329), and the median PFS for each group was 2.3, 1.6, and 1.7 months, respectively, with no significant differences between the groups (P = 0.24). Notably, patients with lower neutrophil-lymphocyte ratio (NLR) (≤5.8) had longer PFS (median, 2.8 vs 1.6 months, P < 0.001), while those with lower platelet-lymphocyte ratio (PLR) (≤491.2) exhibited longer PFS (median, 1.8 vs 1.2 months, P < 0.001).

CONCLUSION

Durvalumab's efficacy was similar, irrespective of the presence of PIK3CA or cell cycle pathway genetic alterations in patients with platinum-resistant HNSCC. The NLR and PLR may be promising predictive biomarkers.

Immune checkpoints between epithelial-mesenchymal transition and autophagy: A conflicting triangle

Inhibitory immune checkpoint (ICP) molecules are pivotal in inhibiting innate and acquired antitumor immune responses, a mechanism frequently exploited by cancer cells to evade host immunity. These evasion strategies contribute to the complexity of cancer progression and therapeutic resistance. For this reason, ICP molecules have become targets for antitumor drugs, particularly monoclonal antibodies, collectively referred to as immune checkpoint inhibitors (ICI), that counteract such cancer-associated immune suppression and restore antitumor immune responses. Over the last decade, however, it has become clear that tumor cell-associated ICPs can also induce tumor cell-intrinsic effects, in particular epithelial-mesenchymal transition (EMT) and macroautophagy (hereafter autophagy). Both of these processes have profound implications for cancer metastasis and drug responsiveness. This article reviews the positive or negative cross-talk that tumor cell-associated ICPs undergo with autophagy and EMT. We discuss that tumor cell-associated ICPs are upregulated in response to the same stimuli that induce EMT. Moreover, ICPs themselves, when overexpressed, become an EMT-inducing stimulus. As regards the cross-talk with autophagy, ICPs have been shown to either stimulate or inhibit autophagy, while autophagy itself can either up- or downregulate the expression of ICPs. This dynamic equilibrium also extends to the autophagy-apoptosis axis, further emphasizing the complexities of cellular responses. Eventually, we delve into the intricate balance between autophagy and apoptosis, elucidating its role in the broader interplay of cellular dynamics influenced by ICPs. In the final part of this article, we speculate about the driving forces underlying the contradictory outcomes of the reciprocal, inhibitory, or stimulatory effects between ICPs, EMT, and autophagy. A conclusive identification of these driving forces may allow to achieve improved antitumor effects when using combinations of ICIs and compounds acting on EMT and/or autophagy. Prospectively, this may translate into increased and/or broadened therapeutic efficacy compared to what is currently achieved with ICI-based clinical protocols.

Epithelial-to-mesenchymal transition in cancer progression: unraveling the immunosuppressive module driving therapy resistance

Cancer cells undergo phenotypic switching (cancer cell plasticity) in response to microenvironmental cues, including exposure to therapy/treatment. Phenotypic plasticity enables the cancer cells to acquire more mesenchymal traits promoting cancer cells' growth, survival, therapy resistance, and disease recurrence. A significant program in cancer cell plasticity is epithelial-to-mesenchymal transition (EMT), wherein a comprehensive reprogramming of gene expression occurs to facilitate the translational shift from epithelial-to-mesenchymal phenotypes resulting in increased invasiveness and metastasis. In addition, EMT plays a pivotal role in facilitating cancer cells' escape from the body's immune system using several mechanisms, such as the downregulation of major histocompatibility complex-mediated antigen presentation, upregulation of immune checkpoint molecules, and recruitment of immune-suppressive cells. Cancer cells' ability to undergo phenotypic switching and EMT-driven immune escape presents a formidable obstacle in cancer management, highlighting the need to unravel the intricate mechanisms underlying these processes and develop novel therapeutic strategies. This article discusses the role of EMT in promoting immune evasion and therapy resistance. We also discuss the ongoing research on developing therapeutic approaches targeting intrinsic and induced cell plasticity within the immune suppressive microenvironment. We believe this review article will update the current research status and equip researchers, clinicians, and other healthcare professionals with valuable insights enhancing their existing knowledge and shedding light on promising directions for future cancer research. This will facilitate the development of innovative strategies for managing therapy-resistant cancers and improving patient outcomes.

Exploring the Functions of Mutant p53 through TP53 Knockout in HaCaT Keratinocytes

Approximately 50% of tumors carry mutations in TP53; thus, evaluation of the features of mutant p53 is crucial to understanding the mechanisms underlying cell transformation and tumor progression. HaCaT keratinocytes represent a valuable model for research in this area since they are considered normal, although they bear two gain-of-function mutations in TP53. In the present study, transcriptomic and proteomic profiling were employed to examine the functions of mutant p53 and to investigate the impact of its complete abolishment. Our findings indicate that CRISPR-mediated TP53 knockout results in significant changes at the transcriptomic and proteomic levels. The knockout of TP53 significantly increased the migration rate and altered the expression of genes associated with invasion, migration, and EMT but suppressed the epidermal differentiation program. These outcomes suggest that, despite being dysfunctional, p53 may still possess oncosuppressive functions. However, despite being considered normal keratinocytes, HaCaT cells exhibit oncogenic properties.

Prognostic significance of programmed cell death-ligand 1 expression on immune cells and epithelial-mesenchymal transition expression in patients with hepatocellular carcinoma

Purpose

Immune checkpoint inhibitors (ICIs) have been shown significant oncological improvements in several cancers. However, ICIs are still in their infancy in hepatocellular carcinoma (HCC). Programmed cell death-ligand 1 (PD-L1), tumor-infiltrating lymphocytes (TILs), and epithelial-mesenchymal transition (EMT) have been known as prognostic factors in HCC. Therefore, we have focused on identifying the molecular mechanisms between each marker to evaluate a predictive role.

Methods

Formalin-fixed paraffin-embedded samples were obtained from 166 patients with HCC who underwent surgery. The expression of PD-L1 and TILs and EMT marker were evaluated by immunohistochemical analysis.

Results

The multivariate analysis showed that TIL expression (hazard ratio [HR], 0.483; 95% confidence interval [CI], 0.269-0.866; P = 0.015) were independent prognostic factors for overall survival. The prognostic factors for disease-free survival were EMT marker expression (HR, 1.565; 95% CI, 1.019-2.403; P = 0.005). Patients with high expression of TILs had significantly better survival compared to patients with low expression (P = 0.023). Patients who were TIL+/EMT- showed a significantly better prognosis than those who were TIL-/EMT+ (P = 0.049).

Conclusion

This study demonstrates that PD-L1 expression of TILs is closely associated with EMT marker expression in HCC. Clinical investigations using anti-PD-1/PD-L1 inhibitors in patients with EMT-associated PD-L1 upregulation are warranted.

Unpacking the Complexity of Epithelial Plasticity: From Master Regulator Transcription Factors to Non-Coding RNAs

Cellular plasticity in cancer enables adaptation to selective pressures and stress imposed by the tumor microenvironment. This plasticity facilitates the remodeling of cancer cell phenotype and function (such as tumor stemness, metastasis, chemo/radio resistance), and the reprogramming of the surrounding tumor microenvironment to enable immune evasion. Epithelial plasticity is one form of cellular plasticity, which is intrinsically linked with epithelial-mesenchymal transition (EMT). Traditionally, EMT has been regarded as a binary state. Yet, increasing evidence suggests that EMT involves a spectrum of quasi-epithelial and quasi-mesenchymal phenotypes governed by complex interactions between cellular metabolism, transcriptome regulation, and epigenetic mechanisms. Herein, we review the complex cross-talk between the different layers of epithelial plasticity in cancer, encompassing the core layer of transcription factors, their interacting epigenetic modifiers and non-coding RNAs, and the manipulation of cancer immunogenicity in transitioning between epithelial and mesenchymal states. In examining these factors, we provide insights into promising therapeutic avenues and potential anti-cancer targets.

The effects of anti-PD-L1 monoclonal antibody on the expression of angiogenesis and invasion-related genes

Background/aim

The role of PD-L1 in regulating the immunosuppressive tumor microenvironment via its binding on PD-1 receptors is extensively studied. The PD-1/PD-L1 axis is a significant way of cancer immune escape, and PD-L1 expression on tumor cells is suggested as a predictive marker for anti-PD-1/PD-L1 monoclonal antibodies (MoAbs). However, the tumor-intrinsic role of PD-L1 is not known well. Therefore, we aimed to investigate the effects of anti-PD-L1 antibodies on the expression of angiogenesis and metastasis-related genes in tumor cells.

Materials and methods

The experiments were done with prostate cancer and melanoma cells with low PD-L1 expression (<5%) and prostate and breast cancer cells with high PD-L1 expression (>50%). The gene and protein expressions of VEGFA, E-cadherin, TGFβ1, EGFR, and bFGF in tumor cells were assayed at the 3 different doses of the anti-PD-L1 antibody.

Results

We found that VEGFA, E-cadherin and TGFβ1 expressions increased in PD-L1 high cells but decreased in PD-L1 low cells after anti-PD-L1 treatment. EGFR expression levels were variable in PD-L1 high cells, while decreased in PD-L1 low cells upon treatment. Also, the anti-PD-L1 antibody was found to increase bFGF expression in the prostate cancer cell line with high PD-L1 expression.

Conclusion

Our results suggest that the binding of PD-L1 on tumor cells by an anti-PD-L1 monoclonal antibody may affect tumor-intrinsic mechanisms. The activation of angiogenesis and metastasis-related pathways by anti-PD-L1 treatment in PD-L1 high tumors might be a tumor-promoting mechanism. The decrease of VEGFA, TGFβ1 and EGFR upon anti-PD-L1 treatment in PD-L1 low tumor cells provides a rationale for the use of those antibodies in PD-L1 low tumors.

Sarcomatoid urothelial carcinoma of the renal pelvis treated with immunotherapy

BACKGROUND

Sarcomatoid carcinoma is a rare, high-grade malignancy with epithelial and mesenchymal components. It may be a good candidate for immunotherapy because it is associated with overexpression of programmed cell death ligand 1. Sarcomatoid urothelial carcinoma (UC) of the upper urinary tract is extremely rare. Here we report the first case of sarcomatoid UC of the renal pelvis that responded to immunotherapy.

CASE PRESENTATION

A 79-year-old man was referred to our hospital complaining of various symptoms, including anorexia and abdominal pain. A computed tomography scan revealed a right atrial tumor, a 9 cm left renal mass with a renal vein tumor thrombus, para-aortic lymphadenopathy, and multiple small lung nodules. The patient underwent resection of the right atrial tumor. Pathological analysis of the tumor did not lead to an accurate diagnosis even after several rounds of immunohistochemistry. He underwent a needle biopsy of the left kidney and was initially diagnosed with collecting duct carcinoma, a rare subtype of renal cell carcinoma (RCC). Following the initial diagnosis, immunotherapy with nivolumab and ipilimumab commenced. Thereafter, almost all lesions, including the left renal tumor, were reduced in size. However, he underwent a left nephrectomy approximately a year after beginning immunotherapy due to repeated left renal bleeding. Histological examination of the nephrectomy specimen revealed two forms of cancer-sarcomatoid UC and conventional high-grade UC. Two months after surgery, the patient was found to have new lung metastases. He underwent chemotherapy with gemcitabine and cisplatin, followed by immunotherapy with pembrolizumab. However, both treatments were ineffective. The patient died of cancer 19 months after his first admission.

CONCLUSIONS

The presented case of sarcomatoid UC of the renal pelvis that partially responded to immunotherapy suggests that immunotherapy can be a promising treatment for sarcomatoid UC.

KCNQ1OT1 sponges miR-34a to promote malignant progression of malignant melanoma via upregulation of the STAT3/PD-L1 axis

BACKGROUND

Malignant melanoma is a leading cause of skin cancer-related death. In over 30% of cases, the melanoma is invasive and has a metastatic phenotype. KCNQ1 overlapping transcript 1 (KCNQ1OT1) was previously identified as an oncogenic long noncoding RNA (lncRNA). Our study intends to uncover the mechanism of KCNQ1OT1 functioning in melanoma.

METHODS

qRT-PCR, immunohistochemical analysis, and Western blotting were used to investigate mechanisms of the lncRNA KCNQ1OT1, on its downstream genes in melanoma tissues, cells as well as the impact on CD8+ T cells. Proliferation, apoptosis, and migration/invasion were assessed in melanoma cells to evaluate the effects of KCNQ1OT1, miR-34a, and signal transducer and activator of transcription 3 (STAT3). The RNA interactions were determined by dual-luciferase reporter, and melanoma cells were co-cultured with CD8+ T cells to study immune evasion. A lactate dehydrogenase (LDH) cytotoxicity assay was used to investigate the cytotoxicity of CD8+ T cells toward melanoma cells. The in vivo tumorigenic potential of KCNQ1OT1 was defined using xenograft models.

RESULTS

KCNQ1OT1 was upregulated in melanoma tissues leading to a poor prognosis, and knocking down it inhibited melanoma cell proliferation, migration, and invasion. KCNQ1OT1 regulated the progression of the melanoma via its action as a miR-34a sponge. STAT3 was found to be a downstream target of miR-34a, resulting in transcriptional regulation of Programmed cell death 1 ligand 1 (PD-L1). KCNQ1OT1 regulated STAT3 by targeting miR-34a. Knockdown of KCNQ1OT1 reduced PD-L1 level, enhanced CD8+ T cell cytotoxicity, and proliferation and inhibited apoptosis of CD8+ T cells.

CONCLUSION

Melanoma cells overexpressed KCNQ1OT1, which influenced the miR-34a/STAT3 axis, to promote proliferation, migration, and invasion of melanoma cells. In addition, KCNQ1OT1 inhibited CD8+ T cell function, also via the miR-34a/STAT3/PD-L1 axis, thus promoting immune evasion of melanoma cells. The current findings expose a potential therapeutic target of melanoma.

Coexpression of PD-L1/PD-1 with CXCR3/CD36 and IL-19 Increase in Extranodal Lymphoma

Many studies have demonstrated that PD-L1/PD-1 signaling is an immune evasion mechanism in tumors. PD-L1/PD-1 coexpression with CXCR3/CD36 in peripheral lymphocytes in lymphoma still needs to be clarified. The current study investigated PD-L1/PD-1 coexpression with CXCR3/CD36 in circulating lymphocytes, serum IL-19 levels, and their correlation with clinical outcome and extranodal involvement in lymphoma. Subjects and Methods. The coexpression of PD-L1/PD-1 with CXCR3/CD36 on circulating lymphocytes was analyzed by flow cytometry in 78 lymphoma patients before and after therapy and in 50 healthy controls. The concentration levels of IL-19 in serum were assessed by an ELISA. Results. PD-L1 and PD-1 were expressed on circulating CXCR3+ and CD36+ lymphocytes in lymphoma and were significantly higher in patients with extranodal involvement than in lymphoma patients without extranodal involvement (P < 0.001). Elevated IL-19 levels were observed in lymphoma patients and increased significantly in extranodal involvement (P < 0.001). High percentages of PD-L1+CXCR3+ and PD-1+CXCR3+ lymphocytes were associated with high LDH levels, hepatomegaly, lymphedema, advanced tumor stage, and recurrence. Furthermore, patients with splenomegaly and generalized lymphadenopathy had high percentages of PD-L1+CXCR3+ lymphocytes. In addition, levels of PD-L1/PD-1 coexpression with CXCR3 and IL-19 were significantly associated with bone marrow, lung, and lymph vessel involvement. Further analysis revealed that high percentages of PD-L1+CD36+ and PD-1+CD36+ lymphocytes were associated with lung and bone marrow involvement. Patients with high levels of PD-L1/PD-1 coexpression with CXCR3 and IL-19 had inferior event-free survival (EFS) compared with that in lymphoma patients with low levels. EFS was decreased in patients with high percentages of PD-L1+CD36+ and PD-1+CD36+ lymphocytes. When using the receiver operating characteristic (ROC) curve, the superiority of IL-19 (area under the curve (AUC): 0.993) and PD-L1+CXCR3+% (AUC: 0.961) to PD-1+CXCR3+% (AUC: 0.805), PD-L1+CD36+% (AUC: 0.694), and PD-1+CD36+% (AUC 0.769) was evident in the diagnosis of extranodal involvement, identifying lymphoma patients with extranodal involvement from patients without extranodal involvement. Conclusions. Coexpression of PD-L1/PD-1 with CXCR3/CD36 in circulating lymphocytes and serum IL-19 levels contributes to poor prognosis and might be potential markers for extranodal involvement in lymphoma.

EMT and Tumor Turning Point Analysis in 3D Spheroid Culture of HNSCC and Mesenchymal Stem Cells

The prognosis, metastasis, and behavior of head and neck squamous cancer cells are influenced by numerous factors concerning the tumor microenvironment, intercellular communication, and epithelial-to-mesenchymal transition (EMT). The aim of this study was to examine the codependent interaction of the mesenchymal stroma with head and neck squamous cell carcinoma (HNSCC) in a 3D spheroid structure. To simulate stroma-rich and -poor 3D tumor microenvironments, cells of the established cell SCC-040 were cultured with human mesenchymal stromal cells (MSCs), forming 3D stroma-tumor spheroids (STSs). STSs were compared to uniform spheroids of SCC-040 and MSC, respectively. The expressions of CD24, β-catenin, SNAI2, and ZEB2 were analyzed via RT-qPCR. The immunohistochemical expressions of E-cadherin, connexin 43, vimentin, and emmprin were analyzed, and protein expression pathways as well as Akt signaling were assessed via protein analysis. A promotive effect on the expressions of EMT markers ZEB2 (p = 0.0099), SNAI2 (p = 0.0352), and β-catenin (p = 0.0031) was demonstrated in STSs, as was the expression of Akt pathway proteins mTOR (p = 0.007), Erk1/2 (p = 0.0045), and p70 S6 Kinase (p = 0.0016). Our study demonstrated a change in genetic expression patterns early on in tumor development, indicating a tumor turning point.

Genomic and Transcriptomic Predictors of Response to Immune Checkpoint Inhibitors in Melanoma Patients: A Machine Learning Approach

Immune checkpoint inhibitors (ICIs) became one of the most revolutionary cancer treatments, especially in melanoma. While they have been proven to prolong survival with lesser side effects compared to chemotherapy, the accurate prediction of response remains to be an unmet gap. Thus, we aim to identify accurate clinical and transcriptomic biomarkers for ICI response in melanoma. We also provide mechanistic insight into how high-performing markers impose their effect on the tumor microenvironment (TME). Clinical and transcriptomic data were retrieved from melanoma studies administering ICIs from cBioportal and GEO databases. Four machine learning models were developed using random-forest classification (RFC) entailing clinical and genomic features (RFC7), differentially expressed genes (DEGs, RFC-Seq), survival-related DEGs (RFC-Surv) and a combination model. The xCELL algorithm was used to investigate the TME. A total of 212 ICI-treated melanoma patients were identified. All models achieved a high area under the curve (AUC) and bootstrap estimate (RFC7: 0.71, 0.74; RFC-Seq: 0.87, 0.75; RFC-Surv: 0.76, 0.76, respectively). Tumor mutation burden, GSTA3, and VNN2 were the highest contributing features. Tumor infiltration analyses revealed a direct correlation between upregulated genes and CD8+, CD4+ T cells, and B cells and inversely correlated with myeloid-derived suppressor cells. Our findings confirmed the accuracy of several genomic, clinical, and transcriptomic-based RFC models, that could further support the use of TMB in predicting response to ICIs. Novel genes (GSTA3 and VNN2) were identified through RFC-seq and RFC-surv models that could serve as genomic biomarkers after robust validation.

PD-L1 Activity Is Associated with Partial EMT and Metabolic Reprogramming in Carcinomas

Immune evasion and metabolic reprogramming are hallmarks of cancer progression often associated with a poor prognosis and frequently present significant challenges for cancer therapies. Recent studies have highlighted the dynamic interaction between immunosuppression and the dysregulation of energy metabolism in modulating the tumor microenvironment to promote cancer aggressiveness. However, a pan-cancer association among these two hallmarks, and a potent common driver for them-epithelial-mesenchymal transition (EMT)-remains to be done. This meta-analysis across 184 publicly available transcriptomic datasets as well as The Cancer Genome Atlas (TCGA) data reveals that an enhanced PD-L1 activity signature along with other immune checkpoint markers correlate positively with a partial EMT and an elevated glycolysis signature but a reduced OXPHOS signature in many carcinomas. These trends were also recapitulated in single-cell, RNA-seq, time-course EMT induction data across cell lines. Furthermore, across multiple cancer types, concurrent enrichment of glycolysis and PD-L1 results in worse outcomes in terms of overall survival as compared to enrichment for only PD-L1 activity or expression. These results highlight potential functional synergy among these interconnected axes of cellular plasticity in enabling metastasis and multi-drug resistance in cancer.

Prognostic value of PD-1, PD-L1 and PD-L2 deserves attention in head and neck cancer

Head and neck cancer has high heterogeneity with poor prognosis, and emerging researches have been focusing on the prognostic markers of head and neck cancer. PD-L1 expression is an important basis for strategies of immunosuppressive treatment, but whether it has prognostic value is still controversial. Although meta-analysis on PD-L1 expression versus head and neck cancer prognosis has been performed, the conclusions are controversial. Since PD-L1 and PD-L2 are two receptors for PD-1, here we summarize and analyze the different prognostic values of PD-1, PD-L1, and PD-L2 in head and neck cancer in the context of different cell types, tissue localization and protein forms. We propose that for head and neck cancer, the risk warning value of PD-1/PD-L1 expression in precancerous lesions is worthy of attention, and the prognostic value of PD-L1 expression at different subcellular levels as well as the judgment convenience of prognostic value of PD-1, PD-L1, PD-L2 should be fully considered. The PD-L1 evaluation systems established based on immune checkpoint inhibitors (ICIs) are not fully suitable for the evaluation of PD-L1 prognosis in head and neck cancer. It is necessary to establish a new PD-L1 evaluation system based on the prognosis for further explorations. The prognostic value of PD-L1, PD-L2 expression in head and neck cancer may be different for early-stage and late-stage samples, and further stratification is required.

STAT1/IFIT2 signaling pathway is involved in PD-L1-mediated epithelial-to-mesenchymal transition in human esophageal cancer

Background

We have previously reported significant change of epithelial to mesenchymal transition (EMT) phenotype of Eca-109 cells upon PD-L1 operation, and the cytoplasmic domain of PD-L1 played an essential role in promoting EMT of esophageal cancer cells. However, the underlying mechanism of how PD-L1 regulated EMT in esophageal cancer remained unclear.

Methods

The overexpression and knockdown expression models of PD-L1 and IFIT2 were established by using lenti-virus transfection and RNAi method. Western blotting, qRT-PCR, CCK8 assay, transwell assay and wound healing assay were chosen to investigate their impact on the cells. The expression levels of IFIT2 and EMT markers in esophageal cancer tissues were examined by immunohistochemical staining. The rescue experiments were further applied to investigate the role of STAT1/IFIT2 signal pathway in the PD-L1-mediated EMT. Luciferase reporter assays were performed to examine the IFIT2 promoter activities upon knockdown expression of PD-L1 to identify the putative targeted region of IFIT2 promoter.

Results

The STAT1/IFIT2 signal pathway was activated when PD-L1 was knockdown in human esophageal cancer cells. Decreased IFIT2 expression significantly increased the cellular abilities of viability, invasion and migration by using RNAi method in human esophageal cancer cells. Decreased IFIT2 expression in esophageal cancer tissues significantly correlated with EMT status, and could be used as an independent prognostic predictor for the patients. Rescue experiments in PD-L1 knockdown cells further confirmed that STAT1/IFIT2 pathway was involved in the PD-L1 mediated EMT of esophageal cancer cells. Moreover, the luciferase reporter assay also confirmed that in esophageal cancer cells, the promoter region of IFIT2 (-3K~-1K) remains more active in PD-L1 knockdown expression cells compared with controls.

Conclusion

Our present work reveals a novel mechanism of how PD-L1 regulates EMT of cancer cells, namely STAT1/IFIT2 signal pathway is required in PD-L1 mediated EMT in human esophageal cancer.

Melatonin Inhibits EMT and PD-L1 Expression through the ERK1/2/FOSL1 Pathway and Regulates Anti-Tumor Immunity in HNSCC

Melatonin is an endogenous hormone with various biological functions and possesses anti-tumor properties in multiple malignancies. Immune evasion is one of the most important hallmarks of head and neck squamous cell carcinoma (HNSCC) and is closely related to tumor progression. However, as an immune modulator under physiological conditions, the roles of melatonin in tumor immunity in HNSCC remains unclear. In this study, we found that the endogenous melatonin levels in HNSCC patients were lower than those in patients with benign tumors in head and neck. Importantly, lower melatonin levels were related to lymph node metastasis among HNSCC patients. Moreover, melatonin significantly suppressed programmed death-ligand 1 (PD-L1) expression and inhibited epithelial-mesenchymal transition (EMT) of HNSCC through the ERK1/2/FOSL1 pathway in vitro and vivo. In SCC7/C3H syngeneic mouse models, anti-programmed death-1 (PD-1) antibody combined with melatonin significantly inhibited tumor growth and modulated anti-tumor immunity by increasing CD8⁺ T cell infiltration and decreasing regulatory T cell (Treg) proportion in tumor microenvironment. Taken together, melatonin inhibited EMT and downregulated PD-L1 expression in HNSCC through the ERK1/2/FOSL1 pathway and exerted synergistic effects with anti-PD-1 antibody in vivo, which could provide promising strategies for HNSCC treatment.

Inhibition of DCLK1 kinase reverses epithelial-mesenchymal transition and restores T-cell activity in pancreatic ductal adenocarcinoma

Immunotherapy has recently become a promising cancer therapy with extensive applications of immune checkpoint inhibitors (ICIs). However, pancreatic ductal adenocarcinoma (PDAC) appears to be unresponsive to immunotherapy due to the immunosuppressive microenvironment. Recent studies showed that cancer stem cell marker DCLK1 promoted the initiation and development of PDAC. Nevertheless, the mechanism driving this process remains unclear. Here, by performing gain-of-function investigations in PDAC cell lines, we demonstrate that both DCLK1 long (DCLK1-iso1, DCLK1-AS) and short (DCLK1-iso4, DCLK1-BL) isoforms can efficiently activate EMT leading to tumor migration and invasion. Consistent with experiments in vitro, bioinformatic analysis demonstrates that DCLK1 may act as a driver of EMT activation in PDAC. Further analysis showed that EMT was associated with an immunosuppressive microenvironment, which includes more immunosuppressive cells and chemokines, and patients with a higher EMT score were less sensitive to immune checkpoint inhibitors according to the TIDE (Tumor Immune Dysfunction and Exclusion) algorithm. Multiplexed immunofluorescence results demonstrated the close correlation between DCLK1, EMT and immunosuppression in PDAC patients. The findings were further confirmed in vivo reflected by decreased CD4+, CD8+ T cells and increased M2 macrophages as well as E-cad loss in DCLK1-overexpressing subcutaneous tumors. Importantly, the highly-specific DCLK1 inhibitor (DCLK1-IN-1) was able to effectively block EMT process and restore T-cell activity. Altogether, our data demonstrate that DCLK1 is strongly associated with tumor immune escape in PDAC and inhibiting DCLK1 kinase activity may be a promising therapeutic modality.

Tracking the Molecular Fingerprint of Head and Neck Cancer for Recurrence Detection in Liquid Biopsies

The 5-year relative survival for patients with head and neck cancer, the seventh most common form of cancer worldwide, was reported as 67% in developed countries in the second decade of the new millennium. Although surgery, radiotherapy, chemotherapy, or combined treatment often elicits an initial satisfactory response, relapses are frequently observed within two years. Current surveillance methods, including clinical exams and imaging evaluations, have not unambiguously demonstrated a survival benefit, most probably due to a lack of sensitivity in detecting very early recurrence. Recently, liquid biopsy monitoring of the molecular fingerprint of head and neck squamous cell carcinoma has been proposed and investigated as a strategy for longitudinal patient care. These innovative methods offer rapid, safe, and highly informative genetic analysis that can identify small tumors not yet visible by advanced imaging techniques, thus potentially shortening the time to treatment and improving survival outcomes. In this review, we provide insights into the available evidence that the molecular tumor fingerprint can be used in the surveillance of head and neck squamous cell carcinoma. Challenges to overcome, prior to clinical implementation, are also discussed.

Prognostic Value of Programmed Death Ligand-1 Expression in Solid Tumors Irrespective of Immunotherapy Exposure: A Systematic Review and Meta-Analysis

BACKGROUND

The programmed cell death-1/programmed cell death ligand-1 (PD-L1) pathway, which plays a crucial role in cancer immune surveillance, is the target of several approved immunotherapeutic agents and is used as a predictive biomarker in some solid tumors. However, its use as a prognostic marker (i.e., regardless of therapy used) is not established clearly with available data demonstrating inconsistent prognostic impact of PD-L1 expression in solid tumors.

METHODS

We conducted a systematic literature search of electronic databases and identified publications exploring the effect of PD-L1 expression on overall survival and/or disease-free survival. Hazard ratios were pooled in a meta-analysis using generic inverse-variance and random-effects modeling. We used the Deeks method to explore subgroup differences based on disease site, stage of disease, and method of PD-L1 quantification.

RESULTS

One hundred and eighty-six studies met the inclusion criteria. Programmed cell death ligand-1 expression was associated with worse overall survival (hazard ratio 1.33, 95% confidence interval 1.26-1.39; p < 0.001). There was significant heterogeneity between disease sites (subgroup p = 0.002) with pancreatic, hepatocellular, and genitourinary cancers associated with the highest magnitude of adverse outcomes. Programmed cell death ligand-1 was also associated with worse overall disease-free survival (hazard ratio 1.19, 95% confidence interval 1.09-1.30; p < 0.001). Stage of disease did not significantly affect the results (subgroup p = 0.52), nor did the method of quantification via immunohistochemistry or messenger RNA (subgroup p = 0.70).

CONCLUSIONS

High expression of PD-L1 is associated with worse survival in solid tumors albeit with significant heterogeneity among tumor types. The effect is consistent in early-stage and metastatic disease and is not sensitive to method of PD-L1 quantification. These data can provide additional information for the counseling of patients with cancer about prognosis.

Checkpoint blockade-induced CD8+ T cell differentiation in head and neck cancer responders

Background

Immune checkpoint blockade (ICB) response in recurrent/metastatic head and neck squamous cell carcinoma (HNSCC) is limited to 15%–20% of patients and underpinnings of resistance remain undefined.

Methods

Starting with an anti-PD1 sensitive murine HNSCC cell line, we generated an isogenic anti-PD1 resistant model. Mass cytometry was used to delineate tumor microenvironments of both sensitive parental murine oral carcinoma (MOC1) and resistant MOC1esc1 tumors. To examine heterogeneity and clonal dynamics of tumor infiltrating lymphocytes (TILs), we applied paired single-cell RNA and TCR sequencing in three HNSCC models.

Results

Anti-PD1 resistant MOC1esc1 line displayed a conserved cell intrinsic immune evasion signature. Immunoprofiling showed distinct baseline tumor microenvironments of MOC1 and MOC1esc1, as well as the remodeling of immune compartments on ICB in MOC1esc1 tumors. Single cell sequencing analysis identified several CD8 +TIL subsets including Tcf7 +Pd1− (naïve/memory-like), Tcf7 +Pd1+ (progenitor), and Tcf7-Pd1+ (differentiated effector). Mapping TCR shared fractions identified that successful anti-PD1 or anti-CTLA4 therapy-induced higher post-treatment T cell lineage transitions.

Conclusions

These data highlight critical aspects of CD8 +TIL heterogeneity and differentiation and suggest facilitation of CD8 +TIL differentiation as a strategy to improve HNSCC ICB response.

Immunosuppressive Traits of the Hybrid Epithelial/Mesenchymal Phenotype

Recent preclinical and clinical data suggests enhanced metastatic fitness of hybrid epithelial/mesenchymal (E/M) phenotypes, but mechanistic details regarding their survival strategies during metastasis remain unclear. Here, we investigate immune-evasive strategies of hybrid E/M states. We construct and simulate the dynamics of a minimalistic regulatory network encompassing the known associations among regulators of EMT (epithelial-mesenchymal transition) and PD-L1, an established immune-suppressor. Our simulations for the network consisting of SLUG, ZEB1, miR-200, CDH1 and PD-L1, integrated with single-cell and bulk RNA-seq data analysis, elucidate that hybrid E/M cells can have high levels of PD-L1, similar to those seen in cells with a full EMT phenotype, thus obviating the need for cancer cells to undergo a full EMT to be immune-evasive. Specifically, in breast cancer, we show the co-existence of hybrid E/M phenotypes, enhanced resistance to anti-estrogen therapy and increased PD-L1 levels. Our results underscore how the emergent dynamics of interconnected regulatory networks can coordinate different axes of cellular fitness during metastasis.

NHS-IL12 and bintrafusp alfa combination therapy enhances antitumor activity in preclinical cancer models

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Combination therapy induced both adaptive and innate antitumor immunity.

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Combination therapy significantly enhanced antitumor activity.

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Combination therapy generated tumor antigen specific immune memory.

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Bintrafusp alfa mediated the reduction of lung metastases.

Combinatorial immunotherapy approaches are emerging as viable cancer therapeutic strategies for improving patient responses and outcomes. This study investigated whether two such immunotherapies, with complementary mechanisms of action, could enhance antitumor activity in murine tumor models. The immunocytokine NHS-IL12, and surrogate NHS-muIL12, are designed to deliver IL-12 and muIL-12, respectively, to the tumor microenvironment (TME) to activate NK cells and CD8⁺ T cells and increase their cytotoxic functions. Bintrafusp alfa (BA) is a bifunctional fusion protein composed of the extracellular domains of the TGF-β receptor II to function as a TGF-β “trap” fused to a human IgG1 antibody blocking PD-L1. With this dual-targeting strategy, BA enhances efficacy over that of monotherapies in preclinical studies. In this study, NHS-muIL12 and BA combination therapy enhanced antitumor activity, prolonged survival, and induced tumor-specific antitumor immunity. This combination therapy increased tumor-specific CD8⁺ T cells and induced immune profiles, consistent with the activation of both adaptive and innate immune systems. In addition, BA reduced lung metastasis in the 4T1 model. Collectively, these findings could support clinical trials designed to investigate NHS-IL12 and BA combination therapy for patients with advanced solid tumors

Correlation between High PD-L1 and EMT/Invasive Genes Expression and Reduced Recurrence-Free Survival in Blood-Circulating Tumor Cells from Patients with Non-Muscle-Invasive Bladder Cancer

BACKGROUND

PD-L1 represents a crucial immune checkpoint molecule in the tumor microenvironment, identified as a key target for cancer immunotherapy. A correlation between PD-L1 and EMT-related genes expression in various human cancers has been suggested.

METHODS

By ScreenCell filtration, digital droplet PCR and confocal microscopy analysis, we aimed to investigate the expression of PD-L1 and EMT/invasive genes (TWIST1, ZEB1, VIMENTIN, TIMP2) in circulating tumor cells (CTCs) collected from the blood of non-muscle-invasive bladder cancer (NMIBC) patients, assessing the prognostic value of these biomarkers in the disease. Welchs' test and Mann-Whitney U test, correlation index, Kaplan-Meier, Univariate and Multivariate Cox hazard proportional analysis were used.

RESULTS

Higher PD-L1, TIMP2 and VIM mRNA levels were found in pT1 compared to pTa NMIBC. As evaluated by Kaplan-Meier and Univariate and Multivariate Cox analysis, enhancement of PD-L1, TWIST1 and TIMP2 expression reduces the recurrent free survival in NMIBC patients.

CONCLUSIONS

High PD-L1, TWIST1 and TIMP2 mRNAs mark the recurrent-NMIBC patients and by reducing the RFS represent negative prognostic biomarkers in these patients.

Cytokine and epigenetic regulation of programmed death-ligand 1 in stem cell differentiation and cancer cell plasticity

Programmed death-ligand 1 (PD-L1), an immune checkpoint ligand, is recognized as a potential target for cancer immunotherapy as well as for the induction of transplantation tolerance. However, how the crosstalk between stem cell programming and cytokine signaling regulates PD-L1 expression during stem cell differentiation and cancer cell plasticity remains unclear. Herein, we reported that PD-L1 expression was regulated by SOX2 during embryonic stem cell (ESC) differentiation and lung cancer cell plasticity. PD-L1 was induced during ESC differentiation to fibroblasts and was downregulated during SOX2-mediated reprogramming of fibroblasts to induced pluripotent stem cells (iPSCs). Furthermore, SOX2 activation affected cancer cell plasticity and inhibited PD-L1 expression in lung cancer cells. We discovered that the H3K27ac signal at the PD-L1 locus was enhanced during ESC differentiation to fibroblasts as well as during cancer plasticity of SOX2-positive lung cancer cells to SOX2-negative counterparts. Romidepsin, an epigenetic modifier, induced PD-L1 expression in lung cancer cells, whereas TGF-β stimulation downregulated SOX2 but upregulated PD-L1 expression in lung cancer cells. Furthermore, in addition to PD-L1, the expressions of EGFR and its ligand HBEGF were downregulated by activation of endogenous SOX2 expression during lung cancer cell plasticity and iPSC reprogramming, and the activation of EGFR signaling by HBEGF upregulated PD-L1 expression in lung cancer cells. Together, our results reveal the crosstalk between SOX2 programming and cytokine stimulation influences PD-L1 expression, and these findings may provide insights into PD-L1-mediated therapeutics.

CMTM4 regulates epithelial-mesenchymal transition and PD-L1 expression in head and neck squamous cell carcinoma

The epithelial-mesenchymal transition (EMT) is a pivotal step involved in cancer recurrence and metastasis. In addition, the activation of the EMT program can induce a cancer stem cell (CSC)-like phenotype and programmed death-ligand 1 (PD-L1) expression in head and neck squamous cell carcinoma (HNSCC). The CMTM family has reported as an important regulator in this process. Here, we investigated the role of CMTM4 in HNSCC. We indicated that CMTM4 was overexpressed in human and mouse HNSCC samples and in HNSCC cell lines by immunohistochemistry and Western blot. A high expression level of CMTM4 was correlated with advanced lymph node metastasis and a negative prognosis. CMTM4-knockdown by small interfering RNA downregulated the EMT process and inhibited the migration and invasion abilities of tumor cells. Moreover, knockdown of CMTM4 decreased CSC-associated markers via the protein kinase B pathway. Notably, CMTM4-knockdown inhibited the expression of interferon-γ induced PD-L1 in HNSCC cells. A positive correlation was found between CMTM4 expression and CD8⁺ and PD-1⁺ cell density in the stroma. Our findings indicated that CMTM4 may play an important role in regulating EMT/CSC phenotypes and PD-L1 expression. This study may reinforce the interest in CMTM4 as a potential target for the prognosis and treatment of HNSCC.

Not Only Immune Escape-The Confusing Role of the TRP Metabolic Pathway in Carcinogenesis

BACKGROUND

The recently discovered phenomenon that cancer cells can avoid immune response has gained scientists' interest. One of the pathways involved in this process is tryptophan (TRP) metabolism through the kynurenine pathway (KP). Individual components involved in TRP conversion seem to contribute to cancerogenesis both through a direct impact on cancer cells and the modulation of immune cell functionality. Due to this fact, this pathway may serve as a target for immunotherapy and attempts are being made to create novel compounds effective in cancer treatment. However, the results obtained from clinical trials are not satisfactory, which raises questions about the exact role of KP elements in tumorigenesis. An increasing number of experiments reveal that TRP metabolites may either be tumor promoters and suppressors and this is why further research in this field is highly needed. The aim of this study is to present KP as a modulator of cancer development through multiple mechanisms and to point to its ambiguity, which may be a reason for failures in treatment based on the inhibition of tryptophan metabolism.

Polyphenols Modulating Effects of PD-L1/PD-1 Checkpoint and EMT-Mediated PD-L1 Overexpression in Breast Cancer

Investigating dietary polyphenolic compounds as antitumor agents are rising due to the growing evidence of the close association between immunity and cancer. Cancer cells elude immune surveillance for enhancing their progression and metastasis utilizing various mechanisms. These mechanisms include the upregulation of programmed death-ligand 1 (PD-L1) expression and Epithelial-to-Mesenchymal Transition (EMT) cell phenotype activation. In addition to its role in stimulating normal embryonic development, EMT has been identified as a critical driver in various aspects of cancer pathology, including carcinogenesis, metastasis, and drug resistance. Furthermore, EMT conversion to another phenotype, Mesenchymal-to-Epithelial Transition (MET), is crucial in developing cancer metastasis. A central mechanism in the upregulation of PD-L1 expression in various cancer types is EMT signaling activation. In breast cancer (BC) cells, the upregulated level of PD-L1 has become a critical target in cancer therapy. Various signal transduction pathways are involved in EMT-mediated PD-L1 checkpoint overexpression. Three main groups are considered potential targets in EMT development; the effectors (E-cadherin and Vimentin), the regulators (Zeb, Twist, and Snail), and the inducers that include members of the transforming growth factor-beta (TGF-β). Meanwhile, the correlation between consuming flavonoid-rich food and the lower risk of cancers has been demonstrated. In BC, polyphenols were found to downregulate PD-L1 expression. This review highlights the effects of polyphenols on the EMT process by inhibiting mesenchymal proteins and upregulating the epithelial phenotype. This multifunctional mechanism could hold promises in the prevention and treating breast cancer.

Cancer drug resistance induced by EMT: novel therapeutic strategies

Over the last decade, important clinical benefits have been achieved in cancer patients by using drug-targeting strategies. Nevertheless, drug resistance is still a major problem in most cancer therapies. Epithelial-mesenchymal plasticity (EMP) and tumour microenvironment have been described as limiting factors for effective treatment in many cancer types. Moreover, epithelial-to-mesenchymal transition (EMT) has also been associated with therapy resistance in many different preclinical models, although limited evidence has been obtained from clinical studies and clinical samples. In this review, we particularly deepen into the mechanisms of which intermediate epithelial/mesenchymal (E/M) states and its interconnection to microenvironment influence therapy resistance. We also describe how the use of bioinformatics and pharmacogenomics will help to figure out the biological impact of the EMT on drug resistance and to develop novel pharmacological approaches in the future.

APE1 facilitates PD-L1-mediated progression of laryngeal and hypopharyngeal squamous cell carcinoma

Laryngeal squamous cell carcinoma (LSCC) and hypopharyngeal squamous cell carcinoma (HSCC) seriously affect the life quality of patients. Nowadays, immunotherapy is widely used in the treatment of cancer. Tumor-infiltrating lymphocytes (TILs), programmed cell death 1 (PD-1) and its ligand programmed cell death ligand 1 (PD-L1) play key roles in the immunotherapy of cancer. Moreover, study has reported that the upregulation of PD-L1 and apurinic/apyrimidinic endonuclase 1 (APE1) are associated with tumorigenesis and poor prognosis of gastric cancer. In the present study, the number of CD3+ T lymphocytes and the expressions of PD-1 and PD-L1 in LSCC and HSCC were detected in clinical samples. In addition, the expressions of PD-L1 and APE1 and their correlation were explored. The results showed that PD-1+ T lymphocytes were wildly infiltrated and PD-L1 was overexpressed in LSCC and HSCC tissues. PD-1 had a positive correlation with cancer progression, and glottic and subglottic LSCC tissues might have a more active immune microenvironment. Moreover, the results showed that upregulated co-expression of PD-L1 and APE1 was a biomarker of LSCC, and APE1 could regulate the expression of PD-L1 through NF-κB signaling pathway. In conclusion, the combine detection of the expressions of PD-1, PD-L1 and APE1 will provide predictive value for the treatment of LSCC and HSCC via immune checkpoint inhibitors, which will help us to identify the patient population more likely to benefit from the immune checkpoint inhibitors based on the tumor immune microenvironment.

PD-L1 tumor-intrinsic signaling and its therapeutic implication in triple-negative breast cancer

Although the immune checkpoint role of programmed death ligand 1 (PD-L1) has been established and targeted in cancer immunotherapy, the tumor-intrinsic role of PD-L1 is less appreciated in tumor biology and therapeutics development, partly because of the incomplete mechanistic understanding. Here we demonstrate a potentially novel mechanism by which PD-L1 promotes the epithelial-mesenchymal transition (EMT) in triple-negative breast cancer (TNBC) cells by suppressing the destruction of the EMT transcription factor Snail. PD-L1 directly binds to and inhibits the tyrosine phosphatase PTP1B, thus preserving p38-MAPK activity that phosphorylates and inhibits glycogen synthase kinase 3β (GSK3β). Via this mechanism, PD-L1 prevents the GSK3β-mediated phosphorylation, ubiquitination, and degradation of Snail and consequently promotes the EMT and metastatic potential of TNBC. Significantly, PD-L1 antibodies that confine the tumor-intrinsic PD-L1/Snail pathway restricted TNBC progression in immunodeficient mice. More importantly, targeting both tumor-intrinsic and tumor-extrinsic functions of PD-L1 showed strong synergistic tumor suppression effect in an immunocompetent TNBC mouse model. Our findings support that PD-L1 intrinsically facilitates TNBC progression by promoting the EMT, and this potentially novel PD-L1 signaling pathway could be targeted for better clinical management of PD-L1–overexpressing TNBCs.

Circular RNA hsa_circ_0003288 induces EMT and invasion by regulating hsa_circ_0003288/miR-145/PD-L1 axis in hepatocellular carcinoma

Background

Epithelial-mesenchymal transition (EMT) has been associated with wound healing, tumorigenesis, and metastasis. Circular RNAs (circRNAs) are functional non-coding RNAs involved in multiple human cancers. However, whether and how circRNAs contribute to the EMT in hepatocellular carcinomas (HCC) remains to be deciphered. In this study, we investigated the regulation and function of hsa_circ_0003288 on programmed death-1 ligand 1 (PD-L1) during EMT and HCC invasiveness.

Methods

Hsa_circ_0003288 expression was measured by real-time quantitative reverse transcriptase PCR (qRT-PCR). Luciferase reporter assays, RNA pull-down assay and fluorescence in situ hybridization (FISH) were used to determine the correlation between hsa_circ_0003288 and miR-145 and between miR-145 and PD-L1. Furthermore, ectopic overexpression and siRNA-mediated downregulation of hsa_circ_0003288, transwell assays, and in vivo studies were used to determine the function of hsa_circ_0003288 on the EMT and invasiveness of L02 and HCC cells.

Results

miR-145 directly targeted the PD-L1 3′-untranslated region (UTR) region, and hsa_circ_0003288 acted as a miR-145 sponge to regulate PD-L1 expression. Overexpression of hsa_circ_0003288 increased PD-L1 levels and promoted EMT, migration, and invasiveness of L02 cells. These observations were reversed after knockdown of hsa_circ_0003288 in HepG2 and Huh7 cells. Overexpression of PD-L1 rescued EMT, migration, and invasiveness of HepG2 and Huh7 cells after knockdown of hsa_circ_0003288. Furthermore, hsa_circ_0003288 knockdown reduced EMT in in vivo studies. Hsa_circ_0003288/PD-L1 axis was found to mediate the metastatic phenotypes via the PI3K/Akt pathway in HCC. Additionally, expression levels of hsa_circ_0003288 were increased and positively correlated with PD-L1 expression in HCC tissues.

Conclusion

Our findings demonstrated that hsa_circ_0003288 promoted EMT and invasion of HCC via the hsa_circ_0003288/miR-145/PD-L1 axis through the PI3K/Akt pathway. Targeting hsa_circ_0003288 may be a therapeutic strategy for the treatment of HCC.

Depleting Tumor Cells Expressing Immune Checkpoint Ligands-A New Approach to Combat Cancer

Antibodies against inhibitory immune checkpoint molecules (ICPMs), referred to as immune checkpoint inhibitors (ICIs), have gained a prominent place in cancer therapy. Several ICIs in clinical use have been engineered to be devoid of effector functions because of the fear that ICIs with preserved effector functions could deplete immune cells, thereby curtailing antitumor immune responses. ICPM ligands (ICPMLs), however, are often overexpressed on a sizeable fraction of tumor cells of many tumor types and these tumor cells display an aggressive phenotype with changes typical of tumor cells undergoing an epithelial-mesenchymal transition. Moreover, immune cells expressing ICPMLs are often endowed with immunosuppressive or immune-deviated functionalities. Taken together, these observations suggest that compounds with the potential of depleting cells expressing ICPMLs may become useful tools for tumor therapy. In this article, we summarize the current state of the art of these compounds, including avelumab, which is the only ICI targeting an ICPML with preserved effector functions that has gained approval so far. We also discuss approaches allowing to obtain compounds with enhanced tumor cell-depleting potential compared to native antibodies. Eventually, we propose treatment protocols that may be applied in order to optimize the therapeutic efficacy of compounds that deplete cells expressing ICPMLs.

Identification of a Novel Epithelial-Mesenchymal Transition Gene Signature Predicting Survival in Patients With HNSCC

Head and neck squamous cell cancer (HNSCC) is one of the most common types of cancer worldwide. There have been many reports suggesting that biomarkers explored via database mining plays a critical role in predicting HNSCC prognosis. However, a single biomarker for prognostic analysis is not adequate. Additionally, there is growing evidence indicating that gene signature could be a better choice for HNSCC prognosis. We performed a comprehensive analysis of mRNA expression profiles using clinical information of HNSCC patients from The Cancer Genome Atlas (TCGA). Gene Set Enrichment Analysis (GSEA) was performed, and we found that a set of genes involved in epithelial mesenchymal transition (EMT) contributed to HNSCC. Cox proportional regression model was used to identify a four-gene (WIPF1, PPIB, BASP1, PLOD2) signature that were significantly associated with overall survival (OS), and all the four genes were significantly upregulated in tumor tissues. We successfully classified the patients with HNSCC into high-risk and low-risk groups, where in high-risk indicated poorer patient prognosis, indicating that this gene signature might be a novel potential biomarker for the prognosis of HNSCC. The prognostic ability of the gene signature was further validated in an independent cohort from the Gene Expression Omnibus (GEO) database. In conclusion, we identified a four-EMT-based gene signature which provides the potentiality to serve as novel independent biomarkers for predicting survival in HNSCC patients, as well as a new possibility for individualized treatment of HNSCC.

High Expression of PD-L1 Is Associated with Better Survival in Pancreatic/Periampullary Cancers and Correlates with Epithelial to Mesenchymal Transition

Periampullary cancers (PACs) are characterized by tumor-infiltrating lymphocytes (TILs), severe fibrosis, and epithelial to mesenchymal transition (EMT). The immune checkpoint marker programmed death-1 (PD-1) and its ligands 1 and 2 have gained popularity in cancers with TILs. Evidence suggests a strong relationship between immune checkpoint markers and EMT in cancers. Here, we evaluated the expression and prognostic significance of immune checkpoint and EMT markers in PAC using an automated image analyzer. Formalin-fixed, paraffin-embedded surgically excised PAC tissues from laboratory archives (1998–2014) were evaluated by immunohistochemical staining for PD-1, PD-L1, and PD-L2 in a tissue microarray. In total, 115 PAC patients (70 males and 45 females) with an average age of 63 years were analyzed. Location, gross type, size, radial resection margin, N-M stage, lymphatic invasion, vascular invasion, perineural invasion, histologically well-differentiated severe inflammation, and high PD-L1 expression were significantly associated with recurrence. Higher PD-L1 expression, but not PD-1 and PD-L2, was significantly related to better overall survival (OS) and disease-free survival (DFS). PD-L1 and PD-L2 were significantly related to EMT markers. Aside from other clinicopathologic parameters, high PD-L1 expression was significantly related to better OS and DFS of PAC patients. Moreover, immune checkpoint markers were significantly associated with EMT markers. Therefore, PD-L1 expression can be a good prognostic marker to guide future immune target-based therapies in PAC patients.

PKD3 promotes metastasis and growth of oral squamous cell carcinoma through positive feedback regulation with PD-L1 and activation of ERK-STAT1/3-EMT signalling

Oral squamous cell carcinoma (OSCC) has a high incidence of metastasis. Tumour immunotherapy targeting PD-L1 or PD-1 has been revolutionary; however, only a few patients with OSCC respond to this treatment. Therefore, it is essential to gain insights into the molecular mechanisms underlying the growth and metastasis of OSCC. In this study, we analysed the expression levels of protein kinase D3 (PKD3) and PD-L1 and their correlation with the expression of mesenchymal and epithelial markers. We found that the expression of PKD3 and PD-L1 in OSCC cells and tissues was significantly increased, which correlated positively with that of mesenchymal markers but negatively with that of epithelial markers. Silencing PKD3 significantly inhibited the growth, metastasis and invasion of OSCC cells, while its overexpression promoted these processes. Our further analyses revealed that there was positive feedback regulation between PKD3 and PD-L1, which could drive EMT of OSCC cells via the ERK/STAT1/3 pathway, thereby promoting tumour growth and metastasis. Furthermore, silencing PKD3 significantly inhibited the expression of PD-L1, and lymph node metastasis of OSCC was investigated with a mouse footpad xenograft model. Thus, our findings provide a theoretical basis for targeting PKD3 as an alternative method to block EMT for regulating PD-L1 expression and inhibiting OSCC growth and metastasis.

Standard of Care and Promising New Agents for the Treatment of Mesenchymal Triple-Negative Breast Cancer

The pathologic definition of triple negative breast cancer (TNBC) relies on the absence of expression of estrogen, progesterone and HER2 receptors. However, this BC subgroup is distinguished by a wide biological, molecular and clinical heterogeneity. Among the intrinsic TNBC subtypes, the mesenchymal type is defined by the expression of genes involved in the epithelial to mesenchymal transition, stromal interaction and cell motility. Moreover, it shows a high expression of genes involved in proliferation and an immune-suppressive microenvironment. Several molecular alterations along different pathways activated during carcinogenesis and tumor progression have been outlined and could be involved in immune evasion mechanisms. Furthermore, reverting epithelial to mesenchymal transition process could lead to the overcoming of immune-resistance. This paper reviews the current knowledge regarding the mesenchymal TNBC subtype and its response to conventional therapeutic strategies, as well as to some promising molecular target agents and immunotherapy. The final goal is a tailored combination of cytotoxic drugs, target agents and immunotherapy in order to restore immunocompetence in mesenchymal breast cancer patients.

Immune Checkpoints Pathways in Head and Neck Squamous Cell Carcinoma

Simple Summary

During the last decades, scientific advances in immuno-oncology and a better understanding of tumors’ immune profile led to the development of novel immunotherapeutic strategies, especially immune checkpoint inhibitors. The blockade of PD-1 by monoclonal antibodies (mAbs) is the only immunotherapy based on immune checkpoint pathways approved for head and neck squamous cell carcinoma. As only a small fraction of patients perceives clinical benefit, understanding the molecular mechanisms and signaling pathways activated by the immune checkpoints and other tumor intrinsic features that modulate the immune infiltrate is crucial to better select patients for immunotherapy treatment and to develop novel therapeutic strategies. We here review the immune escape mechanisms of head and neck tumors, with a particular focus on the immune checkpoints, their role as therapeutic targets, and the predictive biomarkers of response to anti-PD-1/PD-L1 therapy. We also summarize the ongoing clinical trials testing several combinations of immune checkpoint inhibitors with other therapeutic approaches to improve patient outcomes.

Abstract

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of tumors usually diagnosed at an advanced stage and characterized by a poor prognosis. The main risk factors associated with its development include tobacco and alcohol consumption and Human Papillomavirus (HPV) infections. The immune system has a significant role in the oncogenesis and evolution of this cancer type. Notably, the immunosuppressive tumor microenvironment triggers immune escape through several mechanisms. The improved understanding of the antitumor immune response in solid tumors and the role of the immune checkpoint molecules and other immune regulators have led to the development of novel therapeutic strategies that revolutionized the clinical management of HNSCC. However, the limited overall response rate to immunotherapy urges identifying predictive biomarkers of response and resistance to treatment. Here, we review the role of the immune system and immune checkpoint pathways in HNSCC, the most relevant clinical findings linked to immunotherapeutic strategies and predictive biomarkers of response and future treatment perspectives.

Molecular homology between canine spontaneous oral squamous cell carcinomas and human head-and-neck squamous cell carcinomas reveals disease drivers and therapeutic vulnerabilities

Spontaneously occurring canine oral squamous cell carcinomas (COSCC) are viewed as a useful model for human head and neck squamous cell carcinomas (HNSCC). To date however, the molecular basis of COSCC remains poorly understood. To identify changes pertinent to cancer cells in COSCC, we specifically analyzed tumor cells and matched normal epithelium from clinical formalin-fixed paraffin-embedded specimens using laser-capture-microdissection coupled with RNA-sequencing (RNAseq). Our results identify strong contributions of epithelial-to-mesenchymal transition (EMT), classical tumor-promoting (such as E2F, KRAS, MYC, mTORC1, and TGFB1 signaling) and immune-related pathways in the tumor epithelium of COSCC. Comparative analyses of COSCC with 43 paired tumor/normal HNSCC from The Cancer Genome Atlas revealed a high homology in transcriptional reprogramming, and identified processes associated with cell cycle progression, immune processes, and loss of cellular differentiation as likely central drivers of the disease. Similar to HNSCC, our analyses suggested a ZEB2-driven partial EMT in COSCC and identified selective upregulation of KRT14 and KRT17 in COSCC. Beyond homology in transcriptional signatures, we also found therapeutic vulnerabilities strongly conserved between the species: these included increased expression of PD-L1 and CTLA-4, coinciding with EMT and revealing the potential for immune checkpoint therapies, and overexpression of CDK4/6 that sensitized COSCC to treatment with palbociclib. In summary, our data significantly extend the current knowledge of molecular aberrations in COSCC and underline the potential of spontaneous COSCC as a model for HNSCC to interrogate therapeutic vulnerabilities and support translation of novel therapies from bench to bedside.

Mesenchymal Characteristics and Predictive Biomarkers on Circulating Tumor Cells for Therapeutic Strategy

Metastasis-related events are the primary cause of cancer-related deaths, and circulating tumor cells (CTCs) have a pivotal role in metastatic relapse. CTCs include a variety of subtypes with different functional characteristics. Interestingly, the epithelial-mesenchymal transition (EMT) markers expressed in CTCs are strongly associated with poor clinical outcome and related to the acquisition of circulating tumor stem cell (CTSC) features. Recent studies have revealed the existence of CTC clusters, also called circulating tumor microemboli (CTM), which have a high metastatic potential. In this review, we present current opinions regarding the clinical significance of CTCs and CTM with a mesenchymal phenotype as clinical surrogate markers, and we summarize the therapeutic strategy according to phenotype characterization of CTCs in various types of cancers for future precision medicine.

Inhibition to Epithelial-Mesenchymal Transition and Metastatic Potential In Colorectal Cancer Cell By Combination of Traditional Chinese Medicine Formulation Jiedu Sangen Decoction and PD-L1 Inhibitor

BACKGROUND

Jiedu Sangen Decoction (JSD), a traditional Chinese medicine formula, has been widely applied in the treatment of gastrointestinal cancer, especially in colorectal cancer. Our study mainly aimed to assess the combined efficacy of Jiedu Sangen aqueous extract (JSAE) and a PD-L1 inhibitor (PI) in colon cancer cells migration and invasion, along with epithelial-mesenchymal transition, and then provide deep insights into the potential mechanism.

METHODS

We explored the inhibitory effects on invasion and metastasis and the reverse effect on EMT process in CT-26 colon cancer cell via Transwell migration assay, Matrigel invasion assay and confocal laser scanning microscopy. Furthermore, regulation in expression of EMT-related proteins and molecular biomarkers and underlying signal pathway proteins were detected through Western blotting and IHC.

RESULTS

The combination of JSD and PD-L1 inhibitor could inhibit migration, invasive ability and EMT of CT-26 cells in a concentration-dependent manner. Meanwhile, JSD combined with PD-L1 inhibitor could also remarkably reverse EMT and metastasis in vivo. In addition, the protein expression of N-cadherin, Slug, Snail, Vimentin was down-regulated along with E-cadherin s up-regulation with the combination of JSD and PD-L1 inhibitor, while that of PI3K/AKT was notably down-regulated.

CONCLUSIONS

These findings indicated that JSAE and a PD-L1 inhibitor could drastically inhibit the migration and invasion of colorectal cancer by reversing EMT through the PI3K/AKT signaling pathway.

PD-L1 Influences Cell Spreading, Migration and Invasion in Head and Neck Cancer Cells

The programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) axis blockade has been implemented in advanced-stage tumor therapy for various entities, including head and neck squamous cell carcinoma (HNSCC). Despite a promising tumor response in a subgroup of HNSCC patients, the majority suffer from disease progression. PD-L1 is known to influence several intrinsic mechanisms in cancer cells, such as proliferation, apoptosis, migration and invasion. Here, we modulated PD-L1 expression in three HNSCC cell lines with differential intrinsic PD-L1 expression. In addition to an alteration in the epithelial-to-mesenchymal transition (EMT) marker expression, we observed PD-L1-dependent cell spreading, migration and invasion in a spheroid spreading assay on four different coatings (poly-L-lysine, collagen type I, fibronectin and Matrigel^®) and a chemotactic transwell migration/invasion assay. Furthermore, the overexpression of PD-L1 led to increased gene expression and small interfering ribonucleic acid (siRNA) knockdown and decreased gene expression of Rho-GTPases and related proteins in a RT² Profiler™ PCR Array. Rac1 and Rho-GTPase pulldown assays revealed a change in the activation state concordantly with PD-L1 expression. In summary, our results suggest a major role for PD-L1 in favoring cell motility, including cell spreading, migration and invasion. This is presumably caused by altered N-cadherin expression and changes in the activation states of small Rho-GTPases Rho and Rac1.

Emerging role of tumor cell plasticity in modifying therapeutic response

Resistance to cancer therapy is a major barrier to cancer management. Conventional views have proposed that acquisition of resistance may result from genetic mutations. However, accumulating evidence implicates a key role of non-mutational resistance mechanisms underlying drug tolerance, the latter of which is the focus that will be discussed here. Such non-mutational processes are largely driven by tumor cell plasticity, which renders tumor cells insusceptible to the drug-targeted pathway, thereby facilitating the tumor cell survival and growth. The concept of tumor cell plasticity highlights the significance of re-activation of developmental programs that are closely correlated with epithelial-mesenchymal transition, acquisition properties of cancer stem cells, and trans-differentiation potential during drug exposure. From observations in various cancers, this concept provides an opportunity for investigating the nature of anticancer drug resistance. Over the years, our understanding of the emerging role of phenotype switching in modifying therapeutic response has considerably increased. This expanded knowledge of tumor cell plasticity contributes to developing novel therapeutic strategies or combination therapy regimens using available anticancer drugs, which are likely to improve patient outcomes in clinical practice.

Epithelial-to-mesenchymal transition and its association with PD-L1 and CD8 in thyroid cancer

Programmed cell death-ligand 1 (PD-L1) has recently been shown to play a role in the regulation of epithelial-to-mesenchymal transition (EMT); however, the relationship between PD-L1 expression, EMT and the inflammatory tumour microenvironment has yet to be investigated in thyroid cancer. To address this issue, we examined the expression of CD8, PD-L1 and the EMT markers E-cadherin and vimentin in a cohort of 74 papillary thyroid cancer (PTC) patients and investigated the association of these with clinicopathologic characteristics and disease-free survival (DFS). The relationship between PD-L1 and EMT was further examined in three thyroid cancer cell lines via Western blot and live cell imaging. In order to expand our in vitro findings, the normalised gene expression profiles of 516 thyroid cancer patients were retrieved and analysed from The Cancer Genome Atlas (TCGA). PD-L1 positivity was significantly higher in PTC patients exhibiting a mesenchymal phenotype (P = 0.012). Kaplan-Meier analysis revealed that PD-L1 (P = 0.045), CD8 (P = 0.038) and EMT status (P = 0.038) were all significant predictors for DFS. Sub-analysis confirmed that the poorest DFS was evident in PD-L1 positive patients with EMT features and negative CD8 expression (P < 0.0001). IFN-γ treatment induced upregulation of PD-L1 and significantly promoted an EMT phenotype in two thyroid cancer cell lines. Our findings suggest that PD-L1 signalling may play a role in stimulating EMT in thyroid cancer. EMT, CD8 and PD-L1 expression may serve as valuable predictive biomarkers in patients with PTC.

Spatial and Temporal Changes in PD-L1 Expression in Cancer: The Role of Genetic Drivers, Tumor Microenvironment and Resistance to Therapy

Immunotherapies blocking immune inhibitory receptors programmed cell death-1 (PD-1) and cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) on T-cells have dramatically improved patient outcomes in a range of advanced cancers. However, the lack of response, and the development of resistance remain major obstacles to long-term improvements in patient outcomes. There is significant interest in the clinical use of biomarkers to improve patient selection, and the expression of PD-1 ligand 1 (PD-L1) is often reported as a potential biomarker of response. However, accumulating evidence suggests that the predictive value of PD-L1 expression in tumor biopsies is relatively low due, in part, to its complex biology. In this review, we discuss the biological consequences of PD-L1 expression by various cell types within the tumor microenvironment, and the complex mechanisms that regulate PD-L1 expression at the genomic, transcriptomic and proteomic levels.

Buparlisib modulates PD-L1 expression in head and neck squamous cell carcinoma cell lines

High expression of the immune checkpoint receptor PD-L1 is associated with worse patient outcome in a variety of human cancers, including head and neck squamous cell carcinoma (HNSCC). Binding of PD-L1 with its partner PD-1 generates an inhibitory signal that dampens the immune system. Immunotherapy, that is blocking the PD-1/PD-L1 checkpoint, has proven to be an effective tool in cancer therapy. However, not all patients are able to benefit from this immune checkpoint inhibition. Therefore, evidence is growing of intrinsic PD-L1 signaling in cancer cells. For example, intrinsic PD-L1 expression was associated with PI3K/Akt/mTOR signaling, which is part of diverse oncogenic processes including cell proliferation, growth and survival. In this study we demonstrate the effects of PI3K/Akt/mTOR pathway inhibition by buparlisib on PD-L1 expression in HNSCC cell lines. After buparlisib treatment for 72 h, PD-L1 was downregulated in total cell lysates of HNSCC cells. Moreover, flow cytometry revealed a downregulation of PD-L1 membrane expression. Interestingly, the buparlisib mediated effects on PD-L1 expression were reduced by additional irradiation. In PD-L1 overexpressing cells, the buparlisib induced inhibition of proliferation was neutralized. In summary, our findings imply that blocking the PI3K/Akt/mTOR pathway could be a good additional therapy for patients who show poor response to immune checkpoint therapy.

LncRNA KCNQ1OT1 sponges miR-15a to promote immune evasion and malignant progression of prostate cancer via up-regulating PD-L1

Background

We focused on the KCNQ1OT1/miR-15a/PD-L1 axis and explored its significance in regulating immune evasion and malignant behaviors of prostate cancer (PC) cells.

Methods

The expression levels of KCNQ1OT1, miR-15a, PD-L1, and CD8 in cells or tissues were examined by RT-qPCR, western blot or immunohistochemistry (IHC) assays. The direct regulations between KCNQ1OT1, miR-15a and PD-L1 were validated by luciferase reporter assay. PC cells were co-cultured with CD8⁺ T cells to study the immune evasion. Proliferation, apoptosis, migration and invasion abilities were detected by MTT, flow cytometry, wound healing and Transwell assays, respectively. The cytotoxicity of CD8⁺ T cells was determined by LDH cytotoxicity Kit. Epithelial–mesenchymal transition (EMT) and Ras/ERK signaling markers were evaluated by western blot.

Results

KCNQ1OT1, PD-L1 and CD8 were increased, while miR-15a was decreased in PC tissues. MiR-15a directly bound to the 3′-UTR of PD-L1 and inhibited the expression of PD-L1. Overexpressing miR-15a in PC cells was sufficient to promote cytotoxicity and proliferation, while inhibit apoptosis of CD8⁺ T cells, and also suppressed viability, migration, invasion and EMT while promoted apoptosis of PC cells. The above anti-tumor effects of miR-15a were reversed by overexpressing PD-L1. KCNQ1OT1 sponged miR-15a and released its inhibition on PD-L1. Functionally, KCNQ1OT1 in PC cells was essential for suppressing the cytotoxicity of CD8⁺ T cells and maintaining multiple malignant phenotypes of PC cells. The Ras/ERK signaling was suppressed after overexpressing miR-15a or knocking down KCNQ1OT1.

Conclusions

LncRNA KCNQ1OT1 sponges miR-15a to promote immune evasion and malignant progression of PC via up-regulating PD-L1.