Chemokines in neoplastic progression

Role of senescent tumor cells in building a cytokine shield in the tumor microenvironment: mathematical modeling

Cellular senescence can induce dual effects (promotion or inhibition) on cancer progression. While immune cells naturally respond and migrate toward various chemotactic sources from the tumor mass, various factors including senescent tumor cells (STCs) in the tumor microenvironment may affect this chemotactic movement. In this work, we investigate the mutual interactions between the tumor cells and the immune cells that either inhibit or facilitate tumor growth by developing a mathematical model that consists of taxis-reaction-diffusion equations and receptor kinetics for the key players in the interaction network. We apply a mathematical model to a transwell Boyden chamber invasion assay used in the experiments to illustrate that STCs can play a pivotal role in negating immune attack through tight regulation of intra- and extra-cellular signaling molecules. In particular, we show that senescent tumor cells in cell cycle arrest can block intratumoral infiltration of CD8+ T cells by secreting a high level of CXCL12, which leads to significant reduction its receptors, CXCR4, on T cells, and thus impaired chemotaxis. The predictions of nonlinear responses to CXCL12 were in good agreement with experimental data. We tested several hypotheses on immune-tumor interactions under various biochemical conditions in the tumor microenvironment and developed new concepts for anti-tumor strategies targeting senescence induced immune impairment.

Chemokines and NSCLC: Emerging role in prognosis, heterogeneity, and therapeutics

Lung cancer persists to contribute to one-quarter of cancer-associated deaths. Among the different histologies, non-small cell lung cancer (NSCLC) alone accounts for 85% of the cases. The development of therapies involving immune checkpoint inhibitors and angiogenesis inhibitors has increased patients' survival probability and reduced mortality rates. Developing targeted therapies against essential genetic alterations also translates to better treatment strategies. But the benefits still seem farfetched due to the development of drug resistance and refractory tumors. In this review, we have highlighted the interplay of different tumor microenvironment components, essentially discussing the chemokine families (CC, CXC, C, and CX3C) that regulate the tumor biology in NSCLC and promote tumor growth, metastasis, and associated heterogeneity. The development of therapeutics and prognostic markers is a complex and multipronged approach. However, some essential chemokines can act as critical players for being considered potential prognostic markers and therapeutic targets.

[The role of CXC and CC chemokines in patients with uveal melanoma]

Uveal melanoma is a malignant neoplasm with high metastatic potential; its pathogenesis is currently being studied. Chemokines play a key role not only in the inflammatory response, but also in enhancing angiogenesis, tumor invasiveness, increasing proliferative potential and metastasis.

PURPOSE

To study the role of chemokines of classes CXC and CC in blood serum and tear fluid of patients with uveal melanoma.

MATERIAL AND METHODS

The study included 118 people aged 53.7±12.2 years, among them 80 patients with uveal melanoma and 38 healthy donors. Group 1 included 32 patients with small tumors, group 2 (medium-sized tumors) - 26 patients; group 3 (large tumors) was comprised of 22 patients. Chemokines of classes CC (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, CCL5/RANTES, CCL11/Eotaxin) and CXC (CXCL1/GRO-α, CXCL8/IL-8, CXCL10/IP-10, CXCL12/SDF-1α) were determined by multiplex analysis of the blood serum and tear fluid. Statistical processing: Student's t-test, Fisher criteria, and Pierson's chi-squared test (χ2), differences were considered significant at p<0.05.

RESULTS

Significantly increased level of chemokines with pro-inflammatory (CCL5/RANTES), proliferative (CXCL10/IP-10) and pro-angiogenic (CXCL12/SDF-1α) effects was found in the blood serum of patients with small-sized uveal melanoma in comparison with healthy donors. Concentration of all studied pro-inflammatory, proliferative, and pro-angiogenic chemokines in the lacrimal fluid was found to be significantly elevated in both the affected and the paired "healthy" eyes in all 3 groups of patients, with the maximum content seen in the large tumor group.

CONCLUSION

The obtained data indicates that early local and systemic immune imbalance can be observed in uveal melanoma, and detection of chemokines can serve as a good reason for developing targeted therapy for small uveal melanoma.

The roles and mechanisms of the circular RNA circ_104640 in early-stage lung adenocarcinoma: a potential diagnostic and therapeutic target

Background

In recent years, there have been increasing reports that dysregulated circular RNAs (circRNAs) play a key role in the carcinogenesis of lung adenocarcinoma (LUAC). However, the role of circRNAs in early-stage LUAC is poorly understood.

Methods

The Gene Expression Omnibus (GEO) database and qRT-PCR were used to verify the abnormal expression of circRNAs, miRNAs and genes in early-stage LUAC tissues. shRNA and miRNA inhibitor are designed and synthesized to knock down circ_104640 and microRNA (miR)-145-5p expression. CCK-8 assay, colony formation assay and flow cytometry were used to study the effect of circ_104640 on cell proliferation and apoptosis. Bioinformatics analysis, dual luciferase reporter assays and argonaute 2 (Ago2) RNA immunoprecipitation (RIP) assays were chosen to find out the potential target of circ_104640.

Results

Based on the GEO database and tissue sample from our institution, we identified that the circRNA circ_104640, the miR-145-5p, and CCL20 (C-C motif chemokine ligand 20) were abnormally expressed in the tissues of early-stage LUAC. In vitro experiments showed that circ_104640 could exist stably in the cytoplasm, and a short pin RNA that targeted circ_104640 (sh-circ) inhibited cell growth and promoted apoptosis of LUAC cells. Dual luciferase reporter assays and Ago2 (RIP) assays confirmed the Ago2-dependent interaction of circ_104640 and miR-145-5p. In terms of mechanisms, we found that circ_104640 increased the expression of CCL20 by sponging miR-145-5p.

Conclusions

Our research demonstrated that circ_104640 could accelerate the proliferation of LUAC cells, while inhibiting LUAC cell apoptosis. circ_104640 may be a potential novel biomarker and therapeutic target for early-stage LUAC.

Baicalein inhibits non-small-cell lung cancer invasion and metastasis by reducing ezrin tension in inflammation microenvironment

Baicalein, a flavonoid phytochemical, has been shown to be effective as an anti‐metastatic agent for various cancers, especially for non‐small‐cell lung cancer (NSCLC). However, the underlying mechanism of how baicalein targets cellular processes during NSCLC cell invasion and metastasis remains elusive. In this study, we found that non‐cytotoxic concentrations of baicalein still retained anti‐dissemination activity both in vitro and in vivo. Using a genetic encoding tension probe based on Förster resonance energy transfer (FRET) theory, baicalein was shown to significantly decrease ezrin tension by downregulating cellular ezrin S‐nitrosylation (SNO) levels in NSCLC cells in the inflammatory microenvironment. Decreased ezrin tension inhibited the formation of an aggressive phenotype of NSCLC cell and leader cell in collective migration, and subsequently suppressed NSCLC dissemination. Baicalein restrained SNO‐mediated ezrin tension by decreasing iNOS expression levels. Overall this study demonstrates the novel mechanism used by baicalein to suppress NSCLC invasion and metastasis from a mechanopharmacology perspective and illustrates a new direction for drug development.

Senescence-Associated Pro-inflammatory Cytokines and Tumor Cell Plasticity

The well-recognized cell phenotypic heterogeneity in tumors is a great challenge for cancer treatment. Dynamic interconversion and movement within a spectrum of different cell phenotypes (cellular plasticity) with the acquisition of specific cell functions is a fascinating biological puzzle, that represent an additional difficulty for cancer treatment and novel therapies development. The understanding of the molecular mechanisms responsible for moving or stabilizing tumor cells within this spectrum of variable states constitutes a valuable tool to overcome these challenges. In particular, cell transitions between epithelial and mesenchymal phenotypes (EMT-MET) and de-and trans-differentiation processes are relevant, since it has been shown that they confer invasiveness, drug resistance, and metastatic ability, due to the simultaneous acquisition of stem-like cell properties. Multiple drivers participate in these cell conversions events. In particular, cellular senescence and senescence-associated soluble factors have been shown to unveil stem-like cell properties and cell plasticity. By modulating gradually the composition of their secretome and the time of exposure, senescent cells may have differential effect not only on tumor cells but also on surrounding cells. Intriguingly, tumor cells that scape from senescence acquire stem-like cell properties and aggressiveness. The reinforcement of senescence and inflammation by soluble factors and the participation of immune cells may provide a dynamic milieu having varied effects on cell transitions, reprogramming, plasticity, stemness and therefore heterogeneity. This will confer different epithelial/mesenchymal traits (hybrid phenotype) and stem-like cell properties, combinations of which, in a particular cell context, could be responsible for different cellular functions during cancer progression (survival, migration, invasion, colonization or proliferation). Additionally, cooperative behavior between cell subpopulations with different phenotypes/stemness functions could also modulate their cellular plasticity. Here, we will discuss the role of senescence and senescence-associated pro-inflammatory cytokines on the induction of cellular plasticity, their effect role in establishing particular states within this spectrum of cell phenotypes and how this is accompanied by stem-like cell properties that, as the epithelial transitions, may also have a continuum of characteristics providing tumor cells with functional adaptability specifically useful in the different stages of carcinogenesis.

lncRNA‑u50535 promotes the progression of lung cancer by activating CCL20/ERK signaling

The ligand/receptor pair C‑C motif chemokine ligand 20 (CCL20)/C‑C motif chemokine receptor 6 (CCR6) is considered to be highly activated in lung cancer and significantly accelerates lung cancer progression through activation of ERK signaling. In addition, it has been shown that long non‑coding RNA‑u50535 (lncRNA‑u50535) upregulates CCL20 expression and facilitates cancer progression in colorectal cancer (CRC). However, the effects of lncRNA‑u50535 in lung cancer progression and whether lncRNA‑u50535 regulates CCL20/CCR6/ERK signaling in lung cancer remain ill‑defined. Therefore, the aim of the present study was to investigate the effects of lncRNA‑u50535 on CCL20/CCR6/ERK signaling in lung cancer progression. The results demonstrated that lncRNA‑u50535 expression was upregulated in lung cancer tissues and cell lines compared with normal tissues and cells. Knockdown of lncRNA‑u50535 decreased lung cancer cell proliferation and migration, induced G0/G1 phase arrest and promoted cell apoptosis. Western blot and luciferase reporter gene assays demonstrated that lncRNA‑u50535 overexpression increased the translation and transcription of CCL20. In addition, knockdown of lncRNA‑u50535 decreased CCL20, CCR6 and p‑ERK levels. The effects of lncRNA‑u50535 on cell proliferation and cell apoptosis were weakened when CCL20 was silenced. Overall, the present study demonstrated that lncRNA‑u50535 may function as an oncogene in lung cancer progression by regulating CCL20/ERK signaling.

Regulation of ezrin tension by S-nitrosylation mediates non-small cell lung cancer invasion and metastasis

Cancer invasion and metastasis depend on accurate and rapid modulation of both chemical and mechanical activities. The S-nitrosylation (SNO) of membrane cytoskeletal cross-linker protein ezrin may regulate the malignant process in a tension-dependent manner. Methods: The level of nitrosylated ezrin in non-small cell lung cancer (NSCLC) tissues and A549 cell line were evaluated by biotin-switch assay. A few cysteine mutated plasmids of ezrin were used to identify active site for SNO. Newly designed ezrin or mutated-ezrin tension probes based on Förster resonance energy transfer (FRET) theory were applied to visually observe real-time tension changes. Cytoskeleton depolymerizing and motor molecular inhibiting experiments were performed to reveal the alternation of the mechanical property of ezrin after SNO. Transwell assays and xenograft mouse model were used to assess aggressiveness of A549 cells in different groups. Fluorescent staining was also applied to examine cellular location and structures. Results: High inducible nitric oxide synthase (iNOS) levels were observed to induce ezrin-SNO, and then promote malignant behaviors of NSCLC cells both in vitro and in vivo. Cys¹¹⁷ was identified as the only active site for ezrin-SNO. Meanwhile, an increased level of ezrin tension was observed after iNOS-induced SNO. Enhanced ezrin tension was positively correlated with aggressiveness of NSCLC. Moreover, Microfilament (MF) forces instead of microtubule (MT) forces played dominant roles in modulating ezrin tension, especially after ezrin nitrosylation. Conclusion: This study revealed a SNO-associated mechanism underlying the mechanical tension of ezrin. Ezrin-SNO promotes NSCLC cells invasion and metastasis through facilitating mechanical transduction from the cytoskeleton to the membrane. These studies implicate the therapeutic potential by targeting ezrin in the inhibition NSCLC invasion and metastasis.

Targeting CXCL12/CXCR4 Axis in Tumor Immunotherapy

Chemokines, which have chemotactic abilities, are comprised of a family of small cytokines with 8-10 kilodaltons. Chemokines work in immune cells by trafficking and regulating cell proliferation, migration, activation, differentiation, and homing. CXCR-4 is an alpha-chemokine receptor specific for stromal-derived-factor-1 (SDF-1, also known as CXCL12), which has been found to be expressed in more than 23 different types of cancers. Recently, the SDF-1/CXCR-4 signaling pathway has emerged as a potential therapeutic target for human tumor because of its critical role in tumor initiation and progression by activating multiple signaling pathways, such as ERK1/2, ras, p38 MAPK, PLC/ MAPK, and SAPK/ JNK, as well as regulating cancer stem cells. CXCL12/CXCR4 antagonists have been produced, which have shown encouraging results in anti-cancer activity. Here, we provide a brief overview of the CXCL12/CXCR4 axis as a molecular target for cancer treatment. We also review the potential utility of targeting CXCL12/CXCR4 axis in combination of immunotherapy and/or chemotherapy based on up-to-date literature and ongoing research progress.

CXCR4 Based Therapeutics for Non-Small Cell Lung Cancer (NSCLC)

Lung cancer is the second most common malignancy. Unfortunately, despite advances in multimodality therapeutics for the disease, the overall five-year survival rate among newly diagnosed lung cancer patients remains in the range region of 15%. In addition, although immune checkpoint inhibitors are increasingly being incorporated into lung cancer treatment protocols, the proportion of patients that respond to these agents remains low and the duration of response is often short. Therefore, novel methodologies to enhance the efficacy of immunotherapy in lung cancer are highly desirable. Chemokines are small chemotactic cytokines that interact with their 7 transmembrane G-protein⁻coupled receptors, to guide immune cell trafficking in the body under both physiologic and pathologic conditions. Tumor cells highjack a small repertoire of the chemokine/chemokine receptor system and utilize it in a manner that benefits local tumor growth and distant spread. The chemokine receptor, CXCR4 is expressed in over 30 types of malignant tumors and, through interaction with its ligand CXCL12, was shown exert pleotropic pro-tumorigenic effects. In this review, the pathologic roles that CXCL12/CXCR4 play in lung cancer propagation are presented. Furthermore, the challenges and potential benefits of incorporating drugs that target CXCL12/CXCR4 into immune-based lung cancer therapeutic protocols are discussed.

Role of CCL20/CCR6 and the ERK signaling pathway in lung adenocarcinoma

Previous studies have revealed that carcinoma-associated fibroblasts communicate microenvironment-derived signals through chemokine/chemokine receptor interaction, resulting in carcinogenesis. C-C motif chemokine ligand 20 (CCL20)/C-C motif chemokine receptor 6 (CCR6) interactions are involved in the pathogenesis of colonic malignancies. The present study aimed to characterize the roles of CCL20/CCR6 and the extracellular signal-regulated kinase (ERK) signaling pathway in lung adenocarcinoma growth. Lung adenocarcinoma samples obtained at surgery were assessed for the expression, tissue localization and production of CCL20/CCR6. In addition, colony formation, ERK signaling and chemokine production were measured to assess the responsiveness of the A549 cell line to CCL20 stimulation. CCL20 and CCR6 were found to be highly expressed in the majority of samples in the recurrence group (76 and 66%, respectively). The staining indexes of CCL20 and CCR6 in the recurrence group were 149.3 and 134.4, respectively, which were significantly higher than those in the non-recurrence group (57.2 and 58.0, respectively); the protein and mRNA expression levels determined by western blot and reverse transcription-quantitative polymerase chain reaction were also found to be high in the recurrence group For A549 cells, the colony-forming capacity was increased by CCL20 stimulation, and this effect was dependent in part on ERK phosphorylation. Collectively, the findings suggest that CCR6 and CCL20 may serve a role in lung adenocarcinoma, leading to proliferation and migration via autocrine or paracrine mechanisms. The disruption of CCL20/CCR6 interactions may be a promising strategy for the treatment of cancer.

Aging of the immune system: Focus on inflammation and vaccination

Major advances in preventing, delaying, or curing individual pathologies are responsible for an increasingly long life span in the developed parts of our planet, and indeed reaching eight to nine decades of life is nowadays extremely frequent. However, medical and sanitary advances have not prevented or delayed the underlying cause of the disparate pathologies occurring in the elderly: aging itself. The identification of the basis of the aging processes that drives the multiple pathologies and loss of function typical of older individuals is a major challenge in current aging research. Among the possible causes, an impairment of the immune system plays a major role, and indeed numerous studies have described immunological changes which occur with age. Far from the intention of being exhaustive, this review will focus on recent advances and views on the role that modifications of cell signalling and remodelling of the immune response play during human aging and longevity, paying particular attention to phenomena which are linked to the so called inflammaging process, such as dysregulation of innate immunity, altered T-cell or B-cell maturation and differentiation, as well as to the implications of immune aging for vaccination strategies in the elderly.

Oncogenic roles and drug target of CXCR4/CXCL12 axis in lung cancer and cancer stem cell

Although the great progress has been made in diagnosis and therapeutic in lung cancer, it induces the most cancer death worldwide in both males and females. Chemokines, which have chemotactic abilities, contain up to 50 family members. By binding to G protein-coupled receptors (GPCR), holding seven-transmembrane domain, they function in immune cell trafficking and regulation of cell proliferation, differentiation, activation, and migration, homing under both physiologic and pathologic conditions. The alpha-chemokine receptor CXCR4 for the alpha-chemokine stromal cell-derived-factor-1 (SDF-1) is most widely expressed by tumors. In addition to human tissues of the bone marrow, liver, adrenal glands, and brain, the CXC chemokine SDF-1 or CXCL12 is also highly expressed in lung cancer tissues and is associated with lung metastasis. Lung cancer cells have the capabilities to utilize and manipulate the CXCL12/CXCR system to benefit growth and distant spread. CXCL12/CXCR4 axis is a major culprit for lung cancer and has a crucial role in lung cancer initiation and progression by activating cancer stem cell. This review provides an evaluation of CXCL12/CXCR4 as the potential therapeutic target for lung cancers; it also focuses on the synergistic effects of inhibition of CXCL12/CXCR4 axis and immunotherapy as well as chemotherapy. Together, CXCL12/CXCR4 axis can be a potential therapeutic target for lung cancers and has additive effects with immunotherapy.

Characterization of novel markers of senescence and their prognostic potential in cancer

Cellular senescence is a terminal differentiation state that has been proposed to have a role in both tumour suppression and ageing. This view is supported by the fact that accumulation of senescent cells can be observed in response to oncogenic stress as well as a result of normal organismal ageing. Thus, identifying senescent cells in in vivo and in vitro has an important diagnostic and therapeutic potential. The molecular pathways involved in triggering and/or maintaining the senescent phenotype are not fully understood. As a consequence, the markers currently utilized to detect senescent cells are limited and lack specificity. In order to address this issue, we screened for plasma membrane-associated proteins that are preferentially expressed in senescent cells. We identified 107 proteins that could be potential markers of senescence and validated 10 of them (DEP1, NTAL, EBP50, STX4, VAMP3, ARMX3, B2MG, LANCL1, VPS26A and PLD3). We demonstrated that a combination of these proteins can be used to specifically recognize senescent cells in culture and in tissue samples and we developed a straightforward fluorescence-activated cell sorting-based detection approach using two of them (DEP1 and B2MG). Of note, we found that expression of several of these markers correlated with increased survival in different tumours, especially in breast cancer. Thus, our results could facilitate the study of senescence, define potential new effectors and modulators of this cellular mechanism and provide potential diagnostic and prognostic tools to be used clinically.

CXCR4/CXCL12 axis in non small cell lung cancer (NSCLC) pathologic roles and therapeutic potential

Lung cancer is the second most common malignancy and the leading cause of cancer-related death in the western world. Moreover, despite advances in surgery, chemotherapy and radiotherapy, the death rate from lung cancer remains high and the reported overall five-year survival rate is only 15%. Thus, novel treatments for this devastating disease are urgently needed. Chemokines, a family of 48 chemotactic cytokines interacts with their 7 transmembrane G-protein-coupled receptors, to guide immune cell trafficking in the body under both physiologic and pathologic conditions. Tumor cells, which express a relatively restricted repertoire of chemokine and chemokine receptors, utilize and manipulate the chemokine system in a manner that benefits both local tumor growth and distant dissemination. Among the 19 chemokine receptors, CXCR4 is the receptor most widely expressed by malignant tumors and whose role in tumor biology is most thoroughly studied. The chemokine CXCL12, which is the sole ligand of CXCR4, is highly expressed in primary lung cancer as well as in the bone marrow, liver, adrenal glands and brain, which are all sites for lung cancer metastasis. This review focuses on the pathologic role of the CXCR4/CXCL12 axis in NSCLC and on the potential therapeutic implication of targeting this axis for the treatment of NSCLC.

[The advancement of cancer-associated fibroblasts in lung cancer]

癌相关成纤维细胞（cancer-associated fibroblasts, CAFs）是肿瘤组织中被癌细胞激活的成纤维细胞，具有成肌纤维细胞的特性。CAFs表型恶性转换与肿瘤演进密切相关，同时CAFs是肿瘤微环境的主要组织成分。本文主要从以下方面结合肺癌进行综述：①CAFs的来源及其形态学特征，CAFs异质性及其表型时、空转换的临床意义；②CAFs的研究现状及临床应用中的问题；③CAFs与肺癌侵袭与转移的关系；④CAFs对肺癌预后及其治疗的影响。

Involvement of CCR6/CCL20/IL-17 axis in NSCLC disease progression

Objectives

Autocrine and paracrine chemokine/chemokine receptor-based interactions promote non-small-cell-lung-cancer (NSCLC) carcinogenesis. CCL20/CCR6 interactions are involved in prostatic and colonic malignancy pathogenesis. The expression and function of CCL20/CCR6 and its related Th-17 type immune response in NSCLC is not yet defined. We sought to characterize the role of the CCL20/CCR6/IL-17 axis in NSCLC tumor growth.

Methods

A specialized histopathologist blindly assessed CCL20/CCR6 expression levels in 49 tissue samples of NSCLC patients operated in our department. Results were correlated to disease progression. Colony assays, ERK signaling and chemokine production were measured to assess cancer cell responsiveness to CCL20 and IL-17 stimulation.

Results

CCL20 was highly expressed in the majority (38/49, 77.5%) of tumor samples. Only a minority of samples (8/49, 16.5%) showed high CCR6 expression. High CCR6 expression was associated with a shorter disease-free survival (P = 0.008) and conferred a disease stage-independent 4.87-fold increased risk for disease recurrence (P = 0.0076, CI 95% 1.52–15.563). Cancerous cell colony-forming capacity was increased by CCL20 stimulation; this effect was dependent in part on ERK phosphorylation and signaling. IL-17 expression was detected in NSCLC; IL-17 potentiated the production of CCL20 by cancerous cells.

Conclusion

Our findings suggest that the CCL20/CCR6 axis promotes NSCLC disease progression. CCR6 is identified as a potential new prognostic marker and the CCL20/CCR6/IL-17 axis as a potential new therapeutic target. Larger scale studies are required to consolidate these observations.

Epithelial-mesenchymal transition induced by senescent fibroblasts

Depending on the cell type and tissue environment, epithelial and mesenchymal cell phenotypes are not static and can be highly dynamic. Epithelial-mesenchymal transitions (EMTs) and reverse EMTs provide flexibility during embryogenesis. While EMTs are a critical normal process during development and wound healing, properties of the EMT have been implicated in human pathology, particularly cancer metastasis. A normal undamaged epithelium does not typically exhibit features of an EMT. However, particularly under the influence of the surrounding microenvironment, cancer cells may reactivate developmental phenotypes out of context in the adult. This reactivation, such as the EMT, can facilitate tumor cell invasion and metastasis, and therefore is a major mechanism of tumor progression. Conversely, cellular senescence, which is associated with aging, is a process by which cells enter a state of permanent cell cycle arrest, thereby constituting a potent tumor suppressive mechanism. However, accumulating evidence shows that senescent cells can have deleterious effects on the tissue microenvironment. The most significant of these effects is the acquisition of a senescence-associated secretory phenotype (SASP) that turns senescent fibroblasts into pro-inflammatory cells having the ability to promote tumor progression, in part by inducing an EMT in nearby epithelial cells. Here, we summarize the potential impacts of SASP factors, particularly interleukins, on tissue microenvironments and their ability to stimulate tumor progression through induction of an EMT.

S100A8/A9 activate key genes and pathways in colon tumor progression

The tumor microenvironment plays an important role in modulating tumor progression. Earlier, we showed that S100A8/A9 proteins secreted by myeloid-derived suppressor cells (MDSC) present within tumors and metastatic sites promote an autocrine pathway for accumulation of MDSC. In a mouse model of colitis-associated colon cancer, we also showed that S100A8/A9-positive cells accumulate in all regions of dysplasia and adenoma. Here we present evidence that S100A8/A9 interact with RAGE and carboxylated glycans on colon tumor cells and promote activation of MAPK and NF-κB signaling pathways. Comparison of gene expression profiles of S100A8/A9-activated colon tumor cells versus unactivated cells led us to identify a small cohort of genes upregulated in activated cells, including Cxcl1, Ccl5 and Ccl7, Slc39a10, Lcn2, Zc3h12a, Enpp2, and other genes, whose products promote leukocyte recruitment, angiogenesis, tumor migration, wound healing, and formation of premetastatic niches in distal metastatic organs. Consistent with this observation, in murine colon tumor models we found that chemokines were upregulated in tumors, and elevated in sera of tumor-bearing wild-type mice. Mice lacking S100A9 showed significantly reduced tumor incidence, growth and metastasis, reduced chemokine levels, and reduced infiltration of CD11b(+)Gr1(+) cells within tumors and premetastatic organs. Studies using bone marrow chimeric mice revealed that S100A8/A9 expression on myeloid cells is essential for development of colon tumors. Our results thus reveal a novel role for myeloid-derived S100A8/A9 in activating specific downstream genes associated with tumorigenesis and in promoting tumor growth and metastasis.

Senescent cells as a source of inflammatory factors for tumor progression

Cellular senescence, which is associated with aging, is a process by which cells enter a state of permanent cell cycle arrest, therefore constituting a potent tumor suppressive mechanism. Recent studies show that, despite the beneficial effects of cellular senescence, senescent cells can also exert harmful effects on the tissue microenvironment. The most significant of these effects is the acquisition of a senescent-associated secretory phenotype (SASP), which entails a striking increase in the secretion of pro-inflammatory cytokines. Here, we summarize our knowledge of the SASP and the impact it has on tissue microenvironments and ability to stimulate tumor progression.

The senescence-associated secretory phenotype: the dark side of tumor suppression

Cellular senescence is a tumor-suppressive mechanism that permanently arrests cells at risk for malignant transformation. However, accumulating evidence shows that senescent cells can have deleterious effects on the tissue microenvironment. The most significant of these effects is the acquisition of a senescence-associated secretory phenotype (SASP) that turns senescent fibroblasts into proinflammatory cells that have the ability to promote tumor progression.

Intratumoral cytokines/chemokines/growth factors and tumor infiltrating dendritic cells: friends or enemies?

The tumor microenvironment consists of a variable combination of tumor cells, stromal fibroblasts, endothelial cells and infiltrating leukocytes, such as macrophages, T lymphocytes, and dendritic cells. A variety of cytokines, chemokines and growth factors are produced in the local tumor environment by different cells accounting for a complex cell interaction and regulation of differentiation, activation, function and survival of multiple cell types. The interaction between cytokines, chemokines, growth factors and their receptors forms a comprehensive network at the tumor site, which is primary responsible for overall tumor progression and spreading or induction of antitumor immune responses and tumor rejection. Although the general thought is that dendritic cells are among the first cells migrating to the tumor site and recognizing tumor cells for the induction of specific antitumor immunity, the clinical relevance of dendritic cells at the site of the tumor remains a matter of debate regarding their role in the generation of successful antitumor immune responses in human cancers. While several lines of evidence suggest that intratumoral dendritic cells play an important role in antitumor immune responses, understanding the mechanisms of dendritic cell/tumor cell interaction and modulation of activity and function of different dendritic cell subtypes at the tumor site is incomplete. This review is limited to discussing the role of intratumoral cytokine network in the understanding immunobiology of tumor-associated dendritic cells, which seems to possess different regulatory functions at the tumor site.