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Background: Loss-of-function of PD-L1 induces therapy resistance of anti-PD-1/L1 therapy, and the complex regulatory mechanisms are not completely understood. We previously reported that stroma-derived interleukin-33 (IL-33) promoted the progression of oral squamous cell carcinoma (OSCC). We here focused on the immune-regulation role of IL-33 and its receptor ST2 signaling in PD-L1-positive OSCC patients.Methods: Activated T cells in in situ and peripheral blood were analyzed by IL-33/ST3 expression. Knockdown or overexpression of ST2 combined with IL-33/IFN-γ stimulation were performed to determine PD-L1 expression and PD-L1-dependent immune escape in OSCC/human T cells co-culture system, and OSCC orthotopic model based on humanized mouse with immune reconstitution and C57BL/6 mice models.Results: High IL-33/ST2 correlated with less activated T cells infiltration in situ and peripheral blood. Knockdown of ST2 down-regulated constitutive PD-L1 expression, whereas ST2 also promoted IL-33-induced PD-L1 Mechanistically, IL-33/ST2 activated JAK2/STAT3 pathway to directly promoted PD-L1 expression, and also activated MyD88/NF-κB signaling to up-regulate IFN-γ receptor (IFN-γR), which indirectly strengthen IFN-γ-induced PD-L1. Furthermore, ST2 is required for PD-L1-mediated immune tolerance in vitro and in vivo. ST2high OSCC patients have more PD-L1 and IFN-γR level in situ.Conclusions: IL-33/ST2 signaling enhanced PD-L1-mediated immune escape, ST2high OSCC patients might benefit from anti-PD-1/L1 therapy. [ABSTRACT FROM AUTHOR]

The Pattern Of Invasion (POI) of tumor cells into adjacent normal tissues clinically predicts postoperative tumor metastasis/recurrence of early oral squamous cell carcinoma (OSCC), but the mechanisms underlying the development of these subtypes remain unclear. Focusing on the highest score of POIs (Worst POI, WPOI) present within each tumor, we observe a disease progression-driven shift of WPOI towards the high-risk type 4/5, associated with a mesenchymal phenotype in advanced OSCC. WPOI 4-5-derived cancer-associated fibroblasts (CAFsWPOI4-5), characterized by high oxytocin receptor expression (OXTRHigh), contribute to local-regional metastasis. OXTRHigh CAFs induce a desmoplastic stroma and CCL26 is required for the invasive phenotype of CCR3+ tumors. Mechanistically, OXTR activates nuclear ERK5 transcription signaling via Gαq and CDC37 to maintain high levels of OXTR and CCL26. ERK5 ablation reprograms the pro-invasive phenotype of OXTRHigh CAFs. Therefore, targeting ERK5 signaling in OXTRHigh CAFs is a potential therapeutic strategy for OSCC patients with WPOI 4-5. Worst pattern of invasion (WPOI) is a parameter used to quantify tumor invasiveness of oral squamous cell carcinoma (OSCC). Here the authors show that a fibroblast subset characterized by the expression of the oxytocin receptor is enriched in highly invasive WPOI 4-5 OSCC tumors and can be targeted to reduce the desmoplastic stroma and tumor metastasis. [ABSTRACT FROM AUTHOR]

Background: Reelin, an extracellular glycoprotein, is expressed on neuronal cells and participates in neuronal migration during brain development. Recently, Reelin also has a vital role in carcinogenesis. However, its role in oral squamous cell carcinoma (OSCC) remains to be explored. The purpose of this study was to explore the roles of Reelin in OSCC. Methods: The expression of Reelin in cancer - associated fibroblasts (ReelinCAF) and tumor cells (ReelinTC) was analyzed by the Gene Expression Omnibus (GEO) database. Immunohistochemistry (IHC) was used to detect the spatial pattern of Reelin in 75 OSCCs. The diagnostic and prognostic values of Reelin were evaluated and also verified by The Cancer Genome Atlas (TCGA) database. Primary CAFs from 13 OSCC patients were isolated to confirm Reelin expression. Thirty-nine OSCC peripheral blood samples were used to analyze the change of immunocytes based on Reelin levels by flow cytometry. The relationship between Reelin and tumor immune microenvironment in head and neck squamous cell carcinoma (HNSCC) tissues was determined by TISIDB and the Tumor Immune Estimation Resource (TIMER) database. Results: In breast cancer, pancreatic cancer and rectal cancer, Reelin in CAFs was significantly upregulated compared with Reelin in TCs. The IHC results in OSCC also showed that Reelin levels were higher in CAFs. Upregulated ReelinTC was related to a decreased pN stage and distant metastasis. Strikingly, patients with enhanced ReelinCAF had a high risk of lymph node metastasis, poor worst pattern of invasion (WPOI), and distant metastasis, but showed comparable Ki-67 level in all OSCC patients, resulting in shorter overall survival (OS) and disease-specific survival (DSS). Unexpectedly, Reelin in tumor-infiltrating lymphocytes (ReelinTIL) was correlated with postoperative relapse. Patients with high ReelinTIL, but not ReelinTC and ReelinCAF, had poor cytotoxicity of CD8+ T cells and higher ratio of CD4/CD8 in peripheral blood. However, Reelin was positively associated with tissue-resident B cells and NK cells in the tumor microenvironment. Conclusion: Reelin has a versatile function in distinct cell types during the development of OSCC via governing tumor cell and stroma microenvironment. [ABSTRACT FROM AUTHOR]

Background: CD38 belongs to the ribosyl cyclase family and is expressed on various hematological cells and involved in immunosuppression and tumor promotion. Although targeting CD38 antibodies has been approved for treatment of multiple myeloma, the function of CD38 in solid tumor, oral squamous cell carcinoma (OSCC) etc. , has not been investigated. Methods: This retrospective study included 92 OSCC samples and analyzed the spatial distribution of CD38 by immunohistochemistry (IHC). The values of diagnosis and prognosis of CD38 were evaluated. Additionally, 53 OSCC preoperative peripheral blood samples were used to be analyzed by flow cytometry. Tumor Immune Estimation Resource (TIMER) and cBioPortal databases were used to study CD38 level in various tumors and its correlation with tumor immune microenvironment in head and neck squamous cell carcinoma (HNSCC). Results: CD38 ubiquitously presented in tumor cells (TCs), fibroblast-like cells (FLCs), and tumor-infiltrating lymphocytes (TILs). Patients with highly expressed CD38 in TCs (CD38TCs) had higher TNM stage and risk of lymph node metastasis. Upregulation of CD38 in FLCs (CD38FLCs) was significantly associated with poor WPOI. Escalated CD38 in TILs (CD38TILs) led to higher Ki-67 level of tumor cells. Moreover, patients with enhanced CD38TCs were susceptible to postoperative metastasis occurrence, and those with highly expressed CD38TILs independently predicted shorter overall and disease-free survival. Strikingly, patients with highly expressed CD38TILs, but not CD38TCs and CD38FLCs, had significantly lower CD3+CD4+ T cells and higher ratio of CD3−CD16+CD56+NK cells. The imbalance of immune system is attributed to dysregulated immune checkpoint molecules (VISTA, PD-1, LAG-3, CTLA-4, TIGIT, GITR) as well as particular immune cell subsets, which were positively correlated with CD38 expression in HNSCC. Conclusion: CD38 is a poor prognostic biomarker for OSCC patients and plays a vital role in governing immune microenvironment and circulating lymphocyte homeostasis. Co-expression between CD38 and immune checkpoint molecules provides new insight into immune checkpoint therapy. [ABSTRACT FROM AUTHOR]

Background: MLL2 (mixed-lineage leukemia 2) is recognized as an essential role in regulating histone 3 lysine 4 tri-methylation (H3K4me3) in mammalian cells. It is frequently mutated to promote developmental diseases and tumor initiation. However, the expression pattern of MLL2 and its clinical significance for patients with early-stage oral squamous cell carcinoma (OSCC) remain totally unknown.Methods: Eighty-five samples of primary early-stage OSCC were enrolled in this retrospective study, and immunohistochemistry (IHC) was performed to detect the spatial pattern of MLL2. The diagnostic and prognostic value of MLL2 were assessed.Results: MLL2 was widely expressed in tumor cells (TCs), fibroblast-like cells (FLCs), and tumor-infiltrating lymphocytes (TILs), both in tumor center and invasive tumor front, and showed no distributive heterogeneity. Moreover, regardless of cell types and microlocalization, patients with high expressed MLL2 had increased depth invasion of tumor (DOI). Besides, upregulation of MLL2TC and MLL2TIL in tumor center were both associated with poor differentiation, but showed no correlation with tumor growth with comparable Ki-67 levels. Prognostic analysis indicated that early-stage OSCC patients with enhanced MLL2TIL in invasive tumor front were susceptible to occur postoperative metastasis and recurrence. Indeed, patients with higher expressed MLL2TIL showed shorter overall survival (OS) and disease-free survival (DFS), and MLL2TIL in invasive tumor front was an independent risk factor of DFS.Conclusion: TIL-derived MLL2 in invasive tumor front was an independent prognostic factor of DFS for early-stage OSCC patients. [ABSTRACT FROM AUTHOR]

Background: Programmed cell death 4 (PDCD4) as a tumor suppressor gene inhibits growth and metastasis of cancer cells, which involved with eIF4A1, the inhibitor of translation initiation. Although the prognosis of early-stage oral squamous cell carcinoma (OSCC) is generally better, but many patients occur recurrence after surgery. Understanding the clinical expression pattern of PDCD4/eIF4A1 signal would provide diagnostic biomarker and target therapy premise for early-stage OSCC patients. Methods: Immunohistochemical analysis was performed on 69 early-stage (T1/2N0M0) OSCC samples to evaluate temporal expression and prognostic value of eIF4A1 and PDCD4 in early-stage OSCC according to cell types and microlocalization. The correlations between PDCD4/eIF4A1 signal and Ki-67, postoperative recurrence and metastasis were determined. Results: We found that PDCD4 was presented in tumor cells (TCs) and tumor-infiltrating lymphocytes (TILs) but absent in fibroblast-like cells (FLCs). eIF4A1 was only presented in TCs. PDCD4TCs was negative associated with eIF4A1TCs in tumor center, and patients with low PDCD4TCs or high eIF4A1TCs had poorer differentiation. Moreover, aberrant PDCD4/eIF4A1 signal led to higher Ki-67 level. Interestingly, patients with low expressed PDCD4TILs had better prognosis, indicating the function heterogeneity of PDCD4 in different cell types. Furthermore, low PDCD4 TCs and high eIF4A1TCs predicted higher postoperative recurrence rate and are significant independent risk factors for early-stage OSCC. Conclusion: Patients with low PDCD4TCs and high eIF4A1TCs have higher recurrence rate and poor clinical outcome. Of note, PDCD4TILs exerts contradictory function. Thus, PDCD4/eIF4A1 targeting therapeutics should consider the function heterogeneity of PDCD4. [ABSTRACT FROM AUTHOR]

Programmed cell death 4 (PDCD4) is a tumor suppressor gene implicated in many cellular functions, including transcription, translation, apoptosis, and the modulation of different signal transduction pathways. The downstream mechanisms of PDCD4 have been well-discussed, but its upstream regulators have not been systematically summarized. Noncoding RNAs (ncRNAs) are gene transcripts with no protein-coding potential but play a pivotal role in the regulation of the pathogenesis of solid tumors, cardiac injury, and inflamed tissue. In recent studies, many ncRNAs, especially microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), were found to interact with PDCD4 to manipulate its expression through transcriptional regulation and function as oncogenes or tumor suppressors. For example, miR-21, as a classic oncogene, was identified as the key regulator of PDCD4 by targeting its 3′-untranslated region (UTR) to promote tumor proliferation, migration, and invasion in colon, breast, and bladder carcinoma. Therefore, we reviewed the recently emerging pleiotropic regulation of PDCD4 by ncRNAs in cancer and inflammatory disorders and aimed to shed light on the mechanisms of associated diseases, which could be conducive to the development of novel treatment strategies for PDCD4-induced diseases. [ABSTRACT FROM AUTHOR]