Small rho GTPases mediate tumor-induced inhibition of endocytic activity of dendritic cells

Relation of Langerhans cell size to buccal carcinoma

Oral cancer decreases quality of life despite timely medical management. The carcinogens in tobacco products and their role in tumorigenesis are well documented. Langerhans cells (LCs) are a subset of antigen-presenting cells (APCs) that monitor the tumor microenvironment and engulf carcinogens and foreign bodies. We investigated the distribution and size of LCs and their relation to the mode of tobacco consumption and clinical outcome in patients with buccal carcinoma. We recruited patients with oral cancer who were scheduled for tumor excision and men with urethral stricture undergoing substitution urethroplasty using buccal mucosa. Normal and tumor-adjacent tissues were stained with CD1a antibody. The distribution and mean diameter of 100 LCs/patient were determined. We found significantly smaller LCs in patients who chewed only tobacco compared to those who consumed tobacco by other means. The size of LCs decreased significantly with progressive stages of malignant disease. We found that patients with larger LCs survived longer than those with smaller LCs during an average follow-up of 24 months. We suggest a relation between the size of LCs and clinical outcomes in patients with buccal carcinoma.

Serum cell division cycle 42 in advanced hepatocellular carcinoma patients: Linkage with clinical characteristics and immune checkpoint inhibitor-related treatment outcomes

OBJECTIVE

Cell division cycle 42 (CDC42) facilitates immune escape and drug resistance towards immunotherapy in several malignancies. This prospective study aimed to explore the predictive value of serum CDC42 for immune checkpoint inhibitor (ICI)-treatment response and survival in advanced hepatocellular carcinoma (HCC) patients.

METHODS

Thirty advanced HCC patients scheduled for ICI or ICI-based treatment were enrolled in this prospective study, whose serum CDC42 was determined via enzyme-linked immunosorbent assay before therapy initiation.

RESULTS

The median (interquartile range) of serum CDC42 level was 766.5 (605.0-1329.5) pg/mL. Serum CDC42 was related to increased tumor size but decreased programmed death-ligand 1 combined positive score (PD-L1 CPS). With respect to ICI or ICI-based treatment outcomes, elevated serum CDC42 was associated with decreased disease control rate, but did not link with objective response rate. Patients with high serum CDC42 (vs. low, cut by its median level) had shortened progression-free survival (PFS), while overall survival (OS) only disclosed a reduced trend (lacked statistical significance) in patients with high serum CDC42 (vs. low). In detail, the median (95%CI) PFS and OS were 3.0 (0.0-6.0) months and 11.7 (2.7-20.7) months in patients with high serum CDC42, while they were 11.1 (6.6-15.6) months and 19.3 (14.5-24.1) months in patients with low CDC42. After adjusted by multivariate cox regression analysis, high serum CDC42 (vs. low) was independently associated with shortened PFS, but not OS.

CONCLUSIONS

Elevated serum CDC42 possesses a potential value in predicting worse ICI or ICI-based treatment outcomes in advanced HCC.

Regulation of biomaterial implantation-induced fibrin deposition to immunological functions of dendritic cells

The performance of implanted biomaterials is largely determined by their interaction with the host immune system. As a fibrous-like 3D network, fibrin matrix formed at the interfaces of tissue and material, whose effects on dendritic cells (DCs) remain unknown. Here, a bone plates implantation model was developed to evaluate the fibrin matrix deposition and DCs recruitment in vivo. The DCs responses to fibrin matrix were further analyzed by a 2D and 3D fibrin matrix model in vitro. In vivo results indicated that large amount of fibrin matrix deposited on the interface between the tissue and bone plates, where DCs were recruited. Subsequent in vitro testing denoted that DCs underwent significant shape deformation and cytoskeleton reorganization, as well as mechanical property alteration. Furthermore, the immune function of imDCs and mDCs were negatively and positively regulated, respectively. The underlying mechano-immunology coupling mechanisms involved RhoA and CDC42 signaling pathways. These results suggested that fibrin plays a key role in regulating DCs immunological behaviors, providing a valuable immunomodulatory strategy for tissue healing, regeneration and implantation.

Semaphorin 3E deficiency dysregulates dendritic cell functions: In vitro and in vivo evidence

Regulation of dendritic cell functions is a complex process in which several mediators play diverse roles as a network in a context-dependent manner. The precise mechanisms underlying dendritic cell functions have remained to be addressed. Semaphorins play crucial roles in regulation of various cell functions. We previously revealed that Semaphorin 3E (Sema3E) contributes to regulation of allergen-induced airway pathology partly mediated by controlling recruitment of conventional dendritic cell subsets in vivo, though the underlying mechanism remained elusive. In this study, we investigate the potential regulatory role of Sema3E in dendritic cells. We demonstrated that bone marrow-derived dendritic cells differentiated from Sema3e^-/- progenitors have an enhanced migration capacity both at the baseline and in response to CCL21. The enhanced migration ability of Sema3E dendritic cells was associated with an overexpression of the chemokine receptor (CCR7), elevated Rac1 GTPase activity and F-actin polymerization. Using a mouse model of allergic airway sensitization, we observed that genetic deletion of Sema3E leads to a time dependent upregulation of CCR7 on CD11b⁺ conventional dendritic cells in the lungs and mediastinal lymph nodes. Furthermore, aeroallergen sensitization of Sema3e^-/- mice lead to an enhanced expression of PD-L2 and IRF-4 as well as enhanced allergen uptake in pulmonary CD11b⁺ DC, compared to wild type littermates. Collectively, these data suggest that Sema3E implicates in regulation of dendritic cell functions which could be considered a basis for novel immunotherapeutic strategies for the diseases associated with defective dendritic cells in the future.

Reviving up dendritic cells can run cancer immune wheel in non-small cell lung cancer: a prospective two-arm study

BACKGROUND AND AIM

Lung cancer is the number one cause of cancer-related deaths. Dendritic cells (DCs) are heterogeneous components of innate immunity that play a crucial role in the anti-tumor T cell immunity and may represent a promising approach for tumor immunotherapy. In this study, we aimed to evaluate the frequency of the two major subsets of DCs; plasmacytoid dendritic cells (pDCs) and monocytic dendritic cells (mDCs) in non-small cell lung cancer (NCSLC) and correlating them with different clinicopathologic features and survival outcomes.

PATIENTS AND METHODS

This study was a case-controlled one, included 50 patients with denovo pathologically confirmed NSCLC and 20 healthy controls of comparable age and gender. After diagnosis and staging of patients, the frequency of DCs was evaluated using flow cytometry.

RESULTS

We unveiled significantly reduced levels of pDCs (P = 0.024), and mDCs (P = 0.013) in NSCLC patients compared to controls. Furthermore, there was a significant accumulation of pDCs in non-metastatic patients compared to metastatic ones (P < 0.0001), while there was no significant (P = 0.6) differences in mDCs, and mDCs/pDCs ratio (P = 0.9). There was a Significant negative correlation (r = - 0.3, P = 0.04) between OS and mDCs. On the other hand, there was a significantly higher OS with pDCs ≥ 0.82 compared to patients with pDCs < 0.82, log rank Ch² = 12.128, P < 0.0001.

CONCLUSION

Despite the controversy about the prognostic role of pDCs not only in NSCLC but also in other solid tumors, our study sheds light on the possible prognostic impact of pDCs and mDCs on treatment outcomes of NSCLC patients.

Tumor microenvironment-related dendritic cell deficiency: a target to enhance tumor immunotherapy

Dendritic cells (DCs), as specialized antigen-presenting cells, are essential for the initiation of specific T cell responses in innate antitumor immunity and, in certain cases, support humoral responses to inhibit tumor development. Mounting evidence suggests that the DC system displays a broad spectrum of dysfunctional status in the tumor microenvironment (TME), which ultimately affects antitumor immune responses. DC-based therapy can restore the function of DCs in the TME, thus showing a promising potential in tumor therapy. In this review, we provide an overview of the DC deficiency caused by various factors in the TME and discuss proposed strategies to reverse DC deficiency and the applications of novel combinatorial DC-based therapy for immune normalization of the tumor.

Induction of Tolerance and Immunity by Dendritic Cells: Mechanisms and Clinical Applications

Dendritic cells (DCs) are key regulators of immune responses that operate at the interface between innate and adaptive immunity, and defects in DC functions contribute to the pathogenesis of a variety of disorders. For instance, cancer evolves in the context of limited DC activity, and some autoimmune diseases are initiated by DC-dependent antigen presentation. Thus, correcting aberrant DC functions stands out as a promising therapeutic paradigm for a variety of diseases, as demonstrated by an abundant preclinical and clinical literature accumulating over the past two decades. However, the therapeutic potential of DC-targeting approaches remains to be fully exploited in the clinic. Here, we discuss the unique features of DCs that underlie the high therapeutic potential of DC-targeting strategies and critically analyze the obstacles that have prevented the full realization of this promising paradigm.

Hide-and-seek: the interplay between cancer stem cells and the immune system

The enhanced ability of cancer stem cells (CSCs) to give rise to new tumors suggests that these cells may also have an advantage in evading immune detection and elimination. This tumor-forming ability, combined with the known plasticity of the immune system, which can play both protumorigenic and antitumorigenic roles, has motivated investigations into the interaction between CSCs and the immune system. Herein, we review the interplay between host immunity and CSCs by examining the immune-related mechanisms that favor CSCs and the CSC-mediated expansion of protumorigenic immune cells. Furthermore, we discuss immune cells, such as natural killer cells, that preferentially target CSCs and the strategies used by CSCs to evade immune detection and destruction. An increased understanding of these interactions and the pathways that regulate them may allow us to harness immune system components to create new adjuvant therapies that eradicate CSCs and improve patient survival.

Taming the immune system through transfusion in oncology patients

Blood transfusion is a clinical replacement therapy with many successes with some benefit and, also, some harm. Cancer is a multifaceted disease potentially associated with the immune system's weakness where the cancerous tumor cells escape from the immune system. Allogeneic blood transfusion, through five major mechanisms including the lymphocyte-T set, myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), natural killer cells (NKCs), and dendritic cells (DCs) can help the recipient's defense mechanisms. On the other hand, the role for each of the listed items includes activation of the antitumor CD8+ cytotoxic T lymphocytes (CD8+/CTL), temporal inactivation of Tregs, inactivation of the STAT3 signaling pathway, the use of bacteria to enhance the antitumor immune response and cellular immunotherapy. The above issues are concisely addressed in this manuscript based on a literature survey on this topic carried out by the first author.

Origin and pharmacological modulation of tumor-associated regulatory dendritic cells

Protumorigenic activity of immune regulatory cells has been proven to play a major role in precluding immunosurveillance and limiting the efficacy of anticancer therapies. Although several approaches have been offered to deplete myeloid-derived suppressor cells (MDSC) and regulatory T cells, there are no data on how to control suppressive dendritic cell (DC) accumulation or function in the tumor environment. Although immunosuppressive function of DC in cancer was implicated to immature and plasmacytoid DC, details of how conventional DC (cDC) develop immunosuppressive properties remain less understood. Here, we show that the development of lung cancer in mice was associated with fast accumulation of regulatory DC (regDC) prior to the appearance of MDSC. Using the in vitro and in vivo approaches, we demonstrated that (i)both cDC and MDSC could be polarized into protumor regDC in the lung cancer environment; (ii) cDC → regDC polarization was mediated by the small Rho GTPase signaling, which could be controlled by noncytotoxic doses of paclitaxel; and (iii) prevention of regDC appearance increased the antitumor potential of DC vaccine in lung cancer. These findings not only bring new players to the family of myeloid regulatory cells and provide new targets for cancer therapy, but offer novel insights into the immunomodulatory capacity of chemotherapeutic agents used in low, noncytotoxic doses.

Cellular and molecular mechanisms in cancer immune escape: a comprehensive review

Immune escape is the final phase of cancer immunoediting process wherein cancer modulates our immune system to escape from being destroyed by it. Many cellular and molecular events govern the cancer's evasion of host immune response. The tumor undergoes continuous remodeling at the genetic, epigenetic and metabolic level to acquire resistance to apoptosis. At the same time, it effectively modifies all the components of the host's immunome so as to escape from its antitumor effects. Moreover, it induces accumulation of suppressive cells like Treg and myeloid derived suppressor cells and factors which also enable it to elude the immune system. Recent research in this area helps in defining the role of newer players like miRNAs and exosomes in immune escape. The immunotherapeutic approaches developed to target the escape phase appear quite promising; however, the quest for a perfect therapeutic agent that can achieve maximum cure with minimal toxicity continues.

The effect of cyclic mechanical strain on activation of dendritic cells cultured on adhesive substrates

Dendritic cells (DCs), key regulators of tolerance and immunity, have been found to reside in mechanically active tissues such as the interior layers of the arterial wall, which experience cyclic radial wall strain due to pulsatile blood flow. Although experimentally difficult to determine in vivo, it is reasonable to postulate DCs experience the mechanical forces in such mechanically active tissues. However, it is currently unknown how DCs respond to cyclic mechanical strain. In order to explore the hypothesis that DCs are responsive to mechanical strain, DCs were cultured in vitro on pre-adsorbed adhesive proteins (e.g., laminin, collagen, fibrinogen) and 1 Hz cyclic strain was applied for various durations and strain magnitudes. It was determined that a strain magnitude of 10% and 24 h duration adversely affected DC viability compared to no-strain controls, but culture on certain adhesive substrates provided modest protection of viability under this harsh strain regime. In contrast, application of 1 h of 1 Hz cyclic 3% strain did not affect DC viability and this strain regime was used for the remaining experiments for quantifying DC activation and T-cell priming capability. Application of 3% strain increased expression of stimulatory (MHC-II) and costimulatory molecules (CD86, CD40), and this effect was generally increased by culture on pre-coated adhesive substrates. Interestingly, the cytokine secretion profile of DCs was not significantly affected by strain. Lastly, strained DCs demonstrated increased stimulation of allogeneic T-cell proliferation, in a manner that was independent of the adhesive substrate. These observations indicate generation of a DC consistent with what has been described as a semi-mature phenotype. This work begins elucidating a potential role for DCs in tissue environments exposed to cyclic mechanical forces.

Dendritic cells in the cancer microenvironment

The complexity of the tumor immunoenvironment is underscored by the emergence and discovery of different subsets of immune effectors and regulatory cells. Tumor-induced polarization of immune cell differentiation and function makes this unique environment even more intricate and variable. Dendritic cells (DCs) represent a special group of cells that display different phenotype and activity at the tumor site and exhibit differential pro-tumorigenic and anti-tumorigenic functions. DCs play a key role in inducing and maintaining the antitumor immunity, but in the tumor environment their antigen-presenting function may be lost or inefficient. DCs might be also polarized into immunosuppressive/tolerogenic regulatory DCs, which limit activity of effector T cells and support tumor growth and progression. Although various factors and signaling pathways have been described to be responsible for abnormal functioning of DCs in cancer, there are still no feasible therapeutic modalities available for preventing or reversing DC malfunction in tumor-bearing hosts. Thus, better understanding of DC immunobiology in cancer is pivotal for designing novel or improved therapeutic approaches that will allow proper functioning of DCs in patients with cancer.

Tumor associated regulatory dendritic cells

Immune effector and regulatory cells in the tumor microenvironment are key factors in tumor development and progression as the pathogenesis of cancer vitally depends on the multifaceted interactions between various microenvironmental stimuli provided by tumor-associated immune cells. Immune regulatory cells participate in all stages of cancer development from the induction of genomic instability to the maintenance of intratumoral angiogenesis, proliferation and spreading of malignant cells, and formation of premetastatic niches in distal tissues. Dendritic cells in the tumor microenvironment serve as a double-edged sword and, in addition to initiating potent anti-tumor immune responses, may mediate genomic damage, support neovascularization, block anti-tumor immunity and stimulate cancerous cell growth and spreading. Regulatory dendritic cells in cancer may directly and indirectly maintain antigen-specific and non-specific T cell unresponsiveness by controlling T cell polarization, MDSC and Treg differentiation and activity, and affecting specific microenvironmental conditions in premalignant niches. Understanding the mechanisms involved in regulatory dendritic cell polarization and operation and revealing pharmacological means for harnessing these pathways will provide additional opportunities for modifying the tumor microenvironment and improving the efficacy of different therapeutic approaches to cancer.

Regulatory dendritic cells in the tumor immunoenvironment

The tumor microenvironment is a pivotal factor in tumorigenesis, and especially in progression, as the pathogenesis of cancer critically depends on the complex interactions between various microenvironmental components. A key component of the tumor immunoenvironment is the infiltration of immune cells, which has been proven to play a dual role in tumor growth and progression. This Janus two-faced function of the tumor immunoenvironment is seen in tumor infiltration by T cells, which correlates with improved patient survival, but also with the homing of multiple subsets of immunoregulatory cells that inhibit the antitumor immune response. Regulatory dendritic cells (regDCs) have recently been shown to be induced by tumor-derived factors and represent a new and potentially important player in supporting tumor progression and suppressing the development of antitumor immune responses. Our recent data reveal that different tumor cell lines produce soluble factors that induce polarization of conventional DCs into regDCs, both in vitro and in vivo. These regDCs can suppress the proliferation of pre-activated T cells and are phenotypically and functionally different from their precursors as well as the classical immature conventional DCs. Understanding the biology of regDCs and the mechanisms of their formation in the tumor immunoenvironment will provide a new therapeutic target for re-polarizing protumorigenic immunoregulatory cells into proimmunogenic effector cells able to induce and support effective antitumor immunity.

Low-dose chemotherapeutic agents regulate small Rho GTPase activity in dendritic cells

Conventional chemotherapy targets dividing tumor cells and might support antitumor immunity by providing tumor antigens from dying tumor cells to antigen-presenting dendritic cells (DCs). Despite emerging evidence to suggest that phagocytosis of dying tumor cells by DCs requires membrane targeting of specific small Rho guanosine triphosphatases (GTPases), nothing is known with regard to the direct effect of chemotherapeutic agents on low molecular weight Rho GTPases in DCs. Prompted by a recent observation that low-dose chemotherapeutic drug paclitaxel could up-regulate DC maturation and function, here we studied putative regulatory roles for various chemotherapeutic agents in modulating small Rho GTPases in DC. Our results demonstrate that different classes of chemotherapeutic drugs at low nontoxic concentrations regulate activity of Rac, RhoA, and RhoE in murine DC, suggesting that small Rho GTPases might serve as new targets for modulating functional activity of DC vaccines or endogenous DCs in various immunotherapeutic or chemoimmunotherapeutic strategies.

Simulation of the regulation of EGFR endocytosis and EGFR-ERK signaling by endophilin-mediated RhoA-EGFR crosstalk

Deregulations of EGFR endocytosis in EGFR-ERK signaling are known to cause cancers and developmental disorders. Mutations that impaired c-Cbl-EGFR association delay EGFR endocytosis and produce higher mitogenic signals in lung cancer. ROCK, an effector of small GTPase RhoA was shown to negatively regulate EGFR endocytosis via endophilin A1. A mathematical model was developed to study how RhoA and ROCK regulate EGFR endocytosis. Our study suggested that over-expressing RhoA as well as ROCK prolonged ERK activation partly by reducing EGFR endocytosis. Overall, our study hypothesized an alternative role of RhoA in tumorigenesis in addition to its regulation of cytoskeleton and cell motility.