Complement 5a Enhances Hepatic Metastases of Colon Cancer via Monocyte Chemoattractant Protein-1-mediated Inflammatory Cell Infiltration

Molecular recognition and interaction between human plasminogen Kringle 5 and A2M domain in human complement C5 by biospecific methods coupled with molecular dynamics simulation

The potent angiogenesis inhibitor known as human plasminogen Kringle 5 has shown promise in the treatment of vascular disorders and malignancies. The study aimed to investigate the recognition and interaction between Kringle 5 and the A2M domain of human complement component C5 using bio-specific methodologies and molecular dynamics (MD) simulation. Initially, the specific interaction between Kringle 5 and A2M was confirmed and characterized through Ligand Blot and ELISA, yielding the dissociation constant (Kd) of 1.70 × 10-7 mol/L. Then, Kringle 5 showcased a dose-dependent inhibition of the production of C5a in lung cancer A549 cells, consequently impeding their proliferation and migration. Following the utilization of frontal affinity chromatography (FAC), it was revealed that there exists a singular binding site with the binding constant (Ka) of 3.79 × 105 L/mol. Following the implementation of homology modeling and MD optimization, the detailed results indicate that only a specific segment of the N-terminal structure of the A2M molecule engages in interaction with Kringle 5 throughout the binding process and the principal driving forces encompass electrostatic force, hydrogen bonding, and van der Waals force. In conclusion, the A2M domain of human complement C5 emerges as a plausible binding target for Kringle 5 in vivo.

Association of complement components with risk of colorectal cancer: A systematic review and meta-analysis

BACKGROUND

Complement components could contribute to the tumor microenvironment and the systemic immune response. Nevertheless, their role in colorectal cancer (CRC) remains a contentious subject.

AIM

To elucidate the relationship between complement components and CRC risk and clinical characteristics.

METHODS

Searches were conducted in PubMed, the Cochrane Library, and the China National Knowledge Infrastructure database until June 1, 2023. We included cohort studies encompassing participants aged ≥ 18 years, investigating the association between complement components and CRC. The studies were of moderate quality or above, as determined by the Agency for Healthcare Research and Quality. The meta-analysis employed fixed-effects or random-effects models based on the I² test, utilizing risk ratio (RR) and their corresponding 95% confidence interval (CI) for outcomes. Sensitivity and subgroup analyses were performed to validate the robustness of the collective estimates and identify the source of heterogeneity.

RESULTS

Data from 15 studies, comprising 1631 participants that met the inclusion criteria, were included in the meta-analysis. Our findings indicated that protein levels of cluster of differentiation 46 (CD46) (RR = 3.66, 95%CI: 1.75-7.64, P < 0.001), CD59 (RR = 2.86, 95%CI: 1.36-6.01, P = 0.005), and component 1 (C1) (RR = 5.88, 95%CI: 1.75-19.73, P = 0.004) and serum levels of C3 (standardized mean difference = 1.82, 95%CI: 0.06-3.58, P = 0.040) were significantly elevated in patients with CRC compared to healthy controls. Strong expression of CD55 or CD59 was associated with a higher incidence of lymph node metastasis, whereas strong CD46 expression correlated with a higher incidence of tumor differentiation compared to low CD46 expression (P < 0.05 for all). Although specific pooled results demonstrated notable heterogeneity, subgroup analyses pointed to regional differences as the primary source of inconsistency among the studies.

CONCLUSION

Our analysis underscores that increased levels of specific complement components are associated with a heightened risk of CRC, emphasizing the potential significance of monitoring elevated complement component levels.

Enhancing prognostic prediction of invasive candidiasis among cancer patients with a serum C5a-based scoring model

PURPOSE

Invasive candidiasis poses a life-threatening risk, and early prognosis assessment is vital for timely interventions to reduce mortality. Serum C5a levels have recently been linked to prognosis, but confirmation in cancer patients is pending.

METHODS

We detected the concentrations of serum C5a in hospitalized cancer patients with invasive candidiasis from 2020 to 2023, and retrospectively analyzed the clinical data.

RESULTS

372 cases were included in this study, with a 90-day mortality rate of 21.8%. Candida albicans (48.7%) remained the predominant pathogen, followed by Candida glabrata (25.5%), Candida tropicalis (12.4%), and Candida parapsilosis (8.3%). Gastrointestinal cancer was the most diagnosed pathology type (37.6%). Serum C5a demonstrated a noteworthy correlation with 90-day mortality, and employing a cutoff value of 36.7 ng/ml revealed significantly higher 90-day mortality in low-C5a patients (41.2%) compared to high-C5a patients (6.3%) (p < 0.001). We also identified no source control, no surgery, metastasis, or chronic renal failure independently correlated with the 90-day mortality. Based on this, a prognostic model combining C5a and clinical parameters was constructed, which performed better than models built solely on C5a or clinical parameters. Furthermore, we weighted scores to each parameter in the model and presented diagnostic sensitivity and specificity corresponding to different score points calculated by the model.

CONCLUSION

We constructed a prognostic scoring model including serum C5a and clinical parameters, which would contribute to precise prognosis assessment and benefit the outcome among cancer patients.

Blockade of C5a receptor unleashes tumor-associated macrophage antitumor response and enhances CXCL9-dependent CD8+ T cell activity

Macrophages play a crucial role in shaping the immune state within the tumor microenvironment (TME) and are often influenced by tumors to hinder antitumor immunity. However, the underlying mechanisms are still elusive. Here, we observed abnormal expression of complement 5a receptor (C5aR) in human ovarian cancer (OC), and identified high levels of C5aR expression on tumor-associated macrophages (TAMs), which led to the polarization of TAMs toward an immunosuppressive phenotype. C5aR knockout or inhibitor treatment restored TAM antitumor response and attenuated tumor progression. Mechanistically, C5aR deficiency reprogrammed macrophages from a protumor state to an antitumor state, associating with the upregulation of immune response and stimulation pathways, which in turn resulted in the enhanced antitumor response of cytotoxic T cells in a manner dependent on chemokine (C-X-C motif) ligand 9 (CXCL9). The pharmacological inhibition of C5aR also improved the efficacy of immune checkpoint blockade therapy. In patients, C5aR expression associated with CXCL9 production and infiltration of CD8+ T cells, and a high C5aR level predicted poor clinical outcomes and worse benefits from anti-PD-1 therapy. Thus, our study sheds light on the mechanisms underlying the modulation of TAM antitumor immune response by the C5a-C5aR axis and highlights the potential of targeting C5aR for clinical applications.

Activation of the alternative complement pathway modulates inflammation in thoracic aortic aneurysm/dissection

Thoracic aortic aneurysm/dissection (TAAD) is a lethal vascular disease, and several pathological factors participate in aortic medial degeneration. We previously discovered that the complement C3a-C3aR axis in smooth muscle cells promotes the development of thoracic aortic dissection (TAD) through regulation of matrix metalloproteinase 2. However, discerning the specific complement pathway that is activated and elucidating how inflammation of the aortic wall is initiated remain unknown. We ascertained that the plasma levels of C3a and C5a were significantly elevated in patients with TAD and that the levels of C3a, C4a, and C5a were higher in acute TAD than in chronic TAD. We also confirmed the activation of the complement in a TAD mouse model. Subsequently, knocking out Cfb (Cfb) or C4 in mice with TAD revealed that the alternative pathway and Cfb played a significant role in the TAD process. Activation of the alternative pathway led to generation of the anaphylatoxins C3a and C5a, and knocking out their receptors reduced the recruitment of inflammatory cells to the aortic wall. Moreover, we used serum from wild-type mice or recombinant mice Cfb as an exogenous source of Cfb to treat Cfb KO mice and observed that it exacerbated the onset and rupture of TAD. Finally, we knocked out Cfb in the FBN1C1041G/+ Marfan-syndrome mice and showed that the occurrence of TAA was reduced. In summary, the alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.NEW & NOTEWORTHY The alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.

The Role of the Complement in Clear Cell Renal Carcinoma (ccRCC)-What Future Prospects Are There for Its Use in Clinical Practice?

In recent years, the first-line available therapeutic options for metastatic renal cell carcinoma (mRCC) have radically changed with the introduction into clinical practice of new immune checkpoint inhibitor (ICI)-based combinations. Many efforts are focusing on identifying novel prognostic and predictive markers in this setting. The complement system (CS) plays a central role in promoting the growth and progression of mRCC. In particular, mRCC has been defined as an "aggressive complement tumor", which encompasses a group of malignancies with poor prognosie and highly expressed complement components. Several preclinical and retrospective studies have demonstrated the negative prognostic role of the complement in mRCC; however, there is little evidence on its possible role as a predictor of the response to ICIs. The purpose of this review is to explore more deeply the physio-pathological role of the complement in the development of RCC and its possible future use in clinical practice as a prognostic and predictive factor.

The Yin Yang of Complement and Cancer

Cancer-related inflammation is a crucial component of the tumor microenvironment (TME). Complement activation occurs in cancer and supports the development of an inflammatory microenvironment. Complement has traditionally been considered a mechanism of immune resistance against cancer, and its activation is known to contribute to the cytolytic effects of antibody-based immunotherapeutic treatments. However, several studies have recently revealed that complement activation may exert protumoral functions by sustaining cancer-related inflammation and immunosuppression through different molecular mechanisms, targeting both the TME and cancer cells. These new discoveries have revealed that complement manipulation can be considered a new strategy for cancer therapies. Here we summarize our current understanding of the mechanisms by which the different elements of the complement system exert antitumor or protumor functions, both in preclinical studies and in human tumorigenesis. Complement components can serve as disease biomarkers for cancer stratification and prognosis and be exploited for tumor treatment.

Complement and coagulation cascades pathway-related signature as a predictor of immunotherapy in metastatic urothelial cancer

BACKGROUND

Immune checkpoint inhibitors (ICIs) have shown efficacy in patients with metastatic urothelial cancer (mUC), however, only a small subset of patients could benefit from ICIs. Identifying predictive biomarkers of ICIs in patients with mUC is clinical meaningful for patient stratification and administration.

METHODS

Clinical and transcriptomic data of mUC patients treated with ICIs from mUC cohort (IMvigor210 study) was utilized to explore the predictive biomarkers. LASSO Cox regression was performed to construct a predictive model. The predictive model was trained and tested in the mUC cohort, and then exploratively tested in clear cell renal cell carcinoma (ccRCC) and melanoma cohorts in which patients also received ICIs regimens.

RESULTS

The differentially expressed genes (DEGs) in complement and coagulation cascades pathway (CCCP) were mainly enriched in non-responders of ICIs in the mUC cohort. A CCCP risk score was constructed based on the DEGs in CCCP. Patients with a low-risk score were more responsive to ICIs and had better overall survival (OS) than those with a high-risk score in the training set (HR, 0.38; 95%CI, 0.27-0.53, P<0.001) and the test set (HR, 0.34; 95%CI, 0.17-0.71, P=0.003). The association between the CCCP risk score and OS remained significant in the multivariable cox regression by adjusting PD-L1 expression and TMB (P<0.05). In addition, there was no difference for OS in the bladder cancer patients without ICIs (TCGA-BLCA cohort, HR, 0.76, 95%CI, 0.49-1.18, P=0.22), suggesting a predictive but not prognostic effect of the risk score. For the exploratory analysis, consistent results were observed that low-risk group showed superior OS in ccRCC cohort (HR, 0.52, 95%CI, 0.37-0.75, P<0.001) and melanoma cohort (HR, 0.27, 95%CI, 0.12-0.62, P=0.001).

CONCLUSIONS

Our study showed that the CCCP risk score is an independent biomarker that predicts the efficacy of ICIs in mUC patients. The patients with a low-risk score tend to have a better response to ICIs and a longer life time probably due to the immune-activated TME. Further studies are needed to validate the clinical utility of the seven-gene signature.

The anaphylatoxin C5a: Structure, function, signaling, physiology, disease, and therapeutics

The complement system is one of the oldest known tightly regulated host defense systems evolved for efficiently functioning cell-based immune systems and antibodies. Essentially, the complement system acts as a pivot between the innate and adaptive arms of the immune system. The complement system collectively represents a cocktail of ∼50 cell-bound/soluble glycoproteins directly involved in controlling infection and inflammation. Activation of the complement cascade generates complement fragments like C3a, C4a, and C5a as anaphylatoxins. C5a is the most potent proinflammatory anaphylatoxin, which is involved in inflammatory signaling in a myriad of tissues. This review provides a comprehensive overview of human C5a in the context of its structure and signaling under several pathophysiological conditions, including the current and future therapeutic applications targeting C5a.

Exosomal proteins as a source of biomarkers in colon cancer-derived peritoneal carcinomatosis - A pilot study

PURPOSE

Peritoneal carcinomatosis (PC), metastasized from colorectal cancer (CRC), remains a highly lethal disease. Outcomes of PC is significantly influenced by the amount of intra-abdominal tumor burden and therefore diagnostic tests that facilitate earlier diagnosis could improve PC treatment and patient outcomes.

EXPERIMENTAL DESIGN

Using mass-spectrometry-based proteomics, we characterized the protein features of circulating exosomes in the context of CRC PC, CRC with liver metastasis, and primary CRC limited to the colon. We profiled exosomes isolated from patient plasma to identify exosome-associated protein cargoes released by these cancer types.

RESULTS

Analysis of the resulting data identified metastasis-specific exosome protein signatures. Bioinformatic analyses confirmed enrichment of proteins annotated to vesicle-associated processes and intracellular compartments, as well as representation of cancer hallmark functions and processes.

CONCLUSION AND CLINICAL RELEVANCE

This research yielded distinct protein profiles for the CRC patient groups and suggests the utility of plasma exosome proteomic analysis for a better understanding of PC development and metastasis.

Neutrophil-activating therapy for the treatment of cancer

Despite their cytotoxic capacity, neutrophils are often co-opted by cancers to promote immunosuppression, tumor growth, and metastasis. Consequently, these cells have received little attention as potential cancer immunotherapeutic agents. Here, we demonstrate in mouse models that neutrophils can be harnessed to induce eradication of tumors and reduce metastatic seeding through the combined actions of tumor necrosis factor, CD40 agonist, and tumor-binding antibody. The same combination activates human neutrophils in vitro, enabling their lysis of human tumor cells. Mechanistically, this therapy induces rapid mobilization and tumor infiltration of neutrophils along with complement activation in tumors. Complement component C5a activates neutrophils to produce leukotriene B4, which stimulates reactive oxygen species production via xanthine oxidase, resulting in oxidative damage and T cell-independent clearance of multiple tumor types. These data establish neutrophils as potent anti-tumor immune mediators and define an inflammatory pathway that can be harnessed to drive neutrophil-mediated eradication of cancer.

Environmental signals perceived by the brain abate pro-metastatic monocytes by dampening glucocorticoids receptor signaling

While positive social-behavioral factors predict longer survival in cancer patients, the underlying mechanisms are unknown. Since tumor metastasis are the major cancer mortality factor, we investigated how an enriched environment (EE) conductive to enhanced sensory, cognitive and motor stimulation impact metastatic progression in lungs following intravasation in the circulation. We find that mice housed in EE exhibited reduced number of lung metastatic foci compared to control mice housed in a standard environment (SE). Compared to SE mice, EE mice increased lung inflammation as early as 4 days after circulating tumor cells extravasation. The impact of environmental signals on lung metastasis is independent of adrenergic receptors signaling. By contrast, we find that serum corticosterone levels are lower in EE mice and that glucocorticoid receptor (GR) antagonist reduces the number of lung metastasis in SE mice. In addition, the difference of the number of lung metastasis between SE and EE mice is abolished when inflammatory monocytes are rendered deficient in GR signaling. This decreased GR signaling in inflammatory monocytes of SE mice results in an exacerbated inflammatory profile in the lung. Our study shows that not only EE reduces late stages of metastatic progression in lungs but disclose a novel anti-tumor mechanism whereby GR-dependent reprogramming of inflammatory monocytes can inhibit metastatic progression in lungs. Moreover, while inflammatory monocytes have been shown to promote cancer progression, they also have an anti-tumor effect, suggesting that their role is more complex than currently thought.

Platelets promote CRC by activating the C5a/C5aR1 axis via PSGL-1/JNK/STAT1 signaling in tumor-associated macrophages

Rationale: Platelets can influence the progression and prognosis of colorectal cancer (CRC) through multiple mechanisms, including crosstalk with tumor-associated macrophages (TAMs). However, the mechanisms underlying the crosstalk between platelets and TAMs remain unclear. The present study aimed to investigate the role of intratumoral platelets in regulating the function of TAMs and to identify the underlying mechanisms. Methods: The interaction of platelets with macrophages was assessed in the presence or absence of the indicated compounds in vivo. An azoxymethane/dextran sodium sulfate (AOM/DSS)-induced CRC mouse model was used to investigate the role of platelets in controlling CRC development. Multiplexed immunofluorescence staining, fluorescence-activated cell sorting (FACS), and RNA sequence analysis were used to examine the changes in TAMs. TAMs and bone marrow-derived macrophages (BMDMs) were treated with the indicated compounds or siRNA against specific targets, and the expression levels of signal transducer and activator of transcription 1 (STAT1), c-Jun N-terminal kinase (JNK), and P-selectin glycoprotein ligand-1 (PSGL-1) were measured by Western blotting. The mRNA expression levels of complement 5 (C5), complement 5a receptor 1 (C5ar1), Arginase 1 (Arg1) and Il10 were measured by real-time RT-PCR, and the complement 5a (C5a) concentration was measured by ELISA. The dual-luciferase reporter assay and ChIP assay were performed to examine the potential regulatory mechanisms of platelet induction of C5 transcription in TAMs. Results: In our study, we found that an increase in platelets exacerbated CRC development, while inhibiting platelet adhesion attenuated tumor growth. Platelets signal TAMs through P-selectin (CD62P) binding to PSGL-1 expressed on TAMs and activating the JNK/STAT1 pathway to induce the transcription of C5 and the release of C5a, shifting TAMs toward a protumor phenotype. Inhibiting the C5a/C5aR1 axis or PSGL-1 significantly reduced CRC growth. Conclusions: An increase in intratumoral platelets promoted CRC growth and metastasis by CD62P binding to PSGL-1 expressed on TAMs, leading to JNK/STAT1 signaling activation, which promoted C5 transcription and activated the C5a/C5aR1 axis in TAMs. Our study examined the mechanism of the crosstalk between platelets and TAMs to exacerbate CRC development and proposed a potential therapeutic strategy for CRC patients.

The effects of radiation therapy on the macrophage response in cancer

The efficacy of radiotherapy, a mainstay of cancer treatment, is strongly influenced by both cellular and non-cellular features of the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are a heterogeneous population within the TME and their prevalence significantly correlates with patient prognosis in a range of cancers. Macrophages display intrinsic radio-resistance and radiotherapy can influence TAM recruitment and phenotype. However, whether radiotherapy alone can effectively "reprogram" TAMs to display anti-tumor phenotypes appears conflicting. Here, we discuss the effect of radiation on macrophage recruitment and plasticity in cancer, while emphasizing the role of specific TME components which may compromise the tumor response to radiation and influence macrophage function. In particular, this review will focus on soluble factors (cytokines, chemokines and components of the complement system) as well as physical changes to the TME. Since the macrophage response has the potential to influence radiotherapy outcomes this population may represent a drug target for improving treatment. An enhanced understanding of components of the TME impacting radiation-induced TAM recruitment and function may help consider the scope for future therapeutic avenues to target this plastic and pervasive population.

Sensory neuron dysfunction in orthotopic mouse models of colon cancer

Reports of neurological sequelae related to colon cancer are largely restricted to rare instances of paraneoplastic syndromes, due to autoimmune reactions. Systemic inflammation associated with tumor development influences sensory neuron function in other disease models, though the extent to which this occurs in colorectal cancer is unknown. We induced orthotopic colorectal cancer via orthotopic injection of two colorectal cancer cell lines (MC38 and CT26) in two different mouse strains (C57BL/6 and Balb/c, respectively). Behavioral tests of pain sensitivity and activity did not detect significant alterations in sensory sensitivity or diminished well-being throughout tumor development. However, immunohistochemistry revealed widespread reductions in intraepidermal nerve fiber density in the skin of tumor-bearing mice. Though loss of nerve fiber density was not associated with increased expression of cell injury markers in dorsal root ganglia, lumbar dorsal root ganglia neurons of tumor-bearing animals showed deficits in mitochondrial function. These neurons also had reduced cytosolic calcium levels in live-cell imaging and reduced spontaneous activity in multi-electrode array analysis. Bulk RNA sequencing of DRGs from tumor-bearing mice detected activation of gene expression pathways associated with elevated cytokine and chemokine signaling, including CXCL10. This is consistent with the detection of CXCL10 (and numerous other cytokines, chemokines and growth factors) in MC38 and CT26 cell-conditioned media, and the serum of tumor-bearing mice. Our study demonstrates in a pre-clinical setting that colon cancer is associated with latent sensory neuron dysfunction and implicates cytokine/chemokine signaling in this process. These findings may have implications for determining risk factors and treatment responsiveness related to neuropathy in colorectal cancer.

Human Melanoma-Associated Mast Cells Display a Distinct Transcriptional Signature Characterized by an Upregulation of the Complement Component 3 That Correlates With Poor Prognosis

Cutaneous melanoma is one of the most aggressive human malignancies and shows increasing incidence. Mast cells (MCs), long-lived tissue-resident cells that are particularly abundant in human skin where they regulate both innate and adaptive immunity, are associated with melanoma stroma (MAMCs). Thus, MAMCs could impact melanoma development, progression, and metastasis by secreting proteases, pro-angiogenic factors, and both pro-inflammatory and immuno-inhibitory mediators. To interrogate the as-yet poorly characterized role of human MAMCs, we have purified MCs from melanoma skin biopsies and performed RNA-seq analysis. Here, we demonstrate that MAMCs display a unique transcriptome signature defined by the downregulation of the FcεRI signaling pathway, a distinct expression pattern of proteases and pro-angiogenic factors, and a profound upregulation of complement component C3. Furthermore, in melanoma tissue, we observe a significantly increased number of C3+ MCs in stage IV melanoma. Moreover, in patients, C3 expression significantly correlates with the MC-specific marker TPSAB1, and the high expression of both markers is linked with poorer melanoma survival. In vitro, we show that melanoma cell supernatants and tumor microenvironment (TME) mediators such as TGF-β, IL-33, and IL-1β induce some of the changes found in MAMCs and significantly modulate C3 expression and activity in MCs. Taken together, these data suggest that melanoma-secreted cytokines such as TGF-β and IL-1β contribute to the melanoma microenvironment by upregulating C3 expression in MAMCs, thus inducing an MC phenotype switch that negatively impacts melanoma prognosis.

Complement activation in cancer: Effects on tumor-associated myeloid cells and immunosuppression

Cancer-related inflammation plays a central role in the establishment of tumor-promoting mechanisms. Tumor-associated myeloid cells, which engage in complex interactions with cancer cells, as well as stromal and tumor immune infiltrating cells, promote cancer cell proliferation and survival, angiogenesis, and the generation of an immunosuppressive microenvironment. The complement system is one of the inflammatory mechanisms activated in the tumor microenvironment. Beside exerting anti-tumor mechanisms such as complement-dependent cytotoxicity and phagocytosis induced by therapeutic monoclonal antibodies, the complement system may promote immunosuppression and tumor growth and invasiveness, in particular, through the anaphylatoxins which target both leukocytes and cancer cells. In this review, we will discuss complement-mediated mechanisms acting on leukocytes, in particular on cells of the myelomonocytic cell lineage (macrophages, neutrophils, myeloid derived suppressor cells), which promote myeloid cell recruitment and functional skewing, leading to immunosuppression and resistance to tumor-specific immunity. Pre-clinical studies, which have elucidated the role of complement in activating pro-tumor mechanisms in myeloid cells, showing the relevance of these mechanisms in human, and therapeutic approaches based on complement targeting support the hypothesis that complement directly and indirectly interferes with many of the effector pathways associated with the cancer-immunity cycle, suggesting the relevance of complement targeting to improve responses to immunotherapeutic approaches.

Complement System: An Immunotherapy Target in Colorectal Cancer

Colorectal cancer (CRC) is the third most common malignant tumor and the second most fatal cancer worldwide. Several parts of the immune system contribute to fighting cancer including the innate complement system. The complement system is composed of several players, namely component molecules, regulators and receptors. In this review, we discuss the complement system activation in cancer specifically CRC and highlight the possible interactions between the complement system and the various TME components. Additionally, the role of the complement system in tumor immunity of CRC is reviewed. Hence, such work could provide a framework for researchers to further understand the role of the complement system in CRC and explore the potential therapies targeting complement activation in solid tumors such as CRC.

Complement C5a induces the formation of neutrophil extracellular traps by myeloid-derived suppressor cells to promote metastasis

Myeloid-derived suppressor cells (MDSCs) play a major role in cancer progression. In this study, we investigated the mechanisms by which complement C5a increases the capacity of polymorphonuclear MDSCs (PMN-MDSCs) to promote tumor growth and metastatic spread. Stimulation of PMN-MDSCs with C5a favored the invasion of cancer cells via a process dependent on the formation of neutrophil extracellular traps (NETs). NETosis was dependent on the production of high mobility group box 1 (HMGB1) by cancer cells. Moreover, C5a induced the surface expression of the HMGB1 receptors TLR4 and RAGE in PMN-MDSCs. In a mouse lung metastasis model, inhibition of C5a, C5a receptor-1 (C5aR1) or NETosis reduced the number of circulating-tumor cells (CTCs) and the metastatic burden. In support of the translational relevance of these findings, C5a was able to stimulate migration and NETosis in PMN-MDSCs obtained from lung cancer patients. Furthermore, myeloperoxidase (MPO)-DNA complexes, as markers of NETosis, were elevated in lung cancer patients and significantly correlated with C5a levels. In conclusion, C5a induces the formation of NETs from PMN-MDSCs in the presence of cancer cells, which may facilitate cancer cell dissemination and metastasis.

Characterization of Biomarkers in Colorectal Cancer Liver Metastases as a Prognostic Tool

BACKGROUND

Unfortunately, the majority of patients with colorectal cancer liver metastases (CRCLM) experience disease recurrence following hepatic surgery. The key challenge is therefore optimal patient selection, which currently relies on anatomical and clinical parameters. Exploring a potential molecular signature may be predictive for seeing a clinical benefit from CRCLM resection.

METHODS

Consecutive patients who underwent CRCLM resection at our medical center between 2006 and 2016 were divided into cohorts of "good prognosis" (GP) or "poor prognosis" (PP) based on the time interval between their resection and disease recurrence. Proteomic analysis was performed on the surgical specimen and correlation analysis was carried out with demographics and clinical outcomes.

RESULTS

Proteomic analysis revealed 99 differentially expressed proteins of which a third were associated with extracellular matrix (ECM) pathways as the matrix metalloproteinases (MMPs). Multivariate analysis yielded a statistically differential proteomic pattern between the cohort regardless of perioperative treatment.

CONCLUSION

Our results indicate a different proteomic landscape in the cohort of patients who had a clinical benefit from CRCLM resection which appears to be correlated with ECM pathways. Further prospective studies are needed to define the role of ECM pathways in prognostics and patient selection for surgical procedures for CRCLM.

Losartan Blocks Osteosarcoma-Elicited Monocyte Recruitment, and Combined With the Kinase Inhibitor Toceranib, Exerts Significant Clinical Benefit in Canine Metastatic Osteosarcoma

PURPOSE

There is increasing recognition that progress in immuno-oncology could be accelerated by evaluating immune-based therapies in dogs with spontaneous cancers. Osteosarcoma (OS) is one tumor for which limited clinical benefit has been observed with the use of immune checkpoint inhibitors. We previously reported the angiotensin receptor blocker losartan suppressed metastasis in preclinical mouse models through blockade of CCL2-CCR2 monocyte recruitment. Here we leverage dogs with spontaneous OS to determine losartan's safety and pharmacokinetics associated with monocyte pharmacodynamic endpoints, and assess its antitumor activity, in combination with the kinase inhibitor toceranib.

PATIENTS AND METHODS

CCL2 expression, monocyte infiltration, and monocyte recruitment by human and canine OS tumors and cell lines were assessed by gene expression, ELISA, and transwell migration assays. Safety and efficacy of losartan-toceranib therapy were evaluated in 28 dogs with lung metastatic OS. Losartan PK and monocyte PD responses were assessed in three dose cohorts of dogs by chemotaxis, plasma CCL2, and multiplex cytokine assays, and RNA-seq of losartan-treated human peripheral blood mononuclear cells.

RESULTS

Human and canine OS cells secrete CCL2 and elicit monocyte migration, which is inhibited by losartan. Losartan PK/PD studies in dogs revealed that a 10-fold-higher dose than typical antihypertensive dosing was required for blockade of monocyte migration. Treatment with high-dose losartan and toceranib was well-tolerated and induced a clinical benefit rate of 50% in dogs with lung metastases.

CONCLUSIONS

Losartan inhibits the CCL2-CCR2 axis, and in combination with toceranib, exerts significant biological activity in dogs with metastatic osteosarcoma, supporting evaluation of this drug combination in patients with pediatric osteosarcoma.

C3a and C5a facilitates the metastasis of myeloma cells by activating Nrf2

Multiple myeloma (MM) is still an incurable hematological malignancy, with even poorer prognosis in MM patients with distant invasion. The present study was designed to explore the effects of C3a and C5a on the migration, invasion, and adhesion of MM tumor cells and to investigate the underlying mechanisms. As a result, the levels of C3a and C5a in plasma of MM patients were significantly higher than those of healthy donors. Consistently, the expression of C3a and C5a receptors on myeloma cells of MM patients was also significantly higher than that on sorted plasma cells of normal donors. C3a and C5a have been confirmed to increase the migration, invasion and adhesion of MM cell lines by activating the MEK/ERK pathway and increasing the nuclear transfer of Nrf2 in vitro. Moreover, the MM cell line U266 with Nrf2 downregulation was incubated with C3a and C5a, followed by injection into the tail vein of NOD-SCID mice. We found that Nrf2 downregulation attenuated the migration of anaphylatoxin C3a and C5a to MM tumor cells in bone marrow, liver and lung in vivo. In conclusion, our results indicate that activation of the complement cascade in MM patients may contribute to the migration, invasion and adhesion of MM cells, and this type of tumor cells dissemination in MM is, at least partially, regulated by Nrf2. Thereby, complement suppression or Nrf2 downregulation might offer a novel therapeutic opportunity for MM.

Type III TGF-β Receptor Down-Regulation Promoted Tumor Progression via Complement Component C5a Induction in Hepatocellular Carcinoma

Simple Summary

The clinical implications of TGFβR3 downregulation are currently unknown in hepatocellular carcinoma (HCC). Clinically, we identified that HCC patients with low expression levels of tumoral TGFβR3 exhibited significantly late tumor stages and shortened survival outcomes. Moreover, HCC patients developed lower plasma levels of TGFβR3 (sTGFβR3) (8.9 ng/mL) compared to healthy individuals (15.9 ng/mL), which represented a potential diagnostic marker. Similar to tumoral TGFβR3, low levels of plasma sTGFβR3 are also associated with poor clinical outcomes in HCC. To determine its tumor-suppressing capacities, continuous injection of sTGFβR3 in an orthotopic liver tumor model was performed, resulting in 2-fold tumor volume reduction compared to control. Decreased expression of TGFβR3 induced the upregulation of tumoral complement component C5a in HCC, which was found to contribute to poor clinical outcomes and promote tumor progression via a novel function in activating the tumor-promoting macrophages.

Abstract

Background and Aims—Transforming growth factor-beta (TGF-β) signaling orchestrates tumorigenesis and one of the family members, TGF-β receptor type III (TGFβR3), are distinctively under-expressed in numerous malignancies. Currently, the clinical impact of TGFβR3 down-regulation and the underlying mechanism remains unclear in hepatocellular carcinoma (HCC). Here, we aimed to identify the tumor-promoting roles of decreased TGFβR3 expression in HCC progression. Materials and Methods—For clinical analysis, plasma and liver specimens were collected from 100 HCC patients who underwent curative resection for the quantification of TGFβR3 by q-PCR and ELISA. To study the tumor-promoting mechanism of TGFβR3 downregulation, HCC mouse models and TGFβR3 knockout cell lines were applied. Results—Significant downregulation of TGFβR3 and its soluble form (sTGFβR3) were found in HCC tissues and plasma compared to healthy individuals (p < 0.01). Patients with <9.4 ng/mL sTGFβR3 exhibited advanced tumor stage, higher recurrence rate and shorter disease-free survival (p < 0.05). The tumor-suppressive function of sTGFβR3 was further revealed in an orthotopic mouse HCC model, resulting in 2-fold tumor volume reduction. In TGFβR3 knockout hepatocyte and HCC cells, increased complement component C5a was observed and strongly correlated with shorter survival and advanced tumor stage (p < 0.01). Interestingly, C5a activated the tumor-promoting Th-17 response in tumor associated macrophages. Conclusion—TGFβR3 suppressed tumor progression, and decreased expression resulted in poor prognosis in HCC patients through upregulation of tumor-promoting complement C5a.

Complement in Tumourigenesis and the Response to Cancer Therapy

In recent years, our knowledge of the complement system beyond innate immunity has progressed significantly. A modern understanding is that the complement system has a multifaceted role in malignancy, impacting carcinogenesis, the acquisition of a metastatic phenotype and response to therapies. The ability of local immune cells to produce and respond to complement components has provided valuable insights into their regulation, and the subsequent remodeling of the tumour microenvironment. These novel discoveries have advanced our understanding of the immunosuppressive mechanisms supporting tumour growth and uncovered potential therapeutic targets. This review discusses the current understanding of complement in cancer, outlining both direct and immune cell-mediated roles. The role of complement in response to therapies such as chemotherapy, radiation and immunotherapy is also presented. While complement activities are largely context and cancer type-dependent, it is evident that promising therapeutic avenues have been identified, in particular in combination therapies.

"Complimenting the Complement": Mechanistic Insights and Opportunities for Therapeutics in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and a leading cause of death in the US and worldwide. HCC remains a global health problem and is highly aggressive with unfavorable prognosis. Even with surgical interventions and newer medical treatment regimens, patients with HCC have poor survival rates. These limited therapeutic strategies and mechanistic understandings of HCC immunopathogenesis urgently warrant non-palliative treatment measures. Irrespective of the multitude etiologies, the liver microenvironment in HCC is intricately associated with chronic necroinflammation, progressive fibrosis, and cirrhosis as precedent events along with dysregulated innate and adaptive immune responses. Central to these immunological networks is the complement cascade (CC), a fundamental defense system inherent to the liver which tightly regulates humoral and cellular responses to noxious stimuli. Importantly, the liver is the primary source for biosynthesis of >80% of complement components and expresses a variety of complement receptors. Recent studies implicate the complement system in liver inflammation, abnormal regenerative responses, fibrosis, carcinogenesis, and development of HCC. Although complement activation differentially promotes immunosuppressive, stimulant, and angiogenic microenvironments conducive to HCC development, it remains under-investigated. Here, we review derangement of specific complement proteins in HCC in the context of altered complement regulatory factors, immune-activating components, and their implications in disease pathogenesis. We also summarize how complement molecules regulate cancer stem cells (CSCs), interact with complement-coagulation cascades, and provide therapeutic opportunities for targeted intervention in HCC.

Integrative Analysis of Complement System to Prognosis and Immune Infiltrating in Colon Cancer and Gastric Cancer

Background

The complement system acts as an integral part of the innate immune response, which acts primarily to remove pathogens and injured cells. Emerging evidence has shown the activation of the immune regulatory function of complements in the tumor microenvironment (TME). We revealed the expression levels of various complements in human cancers and their role in tumor prognosis and immune infiltration.

Methods

The differential expression of complements was explored via the Tumor Immune Estimation Resource (TIMER) site and the Oncomine database. To investigate whether these differentially expressed complements have correlation with the prognosis of gastric cancer (GC) and colon cancer, their impact on survival was assessed using the PrognoScan database and Kaplan-Meier plotter. The correlations between complements and tumor immune-infiltrating levels and immune gene markers were statistically explored in TIMER based on Spearman's correlation coefficients and p-values.

Results

In two colon cancer cohorts, an increased expression level of DAF (CD55) has statistically significant correlation with poor disease-free survival (DFS). High C3, CR4, and C5aR1 expression levels were significantly related with poor prognosis in GC patients. In addition, C3, CR4, and C5aR1 expression was positively related to the tumor purity and infiltration levels of multiple immune cells in stomach adenocarcinoma (STAD). Moreover, the expression levels of C3, CR4, and C5aR1 were also strongly correlated with various immune marker sets, such as those of tumor-associated macrophages (TAMs), M1 and M2 macrophages, T cell exhaustion, Tregs, and DCs, in STAD. Additionally, CD55 has positive correlation with few immune cell infiltration levels in colon adenocarcinoma (COAD), but its correlation with immune marker sets was not statistically significant.

Conclusion

These findings confirm the relationship between various complements and tumor prognosis and immune infiltration in colon cancer and GC. CD55 may serve as an indicator on the survival prognosis of patients with colon cancer. Furthermore, as biomarkers for poor prognosis in GC, complements C3, CR4, and C5aR1 may provide potential biological targets for GC immunotherapy.

Complement activation promoted by the lectin pathway mediates C3aR-dependent sarcoma progression and immunosuppression

Complement has emerged as a component of tumor promoting inflammation. We conducted a systematic assessment of the role of complement activation and effector pathways in sarcomas. C3^-/-, MBL1/2^-/- and C4^-/- mice showed reduced susceptibility to 3-methylcholanthrene sarcomagenesis and transplanted sarcomas, whereas C1q and factor B deficiency had marginal effects. Complement 3a receptor (C3aR), but not C5aR1 and C5aR2, deficiency mirrored the phenotype of C3^-/- mice. C3 and C3aR deficiency were associated with reduced accumulation and functional skewing of tumor-associated macrophages, increased T cell activation and response to anti-PD-1 therapy. Transcriptional profiling of sarcoma infiltrating macrophages and monocytes revealed the enrichment of MHC II-dependent antigen presentation pathway in C3-deficient cells. In patients, C3aR expression correlated with a macrophage population signature and C3 deficiency-associated signatures predicted better clinical outcome. These results suggest that the lectin pathway and C3a/C3aR axis are key components of complement and macrophage-mediated sarcoma promotion and immunosuppression.

Properdin Is a Modulator of Tumour Immunity in a Syngeneic Mouse Melanoma Model

Background and Objectives: Tumours are often low immunogenic. The role of complement, an innate immune defence system, in tumour control has begun to be elucidated, but findings are conflicting. A role for properdin, an amplifier of complement activation, in tumour control has recently been implicated. Materials and Methods: Properdin-deficient and congenic wildtype mice were injected subcutaneously with B16F10 melanoma cells. Tumour mass and chemokine profile were assessed. The frequencies of CD45⁺CD11b⁺ Gr-1⁺ cells were determined from tumours and spleens, and CD206⁺ F4/80⁺ cells were evaluated in spleens. Sera were analysed for C5a, sC5b-9, and CCL2. Results: Whilst there was no difference in tumour growth at study endpoint, properdin-deficient mice had significantly fewer myeloid-derived suppressor cells (MDSCs) in their tumours and spleens. Splenic M2 type macrophages and serum levels of C5a, sC5b-9, and CCL2 were decreased in properdin-deficient compared to wildtype mice. Conclusions: The presence of intact complement amplification sustains an environment that lessens potential anti-tumour responses.

Monocyte Chemoattractant Protein-1 promotes cancer cell migration via c-Raf/MAPK/AP-1 pathway and MMP-9 production in osteosarcoma

Background

Osteosarcoma is generally reported among younger individuals and has a very poor prognosis, particularly for the development of metastasis. However, more effective metastatic biomarkers and therapeutic methods are absent. Monocyte chemoattractant protein-1 (MCP-1) is involved in cancer progression and inflammatory recruitment. Although previous studies have reported higher serum MCP-1 levels in patients with osteosarcoma, the role of MCP-1 in osteosarcoma progression remains to be addressed.

Methods

The osteosarcoma cell migratory ability was assessed by transwell migration assay. The MCP-1 and MMP-9 expression levels were analyzed by Western blot and qPCR. The signal activation was conducted by Western blot. The in vivo mouse experiment and tumor tissue array were performed to confirm our findings in vitro.

Results

The present study demonstrates that MCP-1 regulates cell mobility through matrix metalloproteinase (MMP)-9 expression in osteosarcoma cells. Moreover, MCP-1 promotes MMP-9 expression, cell migration, and cell invasion by mediating CCR2, c-Raf, MAPK, and AP-1 signal transduction. Using MCP-1 knockdown stable cell lines, we found that MCP-1 knockdown reduces MMP-9 expression and cell mobility. Finally, we found high MCP-1 expression levels in osteosarcoma specimens.

Conclusions

Our results provide prognostic value of MCP-1 in osteosarcoma by promoting MMP-9 expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01756-y.

Complement System: Promoter or Suppressor of Cancer Progression?

Constituent of innate immunity, complement is present in the tumor microenvironment. The functions of complement include clearance of pathogens and maintenance of homeostasis, and as such could contribute to an anti-tumoral role in the context of certain cancers. However, multiple lines of evidence show that in many cancers, complement has pro-tumoral actions. The large number of complement molecules (over 30), the diversity of their functions (related or not to the complement cascade), and the variety of cancer types make the complement-cancer topic a very complex matter that has just started to be unraveled. With this review we highlight the context-dependent role of complement in cancer. Recent studies revealed that depending of the cancer type, complement can be pro or anti-tumoral and, even for the same type of cancer, different models presented opposite effects. We aim to clarify the current knowledge of the role of complement in human cancers and the insights from mouse models. Using our classification of human cancers based on the prognostic impact of the overexpression of complement genes, we emphasize the strong potential for therapeutic targeting the complement system in selected subgroups of cancer patients.

C5aR1 is a master regulator in Colorectal Tumorigenesis via Immune modulation

Numerous factors have been claimed to play important roles in colorectal cancer (CRC) tumorigenesis, including myeloid-derived suppressor cells (MDSCs) and other immune cells, cytokines, and chemokines; however, the precise mechanisms of colorectal tumorigenesis remain elusive, and there is a lack of effective preventive treatments. Here, we investigated the role of complement system, a key regulator of immune surveillance and homeostasis, in colorectal tumorigenesis.

Methods: The prototypical CRC model was induced by combined administration of azoxymethane (AOM)/ dextran sulfate sodium (DSS) in Wild-type (WT), C3-, C5-, C5ar1-, and C5ar2-deficient mice. Using flow cytometry, immunohistochemical staining and multiplex bead assay, we profiled the immune cells, cytokines and chemokines. Bone marrow transplantation was employed to determine the contribution of immune cells in colorectal tumorigenesis. Further, we used C5aR1 antagonist PMX205 to investigate the protective role in colorectal tumorigenesis.

Results: Complement was extensively activated in inflamed tissues of AOM/DSS-induced murine CRC model, leading to multifaceted consequences. The deficiency of complement C5 or especially C5ar1, but not C3 almost completely prevented CRC tumorigenesis. C5a/C5aR1 signaling recruited MDSCs into the inflamed colorectum to impair CD8⁺ T cells, and modulated the production of critical cytokines and chemokines, thus initiating CRC. Moreover, the C5aR1 antagonist PMX205 strongly impeded colorectal tumorigenesis. Bone marrow transplantation further revealed that C5aR1 expression by immune cells was critical for colorectal tumorigenesis.

Conclusion: Our study identifies C5a/C5aR1 signaling as a vital immunomodulatory program in CRC tumorigenesis and suggests a feasible preventive strategy.

The unique immune microenvironment of liver metastases: Challenges and opportunities

Liver metastases from gastrointestinal and non-gastrointestinal malignancies remain a major cause of cancer-related mortality and a major clinical challenge. The liver has unique properties that facilitate metastatic expansion, including a complex immune system that evolved to dampen immunity to neoantigens entering the liver from the gut, through the portal circulation. In this review, we describe the unique microenvironment encountered by cancer cells in the liver, focusing on elements of the innate and adaptive immune response that can act as a double-edge sword, contributing to the elimination of cancer cells on the one hand and promoting their survival and growth, on the other. We discuss this microenvironment in a clinical context, particularly for colorectal carcinoma, and highlight how a better understanding of the role of the microenvironment has spurred an intense effort to develop novel and innovative strategies for targeting liver metastatic disease, some of which are currently being tested in the clinic.

Functional Role of Dendritic Cell Subsets in Cancer Progression and Clinical Implications

Dendritic cells (DCs) constitute a complex network of cell subsets with common functions but also with many divergent aspects. All dendritic cell subsets share the ability to prime T cell response and to undergo a complex trafficking program related to their stage of maturation and function. For these reasons, dendritic cells are implicated in a large variety of both protective and detrimental immune responses, including a crucial role in promoting anti-tumor responses. Although cDC1s are the most potent subset in tumor antigen cross-presentation, they are not sufficient to induce full-strength anti-tumor cytotoxic T cell response and need close interaction and cooperativity with the other dendritic cell subsets, namely cDC2s and pDCs. This review will take into consideration different aspects of DC biology, including the functional role of dendritic cell subsets in both fostering and suppressing tumor growth, the mechanisms underlying their recruitment into the tumor microenvironment, as well as the prognostic value and the potentiality of dendritic cell therapeutic targeting. Understanding the specificity of dendritic cell subsets will allow to gain insights on role of these cells in pathological conditions and to design new selective promising therapeutic approaches.

Prognostic Value of Complement Properdin in Cancer

The complement system is readily triggered by the presence of damage-associated molecular patterns on the surface of tumor cells. The complement alternative pathway provides rapid amplification of the molecular stress signal, leading to complement cascade activation to deal with pathogens or malignant cells. Properdin is the only known positive regulator of the alternative pathway. In addition, properdin promotes the phagocytic uptake of apoptotic T cells by macrophages and dendritic cells without activating the complement system, thus, establishing its ability to recognize "altered-self". Dysregulation of properdin has been implicated in substantial tissue damage in the host, and in some cases, chronic unresolved inflammation. A corollary of this may be the development of cancer. Hence, to establish a correlation between properdin presence/levels in normal and cancer tissues, we performed bioinformatics analysis, using Oncomine and UALCAN. Survival analyses were performed using UALCAN and PROGgeneV2 to assess if properdin can serve as a potential prognostic marker for human lung adenocarcinoma (LUAD), liver hepatocellular carcinoma (LIHC), cervical squamous cell carcinoma (CESC), and pancreatic adenocarcinoma (PAAD). We also analyzed levels of tumor-infiltrating immune cells using TIMER, a tool for characterizing immune cell composition in cancers. We found that in LUAD and LIHC, there was a lower expression of properdin in the tumors compared to normal tissues, while no significant difference was observed in CESC and PAAD. Survival analysis demonstrated a positive association between properdin mRNA expression and overall survival in all 4 types of cancers. TIMER analysis revealed that properdin expression correlated negatively with tumor purity and positively with levels of infiltrating B cells, cytotoxic CD8⁺ T cells, CD4⁺ helper T cells, macrophages, neutrophils and dendritic cells in LUAD, CESC and PAAD, and with levels of B cells, CD8⁺ T cells and dendritic cells in LIHC. Immunohistochemical analysis revealed that infiltrating immune cells were the most likely source of properdin in the tumor microenvironment. Thus, complement protein properdin shows promise as a prognostic marker in cancer and warrants further study.

Complement System in Cutaneous Squamous Cell Carcinoma

Epidermal keratinocyte-derived cutaneous squamous cell carcinoma (cSCC) is the most common metastatic skin cancer with high mortality rates in the advanced stage. Chronic inflammation is a recognized risk factor for cSCC progression and the complement system, as a part of innate immunity, belongs to the microenvironment of tumors. The complement system is a double-edged sword in cancer, since complement activation is involved in anti-tumor cytotoxicity and immune responses, but it also promotes cancer progression directly and indirectly. Recently, the role of several complement components and inhibitors in the regulation of progression of cSCC has been shown. In this review, we will discuss the role of complement system components and inhibitors as biomarkers and potential new targets for therapeutic intervention in cSCC.

C5a receptors C5aR1 and C5aR2 mediate opposing pathologies in a mouse model of melanoma

The canonical complement component 5a (C5a) receptor (C5aR) 1 has well-described roles in tumorigenesis but the contribution of the second receptor, C5aR2, is unclear. The present study demonstrates that B16.F0 melanoma cells express mRNA for both C5aR1 and C5aR2 and signal through ERK and p38 MAPKs in response to C5a. Despite this, C5a had no impact on melanoma cell proliferation or migration in vitro. In vivo studies demonstrated that the growth of B16.F0 melanoma tumors was increased in C5aR2^-/- mice but reduced in C5aR1^-/- mice and wild-type mice treated with a C5aR1 antagonist. Analysis of tumor-infiltrating leukocyte populations showed no significant differences between wild-type and C5aR2^-/- mice. Conversely, percentages of myeloid-derived suppressor cells, macrophages, and regulatory T lymphocytes were lower in tumors from C5aR1^-/- mice, whereas total (CD3⁺) T lymphocytes and CD4⁺ subsets were higher. Analysis of cytokine and chemokine levels also showed plasma IFN-γ was higher and tumor C-C motif chemokine ligand 2 was lower in the absence of C5aR1. The results suggest that C5aR1 signaling supports melanoma growth by promoting infiltration of immunosuppressive leukocyte populations into the tumor microenvironment, whereas C5aR2 has a more restricted but beneficial role in limiting tumor growth. Overall, these data support the potential of C5aR1-inhibitory therapies for melanoma.-Nabizadeh, J. A., Manthey, H. D., Panagides, N., Steyn, F. J., Lee, J. D., Li, X. X., Akhir, F. N. M., Chen, W., Boyle, G. M., Taylor, S. M., Woodruff, T. M., Rolfe, B. E. C5a receptors C5aR1 and C5aR2 mediate opposing pathologies in a mouse model of melanoma.

Integrating proteomics and transcriptomics for the identification of potential targets in early colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies worldwide. At present, CRC can often be treated upon diagnosis at stage I or II, or when dysplasia is detected; however, 60-70% of cases are not diagnosed until they have developed into late stages of the disease or until the malignancy is identified. Diagnosis of CRC at an early stage remains a challenge due to the absence of early-stage-specific biomarkers. To identify potential targets of early stage CRC, label-free proteomics analysis was applied to paired tumor-benign tissue samples from patients with stage II CRC (n=21). A total of 2,968 proteins were identified; corresponding RNA-Sequencing data were retrieved from The Cancer Genome Atlas-colon adenocarcinoma. Numerous bioinformatics methods, including differential expression analysis, weighted correlation network analysis, Gene Ontology and protein-protein interaction analyses, were applied to the proteomics and transcriptomics data. A total of 111 key proteins, which appeared as both differentially expressed proteins and mRNAs in the hub module, were identified as key candidates. Among these, three potential targets [protein-arginine deiminase type-2 (PADI2), Fc fragment of IgG binding protein (FCGBP) and phosphoserine aminotransferase 1] were identified from the pathological data. Furthermore, the survival analysis indicated that PADI2 and FCGBP were associated with the prognosis of CRC. The findings of the present study suggested potential targets for the identification of early stage CRC, and may improve understanding of the mechanism underlying the occurrence of CRC.

Preoperative serum carcinoembryonic antigen elevation in stage I colon cancer: improved risk of mortality in stage T1 than in stage T2

PURPOSE

This study aimed to investigate the implications of preoperative serum carcinoembryonic antigen (CEA) elevation in cause-specific survival (CSS) of patients diagnosed with stage I (T1N0M0 and T2N0M0) colon cancer.

METHODS

Eligible patients diagnosed with stage I colon cancer from the Surveillance, Epidemiology, and End Results (SEER) database from January 2004 to December 2010 were included in this respective and propensity score-matched (PSM) study. Some Cox proportional hazards models were constructed to identify prognostic factors associated with oncologic outcomes of colon cancer. Pearson's chi-squared tests and Kaplan-Meier methods were performed.

RESULTS

The median follow-up time of the whole cohort was 79 months. A total of 16,659 patients diagnosed with stage I colon cancer were identified from the SEER database. Multivariate Cox analyses showed that stage T1N0M0 in the context of serum CEA elevation (T1, CEA+) presented up to 158.4% increased risk of colon cancer-specific mortality compared with stage T1N0M0 in the context of normal serum CEA [hazard ratio (HR) = 2.584, 95% confidence interval (CI) = 2.167-3.082, P < 0.001]. After PSM, Kaplan-Meier survival curves of stage T1N0M0 colon cancer showed that 5-year CSS rates of normal and elevated CEA were 94.8% and 96.6% (P < 0.001).

CONCLUSIONS

This large population-based and propensity score-matched study with long follow-up time provides the first evidence that stage T1N0M0 colon cancer with the elevation of preoperative serum CEA would be a surrogate of aggressive tumor biology and predict poor prognosis. In addition, this subgroup of colon cancer might need to be paid more attention of clinicians.

Complementing the Cancer-Immunity Cycle

Reactivation of cytotoxic CD8+ T-cell responses has set a new direction for cancer immunotherapy. Neutralizing antibodies targeting immune checkpoint programmed cell death protein 1 (PD-1) or its ligand (PD-L1) have been particularly successful for tumor types with limited therapeutic options such as melanoma and lung cancer. However, reactivation of T cells is only one step toward tumor elimination, and a substantial fraction of patients fails to respond to these therapies. In this context, combination therapies targeting more than one of the steps of the cancer-immune cycle may provide significant benefits. To find the best combinations, it is of upmost importance to understand the interplay between cancer cells and all the components of the immune response. This review focuses on the elements of the complement system that come into play in the cancer-immunity cycle. The complement system, an essential part of innate immunity, has emerged as a major regulator of cancer immunity. Complement effectors such as C1q, anaphylatoxins C3a and C5a, and their receptors C3aR and C5aR1, have been associated with tolerogenic cell death and inhibition of antitumor T-cell responses through the recruitment and/or activation of immunosuppressive cell subpopulations such as myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), or M2 tumor-associated macrophages (TAMs). Evidence is provided to support the idea that complement blocks many of the effector routes associated with the cancer-immunity cycle, providing the rationale for new therapeutic combinations aimed to enhance the antitumor efficacy of anti-PD-1/PD-L1 checkpoint inhibitors.

The Angiotensin Receptor Blocker Losartan Suppresses Growth of Pulmonary Metastases via AT1R-Independent Inhibition of CCR2 Signaling and Monocyte Recruitment

Inflammatory monocytes have been shown to play key roles in cancer metastasis through promotion of tumor cell extravasation, growth, and angiogenesis. Monocyte recruitment to metastases is mediated primarily via the CCL2-CCR2 chemotactic axis. Thus, disruption of this axis represents an attractive therapeutic target for the treatment of metastatic disease. Losartan, a type I angiotensin II receptor (AT1R) antagonist, has been previously shown to have immunomodulatory actions involving monocyte and macrophage activity. However, the exact mechanisms accounting for these effects have not been fully elucidated. Therefore, we investigated the effects of losartan and its primary metabolite on CCL2-mediated monocyte recruitment and CCR2 receptor function using mouse tumor models and in vitro human monocyte cultures. We show, in this study, that losartan and its metabolite potently inhibit monocyte recruitment through the noncompetitive inhibition of CCL2-induced ERK1/2 activation, independent of AT1R activity. Studies in experimental metastasis models demonstrated that losartan treatment significantly reduced the metastatic burden in mice, an effect associated with a significant decrease in CD11b⁺/Ly6C⁺-recruited monocytes in the lungs. Collectively, these results indicate that losartan can exert antimetastatic activity by inhibiting CCR2 signaling and suppressing monocyte recruitment and therefore suggest that losartan (and potentially other AT1R blocker drugs) could be repurposed for use in cancer immunotherapy.

Complement in Metastasis: A Comp in the Camp

The complement system represents a pillar of the innate immune response. This system, critical for host defense against pathogens, encompasses more than 50 soluble, and membrane-bound proteins. Emerging evidence underscores its clinical relevance in tumor progression and its role in metastasis, one of the hallmarks of cancer. The multistep process of metastasis entails the acquisition of advantageous functions required for the formation of secondary tumors. Thus, targeting components of the complement system could impact not only on tumor initiation but also on several crucial steps along tumor dissemination. This novel vulnerability could be concomitantly exploited with current strategies overcoming tumor-mediated immunosuppression to provide a substantial clinical benefit in the treatment of metastatic disease. In this review, we offer a tour d'horizon on recent advances in this area and their prospective potential for cancer treatment.

Complement C3a promotes proliferation, migration and stemness in cutaneous squamous cell carcinoma

Background

Complement C3 has been shown to be highly expressed in cutaneous squamous cell carcinoma (cSCC) tumour tissues and is correlated with tumour cell growth. This study aimed to investigate the mechanism of C3 in cSCC malignant transformation.

Methods

C3 expression was analysed in cSCC cell lines A431, Tca8113, SCC13, HSC‐5 and HSC‐1 and in immortalized HaCaT keratinocytes. Proliferation and migration of cSCC were determined after C3a exposure. Expression of cyclin D1, cyclin E, vascular endothelial growth factor (VEGF), pro‐matrix metalloproteinase 1 (pro‐MMP1), pro‐matrix metalloproteinase 2 (pro‐MMP2), stemness factors, GSK‐3β, and β‐catenin were analyzed. Tumour growth was examined in a murine xenograft model.

Results

C3 expression was much more highly expressed in all cSCC cell lines than in HaCaT cells. C3a treatment significantly promoted cSCC cell proliferation and migration and upregulated cyclin D1, cyclin E, VEGF, pro‐MMP1 and pro‐MMP2 expression, which were impeded by the C3aR antagonist. Moreover, the expression of stemness factors Sox‐2, Nanog, Oct‐4, c‐Myc and CD‐44 was stimulated by C3a and slowed by C3aR disruption. Knockdown of Sox‐2 by siRNA transfection suppressed cell proliferation and migration, constrained VEGF secretion and inhibited pro‐MMP1 and pro‐MMP2 expression. C3a also activated the Wnt and β‐catenin pathway in cSCC cells. Disruption of C3aR expression dampened tumour growth and the expression of Wnt‐1, β‐catenin and Sox‐2 in the xenograft model.

Conclusions

C3a enhanced cell proliferation, migration and stemness in cSCC, and this activity was correlated with activation of the Wnt and β‐catenin pathway.

Role of the complement system in the tumor microenvironment

The complement system has traditionally been considered a component of innate immunity against invading pathogens and "nonself" cells. Recent studies have demonstrated the immunoregulatory functions of complement activation in the tumor microenvironment (TME). The TME plays crucial roles in tumorigenesis, progression, metastasis and recurrence. Imbalanced complement activation and the deposition of complement proteins have been demonstrated in many types of tumors. Plasma proteins, receptors, and regulators of complement activation regulate several biological functions of stromal cells in the TME and promote the malignant biological properties of tumors. Interactions between the complement system and cancer cells contribute to the proliferation, epithelial-mesenchymal transition, migration and invasion of tumor cells. In this review, we summarize recent advances related to the function of the complement system in the TME and discuss the therapeutic potential of targeting complement-mediated immunoregulation in cancer immunotherapy.

Plant galactolipid dLGG suppresses lung metastasis of melanoma through deregulating TNF-α-mediated pulmonary vascular permeability and circulating oxylipin dynamics in mice

This study demonstrates the bioefficacy and gives mechanistic insights into a plant galactolipid 1,2-di-O-linolenoyl-3-O-β-galactopyranosyl-sn-glycerol (dLGG) against metastatic melanoma using a syngeneic mouse model implanted with B16^COX-2/Luc melanoma. dLGG-20 (p.o. dLGG 20 mg/kg) and anti-cancer drug CP-2 (i.p. cisplatin 2 mg/kg) treatment significantly inhibited lung metastasis of melanoma in mice 91 and 57%, respectively, as determined by bioluminescence intensity. Moreover, dLGG-20 and CP-2 treatment prolonged mouse mean survival time. dLGG-20 treatment significantly inhibited the expression levels of several molecular markers, that is, PCNA, MMP2, COX-2, VEGF, vimentin, snail, TGF-β, β-catenin, TNF-α, PD-1 and PD-L1 in mouse lung tissues compared to tumor control mice. Significant inhibition of macrophage and neutrophil infiltration and promotion of CD8 + Tc cell recruitment in the lung microenvironment was observed in dLGG-20-treated mice. A LC/MS-based comparative oxylipin metabolomics study showed that dLGG-20 treatment significantly induced (5.0- to 12.8-fold) the 12/15-LOX catalyzed oxylipin products in mouse serum including 17-HDHA from DHA, 15-HEPE from EPA, 8- and 12-HETEs from AA, and CYP450-derived 20-HETE from AA. CP-2 treatment increased 12/15-LOX derived 8-, 11- and 12-HETEs from AA, and CYP450 derived 11,12-EET from AA ad 9,10-DHOME from LA by 5.3- to 8.1-fold. Of note, dLGG and 17-HDHA were more effective than CP in preventing B16 melanoma cell-induced pulmonary vascular permeability in mice through inhibition of TNF-α production, up-regulation of tight junction proteins claudin1 and ZO-2 and deregulation of Src activation. In conclusion, this study shows the novel therapeutic effect of phytoagent dLGG and suggests its potential as a therapeutic agent for metastatic melanoma.

C5a induces A549 cell proliferation of non-small cell lung cancer via GDF15 gene activation mediated by GCN5-dependent KLF5 acetylation

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, and multiple evidence has confirmed that C5a production is elevated in NSCLC microenvironment. Although NSCLC cell proliferation induced by C5a has been reported, the involved mechanism has not been elucidated. In this study, we examined the proliferation-related genes (i.e., KLF5, GCN5, and GDF15) and C5a receptor (C5aR) expression in tumor tissues as well as C5a concentration in plasma of NSCLC patients, and then determined the roles of KLF5, GCN5, and GDF15 in C5a-triggered NSCLC cell proliferation and the related mechanism both in vitro and in vivo. Our results found that the expression of KLF5, GCN5, GDF15, C5aR, and C5a was significantly upregulated in NSCLC patients. Mechanistic exploration in vitro revealed that C5a could facilitate A549 cell proliferation through increasing KLF5, GCN5, and GDF15 expression. Besides, KLF5 and GCN5 could form a complex, binding to GDF15 promoter in a KLF5-dependent manner and leading to GDF15 gene transcription. More importantly, GCN5-mediated KLF5 acetylation contributing to GDF15 gene transcription and cell proliferation upon C5a stimulation, the region (−103 to +58 nt) of GDF15 promoter which KLF5 could bind to, and two new KLF5 lysine sites (K335 and K391) acetylated by GCN5 were identified for the first time. Furthermore, our experiment in vivo demonstrated that the growth of xenograft tumors in BALB/c nude mice was greatly suppressed by the silence of KLF5, GCN5, or GDF15. Collectively, these findings disclose that C5a-driven KLF5–GCN5–GDF15 axis had a critical role in NSCLC proliferation and might serve as targets for NSCLC therapy.

Apigenin inhibits C5a-induced proliferation of human nasopharyngeal carcinoma cells through down-regulation of C5aR

Complement 5a (C5a) is able to induce the proliferation of human nasopharyngeal carcinoma (NPC) cells. Therefore, an effective method or drug that can specifically inhibit C5a-induced proliferation of human NPC cells needs to be developed. Reportedly, Apigenin has antiproliferative effects on a variety of cancer cells. However, the effect of Apigenin on NPC cell proliferation and its underlying mechanism are still unclear. Herein, the present study aimed to evaluate the effect of Apigenin on C5a-induced proliferation of human NPC cells and its possible mechanism through down-regulation of C5aR. We revealed that Apigenin in vitro could not only inhibit proliferation of NPC cells and but also reduce the expression of C5aR and P300/CBP-associated factor (PCAF) as well as the activation of signal transducer and activator of transcription 3 (STAT3) in NPC cells. Furthermore, Apigenin reduced the proliferation of human NPC cells triggered by C5a through negative regulation of C5aR/PCAF/STAT3 axis. These might provide a new insight into the function of Apigenin in cancer treatment, and also provide a potential strategy for treating human NPC through inhibition of C5aR expression on cancer cells.

Activation of the complement system in an osteosarcoma cell line promotes angiogenesis through enhanced production of growth factors

There is increasing evidence that the complement system is activated in various cancer tissues. Besides being involved in innate immunity against pathogens, the complement system also participates in inflammation and the modulation of tumor microenvironment. Recent studies suggest that complement activation promotes tumor progression in various ways. Among some cancer cell lines, we found that human bone osteosarcoma epithelial cells (U2-OS) can activate the alternative pathway of the complement system by pooled normal human serum. Interestingly, U2-OS cells showed less expression of complement regulatory proteins, compared to other cancer cell lines. Furthermore, the activated complement system enhanced the production of growth factors, which promoted angiogenesis of human endothelial cells. Our results demonstrated a direct linkage between the complement system and angiogenesis using the in vitro model, which suggest the complement system and related mechanisms might be potential targets for cancer treatment.

Complement 5a stimulates macrophage polarization and contributes to tumor metastases of colon cancer

Inflammatory cells such as macrophages can play a pro-tumorigenic role in the tumor stroma. Tumor-associated macrophages (TAMs) generally display an M2 phenotype with tumor-promoting activity; however, the mechanisms regulating the TAM phenotype remain unclear. Complement 5a (C5a) is a cytokine-like polypeptide that is generated during complement system activation and is known to promote tumor growth. Herein, we investigated the role of C5a on macrophage polarization in colon cancer metastasis in mice. We found that deficiency of the C5a receptor (C5aR) severely impairs the metastatic ability of implanted colon cancer cells. C5aR was expressed on TAMs, which exhibited an M2-like functional profile in colon cancer liver metastatic lesions. Furthermore, C5a mediated macrophage polarization and this process relied substantially on activation of the nuclear factor-kappa B (NF-κB) pathway. Finally, analysis of human colon carcinoma indicated that C5aR expression is negatively associated with tumor differentiation grade. Our results demonstrate that C5aR has a central role in regulating the M2 phenotype of TAMs, which in turn, contributes to hepatic metastasis of colon cancer through NF-κB signaling. C5a is a potential novel marker for cancer prognosis and drugs targeting complement system activation, specifically the C5aR pathway, may offer new therapeutic opportunities for colon cancer management.

C5a receptor (CD88) promotes motility and invasiveness of gastric cancer by activating RhoA

PURPOSE

Anaphylatoxin C5a is a strong chemoattractant of the complement system that binds the C5a receptor (C5aR). The expression of C5aR is associated with poor prognosis in several cancers. However, the role of C5aR in gastric cancer (GC) is unknown. The aim of this study was to examine the role of C5aR on GC cell motility and invasion.

EXPERIMENTAL DESIGN

The mechanism of invasion via C5aR was assessed by analyzing cytoskeletal rearrangement and RhoA activity after C5a treatment. Moreover, we investigated the relationship between C5aR expression and the prognosis of GC patients.

RESULTS

Two human GC cell lines (MKN1 and MKN7) had high C5aR expression. An invasion assay revealed that C5a stimulation promoted the invasive ability of MKN1 and MKN7 cells and that this was suppressed by knockdown of C5aR using siRNA or a C5aR-antagonist. Moreover, overexpression of C5aR in GC cells enhanced the conversion of RhoA-guanosine diphosphate (RhoA-GDP) to RhoA-guanosine triphosphate (RhoA-GTP) after C5a stimulation and caused morphological changes, including increased expression of stress fibers and filopodia. Examination of tumor specimens from 100 patients with GC revealed that high C5aR expression (35 of 100 samples, 35.0%) was associated with increased invasion depth, vascular invasion and advanced stage. The 5-year overall survival of patients with high or low C5aR expression was 58.2% and 68.5%, respectively (p=0.008).

CONCLUSIONS

This study is the first to demonstrate that C5aR promotes GC cell invasion by activating RhoA and is associated with a poor prognosis in GC patients. Therefore, this study provides a biomarker for GC patients who require an advanced therapeutic strategy.