Macrophages kill human papillomavirus type 16 E6-expressing tumor cells by tumor necrosis factor alpha- and nitric oxide-dependent mechanisms

Epidemiology, Molecular Pathogenesis, Immuno-Pathogenesis, Immune Escape Mechanisms and Vaccine Evaluation for HPV-Associated Carcinogenesis

Human papillomavirus (HPV) is implicated in over 90% of cervical cancer cases, with factors like regional variability, HPV genotype, the population studied, HPV vaccination status, and anatomical sample collection location influencing the prevalence and pathology of HPV-induced cancer. HPV-16 and -18 are mainly responsible for the progression of several cancers, including cervix, anus, vagina, penis, vulva, and oropharynx. The oncogenic ability of HPV is not only sufficient for the progression of malignancy, but also for other tumor-generating steps required for the production of invasive cancer, such as coinfection with other viruses, lifestyle factors such as high parity, smoking, tobacco chewing, use of contraceptives for a long time, and immune responses such as stimulation of chronic stromal inflammation and immune deviation in the tumor microenvironment. Viral evasion from immunosurveillance also supports viral persistence, and virus-like particle-based prophylactic vaccines have been licensed, which are effective against high-risk HPV types. In addition, vaccination awareness programs and preventive strategies could help reduce the rate and incidence of HPV infection. In this review, we emphasize HPV infection and its role in cancer progression, molecular and immunopathogenesis, host immune response, immune evasion by HPV, vaccination, and preventive schemes battling HPV infection and HPV-related cancers.

Oral Papillomatosis: Its Relation with Human Papilloma Virus Infection and Local Immunity—An Update

Oral papilloma lesions may appear as a result of HPV infection, or not, and only special molecular methods could differentiate them. Low-risk and high-risk HPV types could induce oral HPV papillomatosis with different natural evolution, clearance and persistence mechanisms. The pathogenic mechanisms are based on the crosstalk between the oral epithelial and immune cells and this very efficient virus. HPV acts as a direct inducer in the process of transforming a benign lesion into a malignant one, the cancerization process being also debated in this paper. According to the degree of malignity, three types of papillomatous lesions can be described in the oral cavity: benign lesions, potential malign disorders and malignant lesions. The precise molecular diagnostic is important to identify the presence of various virus types and also the virus products responsible for its oncogenicity. An accurate diagnostic of oral papilloma can be established through a good knowledge of etiological and epidemiological factors, clinical examination and laboratory tests. This review intends to update the pathogenic mechanisms driving the macroscopic and histological features of oral papillomatosis having HPV infection as the main etiological factor, focusing on its interreference in the local immunity. In the absence of an accurate molecular diagnostic and knowledge of local immunological conditions, the therapeutic strategy could be difficult to decide.

Role of Immunity and Vaginal Microbiome in Clearance and Persistence of Human Papillomavirus Infection

Cervical cancer disproportionately affects women of reproductive age, with 80% of cases occurring in low- and middle-income countries. Persistent infection with high-risk human papillomavirus (HPV) genotypes has been described as the most common non-systemic biological risk factor for the development of cervical cancer. The mucosal immune system plays a significant role in controlling HPV infection by acting as the first line of host defense at the mucosal surface. However, the virus can evade host immunity using various mechanisms, including inhibition of the antiviral immune response necessary for HPV clearance. Pro-inflammatory cytokines and the vaginal microbiome coordinate cell-mediated immune responses and play a pivotal role in modulating immunity. Recently, diverse vaginal microbiome (associated with bacterial vaginosis) and genital inflammation have emerged as potential drivers of high-risk HPV positivity and disease severity in women. The potential role of these risk factors on HPV recurrence and persistence remains unclear. This article reviews the role of cellular or cytokine response and vaginal microbiome dysbiosis in the clearance, persistence, and recurrence of HPV infection.

HPV and the Risk of HIV Acquisition in Women

The risk of HIV acquisition is low on a per-contact basis but increased by transmission co-factors such as other sexually transmitted infections (STIs). Human papillomavirus (HPV) is a prevalent STI that most individuals will acquire HPV in their lifetime. Current HPV vaccines can prevent newly acquired infections, but are largely ineffective against established HPV, complicating worldwide eradication efforts. In addition to being the causative agent of cervical cancer, accumulating evidence suggests that HPV infection and/or accompanying cervical inflammation increase the risk of HIV infection in men and women. The fact that immunological features observed during HPV infection overlap with cellular and molecular pathways known to enhance HIV susceptibility underscore the potential interplay between these two viral infections that fuel their mutual spread. Here we review current insights into how HPV infection and the generation of anti-HPV immunity contribute to higher HIV transmission rates, and the impact of HPV on mucosal inflammation, immune cell trafficking, and epithelial barrier function.

Distinct Responsiveness of Tumor-Associated Macrophages to Immunotherapy of Tumors with Different Mechanisms of Major Histocompatibility Complex Class I Downregulation

Simple Summary

Tumor-associated macrophages (TAMs) are one of the major cell subpopulations in the tumor microenvironment (TME) where they can either be pro-tumorigenic or contribute to an anti-tumor immunity. The TME and TAM phenotype were analyzed after combined immuno-therapy (IT) in tumor models characterized by distinct expression of major histocompatibility class I complex (MHC-I) molecules, i.e., tumors induced with TC-1 (MHC-I-proficient), TC-1/A9 (reversibly downregulated), and TC-1/dB2m (irreversibly downregulated) cells. We found out that combined IT highly activated immune reactions in the TME of TC-1 and TC-1/A9 tumors, but the TME of TC-1/dB2m tumors remained almost unchanged. Correspondingly, TAMs from TC-1/A9 tumors were able to destroy tumor cells in vitro, while TAMs isolated from TC-1/dB2m tumors showed profoundly decreased cytotoxicity. Hence, various capabilities of TAMs in tumors with distinct expression of MHC-I molecules should be considered when applying IT, particularly IT focused on TAMs.

Abstract

Tumor-associated macrophages (TAMs) plentifully infiltrate the tumor microenvironment (TME), but their role in anti-tumor immunity is controversial. Depending on the acquired polarization, they can either support tumor growth or participate in the elimination of neoplastic cells. In this study, we analyzed the TME by RNA-seq and flow cytometry and examined TAMs after ex vivo activation. Tumors with normal and either reversibly or irreversibly decreased expression of major histocompatibility complex class I (MHC-I) molecules were induced with TC-1, TC-1/A9, and TC-1/dB2m cells, respectively. We found that combined immunotherapy (IT), composed of DNA immunization and the CpG oligodeoxynucleotide (ODN) ODN1826, evoked immune reactions in the TME of TC-1- and TC-1/A9-induced tumors, while the TME of TC-1/dB2m tumors was mostly immunologically unresponsive. TAMs infiltrated both tumor types with MHC-I downregulation, but only TAMs from TC-1/A9 tumors acquired the M1 phenotype upon IT and were cytotoxic in in vitro assay. The anti-tumor effect of combined IT was markedly enhanced by a blockade of the colony-stimulating factor-1 receptor (CSF-1R), but only against TC-1/A9 tumors. Overall, TAMs from tumors with irreversible MHC-I downregulation were resistant to the stimulation of cytotoxic activity. These data suggest the dissimilarity of TAMs from different tumor types, which should be considered when utilizing TAMs in cancer IT.

Profiling of miRNAs in Mouse Peritoneal Macrophages Responding to Echinococcus multilocularis Infection

Alveolar echinococcosis (AE) is a zoonotic helminthic disease caused by infection with the larval of Echinococcus multilocularis in human and animals. Here, we compared miRNA profiles of the peritoneal macrophages of E. multilocularis-infected and un-infected female BALB/c mice using high-throughput sequencing. A total of 87 known miRNAs were differentially expressed (fold change ≥ 2, p < 0.05) in peritoneal macrophages in mice 30- and 90-day post infection compared with ones in un-infected mice. An increase of mmu-miR-155-5p expression was observed in peritoneal macrophages in E. multilocularis-infected mice. Compared with the control group, the production of nitric oxide (NO) was increased in peritoneal macrophages transfected with mmu-miR-155-5p mimics at 12 h after transfection (p < 0.001). Two key genes (CD14 and NF-κB) in the LPS/TLR4 signaling pathway were also markedly altered in mmu-miR-155-5p mimics transfected cells (p < 0.05). Moreover, mmu-miR-155-5p mimics suppressed IL6 mRNA expression and promoted IL12a and IL12b mRNA expression. Luciferase assays showed that mmu-miR-155-5p was able to bind to the 3′ UTR of the IKBKE gene and decreased luciferase activity. Finally, we found the expression of IKBKE was significantly downregulated in both macrophages transfected with mmu-miR-155-5p and macrophages isolated from E. multilocularis-infected mice. These results demonstrate an immunoregulatory effect of mmu-miR-155 on macrophages, suggesting a role in regulation of host immune responses against E. multilocularis infection.

The Host-Microbe Interplay in Human Papillomavirus-Induced Carcinogenesis

Every year nearly half a million new cases of cervix cancer are diagnosed worldwide, making this malignancy the fourth commonest cancer in women. In 2018, more than 270,000 women died of cervix cancer globally with 85% of them being from developing countries. The majority of these cancers are caused by the infection with carcinogenic strains of human papillomavirus (HPV), which is also causally implicated in the development of other malignancies, including cancer of the anus, penis cancer and head and neck cancer. HPV is by far the most common sexually transmitted infection worldwide, however, most infected people do not develop cancer and do not even have a persistent infection. The development of highly effective HPV vaccines against most common high-risk HPV strains is a great medical achievement of the 21st century that could prevent up to 90% of cervix cancers. In this article, we review the current understanding of the balanced virus-host interaction that can lead to either virus elimination or the establishment of persistent infection and ultimately malignant transformation. We also highlight the influence of certain factors inherent to the host, including the immune status, genetic variants and the coexistence of other microbe infections and microbiome composition in the dynamic of HPV infection induced carcinogenesis.

Immunopotentiator Aikejia improves the therapeutic efficacy of PD-1/PD-L1 immunosuppressive pathway in CT26.WT cancer cell

Tumors can escape immunosurveillance through immunocheckpoint such as the PD-1/PD-L1 pathway. Aikejia comes from Nocardia rubra cell-wall skeleton and can increase the number of inflammatory factors and immune cells. In this work, we showed that the levels of PD-L1 increase in CT26.WT xenograft after subcutaneous injection of Aikejia in mice, but Aikejia did not induce the expression of PD-L1 in vitro. When we treated the mice with Aikejia and blocked PD-1/PD-L1 pathway in vivo at the same time, the CT26.WT xenografts were significantly inhibited or eliminated, which was better than single treatment alone. Our results suggested that Aikejia may be an effective adjuvant for PD-1/PD-L1 immunotherapy.

The role of interleukin 10 in human papilloma virus infection and progression to cervical carcinoma

Although Human Papillomavirus (HPV) exerts a vital influence on cervical carcinogenesis, other factors influence the development of a squamous intraepithelial lesion (SIL) that may or not progress to cervical cancer. Among several cytokines, Interleukin 10 (IL-10) stands out as an important anti-inflammatory factor, leading to immune system evasion through an immunosuppressive state. In the cervical microenvironment, during different stages of HPV infection, IL-10 production can be induced and maintained by different cell sources, including infected keratinocytes, some subsets of dendritic cells (DC), tumor associated macrophages (TAM), T regulatory cells (Treg) and tumor cells. Further, a wide range of effects can be exerted by IL-10 on different cell populations, such as inhibiting proinflammatory cytokine production, DCs differentiation, antigen presenting function and T-helper 1 (Th1) polarization. IL-10 is one of several cytokines involved in cancer development and sustenance, although its role in cancer is still controversial and poorly understood. However, cervical IL-10 levels tend to increase in parallel to SIL development and are even higher within cervical tumors. Accumulating data have shown that after HPV infection, IL-10 levels are enhanced as a result of HPV E2, E6 and E7 proteins action over IL-10 gene transcription, while IL-10 stimulates HPV E6 and E7 expression. Therefore, this interplay between HPV and IL-10 creates a vicious cycle that could favor an immunosuppressive microenvironment in the cervix, facilitating the progression of a simple HPV infection to SIL or cervical cancer.

Role of IL-10 and TGF-β1 in local immunosuppression in HPV-associated cervical neoplasia

Cervical cancer is a worldwide disease that constitutes a significant public health problem, especially in developing countries, not only due to its high incidence but also because the most affected population comprises women who belong to marginalized socio-economic classes. Clinical and molecular research has identified immunological impairment in squamous intraepithelial cervical lesions and cervical cancer patients. Human Papillomavirus (HPV) has several mechanisms for avoiding the immune system: it down-regulates the expression of interferon and upregulates interleukin (IL)-10 and transforming growth factor (TGF)-β1 to produce a local immunosuppressive environment, which, along with altered tumor surface antigens, forms an immunosuppressive network that inhibits the antitumor immune response. In this review we analyzed the available data on several deregulated cellular immune functions in patients with NIC I, NIC II and NIC III and cervical cancer. The effects of immunosuppressive cytokines on innate immune response, T-cell activation and cellular factors that promote tumor cell proliferation in cervical cancer patients are summarized. We discuss the functional consequences of HPV E2, E6, and E7 protein interactions with IL-10 and TGF-β1 promoters in the induction of these cytokines and postulate its effect on the cellular immune response in squamous intraepithelial cervical lesions and cervical cancer patients. This review provides a comprehensive picture of the immunological functions of IL-10 and TGF-β1 in response to HPV in humans.

Immune responses against human papillomavirus (HPV) infection and evasion of host defense in cervical cancer

Human papillomavirus (HPV) is the most important etiological factor for cervical cancer. A recent study demonstrated that more than 20 HPV types were thought to be oncogenic for uterine cervical cancer. Notably, more than one-half of women show cervical HPV infections soon after their sexual debut, and about 90 % of such infections are cleared within 3 years. Immunity against HPV might be important for elimination of the virus. The innate immune responses involving macrophages, natural killer cells, and natural killer T cells may play a role in the first line of defense against HPV infection. In the second line of defense, adaptive immunity via cytotoxic T lymphocytes (CTLs) targeting HPV16 E2 and E6 proteins appears to eliminate cells infected with HPV16. However, HPV can evade host immune responses. First, HPV does not kill host cells during viral replication and therefore neither presents viral antigen nor induces inflammation. HPV16 E6 and E7 proteins downregulate the expression of type-1 interferons (IFNs) in host cells. The lack of co-stimulatory signals by inflammatory cytokines including IFNs during antigen recognition may induce immune tolerance rather than the appropriate responses. Moreover, HPV16 E5 protein downregulates the expression of HLA-class 1, and it facilitates evasion of CTL attack. These mechanisms of immune evasion may eventually support the establishment of persistent HPV infection, leading to the induction of cervical cancer. Considering such immunological events, prophylactic HPV16 and 18 vaccine appears to be the best way to prevent cervical cancer in women who are immunized in adolescence.

S100, CD68, and MHC class II molecule expression in cervical high- and low-grade HPV-induced lesions

INTRODUCTION

Some human papillomavirus (HPV) types are involved in malignant processes in the cervical epithelium, with 99% of cases attributed to oncogenic HPV infection. This study aimed to detect S100, CD68, and major histocompatibility complex class II (MHC-II) molecules in cervical uterine epithelial samples in patients with high- and low-grade lesions induced by HPV.

METHODS

Fifty-eight samples from patients who were confirmed positive or negative for high-risk oncogenic HPV DNA, had histopathological diagnosis of cervical intraepithelial neoplasia (CIN) of grades I, II, or III, or were negative for intraepithelial lesion or malignancy were subjected to immunohistochemistry reaction to S100 protein, CD68, and MHC-II (HLA-DR alpha chain).

RESULTS

The presence of MHC-II predominated in samples exhibiting histopathological alterations (p < 0.05). S100 detection was more numerous in carcinoma samples (CIN III) (75%). Presence of this protein correlated significantly (p < 0.05) with histopathological findings and viral load.

CONCLUSIONS

A small expression of CD68 was observed, which may be explained by the observation in our study having been made on random microscopic fields and not on specific areas. The findings, such as the presence of S100 protein and MHC-II expression in samples with histological alterations, could suggest that the immune system fails to control HPV replication at the early stages of infection. Further studies with larger prospective data are necessary to confirm this result.

New Approaches to Immunotherapy for HPV Associated Cancers

Cervical cancer is the second most common cancer of women worldwide and is the first cancer shown to be entirely induced by a virus, the human papillomavirus (HPV, major oncogenic genotypes HPV-16 and -18). Two recently developed prophylactic cervical cancer vaccines, using virus-like particles (VLP) technology, have the potential to prevent a large proportion of cervical cancer associated with HPV infection and to ensure long-term protection. However, prophylactic HPV vaccines do not have therapeutic effects against pre-existing HPV infections and do not prevent their progression to HPV-associated malignancy. In animal models, therapeutic vaccines for persisting HPV infection can eliminate transplantable tumors expressing HPV antigens, but are of limited efficacy in inducing rejection of skin grafts expressing the same antigens. In humans, clinical trials have reported successful immunotherapy of HPV lesions, providing hope and further interest. This review discusses possible new approaches to immunotherapy for HPV associated cancer, based on recent advances in our knowledge of the immunobiology of HPV infection, of epithelial immunology and of immunoregulation, with a brief overview on previous and current HPV vaccine clinical trials.

Association between MBL2 gene functional polymorphisms and high-risk human papillomavirus infection in Brazilian women

We studied the association between high-risk human papillomavirus (HPV) infection and MBL2 functional polymorphisms in a group of 180 high-risk HPV-infected women and 180 healthy control subjects. The most frequent high-risk HPV genotypes were 16 (47.2%), 31 (11.7%), 33 (5%), and 18 (2.2%), respectively. Of the 180 HPV-infected women, 99 presented with uterine cervical cancer and 81 did not. No differences in MBL2 genotype or in allelic or haplotype frequencies were found between HPV patients who developed cervical uterine cancer and those who did not. When considering combined genotypes grouped according to MBL production (designated as high, low, and deficient producers), we detected a significant difference between healthy controls and high-risk HPV-positive patients, the latter group showing increased frequencies of deficient-producer genotypes (14.4% vs 9.4% in the healthy control group, corrected p = 0.04). In conclusion, a correlation between MBL2 polymorphisms and high-risk HPV infection was found in this study.

Lack of TNFα mRNA expression in cervical cancer is not associated with loss of heterozygosity at 6p21.3, inactivating mutations or promoter methylation

Infection with oncogenic human papillomavirus (HPV) is considered to be the major etiologic event for cervical cancer. Tumor necrosis factor alpha (TNFalpha), a proinflammatory cytokine, may be involved in orchestrating an antitumor immune response against human papillomavirus expressing cervical cancer cells. Hence, loss of TNFalpha could be advantageous for tumor cells to escape immune clearance. The aim of our study was to investigate TNFalpha gene expression and epigenetic characteristics associated with the loss of TNFalpha expression in cervical cancer. To this end, we examined TNFalpha expression, loss of heterozygosity (LOH) at 6p21.3, the locus of TNFalpha, mutational status of the TNFalpha locus, loss of the TNFalpha promoter variant 2 allele and CpG hypermethylation of the TNFalpha promoter. RNA in situ hybridization showed absence of TNFalpha expression in 45% of 63 tumors. LOH occurred in 57% of the tumors and was not concordant with absence of TNFalpha mRNA. No mutations in the TNFalpha gene were identified in 15 cases deficient in TNFalpha expression exhibiting LOH. Furthermore, lack of TNFalpha expression did not correlate with promoter methylation. In conclusion, TNFalpha mRNA expression is absent in nearly half of the cervical tumors analyzed. Neither promoter methylation nor genetic causes for lack of expression were evident.

Local profile of cytokines and nitric oxide in patients with bacterial vaginosis and cervical intraepithelial neoplasia

OBJECTIVE

To evaluate the local immune response in patients with bacterial vaginosis (BV) and cervical intraepithelial neoplasia (CIN), as assessed by cytokine and nitric oxide (NO) concentrations.

STUDY DESIGN

Patients attending for routine gynaecological examination were prospectively enrolled in groups: BV (n=25) diagnosed by clinical criteria, CIN graded I to III (n=35, 6 CIN I, 8 CIN II and 21 CIN III) by histological analysis, and controls (n=15) without clinical and cytological findings. Randomly selected patients within CIN group at grades II or III (n=15) were re-evaluated at 60 days after surgical treatment. Endocervical (EC) and vaginal secretion samples were collected by cytobrush and the levels of cytokines (ELISA) and NO metabolite (Griess reaction) were assayed.

RESULTS

NO was assessed in all subjects, and cytokines in all controls, 15 BV and 30 CIN patients. Interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10) and nitrite levels were higher in EC than in vaginal secretions in BV and CIN groups. In CIN group, IL-8, IL-10 and nitrite concentrations were greater in EC and/or vaginal secretions than in BV or controls. Surgical treatment reduced IL-8 levels in EC and vaginal secretions.

CONCLUSION

A similar local immune profile was found in BV and CIN groups. The increased local production of IL-8, IL-10 and NO in CIN suggests a role for these mediators in the immune response against tumour or tumour development.

The interaction of adenovirus E1A with p300 family members modulates cellular gene expression to reduce tumorigenicity

The use of adenovirus serotype 2 or 5 (Ad2/5) E1A as therapy for human malignancy requires an understanding of the mechanisms involved in E1A-induced tumor suppression. The prevailing use of E1A in the treatment of human malignancy stresses the non-immunologically mediated, anti-tumorigenic activities of E1A. However, the capacity of E1A to elicit a NK-cell and T-cell anti-tumor immune response and to sensitize tumor cells to lysis by immune effector molecules utilized by NK cells and T cells is also an important component of the anti-tumorigenic activity of E1A. This immune-mediated anti-tumorigenic activity of E1A is not shared by functionally similar viral oncoproteins such as the human papillomavirus type 16 (HPV16) E7 oncoprotein and is dependent on the capacity of E1A to interact with transcriptional coadapter, p300. To further define the molecular mechanisms whereby E1A reduces tumorigenicity, we compared total cellular gene expression in H4 cells, a human fibrosarcoma cell line, to gene expression in H4 cells stably expressing E1A, E7, or mutant forms of E1A that do not bind p300. The expression of E1A, but not E7, in H4 cells modulated the expression of cellular genes that may promote apoptosis, enhance immunogenicity and reduce tumor cell metastasis. The difference in the ability of E1A and E7 to modulate the expression of cellular genes that may influence tumorigenicity was largely attributable to distinct interactions of E1A and E7 with p300. Results of this study will be useful in designing novel strategies to augment the anti-tumorigenic activities of E1A.

Impact of Biologic Agents on Infectious Diseases

Until recently, inflammatory diseases, collagen vascular diseases, inflammatory bowel diseases, and multiple sclerosis were met with a limited offering for treatment. The introduction of biologic agents has revolutionized the approach to these diseases, offering many patients freedom from disease activity staving off resultant destruction to organs and joints with marked improvement in quality of life and disability. This article focuses on the development of serious infections associated with the use of biologic agents. Presented is a synthesis of case series, reports, and systematic reviews to elucidate implicated pathogens and clinical presentations in patients being treated with biologic agents and to form a cursory backbone for prevention and treatment strategies to which clinicians prescribing these agents or encountering patients already on these agents can readily refer. Maintenance of a high index of suspicion is imperative for the prevention and appropriate treatment of serious life-threatening infections in these patients.

Tumoristatic effects of anti-CD40 mAb-activated macrophages involve nitric oxide and tumour necrosis factor-alpha

Effector cells of the innate immune system have diverse functions that can result in tumour inhibition or tumour progression. Activation of macrophages by CD40 ligation has been shown to induce antitumour effects in vitro and in vivo. Here we investigated the role of nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha) as mediators in the tumoristatic effects of murine peritoneal macrophages activated with agonistic anti-CD40 monoclonal antibody (alphaCD40) alone and following further stimulation with bacterial lipopolysaccharide (LPS). We found that macrophages activated in vivo by alphaCD40 exhibited tumoristatic activity in vitro against B16 melanoma cells; the tumoristatic effect correlated with the level of NO production and was enhanced by LPS. Use of the NO inhibitor L-nitro-arginine-methyl esterase (L-NAME) and evaluation of macrophages from inducible NO synthase (iNOS)-knockout (KO) mice following alphaCD40 activation showed reduced tumoristatic activity. CD40 ligation enhanced expression of TNF-alpha. Macrophage tumoristatic activity following alphaCD40 treatment was reduced by TNF-alpha mAb or use of macrophages from TNF-alpha-KO mice. However, further stimulation of alphaCD40-activated macrophages with LPS resulted in strong tumoristatic activity that was much less dependent on NO or TNF-alpha. Taken together, these results suggest that NO and TNF-alpha are involved in, but not solely responsible for, the antitumour effects of macrophages after activation by CD40 ligation.

Fibulins 3 and 5 antagonize tumor angiogenesis in vivo

Lethal tumor growth and progression cannot occur without angiogenesis, which facilitates cancer cell proliferation, survival, and dissemination. Fibulins (FBLN) 5 and 3 are widely expressed extracellular matrix proteins that regulate cell proliferation in a context-specific manner. Reduced FBLN-5 expression has been associated with cancer formation and progression in humans, whereas its constitutive expression antagonizes endothelial cell angiogenic sprouting in vitro. Thus, FBLN-5 may suppress tumorigenesis by preventing tumor angiogenesis. FBLN-3 is homologous to FBLN-5 and expressed in endothelial cells, yet its role in tumorigenesis and angiogenesis is unknown. We find FBLN-3 expression to be altered in some human tumors and that its constitutive expression in endothelial cells inhibited their proliferation, invasion, and angiogenic sprouting, as well as their response to vascular endothelial growth factor as measured by p38 mitogen-activated protein kinase activation. In endothelial cells, both FBLNs (a) reduced angiogenic sprouting stimulated by basic fibroblast growth factor (bFGF); (b) inhibited matrix metalloproteinase expression and activity; and (c) stimulated tissue inhibitor of metalloproteinase expression. More importantly, both FBLNs prevented angiogenesis and vessel infiltration into bFGF-supplemented Matrigel plugs implanted in genetically normal mice, as well as decreased the growth and blood vessel density in tumors produced by MCA102 fibrosarcoma cells implanted s.c. into syngeneic mice. Our findings establish FBLN-3 and FBLN-5 as novel angiostatic agents capable of reducing tumor angiogenesis and, consequently, tumor growth in vivo and suggest that these angiostatic activities may one day be exploited to combat tumor angiogenesis and metastasis in cancer patients.