OBJECTIVES:Mandibular bone invasion (MBI) in oral squamous cell carcinoma (OSCC) reflects advanced disease and poor prognosis. The role of the tumor immune microenvironment (TME) in MBI remains incompletely defined. We investigated the prognostic relevance of CCL5 and its association with bone invasion. MATERIALS AND METHODS:CCL5 mRNA expression was analyzed in the TCGA HNSCC cohort (n = 327) across T stages and correlated with overall survival (OS). Single-cell RNA sequencing data were used to identify the cellular sources of CCL5. Protein expression of CCL5 and FoxP3 was assessed by immunohistochemistry in a retrospective cohort of 206 OSCC patients using tissue microarrays, distinguishing tumor and TME compartments. Systemic inflammatory markers (neutrophil-to-lymphocyte ratio [NLR], C-reactive protein-to-albumin ratio [CAR]) were also evaluated. RESULTS:CCL5 mRNA expression decreased with increasing T stage and was lowest in T4a tumors with bone invasion (p = 0.038). High CCL5 levels were associated with improved OS (p = 0.026). Single-cell analysis identified CD8⁺ T cells, regulatory T cells, and natural killer cells as principal sources of CCL5. In the clinical cohort, low CCL5 and FoxP3 expression in the TME correlated with MBI (p = 0.008 and p < 0.001). Multivariable analysis confirmed high CCL5 expression in the TME as an independent predictor of favorable OS (HR = 0.294, p = 0.015), whereas high NLR predicted poor survival (HR = 2.664, p = 0.044). CONCLUSIONS:A CCL5- and FoxP3-deficient TME characterizes bone-invasive OSCC and independently predicts poor survival, supporting their value as biomarkers for risk stratification.

BACKGROUND:Predictive biomarkers for response to PD-1 blockade in recurrent or metastatic HNSCC remain limited. We investigated whether coordinated expression of multiple inhibitory immune checkpoints defines a clinically relevant biomarker phenotype. METHODS:Clinical and immunohistochemical data from 78 patients with recurrent or metastatic HNSCC treated with nivolumab or pembrolizumab were retrospectively analyzed. Expression of PD-L1, LAG-3, TIM-3, and IDO1 on tumor-infiltrating immune cells was assessed. A composite immune checkpoint phenotype was defined by concurrent immune-cell expression of these markers. Associations with treatment response and survival were analyzed. RESULTS:The composite immune checkpoint phenotype was observed in 10.1% of tumors and was strongly associated with objective response (p < 0.001), disease control (p = 0.006), and improved overall, disease-specific, and progression-free survival (all p ≤ 0.030). In multivariable analysis, this phenotype independently predicted overall (p = 0.031) and disease-specific survival (p = 0.011). CONCLUSION:Coordinated expression of multiple inhibitory immune checkpoints identifies an inflamed tumor microenvironment associated with improved outcomes following PD-1 blockade in HNSCC.

Background: Factor H (FH) and FH-Related (FHR) proteins are crucial complement regulators. Their roles may extend beyond extracellular functions, potentially influencing cellular processes in inflammatory diseases like Osteoarthritis (OA) and malignancies such as Head and Neck Cancer (HNC). However, comparative expression profiles across different disease contexts and their intracellular presence require detailed investigation. Methods: We quantified FH and FHRs (−2, −3, −4, −5) levels via ELISA in synovial fluid (SF) from OA patients (n = 175), non-OA controls (n = 15), and in serum from HNC patients (n = 20) pre- and post-tumor removal versus controls. RNA sequencing and mendelian randomization (MR) analyses compared gene expression of CFH and CFHRs in OA vs non-OA tissues. To investigate subcellular protein distribution in HNC tumors, FH, FHR-1, FHR-2, FHR-3, and FHR-5 was assessed in cellular fractions (total lysate, membrane, cytoplasm, cytoskeleton, nucleus, chromatin), followed by protein identification and abundance measurement using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results: Distinct protein profiles emerged significant elevated FHR-4 levels in OA-SF in male and female patients, while FHR-5 (males) and FH (females) also showed significant increased levels. Notably, FHR-2 and FHR-3 levels were unchanged in OA-SF compared to non-OA-SF. Conversely, sera from HNC patients exhibited significantly elevated FHR-2, FHR-3, FHR-4, and FHR-5 pre-operatively compared to healthy controls, which remained elevated post-surgery. Mass spectrometry analysis of subcellular fractions revealed widespread distribution. Remarkably, FH, FHR-1, FHR-2 and FHR-5 were found in the nucleus, indicating possible nuclear functions. MR analysis indicated that genetically predicted higher expression of CFH was associated with an increased risk of knee-OA. Conclusion: FH-family proteins display context-dependent dysregulation: specific elevations (notably FHR-4) typify the local OA joint environment, contrasting with broad systemic FHR increases in HNC. The confirmed intracellular, particularly nuclear, localization points towards non-canonical functions of FHRs. Together, these findings reveal disease-specific molecular signatures and potential genetic contributions involving FH/FHR pathways in OA and HNC pathogenesis, highlighting avenues for biomarker development and therapeutic targeting.

Background:Immune checkpoint inhibitors (ICIs) have become an integral part of cancer therapy, but only a minority of patients experience durable responsiveness. Response rates vary greatly and are often unpredictable, highlighting the urgent need for predictive biomarkers to guide treatment decisions. Methods:We investigated immune- and tumor-specific expression and secretion profiles in peripheral blood and tumor samples derived from patients with head and neck squamous cell carcinoma (HNSCC). We combined flow cytometry, LEGENDplex™ immune profiling, and preoperative/postoperative serum cytokine analyses to determine checkpoint molecules (e.g., PD-1, TIM-3, LAG-3), immune cell profiles, as well as key markers on tumor cells (CD44, PD-L1, MHC class I/II). In addition, a 3D co-culture model using tumor slices and autologous mononuclear cells from selected HNSCC patients were analyzed upon atezolizumab and pembrolizumab treatment. Results:Co-expression of PD-1 and TIM-3 on a subset of CD8+ tumor-infiltrating T cells was frequently observed, alongside a pronounced infiltration of myeloid cells in the tumor microenvironment. In the peripheral blood, we detected elevated levels of soluble CD27 in patients compared to controls and distinct preoperative cytokine profiles (e.g., reduced IFN-γ, CCL3, CCL20; elevated IL-15/IL-16). Postoperatively, most cytokines showed lower levels compared to healthy controls but significantly higher CCL2 levels. Furthermore, tumor-immune co-cultures from selected patients showed a stronger apoptotic response and phenotypic differences (e.g., increased PD-1 and CD137 expression) upon atezolizumab treatment. Individual changes in soluble factor release (e.g., Gal-9, sPD-L1, sCD25, and sTIM-3) was noticeable upon co-culture under immune checkpoint therapy. Conclusions:This study provides proof-of-principle data suggesting that a combined multiplexed marker profiling and a functional 3D co-culture assay may help to explore predictive ICI response for HNSCC patients in the future. However, extensive studies with larger cohorts are warranted to validate and refine this approach.

BACKGROUND:The objective of our study was to examine the role of Chemerin, Chemokine like receptor 1 (CMKLR1), receptor activator of nuclear factor kappa-Β ligand (RANKL), and Osteoprotegerin (OPG) in the development of bone-invasive oral squamous cell carcinoma. METHODS:In order to evaluate the presence of these markers at the interface between bone and tumor, immunohistochemical analyses were conducted using tissue microarrays obtained from 164 patients with oral squamous cell carcinoma growing in close contact with jaw bone. RESULTS:The findings indicate that Chemerin and Osteoprotegerin are notably reduced in tumors that have invaded the bone. Only 21 (32.8%) of pT4a tumors (defined as bone invasive) had a high Osteoprotegerin expression, whereas 36 (66.7%) of pT2 and pT3 tumors demonstrated high expression of Osteoprotegerin (p < 0.001). Similarly, we saw a downregulation of Chemerin in 50 (60.2%) bone invasive oral squamous cell carcinoma samples compared to 28 (35.0%) in non-bone invasive tumors (p = 0.002). In addition, our data indicated a connection between worst pattern of invasion score and less favorable overall and disease-specific survival (p = 0.007 and p = 0.024, respectively). CONCLUSIONS:The findings suggest that Chemerin and Osteoprotegerin have the potential to serve as indicators for bone invasion in oral squamous cell carcinoma, which could have significant implications for diagnosis and treatment approaches.

Abstract Head and neck squamous cell carcinoma (HNSCC) is a global cancer burden with a 5‐year overall survival rate of around 50%, stagnant for decades. A tumour‐induced immunosuppressive microenvironment contributes to HNSCC progression, with the adenosine (ADO) pathway and an upregulated expression of inhibitory immune checkpoint regulators playing a key role in this context. The correlation between high neutrophil‐to‐lymphocyte ratio (NLR) with advanced tumour staging suggests involvement of neutrophils (NØ) in cancer progression. Interestingly, we associated a high NLR with an increased intracellular PD‐L1 localization in primary HNSCC samples, potentially mediating more aggressive tumour characteristics and therefore synergistically favouring tumour progression. Still, further research is needed to harness this knowledge for effective treatments and overcome resistance. Since it is hypothesized that the tumour microenvironment (TME) may be influenced by small extracellular vesicles (sEVs) secreted by tumours (TEX), this study aims to investigate the impact of HNSCC‐derived TEX on NØ and blockade of ADO receptors as a potential strategy to reverse the pro‐tumour phenotype of NØ. UMSCC47‐TEX exhibited CD73 enzymatic activity involved in ADO signalling, as well as the immune checkpoint inhibitor PD‐L1. Data revealed that TEX induce chemotaxis of NØ and the sustained interaction promotes a shift into a pro‐tumour phenotype, dependent on ADO receptors (P1R), increasing CD170high subpopulation, CD73 and PD‐L1 expression, followed by an immunosuppressive secretome. Blocking A3R reduced CD73 and PD‐L1 expression. Co‐culture experiments with HNSCC cells demonstrated that TEX‐modulated NØ increase the CD73/PD‐L1 axis, through Cyclin D‐CDK4/6 signalling. To support these findings, the CAM model with primary tumour was treated with NØ supernatant. Moreover, these NØ promoted an increase in migration, invasion, and reduced cell death. Targeting P1R on NØ, particularly A3R, exhibited potential therapeutic strategy to counteract immunosuppression in HNSCC. Understanding the TEX‐mediated crosstalk between tumours and NØ offers insights into immunomodulation for improving cancer therapies.

The programmed cell death 1 ligand 1 (PD‐L1)/programmed cell death protein 1 (PD‐1) axis is primarily associated with immunosuppression in cytotoxic T lymphocytes (CTLs). However, mounting evidence is supporting the thesis that PD‐L1 not only functions as a ligand but mediates additional cellular functions in tumor cells. Moreover, it has been demonstrated that PD‐L1 is not exclusively localized at the cellular membrane. Subcellular fractionation revealed the presence of PD‐L1 in various cellular compartments of six well‐characterized head and neck cancer (HNC) cell lines, including the nucleus. Via Western blotting, we detected PD‐L1 in its well‐known glycosylated/deglycosylated state at 40–55 kDa. In addition, we detected previously unknown PD‐L1 variants with a molecular weight at approximately 70 and > 150 kDa exclusively in nuclear protein fractions. These in vitro findings were confirmed with primary tumor samples from head and neck squamous cell carcinoma (HNSCC) patients. Furthermore, we demonstrated that nuclear PD‐L1 variant expression is cell‐cycle‐dependent. Immunofluorescence staining of PD‐L1 in different cell cycle phases of synchronized HNC cells supported these observations. Mechanisms of nuclear PD‐L1 trafficking remain less understood; however, proximity ligation assays showed a cell‐cycle‐dependent interaction of the cytoskeletal protein vimentin with PD‐L1, whereas vimentin could serve as a potential shuttle for nuclear PD‐L1 transportation. Mass spectrometry after PD‐L1 co‐immunoprecipitation, followed by gene ontology analysis, indicated interaction of nuclear PD‐L1 with proteins involved in DNA remodeling and messenger RNA (mRNA) splicing. Our results in HNC cells suggest a highly complex regulation of PD‐L1 and multiple tumor cell‐intrinsic functions, independent of immune regulation. These observations bear significant implications for the therapeutic efficacy of immune checkpoint inhibition.

Bone marrow-derived mesenchymal stromal cells (BMSCs) respond to a variety of tumor cell-derived signals, such as inflammatory cytokines and growth factors. As a result, the inflammatory tumor microenvironment may lead to the recruitment of BMSCs. Whether BMSCs in the tumor environment are more likely to promote tumor growth or tumor suppression is still controversial. In our experiments, direct 3D co-culture of BMSCs with tumor cells from the head and neck region (HNSCC) results in strong expression and secretion of MMP-9. The observed MMP-9 secretion mainly originates from BMSCs, leading to increased invasiveness. In addition to our in vitro data, we show in vivo data based on the chorioallantoic membrane (CAM) model. Our results demonstrate that MMP-9 induces hemorrhage and increased perfusion in BMSC/HNSCC co-culture. While we had previously outlined that MMP-9 expression and secretion originate from BMSCs, our data showed a strong downregulation of MMP-9 promoter activity in HNSCC cells upon direct contact with BMSCs using the luciferase activity assay. Interestingly, the 2D and 3D models of direct co-culture suggest different drivers for the downregulation of MMP-9 promoter activity. Whereas the 3D model depicts a BMSC-dependent downregulation, the 2D model shows cell density-dependent downregulation. In summary, our data suggest that the direct interaction of HNSCC cells and BMSCs promotes tumor progression by significantly facilitating angiogenesis via MMP-9 expression. On the other hand, data from 3D and 2D co-culture models indicate opposing regulation of the MMP-9 promoter in tumor cells once stromal cells are involved.

In orthopedics, musculoskeletal disorders, i.e., non-union of bone fractures or osteoporosis, can have common histories and symptoms related to pathological hypoxic conditions induced by aging, trauma or metabolic disorders. Here, we observed that hypoxic conditions (2% O2) suppressed the osteogenic differentiation of human bone marrow-derived mesenchymal cells (hBMSC) in vitro and simultaneously increased reactive oxygen species (ROS) production. We assumed that cellular origin and cargo of extracellular vesicles (EVs) affect the osteogenic differentiation capacity of hBMSCs cultured under different oxygen pressures. Proteomic analysis revealed that EVs isolated from osteogenic differentiated hBMSC cultured under hypoxia (hypo-osteo EVs) or under normoxia (norm-osteo EVs) contained distinct protein profiles. Extracellular matrix (ECM) components, antioxidants and pro-osteogenic proteins were decreased in hypo-osteo EVs. The proteomic analysis in our previous study revealed that under normoxic culture conditions, pro-osteogenic proteins and ECM components have higher concentrations in norm-osteo EVs than in EVs derived from naïve hBMSCs (norm-naïve EVs). When selected for further analysis, five anti-hypoxic proteins were significantly upregulated (response to hypoxia) in norm-osteo EVs. Three of them are characterized as antioxidant proteins. We performed qRT-PCR to verify the corresponding gene expression levels in the norm-osteo EVs’ and norm-naïve EVs’ parent cells cultured under normoxia. Moreover, we observed that norm-osteo EVs rescued the osteogenic ability of naïve hBMSCs cultured under hypoxia and reduced hypoxia-induced elevation of ROS production in osteogenic differentiated hBMSCs, presumably by inducing expression of anti-hypoxic/ antioxidant and pro-osteogenic genes.

In recent research, the tumor microenvironment has been shown to attract mesenchymal stromal cells (MSCs), which is of particular interest due to its implications for cancer progression. The study focused on understanding the interaction between bone marrow-derived MSCs (BMSCs) and head and neck cancer (HNC) cells. This interaction was found to activate specific markers, notably the osteogenic marker alkaline phosphatase and the oncogene Runx2. These activations corresponded with the release of collagenase enzymes, MMP9 and MMP2. To gain insights into bone resorption related to this interaction, bovine bone slices were used, supporting the growth of “heterogeneous spheroids” that contained both BMSCs and HNC cells. Through scanning electron microscopy and energy-dispersive X-ray (EDX) analysis, it was observed that these mixed spheroids were linked to a notable increase in bone degradation and collagen fiber exposure, more so than spheroids of just BMSCs or HNC cells. Furthermore, the EDX results highlighted increased nitrogen content on bone surfaces with these mixed clusters. Overall, the findings underscore the significant role of BMSCs in tumor growth, emphasizing the need for further exploration in potential cancer treatment strategies.

Invasion of the mandibular bone is frequent in oral squamous cell carcinoma (OSCC), which often results in extensive ablative and reconstructive procedures for the patient. The purpose of this single-center, retrospective study was to identify and evaluate potential biomarkers and risk factors for bone invasion in OSCC. Initially, in silico gene expression analysis was performed for different HNSCC tumor T-stages to find factors associated with invasive (T4a) tumor growth. Afterwards, the protein expression of bone-metabolizing MMP-27, TNFRSF11B (Osteoprotegerin, OPG), and TNFSF11 (RANKL) was investigated via Tissue Microarrays (TMAs) for their impact on mandibular bone invasion. TMAs were assembled from the bone–tumor interface of primary OSCCs of the floor of the mouth and gingiva from 119 patients. Sixty-four carcinomas with patho-histological jaw invasion (pT4a) were compared to 55 carcinomas growing along the mandible without invasion (pT2, pT3). Tissue samples were additionally evaluated for patterns of invasion using the WPOI grading system. Statistical analysis of in silico data revealed decreased MMP-27 mRNA expression to be strongly associated with the pT4a-stage in OSCC, indicating invasive tumor growth with infiltration of adjacent anatomical structures. Our own clinico-pathological data on OSCCs presented a significant decrease of MMP-27 in tumors invading the nearby mandible (pT4a), compared to pT2 and pT3 tumors without bone invasion. Loss of MMP27 evolved as the strongest predictor of mandibular bone invasion in binary logistic regression analysis. To our knowledge, this is the first study investigating the role of MMP-27 expression in OSCC and demonstrating the importance of the loss of MMP-27 in mandibular bone invasion.

Recently, considerable progress has been achieved in cancer immunotherapy. Targeted immune checkpoint therapies have been established for several forms of cancers, which resulted in a tremendous positive impact on patient survival, even in more advanced tumor stages. With a better understanding of cellular responses to immune checkpoint therapies, it will soon be feasible to find targeted compounds which will make personalized medicine practicable. This is a great opportunity, but it also sets tremendous challenges on both the scientific and clinical aspects. Head and neck tumors evade immune surveillance through various mechanisms. They contain fewer lymphocytes (natural killer cells) than normal tissue with an accumulation of immunosuppressive regulatory T cells. Standard therapies for HNSCC, such as surgery, radiation, and chemotherapy, are becoming more advantageous by targeting immune checkpoints and employing combination therapies. The purpose of this review is to provide an overview of the expanded therapeutic options, particularly the combination of immune checkpoint inhibition with various conventional and novel therapeutics for head and neck tumor patients.

AbstractTransforming growth factor β (TGFβ) is a major component of tumor‐derived small extracellular vesicles (TEX) in cancer patients. Mechanisms utilized by TGFβ+ TEX to promote tumor growth and pro‐tumor activities in the tumor microenvironment (TME) are largely unknown. TEX produced by head and neck squamous cell carcinoma (HNSCC) cell lines carried TGFβ and angiogenesis‐promoting proteins. TGFβ+ TEX stimulated macrophage chemotaxis without a notable M1/M2 phenotype shift and reprogrammed primary human macrophages to a pro‐angiogenic phenotype characterized by the upregulation of pro‐angiogenic factors and functions. In a murine basement membrane extract plug model, TGFβ+ TEX promoted macrophage infiltration and vascularization (p < 0.001), which was blocked by using the TGFβ ligand trap mRER (p < 0.001). TGFβ+ TEX injected into mice undergoing the 4‐nitroquinoline‐1‐oxide (4‐NQO)‐driven oral carcinogenesis promoted tumor angiogenesis (p < 0.05), infiltration of M2‐like macrophages in the TME (p < 0.05) and ultimately tumor progression (p < 0.05). Inhibition of TGFβ signaling in TEX with mRER ameliorated these pro‐tumor activities. Silencing of TGFβ emerges as a critical step in suppressing pro‐angiogenic functions of TEX in HNSCC.

Cyclin-dependent kinases (CDK) regulate cell cycle progression. During tumor development, altered expression and availability of CDKs strongly contribute to impaired cell proliferation, a hallmark of cancer. In recent years, targeted inhibition of CDKs has shown considerable therapeutic benefit in a variety of tumor entities. Their success is reflected in clinical approvals of specific CDK4/6 inhibitors for breast cancer. This review provides a detailed insight into the molecular mechanisms of CDKs as well as a general overview of CDK inhibition. It also summarizes the latest research approaches and current advances in the treatment of head and neck cancer with CDK inhibitors. Instead of monotherapies, combination therapies with CDK inhibitors may especially provide promising results in tumor therapy. Indeed, recent studies have shown a synergistic effect of CDK inhibition together with chemo- and radio- and immunotherapy in cancer treatment to overcome tumor evasion, which may lead to a renaissance of CDK inhibitors.

The expression of PD-L1 by tumor cells is mainly associated with its immunosuppressive effect. In fact, PD-1/PD-L1 immune checkpoint inhibitors demonstrated remarkable effects in advanced cancer patients including HNSCC. In this context, irradiation is currently being investigated as a synergistic treatment modality to immunotherapy. However, the majority of HNSCC patients still show little improvement or even hyperprogression. Interestingly, there is increasing evidence for additional cell-intrinsic functions of PD-L1 in tumor cells. In previous studies, we showed that PD-L1 has a strong influence on proliferation, migration, invasion, and survival after irradiation. We demonstrated that cellular expression and localization of PD-L1 differed depending on sensitivity to irradiation. Here, we show that PD-L1 is also differentially expressed during cell cycle progression of HNSCC. Furthermore, cellular localization of PD-L1 also changes depending on a particular cell cycle phase. Moreover, distinct observations occurred depending on the general differentiation status. Overall, the function of PD-L1 cannot be generalized. Rather, it depends on the differentiation status and microenvironment. PD-L1 expression and localization are variable, depending on different factors. These findings may provide insight into why differential response to PD-1/PD-L1 antibody therapy can occur. Detailed understanding of cell-intrinsic PD-L1 functions will further allow antibody-based immunotherapy to be optimized.

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.

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.

Despite considerable progress in the field of perinatal care, infectious diseases, especially when caused by gram negative bacteria, remain a major reason for neonatal morbidity and mortality. Notably infants born prematurely and those with very low birth weight are at risk due to their immature and deficient immune system and their prolonged hospitalization which promotes nosocomial infections. In case of impending preterm birth, betamethasone is given to induce lung maturation and tocolytic agents like indomethacin or fenoterol are administered to suppress premature labor. The aim of this study was to analyze the effects of these drugs on the immune system of mothers and neonates. Therefore, mononuclear cells from cord blood and peripheral maternal blood were stimulated with Escherichia coli and incubated with betamethasone, indomethacin and fenoterol. Subsequently the effect of the treatment on cytokine production was determined. Betamethasone alone and in combination with tocolytic agents inhibited the production of pro- and anti-inflammatory cytokines. Not only does betamethasone dampen the immune response by reducing the production of cytokines, it also has a variety of other detrimental short- and long-term effects on the neonate. In conclusion we would recommend using biological markers to determine if premature labor actually leads to preterm birth and subsequently administer betamethasone only to mothers giving birth prematurely.

Immunotherapy by blockade of the PD-1/PD-L1 checkpoint demonstrated amazing tumor response in advanced cancer patients including head and neck squamous cell carcinoma (HNSCC). However, the majority of HNSCC patients still show little improvement or even hyperprogression. Irradiation is currently investigated as synergistic treatment modality to immunotherapy as it increases the number of Tcells thereby enhancing efficacy of immunotherapy. Apart from this immunogenic context a growing amount of data indicates that PD-L1 also plays an intrinsic role in cancer cells by regulating different cellular functions like cell proliferation or migration. Here, we demonstrate opposing membrane localization of PD-L1 in vital and apoptotic cell populations of radioresistant (RR) and radiosensitive (RS) HNSCC cell lines up to 72 h after irradiation using flow cytometry. Moreover, strong PD-L1 expression was found in nuclear and cytoplasmic cell fractions of RR. After irradiation PD-L1 decreased in nuclear fractions and increased in cytoplasmic fractions of RR cells. In contrast, RS cell lines did not express PD-L1, neither in the nucleus nor in cytoplasmic fractions. Additionally, overexpression of PD-L1 in RS cells led to a proportional increase of vital PD-L1 positive cells after irradiation. Moreover, co-immunoprecipitation experiments revealed an interaction between Akt-1 and PD-L1, mostly in irradiated RR cells compared to RS cells suggesting a differential influence of PD-L1 on cell signaling. In summary, our data imply the need for different therapeutic strategies dependent on the molecular context in which PD-L1 is embedded.