Antibody-dependent antitumor cytotoxicity by human monocytes cultured with recombinant macrophage colony-stimulating factor. Induction of efficient antibody-mediated antitumor cytotoxicity not detected by isotope release assays

Targeting the myeloid microenvironment in neuroblastoma

Myeloid cells (granulocytes and monocytes/macrophages) play an important role in neuroblastoma. By inducing a complex immunosuppressive network, myeloid cells pose a challenge for the adaptive immune system to eliminate tumor cells, especially in high-risk neuroblastoma. This review first summarizes the pro- and anti-tumorigenic functions of myeloid cells, including granulocytes, monocytes, macrophages, and myeloid-derived suppressor cells (MDSC) during the development and progression of neuroblastoma. Secondly, we discuss how myeloid cells are engaged in the current treatment regimen and explore novel strategies to target these cells in neuroblastoma. These strategies include: (1) engaging myeloid cells as effector cells, (2) ablating myeloid cells or blocking the recruitment of myeloid cells to the tumor microenvironment and (3) reprogramming myeloid cells. Here we describe that despite their immunosuppressive traits, tumor-associated myeloid cells can still be engaged as effector cells, which is clear in anti-GD2 immunotherapy. However, their full potential is not yet reached, and myeloid cell engagement can be enhanced, for example by targeting the CD47/SIRPα axis. Though depletion of myeloid cells or blocking myeloid cell infiltration has been proven effective, this strategy also depletes possible effector cells for immunotherapy from the tumor microenvironment. Therefore, reprogramming of suppressive myeloid cells might be the optimal strategy, which reverses immunosuppressive traits, preserves myeloid cells as effectors of immunotherapy, and subsequently reactivates tumor-infiltrating T cells.

Biology of GD2 ganglioside: implications for cancer immunotherapy

Part of the broader glycosphingolipid family, gangliosides are composed of a ceramide bound to a sialic acid-containing glycan chain, and locate at the plasma membrane. Gangliosides are produced through sequential steps of glycosylation and sialylation. This diversity of composition is reflected in differences in expression patterns and functions of the various gangliosides. Ganglioside GD2 designates different subspecies following a basic structure containing three carbohydrate residues and two sialic acids. GD2 expression, usually restrained to limited tissues, is frequently altered in various neuroectoderm-derived cancers. While GD2 is of evident interest, its glycolipid nature has rendered research challenging. Physiological GD2 expression has been linked to developmental processes. Passing this stage, varying levels of GD2, physiologically expressed mainly in the central nervous system, affect composition and formation of membrane microdomains involved in surface receptor signaling. Overexpressed in cancer, GD2 has been shown to enhance cell survival and invasion. Furthermore, binding of antibodies leads to immune-independent cell death mechanisms. In addition, GD2 contributes to T-cell dysfunction, and functions as an immune checkpoint. Given the cancer-associated functions, GD2 has been a source of interest for immunotherapy. As a potential biomarker, methods are being developed to quantify GD2 from patients' samples. In addition, various therapeutic strategies are tested. Based on initial success with antibodies, derivates such as bispecific antibodies and immunocytokines have been developed, engaging patient immune system. Cytotoxic effectors or payloads may be redirected based on anti-GD2 antibodies. Finally, vaccines can be used to mount an immune response in patients. We review here the pertinent biological information on GD2 which may be of use for optimizing current immunotherapeutic strategies.

Development of minimally invasive cancer immunotherapy using anti-disialoganglioside GD2 antibody-producing mesenchymal stem cells for a neuroblastoma mouse model

PURPOSE

Mouse IgG anti-disialoganglioside GD2 antibody-secreting mouse mesenchymal stem cells (anti-GD2-MSCs) were developed, and their anti-tumor effects were validated in an in vivo neuroblastoma mouse model.

METHODS

Anti-GD2 antibody constructs were generated, incorporating FLAG-tagged single-chain fragment variables against GD2 fused to a linker sequence, and a fragment of a stationary portion was changed from human IgG to mouse IgG and GFP protein. The construct was lentivirally introduced into mouse MSCs. A syngeneic mouse model was established through the subcutaneous transplantation of a tumor tissue fragment from a TH-MYCN transgenic mouse, and the homing effects of anti-GD2-MSCs were validated by In vivo imaging system imaging. The syngeneic model was divided into three groups according to topical injection materials: anti-GD2-MSCs with IL-2, IL-2, and PBS. The tumors were removed, and natural killer (NK) cells were counted.

RESULTS

Anti-GD2-MSCs showed homing effects in syngeneic models. The growth rate of subcutaneous tumors was significantly suppressed by anti-GD2-MSCs with IL-2 (p < 0.05). Subcutaneous tumor immunostaining showed an increased NK cell infiltration in the same group (p < 0.01).

CONCLUSION

Anti-GD2-MSCs using mouse IgG showed a homing effect and significant tumor growth suppression in syngeneic models. Anti-GD2-MSC-based cellular immunotherapy could be a novel therapeutic strategy for intractable neuroblastoma.

Clinical and Pathological Evidence of Anti-GD2 Immunotherapy Induced Differentiation in Relapsed/Refractory High-Risk Neuroblastoma

Simple Summary

The anti-tumor activity of anti-GD2 monoclonal antibodies (mAbs) have been demonstrated by the capacity to mediate immunological cytotoxicity but also through direct cell death induction. Recently, studies with anti-GD2 mAbs for high-risk (HR)-neuroblastoma (NB) patients with measurable disease, with or without chemotherapy, have reported significant objective responses. In this subgroup of patients, we observed that, while being treated with the mAb naxitamab, some chemorefractory lesions showed long periods of stable disease. Here, we report a comprehensive imaging evaluation of those lesions correlating with histopathological demonstration of naxitamab-induced tissue differentiation. Our results suggest an undescribed mechanism of action for anti-GD2 mAbs.

Abstract

Background: Neuroblastic tumors (NBTs) originate from a block in the process of differentiation. Histologically, NBTs are classified in neuroblastoma (NB), ganglioneuroblastoma (GNB), and ganglioneuroma (GN). Current therapy for high-risk (HR) NB includes chemotherapy, surgery, radiotherapy, and anti-GD2 monoclonal antibodies (mAbs). Anti-GD2 mAbs induce immunological cytoxicity but also direct cell death. Methods: We report on patients treated with naxitamab for chemorefractory NB showing lesions with long periods of stable disease. Target lesions with persisting ¹²³I-Metaiodobenzylguanidine (MIBG) uptake after 4 cycles of immunotherapy were further evaluated by functional Magnetic Resonance Imaging (MRI) and/or Fluorodeoxyglucose (FDG)-positron emission tomography (PET). MIBG avid lesions that became non-restrictive on MRI (apparent diffusion coefficient (ADC) > 1) and/or FDG-PET negative (SUV < 2) were biopsied. Results: Twenty-seven relapse/refractory (R/R) HR-NB patients were enrolled on protocol Ymabs 201. Two (7.5%) of the 27 showed persistent bone lesions on MIBG, ADC high, and/or FDG-PET negative. Forty-four R/R HR-NB patients received chemo-immunotherapy. Twelve (27%) of the 44 developed persistent MIBG+ but FDG-PET- and/or high ADC lesions. Twelve (86%) of the 14 cases identified were successfully biopsied producing 16 evaluable samples. Histology showed ganglioneuroma maturing subtype in 6 (37.5%); ganglioneuroma mature subtype with no neuroblastic component in 4 (25%); differentiating NB with no Schwannian stroma in 5 (31%); and undifferentiated NB without Schwannian stroma in one (6%). Overall, 10 (62.5%) of the 16 specimens were histopathologically fully mature NBTs. Conclusions: Our results disclose an undescribed mechanism of action for naxitamab and highlight the limitations of conventional imaging in the evaluation of anti-GD2 immunotherapy clinical efficacy for HR-NB.

Immunotherapeutic Strategies for Neuroblastoma: Present, Past and Future

Neuroblastoma is the most common extracranial pediatric solid tumor with a heterogeneous clinical course, ranging from spontaneous regression to metastatic disease and death, irrespective of intensive chemotherapeutic regimen. On the basis of several parameters, children affected by neuroblastoma are stratified into low, intermediate and high risk. At present, more than 50% of high-risk patients with metastatic spread display an overall poor long-term outcome also complicated by devastating long-term morbidities. Thus, novel and more effective therapies are desperately needed to improve lifespan of high-risk patients. In this regard, adoptive cell therapy holds great promise and several clinical trials are ongoing, demonstrating safety and tolerability, with no toxicities. Starting from the immunological and clinical features of neuroblastoma, we here discuss the immunotherapeutic approaches currently adopted for high-risk patients and different innovative therapeutic strategies currently under investigation. The latter are based on the infusion of natural killer (NK) cells, as support of consolidation therapy in addition to standard treatments, or chimeric antigen receptor (CAR) T cells directed against neuroblastoma associated antigens (e.g., disialoganglioside GD2). Finally, future perspectives of adoptive cell therapies represented by γδ T lymphocyes and CAR NK cells are envisaged.

Targets and Antibody Formats for Immunotherapy of Neuroblastoma

Neuroblastoma (NB) is a malignant embryonal tumor of the sympathetic nervous system that is most commonly diagnosed in the abdomen, often presenting with signs and symptoms of metastatic spread. Three decades ago, high-risk NB metastatic to bone and bone marrow in children was not curable. Today, with multimodality treatment, 50% of these patients will survive, but most suffer from debilitating treatment-related complications. Novel targeted therapies to improve cure rates while minimizing toxicities are urgently needed. Recent molecular discoveries in oncology have spawned the development of an impressive array of targeted therapies for adult cancers, yet the paucity of recurrent somatic mutations or activated oncogenes in pediatric cancers poses a major challenge to the evolving paradigm of personalized medicine. Although low tumor mutational burden is a major hurdle for immune checkpoint inhibitors, an immature or impaired immune system and inhibitory tumor microenvironment can further complicate the prospects for successful immunotherapy. In this regard, despite the poor immunogenic properties of NB, the success of antibody-based immunotherapy and radioimmunotherapy directed at single targets (eg, GD2 and B7-H3) is both encouraging and surprising, given that most solid tumor antibodies that use Fc-dependent mechanisms or radioimmunotargeting have largely failed. Here, we summarize the current information on the immunologic properties of this tumor, its potential immunotherapeutic targets, and novel antibody-based strategies on the horizon.

Nanomedicinal strategies as efficient therapeutic interventions for delivery of cancer vaccines

The applications of gene therapy-based treatment of cancers were started almost two decades back as a boon over the chemotherapeutic treatment strategies. Gene therapy helps in correcting the genetic sequences for treatment of cancers, thus also acts like a vaccine to induce the cellular and humoral immunity. However, the cancer vaccines typically suffer from a series of biopharmaceutical challenges due to poor solubility, low systemic availability and lack of targeting ability. Owing to these challenges, the physicians and pharmaceutical scientists have explored the applications of nanocarriers as quite promising systems for effective treatment against the tumors. A series of nanotherapeutic systems are available to date for diverse drug therapy applications. Systematic understanding on the preparation, evaluation and application of nanomedicines as a carrier system for delivering the cancer vaccines is highly important. The present review article provides an in-depth understanding on the challenges associated with cancer vaccine delivery and current opportunities with diverse nanomedicinal carriers being available for treatment of cancers.

Spotlight on dinutuximab in the treatment of high-risk neuroblastoma: development and place in therapy

Neuroblastoma (NB) is a pediatric cancer of the sympathetic nervous system which accounts for 8% of childhood cancers. Most NBs express high levels of the disialoganglioside GD2. Several antibodies have been developed to target GD2 on NB, including the human/mouse chimeric antibody ch14.18, known as dinutuximab. Dinutuximab used in combination with granulocyte-macrophage colony-stimulating factor, interleukin-2, and isotretinoin (13-cis-retinoic acid) has a US Food and Drug Administration (FDA)-registered indication for treating high-risk NB patients who achieved at least a partial response to prior first-line multi-agent, multimodality therapy. The FDA registration resulted from a prospective randomized trial assessing the benefit of adding dinutuximab + cytokines to post-myeloablative maintenance therapy for high-risk NB. Dinutuximab has also shown promising antitumor activity when combined with temozolomide and irinotecan in treating NB progressive disease. Clinical activity of dinutuximab and other GD2-targeted therapies relies on the presence of the GD2 antigen on NB cells. Some NBs have been reported as GD2 low or negative, and such tumor cells could be nonresponsive to anti-GD2 therapy. As dinutuximab relies on complement and effector cells to mediate NB killing, factors affecting those components of patient response may also decrease dinutuximab effectiveness. This review summarizes the development of GD2 antibody-targeted therapy, the use of dinutuximab in both up-front and salvage therapy for high-risk NB, and the potential mechanisms of resistance to dinutuximab.

BiHC, a T-Cell-Engaging Bispecific Recombinant Antibody, Has Potent Cytotoxic Activity Against Her2 Tumor Cells

Among different cancer immunotherapy approaches, bispecific antibodies (BsAbs) are of great interest due to their ability to recruit immune cells to kill tumor cells directly. Various BsAbs against Her2 tumor cells have been proposed with potent cytotoxic activities. However, most of these formats require extensive processing to obtain heterodimeric bispecific antibodies. In this study, we describe a bispecific antibody, BiHC (bispecific Her2-CD3 antibody), constructed with a single-domain anti-Her2 and a single-chain Fv (variable fragment) of anti-CD3 in an IgG-like format. In contrast to most IgG-like BsAbs, the two arms in BiHC have different molecular weights, making it easier to separate hetero- or homodimers. BiHC can be expressed in Escherichia coli and purified via Protein A affinity chromatography. The purified BiHC can recruit T cells and induce specific cytotoxicity of Her2-expressing tumor cells in vitro. The BiHC can also efficiently inhibit the tumor growth in vivo. Thus, BiHC is a promising candidate for the treatment of Her2-positive cancers.

Human eosinophils constitutively express a unique serine protease, PRSS33

BACKGROUND

Eosinophils play important roles in asthma, especially airway remodeling, by producing various granule proteins, chemical mediators, cytokines, chemokines and proteases. However, protease production by eosinophils is not fully understood. In the present study, we investigated the production of eosinophil-specific proteases/proteinases by transcriptome analysis.

METHODS

Human eosinophils and other cells were purified from peripheral blood by density gradient sedimentation and negative/positive selections using immunomagnetic beads. Protease/proteinase expression in eosinophils and release into the supernatant were evaluated by microarray analysis, qPCR, ELISA, flow cytometry and immunofluorescence staining before and after stimulation with eosinophil-activating cytokines and secretagogues. mRNAs for extracellular matrix proteins in human normal fibroblasts were measured by qPCR after exposure to recombinant protease serine 33 (PRSS33) protein (rPRSS33), created with a baculovirus system.

RESULTS

Human eosinophils expressed relatively high levels of mRNA for metalloproteinase 25 (MMP25), a disintegrin and metalloprotease 8 (ADAM8), ADAM10, ADAM19 and PRSS33. Expression of PRSS33 was the highest and eosinophil-specific. PRSS33 mRNA expression was not affected by eosinophil-activating cytokines. Immunofluorescence staining showed that PRSS33 was co-localized with an eosinophil granule protein. PRSS33 was not detected in the culture supernatant of eosinophils even after stimulation with secretagogues, but its cell surface expression was increased. rPRSS33 stimulation of human fibroblasts increased expression of collagen and fibronectin mRNAs, at least in part via protease-activated receptor-2 activation.

CONCLUSIONS

Activated eosinophils may induce fibroblast extracellular matrix protein synthesis via cell surface expression of PRSS33, which would at least partly explain eosinophils' role(s) in airway remodeling.

Role for cFMS in maintaining alternative macrophage polarization in SIV infection: implications for HIV neuropathogenesis

BACKGROUND

Macrophage-colony stimulating factor (M-CSF) has been implicated in HIV neuropathogenesis through its ability to modulate activation of macrophages (MΦs) and microglia, as well as enhance the susceptibility of these cells to infection and promote virus production. We have recently reported that MΦs accumulating perivascularly and within nodular lesions in archival brain tissue of simian immunodeficiency virus (SIV)-infected rhesus macaques with encephalitis (SIVE) express M-CSF. In contrast, IL-34, which shares the same receptor, cFMS, was observed more often in parenchymal cells.

METHODS

Frontal white and grey matter from non-infected and SIV-infected rhesus macaques with and without SIVE were examined by single- and double-label immunohistochemistry for M-CSF, IL-34, and CD163 expression. Primary rhesus macaque and human peripheral blood mononuclear cells were cultured with and without 2.5 ng/ml M-CSF or IL-34 alone and with 470 nM or 4.7 μM of GW2580, a receptor tyrosine kinase inhibitor with high specificity for cFMS. After 24 h, cells were analyzed by flow cytometry to examine the effect of these cytokines on promoting an M2 monocyte/MΦ phenotype.

RESULTS

Here, we demonstrate that in SIVE brain, accumulating M-CSF(+) MΦs are also CD163(+), while IL-34 does not appear to co-localize significantly with CD163 in the parenchyma. We further demonstrate that M-CSF and IL-34 are expressed by neurons in normal brain but are altered in SIV and SIVE. Through in vitro studies, we show that M-CSF and IL-34 upregulate CD163, a marker for type 2 activation of MΦs (M2), by primary monocytes, which is attenuated by the addition of GW2580.

CONCLUSIONS

Together, these data suggest that both cFMS ligands may promote and/or prolong M2 activation of MΦs and microglia in brains of SIV-infected animals with encephalitis. As such, cFMS signaling may be an attractive target for eliminating long-lived MΦ reservoirs of HIV infection in brain, as well as other tissues.

Disialoganglioside GD2 as a therapeutic target for human diseases

INTRODUCTION

Ganglioside GD2 is found in vertebrates and invertebrates, overexpressed among pediatric and adult solid tumors, including neuroblastoma, glioma, retinoblastoma, Ewing's family of tumors, rhabdomyosarcoma, osteosarcoma, leiomyosarcoma, liposarcoma, fibrosarcoma, small cell lung cancer and melanoma. It is also found on stem cells, neurons, some nerve fibers and basal layer of the skin.

AREAS COVERED

GD2 provides a promising clinical target for radiolabeled antibodies, bispecific antibodies, chimeric antigen receptor (CAR)-modified T cells, drug conjugates, nanoparticles and vaccines. Here, we review its biochemistry, normal physiology, role in tumorigenesis, important characteristics as a target, as well as anti-GD2-targeted strategies.

EXPERT OPINION

Bridging the knowledge gaps in understanding the interactions of GD2 with signaling molecules within the glycosynapses, and the regulation of its cellular expression should improve therapeutic strategies targeting this ganglioside. In addition to anti-GD2 IgG mAbs, their drug conjugates, radiolabeled forms especially when genetically engineered to improve therapeutic index and novel bispecific forms or CARs to retarget T-cells are promising candidates for treating metastatic cancers.

Monocytes with angiogenic potential are selectively induced by liver resection and accumulate near the site of liver regeneration

Background

Monocytes reportedly contribute to liver regeneration. Three subsets have been identified to date: classical, intermediate, non-classical monocytes. The intermediate population and a subtype expressing TIE2 (TEMs) were suggested to promote angiogenesis. In a clinical setting, we investigated which monocyte subsets are regulated after liver resection and correlate with postoperative liver function.

Methods

In 38 patients monocyte subsets were evaluated in blood and subhepatic wound fluid by flow cytometry before and 1-3 days after resection of colorectal liver metastases. The monocyte-regulating cytokines macrophage colony stimulating factor (M-CSF), transforming growth factor beta 1 (TGFβ1), and angiopoietin 2 (ANG-2) were measured in patient plasma by ELISA. C-reactive protein (CRP) and liver function parameters were retrieved from routine hospital analyses.

Results

On post-operative day (POD) 1 blood monocytes shifted to significantly elevated levels of intermediate monocytes. In wound fluid, a delayed surge in intermediate monocytes was detected by POD 3. Furthermore, TEMs were highly enriched in wound fluid as compared to circulation. CRP and M-CSF levels were substantially increased in patient blood after surgery and correlated significantly with the frequency of intermediate monocytes. In addition, liver function parameters showed a significant association with intermediate monocyte levels on POD 3.

Conclusions

The reportedly pro-angiogenic subsets of monocytes are selectively increased upon liver resection and accumulate next to the site of liver regeneration. As previously proposed by in vitro experiments, the release of CRP and M-CSF may trigger the induction of intermediate monocytes. The correlation with liver parameters points to a functional involvement of these monocyte populations in liver regeneration which warrants further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-014-0050-3) contains supplementary material, which is available to authorized users.

Anti-GD2 antibody 3F8 and barley-derived (1 → 3),(1 → 4)-β-D-glucan: A Phase I study in patients with chemoresistant neuroblastoma

β-glucans are complex, naturally-occurring polysaccharides that prime leukocyte dectin and complement receptor 3. Based on our preclinical findings, indicating that oral barley-derived (1 → 3),(1 → 4)-β-D-glucan (BG) synergizes with the murine anti-GD2 antibody 3F8 against neuroblastoma, we conducted a Phase I clinical study to evaluate the safety of this combinatorial regimen in patients affected by chemoresistant neuroblastoma. In this setting, four cohorts of six heavily pre-treated patients bearing recurrent or refractory advanced-stage neuroblastoma were treated with 3F8 plus BG. Each cycle consisted of intravenous 3F8 at a fixed dose of 10 mg/m²/day plus concurrent oral BG, dose-escalated from 10 to 80 mg/Kg/day, for 10 d. Patients who did not develop human anti-mouse antibodies could be treated for up to 4 cycles. Twenty-four patients completed 50 cycles of therapy. All patients completed at least one cycle and were evaluable for the assessment of toxicity and responses. The maximum tolerated dose of BG was not reached, but two patients developed dose-limiting toxicities. These individuals developed grade 4 thrombocytopenia after one cycle of BG at doses of 20 mg/Kg/day and 40 mg/Kg/day, respectively. Platelet counts recovered following the administration of idiopathic thrombocytopenic purpura therapy. There were no other toxicities of grade > 2. Eleven and 13 patients manifested stable and progressive disease, respectively. Thirteen out of 22 patients with pre-treatment positive ¹²³I-MIBG scans demonstrated clinical improvement on semiquantitative scoring. Responses did not correlate with BG dose or with in vitro cytotoxicity. In summary, 3F8 plus BG is well tolerated and shows antineoplastic activity in recurrent or refractory advanced-stage neuroblastoma patients. Further clinical investigation of this novel combinatorial immunotherapeutic regimen is warranted.

Evidence for cFMS signaling in HIV production by brain macrophages and microglia

Combination antiretroviral therapy (cART) has improved the longevity and quality of life for people living with HIV; however, it does not target virus that persists in long-lived cells, such as macrophages (MΦs). This allows for the development of viral reservoirs in various anatomical compartments where these cells reside, including the central nervous system (CNS), where perivascular MΦs and resident microglia constitute the principle cellular reservoir of HIV. How HIV persists in MΦs/microglia is not completely understood; however, prosurvival signaling that protects infected MΦs/microglia from apoptosis is likely important to viral persistence. Macrophage colony-stimulating factor (M-CSF) is an important factor in MΦ survival and has been implicated in HIV neuropathogenesis through its ability to enhance the susceptibility of MΦs to infection and promote virus production. While M-CSF has been detected in cerebrospinal fluid of HIV-infected patients, the cellular source of M-CSF in the CNS is unknown. Here, we demonstrate, for the first time, that MΦs comprising perivascular cuffs and nodular lesions in SIV encephalitis (SIVE) brain are the principle source of M-CSF. These cells also serve as the primary reservoir of productive SIV infection in the brain. We further demonstrate that M-CSF and IL-34, which signal through the same receptor, cFMS, enhance HIV-1 production by microglia in vitro. This is attenuated by the addition of a receptor tyrosine kinase inhibitor with high specificity for cFMS, GW2580. Together, these data suggest that cFMS signaling may be an attractive target for eliminating long-lived MΦ reservoirs of HIV in the brain and other tissues.

GD2-targeted immunotherapy and radioimmunotherapy

Ganglioside GD2 is a tumor-associated surface antigen found in a broad spectrum of human cancers and stem cells. They include pediatric embryonal tumors (neuroblastoma, retinoblastoma, brain tumors, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma), as well as adult cancers (small cell lung cancer, melanoma, soft tissue sarcomas). Because of its restricted normal tissue distribution, GD2 has been proven safe for antibody targeting. Anti-GD2 antibody is now incorporated into the standard of care for the treatment of high-risk metastatic neuroblastoma. Building on this experience, novel combinations of antibodies, cytokines, cells, and genetically engineered products all directed at GD2 are rapidly moving into the clinic. In this review, past and present immunotherapy trials directed at GD2 will be summarized, highlighting the lessons learned and the future directions.

Macrophages inhibit human osteosarcoma cell growth after activation with the bacterial cell wall derivative liposomal muramyl tripeptide in combination with interferon-γ

Background

In osteosarcoma, the presence of tumor-infiltrating macrophages positively correlates with patient survival in contrast to the negative effect of tumor-associated macrophages in patients with other tumors. Liposome-encapsulated muramyl tripeptide (L-MTP-PE) has been introduced in the treatment of osteosarcoma patients, which may enhance the potential anti-tumor activity of macrophages. Direct anti-tumor activity of human macrophages against human osteosarcoma cells has not been described so far. Hence, we assessed osteosarcoma cell growth after co-culture with human macrophages.

Methods

Monocyte-derived M1-like and M2-like macrophages were polarized with LPS + IFN-γ, L-MTP-PE +/− IFN-γ or IL-10 and incubated with osteosarcoma cells. Two days later, viable tumor cell numbers were analyzed. Antibody-dependent effects were investigated using the therapeutic anti-EGFR antibody cetuximab.

Results

M1-like macrophages inhibited osteosarcoma cell growth when activated with LPS + IFN-γ. Likewise, stimulation of M1-like macrophages with liposomal muramyl tripeptide (L-MTP-PE) inhibited tumor growth, but only when combined with IFN-γ. Addition of the tumor-reactive anti-EGFR antibody cetuximab did not further improve the anti-tumor activity of activated M1-like macrophages. The inhibition was mediated by supernatants of activated M1-like macrophages, containing TNF-α and IL-1β. However, specific blockage of these cytokines, nitric oxide or reactive oxygen species did not inhibit the anti-tumor effect, suggesting the involvement of other soluble factors released upon macrophage activation. While LPS + IFN-γ–activated M2-like macrophages had low anti-tumor activity, IL-10–polarized M2-like macrophages were able to reduce osteosarcoma cell growth in the presence of the anti-EGFR cetuximab involving antibody-dependent tumor cell phagocytosis.

Conclusion

This study demonstrates that human macrophages can be induced to exert direct anti-tumor activity against osteosarcoma cells. Our observation that the induction of macrophage anti-tumor activity by L-MTP-PE required IFN-γ may be of relevance for the optimization of L-MTP-PE therapy in osteosarcoma patients.

Neuroblastoma: developmental biology, cancer genomics and immunotherapy

Neuroblastoma is a solid tumour that arises from the developing sympathetic nervous system. Over the past decade, our understanding of this disease has advanced tremendously. The future challenge is to apply the knowledge gained to developing risk-based therapies and, ultimately, improving outcome. In this Review we discuss the key discoveries in the developmental biology, molecular genetics and immunology of neuroblastoma, as well as new translational tools for bringing these promising scientific advances into the clinic.

Particle platforms for cancer immunotherapy

Elevated understanding and respect for the relevance of the immune system in cancer development and therapy has led to increased development of immunotherapeutic regimens that target existing cancer cells and provide long-term immune surveillance and protection from cancer recurrence. This review discusses using particles as immune adjuvants to create vaccines and to augment the anticancer effects of conventional chemotherapeutics. Several particle prototypes are presented, including liposomes, polymer nanoparticles, and porous silicon microparticles, the latter existing as either single- or multiparticle platforms. The benefits of using particles include immune-cell targeting, codelivery of antigens and immunomodulatory agents, and sustained release of the therapeutic payload. Nanotherapeutic-based activation of the immune system is dependent on both intrinsic particle characteristics and on the immunomodulatory cargo, which may include danger signals known as pathogen-associated molecular patterns and cytokines for effector-cell activation.

Intermediate monocytes but not TIE2-expressing monocytes are a sensitive diagnostic indicator for colorectal cancer

We have conducted the first study to determine the diagnostic potential of the CD14++CD16+ intermediate monocytes as compared to the pro-angiogenic subset of CD14++CD16+TIE2+ TIE2-expressing monocytes (TEMs) in cancer. These monocyte populations were investigated by flow cytometry in healthy volunteers (N = 32) and in colorectal carcinoma patients with localized (N = 24) or metastatic (N = 37) disease. We further determined blood levels of cytokines associated with monocyte regulation. The results revealed the intermediate monocyte subset to be significantly elevated in colorectal cancer patients and to show the highest frequencies in localized disease. Multivariate regression analysis identified intermediate monocytes as a significant independent variable in cancer prediction. With a cut-off value at 0.37% (intermediate monocytes of total leukocytes) the diagnostic sensitivity and specificity ranged at 69% and 81%, respectively. In contrast, TEM levels were elevated in localized cancer but did not differ significantly between groups and none of the cytokines correlated with monocyte subpopulations. Of interest, in vitro analyses supported the observation that intermediate monocytes were more potently induced by primary as opposed to metastatic cancer cells which may relate to the immunosuppressive milieu established in the advanced stage of metastatic disease. In conclusion, intermediate monocytes as compared to TIE2-expressing monocytes are a more sensitive diagnostic indicator of colorectal cancer.

The Bruton tyrosine kinase inhibitor PCI-32765 ameliorates autoimmune arthritis by inhibition of multiple effector cells

INTRODUCTION

The aim was to determine the effect of the Bruton tyrosine kinase (Btk)-selective inhibitor PCI-32765, currently in Phase I/II studies in lymphoma trials, in arthritis and immune-complex (IC) based animal models and describe the underlying cellular mechanisms.

METHODS

PCI-32765 was administered in a series of murine IC disease models including collagen-induced arthritis (CIA), collagen antibody-induced arthritis (CAIA), reversed passive anaphylactic reaction (RPA), and passive cutaneous anaphylaxis (PCA). Clinical and pathologic features characteristic of each model were examined following treatment. PCI-32765 was then examined in assays using immune cells relevant to the pathogenesis of arthritis, and where Btk is thought to play a functional role. These included proliferation and calcium mobilization in B cells, cytokine and chemokine production in monocytes/macrophages, degranulation of mast cells and its subsequent cytokine/chemokine production.

RESULTS

PCI-32765 dose-dependently and potently reversed arthritic inflammation in a therapeutic CIA model with an ED(50) of 2.6 mg/kg/day. PCI-32765 also prevented clinical arthritis in CAIA models. In both models, infiltration of monocytes and macrophages into the synovium was completely inhibited and importantly, the bone and cartilage integrity of the joints were preserved. PCI-32765 reduced inflammation in the Arthus and PCA assays. In vitro, PCI-32765 inhibited BCR-activated primary B cell proliferation (IC(50) = 8 nM). Following FcγR stimulation, PCI-32765 inhibited TNFα, IL-1β and IL-6 production in primary monocytes (IC(50) = 2.6, 0.5, 3.9 nM, respectively). Following FcεRI stimulation of cultured human mast cells, PCI-32765 inhibited release of histamine, PGD(2), TNF-α, IL-8 and MCP-1.

CONCLUSIONS

PCI-32765 is efficacious in CIA, and in IC models that do not depend upon autoantibody production from B cells. Thus PCI-32765 targets not only B lymphocytes but also monocytes, macrophages and mast cells, which are important Btk-expressing effector cells in arthritis.

Successful multifold dose escalation of anti-GD2 monoclonal antibody 3F8 in patients with neuroblastoma: a phase I study

PURPOSE

Pain can hinder immunotherapy with anti-G(D2) monoclonal antibodies (MoAbs) like 3F8. Heat-modified 3F8 (HM3F8) lacks effector functions and could mask G(D2) or cross-reactive epitopes on nerves, thereby preventing a subsequent dose of unmodified 3F8 from activating pain fibers. We hypothesized that 3F8 dose escalation is possible without increased analgesic requirements in patients pretreated with HM3F8.

PATIENTS AND METHODS

Thirty patients with resistant neuroblastoma (NB) received one to two cycles of 3F8 plus granulocyte-macrophage colony-stimulating factor. 3F8 dosing began at 20 mg/m(2)/d and increased by 20 mg/m(2)/d in the absence of dose-limiting toxicity (DLT). Premedication included analgesics, antihistamines, and 5-minute infusions of HM3F8. On the basis of experience with 3F8 10 mg/m(2)/d in prior protocols, the DLT of pain was defined as more than seven doses of opioids administered within 2 hours. Opioid use was compared with a contemporary control group treated with 3F8 20 mg/m(2)/d but no HM3F8. Disease response was assessed.

RESULTS

Treatment was administered in the outpatient setting. Dose escalation stopped at 160 mg/m(2)/d because of drug supply limitations; even through this dosage level, analgesic requirements were similar to historical controls, and there were no DLTs. Analgesic requirements at 3F8 dosage levels through 80 mg/m(2)/d were significantly less compared with controls. Anti-NB activity occurred at all dosages.

CONCLUSION

Multifold dose escalation of 3F8 is feasible. The findings can be interpreted as compatible with the possibility that HM3F8 can modify toxicity without blunting anti-NB activity. This pain control strategy may help achieve dose escalation with other anti-G(D2) MoAbs.

Neuroblastoma: Therapeutic strategies for a clinical enigma

Neuroblastoma, the most common extracranial pediatric solid tumor remains a clinical enigma with outcomes ranging from cure in >90% of patients with locoregional tumors with little to no cytotoxic therapy, to <30% for those >18months of age at diagnosis with metastatic disease despite aggressive multimodality therapy. Age, stage and amplification of the MYCN oncogene are the most validated prognostic markers. Recent research has shed light on the biology of neuroblastoma allowing more accurate stratification of patients which has permitted reducing or withholding cytotoxic therapy without affecting outcome for low-risk patients. However, for children with high-risk disease, the development of newer therapeutic strategies is necessary. Current surgery and radiotherapy techniques in conjunction with induction chemotherapy have greatly reduced the risk of local relapse. However, refractory or recurrent osteomedullary disease occurs in most patients with high-risk neuroblastoma. Toxicity limits for high-dose chemotherapy appear to have been reached without further clinical benefit. Neuroblastoma is the first pediatric cancer for which monoclonal-antibody-based immunotherapy has been shown to be effective, particularly for metastatic osteomedullary disease. Radioimmunotherapy appears to be a critical component of a recent, successful regimen for treating patients who relapse in the central nervous system, a possible sanctuary site. Efforts are under way to refine and enhance antibody-based immunotherapy and to determine its optimal use. The identification of newer tumor targets and the harnessing of cell-mediated immunotherapy may generate novel therapeutic approaches. It is likely that a combination of therapeutic modalities will be required to improve survival and cure rates.

Development of macrophages of cyprinid fish

The innate immune responses of early vertebrates, such as bony fishes, play a central role in host defence against infectious diseases and one of the most important effector cells of innate immunity are macrophages. In order for macrophages to be effective in host defence they must be present at all times in the tissues of their host and importantly, the host must be capable of rapidly increasing macrophage numbers during times of need. Hematopoiesis is a process of formation and development of mature blood cells, including macrophages. Hematopoiesis is controlled by soluble factors known as cytokines, that influence changes in transcription factors within the target cells, resulting in cell fate changes and the final development of specific effector cells. The processes involved in macrophage development have been largely derived from mammalian model organisms. However, recent advancements have been made in the understanding of macrophage development in bony fish, a group of organisms that rely heavily on their innate immune defences. Our understanding of the growth factors involved in teleost macrophage development, as well as the receptors and regulatory mechanisms in place to control them has increased substantially. Furthermore, model organisms such as the zebrafish have emerged as important instruments in furthering our understanding of the transcriptional control of cell development in fish as well as in mammals. This review highlights the recent advancements in our understanding of teleost macrophage development. We focused on the growth factors identified to be important in the regulation of macrophage development from a progenitor cell into a functional macrophage and discuss the important transcription factors that have been identified to function in teleost hematopoiesis. We also describe the findings of in vivo studies that have reinforced observations made in vitro and have greatly improved the relevance and importance of using teleost fish as model organisms for studying developmental processes.

Disialoganglioside directed immunotherapy of neuroblastoma

Achieving a cure for metastatic neuroblastoma remains a challenge despite sensitivity to chemotherapy and radiotherapy. Most patients achieve remission, but a failure to eliminate minimal residual disease (MRD) often leads to relapse. Immunotherapy is potentially useful for chemotherapy-resistant disease and may be particularly effective for low levels of MRD that are below the threshold for detection by routine radiological and histological methods. Disialoganglioside (GD2), a surface glycolipid antigen that is ubiquitous and abundant on neuroblastoma cells is an ideal target for immunotherapy. Anti-GD2 monoclonal antibodies currently form the mainstay of neuroblastoma immunotherapy and their safety profile has been well-established. Although responses in patients with gross disease have been observed infrequently, histologic responses of bone marrow disease are consistently achieved in >75 percent of patients with primary refractory neuroblastoma. The advent of highly sensitive and specific molecular assays to measure MRD has confirmed the efficacy anti-GD2 antibody immunotherapy in patients with subclinical disease. Such markers will allow further optimization of other anti-MRD therapies. We review the current status of anti-GD2 clinical trials for neuroblastoma and novel preclinical GD2-targeted strategies for this rare but often lethal childhood cancer.

Three-colour flow cytometric method to measure antibody-dependent tumour cell killing by cytotoxicity and phagocytosis

We have developed a three-colour flow cytometric method to assay the contributions of cytotoxicity and phagocytosis to antibody-dependent cell-mediated tumour cell killing. In this assay, tumour target cells are pre-labelled with CFSE, and mixed with effector cells and a tumour antigen-specific monoclonal antibody. After incubation of the cells with the antibody, effector cells are labelled with PE and dead cells with PI. Using flow cytometry, dead and phagocytosed tumour cells can be quickly and easily counted and the numbers summed to determine the total number of killed cells. One can thereby measure the phagocytic aspect of antibody-dependent cell-mediated tumour cell killing, otherwise only revealed by microscopic examination. The failure to detect phagocytosed, in addition to live and dead target cells, by standard assays may result in an underestimation of tumour cell killing and hence the potential of an antibody for immunotherapy of cancer. We illustrate the new method by analysing human monocyte-mediated cytotoxic and phagocytic cell killing of IGROV1 ovarian tumour cells by the ovarian tumour antigen-specific anti-folate binding protein monoclonal antibody, MOv18 IgE.

Rapid and strong induction of apoptosis in human eosinophils by anti-CD30 mAb-coated microspheres and phagocytosis by macrophages

BACKGROUND

Eosinophils represent a potential therapeutic target in allergic diseases. We previously reported that two clones of anti-CD30 mAbs (HRS-4 and Ber-H8) induced extremely rapid and intense apoptosis in human eosinophils in vitro, but only when the mAbs were immobilized on plates [Matsumoto K, J Immunol 2004;172:2186]. As the initial step towards clinical application of these anti-CD30 mAbs in the treatment of allergic diseases, we made an attempt to clarify two issues; first, whether or not anti-CD30 mAb-coated microspheres can efficiently induce apoptosis in human eosinophils, and second, whether or not these apoptotic eosinophils can be phagocytosed by macrophages without the release of granular proteins.

METHODS

Purified human eosinophils were treated with anti-CD30 mAb-coated polystyrene microspheres (diameter, 1.44 mum). Apoptosis was determined by annexin V-binding. For the phagocytosis assay, eosinophils were co-cultured with monocyte-derived human macrophages or PMA-pretreated U-937 cells. Phagocytosis was determined by light microscopy and by the eosinophil-derived neurotoxin (EDN) concentration in the supernatant.

RESULTS

Anti-CD30 mAb-coated, but not control IgG1-coated microspheres significantly reduced eosinophil survival in a dose-dependent manner. Marked phagocytosis of the apoptotic eosinophils by macrophages was also observed when the eosinophils were treated with anti-CD30 mAb-coated microspheres. The apoptotic eosinophils released large amounts of EDN in the absence of macrophages; however, the EDN levels were significantly decreased when the eosinophils were co-cultured with macrophages.

CONCLUSIONS

Anti-CD30 mAb-coated microspheres are capable of inducing rapid and strong apoptosis in human eosinophils. Furthermore, the apoptotic eosinophils were also phagocytosed by macrophages with minimal release of the granular proteins.

Influence of immunomodulatory drugs on the cytotoxicity induced by monoclonal antibody 17-1A and interleukin-2

Patients treated with monoclonal antibodies and cytokines for cancer receive often co-medication, which may influence treatment efficacy. Therefore, we investigated with a flowcytometric cytotoxicity assay the effect of several immunomodulatory drugs on antibody dependent cellular cytotoxicity (ADCC), interleukin-2 (IL-2) induced cytotoxicity and IL-2-induced-ADCC. We found that dexamethasone markedly inhibited the IL-2 induced cytotoxicity and the IL-2-induced-ADCC. Ondansetron, a 5-HT-3 serotonin receptor antagonist augmented significantly ADCC. Clemastine, a histamine type-2 receptor antagonist augmented the IL-2-induced-ADCC. The TNF antagonist thalidomide suppressed ADCC whereas pentoxifylline proved to be ineffective. Other tested drugs namely ibuprofen and indomethacin, both prostaglandin E2 antagonists, cimetidine a histamine type-2 receptor antagonist, the opioid pethidine, prostaglandin E2 and histamine exerted minor effects or had no influence on the tested parameters. We conclude that glucocorticosteroids should be avoided with monoclonal antibody and cytokine treatment. According to our in vitro data the other drugs tested did not have a negative impact on cellular cytotoxicity and ADCC.

Effects of histologic type on levels of macrophage colony-stimulating factor in liquid contents of benign ovarian tumors

BACKGROUND

Normal ovarian tissue is rich in cytokines. Cytokines are important in the physiology of ovarian function. Most of the same cytokines that are found in normal ovarian tissue are also found in association with benign and malignant tumors in contrast to their functions in normal tissues. Thus, we measured macrophage colony-stimulating factor (M-CSF) levels in the liquid contents of benign ovarian tumors--serous cystadenoma, mucinous cystadenoma, and mature cystic teratoma--and investigated whether M-CSF levels were associated with the histologic type of the ovarian tumors.

METHODS

We enrolled 65 patients, 52 with benign ovarian tumor and 13 in the early postmenopausal period with symptoms of a menopausal disorder. Among the 52 patients with benign ovarian tumor, 16 had serous cystadenoma, 21 had mucinous cystadenoma, and 15 had mature cystic teratoma. Immediately after surgery, the liquid content was drawn from the ovarian tumor, then centrifuged, and the separated supernatant was stored at -30 degrees C. The M-CSF level was determined by the sandwich enzyme-linked immunosorbent assay method with use of three antibodies.

RESULTS

The level of M-CSF was 12,513 U/mL (median) (range, 0-169,000 U/mL) in serous cystadenoma, 915 U/mL (0-82,500 U/mL) in mucinous cystadenoma, and 149 U/mL (0-6,230 U/mL) in mature cystic teratoma. The M-CSF levels increased significantly from mature cystic teratoma to mucinous cystadenoma to serous cystadenoma. The serum M-CSF levels were 308 to 499 U/mL in patients with benign ovarian tumor. The M-CSF levels did not differ significantly among the three groups. The serum M-CSF levels were 162 U/mL (0-473 U/mL) in menopausal patients.

CONCLUSIONS

Elevation of levels of M-CSF varies according to histologic type in benign ovarian tumors. This implies that the antitumor activities of M-CSF for serous cystadenoma, mucinous cystadenoma, and mature cystic teratoma differ by histologic type.

The CCR4 as a novel-specific molecular target for immunotherapy in Hodgkin lymphoma

Here, we report that tumor cells from some patients (23.8%) with Hodgkin lymphoma (HL) are positive for CC chemokine receptor 4 (CCR4). We therefore tested the chimeric anti-CCR4 monoclonal antibody (mAb), KM2760, the Fc region of which is defucosylated to enhance antibody-dependent cellular cytotoxicity (ADCC), as a novel immunotherapy for refractory HL. KM2760 demonstrated a promising antitumor activity in the CCR4-positive HL-bearing mouse model in the therapeutic setting. Although KM2760 did not induce any ADCC mediated by mouse natural killer (NK) cells, it significantly enhanced phagocytosis mediated by mouse monocytes/macrophages against the CCR4-positive HL cell line in vitro. Together with the findings that KM2760 did not exhibit any complement-dependent cytotoxicity or direct antiproliferation activity in vitro, these data indicated that KM2760 exerted its robust in vivo antitumor activity via monocytes/macrophages in mice. In the human system, KM2760 enhanced phagocytic activity mediated by monocytes/macrophages. Furthermore, it induced robust ADCC mediated by NK cells against the CCR4-positive HL cell line in vitro. Thus, it is conceivable that KM2760 would have much more potent antitumor activity in humans than in mice. Collectively, this study strongly indicates that anti-CCR4 mAb could be a novel treatment modality for patients with CCR4-positive HL.

R406, an orally available spleen tyrosine kinase inhibitor blocks fc receptor signaling and reduces immune complex-mediated inflammation

Recent compelling evidence has lead to renewed interest in the role of antibodies and immune complexes in the pathogenesis of several autoimmune disorders, such as rheumatoid arthritis. These immune complexes, consisting of autoantibodies to self-antigens, can mediate inflammatory responses largely through binding and activating the immunoglobulin Fc receptors (FcRs). Using cell-based structure activity relationships with cultured human mast cells, we have identified the small molecule R406 [N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine] as a potent inhibitor of immunoglobulin E (IgE)- and IgG-mediated activation of Fc receptor signaling (EC(50) for degranulation = 56-64 nM). Here we show that the primary target for R406 is the spleen tyrosine kinase (Syk), which plays a key role in the signaling of activating Fc receptors and the B-cell receptor (BCR). R406 inhibited phosphorylation of Syk substrate linker for activation of T cells in mast cells and B-cell linker protein/SLP65 in B cells. R406 bound to the ATP binding pocket of Syk and inhibited its kinase activity as an ATP-competitive inhibitor (K(i) = 30 nM). Furthermore, R406 blocked Syk-dependent FcR-mediated activation of monocytes/macrophages and neutrophils and BCR-mediated activation of B lymphocytes. R406 was selective as assessed using a large panel of Syk-independent cell-based assays representing both specific and general signaling pathways. Consistent with Syk inhibition, oral administration of R406 to mice reduced immune complex-mediated inflammation in a reverse-passive Arthus reaction and two antibody-induced arthritis models. Finally, we report a first-inhuman study showing that R406 is orally bioavailable, achieving exposures capable of inhibiting Syk-dependent IgE-mediated basophil activation. Collectively, the results show R406 potential for modulating Syk activity in human disease.

FCGR2A Polymorphism Is Correlated With Clinical Outcome After Immunotherapy of Neuroblastoma With Anti-GD2 Antibody and Granulocyte Macrophage Colony-Stimulating Factor

Purpose

Anti-GD2 murine IgG3 antibody 3F8 kills neuroblastoma cells by antibody-dependent cell-mediated cytotoxicity (ADCC). Granulocyte macrophage colony-stimulating factor (GM-CSF) enhances phagocyte-mediated ADCC. The differential affinity of the human FCGR polymorphic alleles for 3F8 may influence the effectiveness of antibody immunotherapy.

Patients and Methods

The entire cohort of high risk neuroblastoma patients (N = 136) treated on protocol using 3F8 and GM-CSF were the subjects of this analysis. Tumor response was measured by standard clinical tools plus sensitive molecular monitoring using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Polymorphic alleles of FCGR2A and FCGR3A were determined by PCR plus direct sequencing using genomic DNA samples obtained from marrow or blood of patients.

Results

FCGR2A (R/R) genotype correlated with progression-free survival for the entire cohort (P = .049) and for the subset of patients with no history of prior relapse (P = .023). FCGR2A (R/R) also correlated with marrow remission 2.5 months after treatment initiation: by histology (P = .021 and P = .036, for the entire cohort and the subset, respectively) and by qRT-PCR (P = .052 and P = .033, respectively).

Conclusion

The favorable outcome associated with FCGR2A (R/R) genotype is consistent with the proposed role of FCGR2A and phagocyte-mediated ADCC in 3F8 plus GM-CSF immunotherapy.

Defective Antitumor Function of Monocyte-Derived Macrophages from Epithelial Ovarian Cancer Patients

PURPOSE

Monocytes/macrophages (MO/MA) are an important but heterogeneous population of immune inflammatory cells that have diverse effector functions. We examined and compared these differences in peripheral blood and ascites of epithelial ovarian cancer patients with peripheral blood of normal donors.

EXPERIMENTAL DESIGN

Comparisons were made of cell surface subsets, cytokine production, and FcR-dependent cytotoxicity of CD14+ MO/MA and the CD14brightCD16-HLA-DR+ MO/MA subset in normal donor peripheral blood and peripheral blood and ascites from epithelial ovarian cancer patients. Studies were done on monocyte-derived macrophages cultured with macrophage colony-stimulating factor and activated with lipopolysaccharide or a combination of lipopolysaccharide plus recombinant IFN-gamma.

RESULTS

We determined that MO/MA or its subset from epithelial ovarian cancer patients had altered morphology and significantly less antibody-dependent cell-mediated cytotoxicity and phagocytic activity than did MO/MA from normal donors. Our findings also showed that monocyte-derived macrophages from both epithelial ovarian cancer patients and normal donors produce macrophage colony-stimulating factor-stimulated cytokines, including interleukin-8, tumor necrosis factor-alpha, and interleukin-6.

CONCLUSIONS

These findings highlight for the first time the defective antibody-dependent cell-mediated cytotoxicity and phagocyte functions of epithelial ovarian cancer-associated MO/MA, which could have implications for immunobiotherapeutic strategies.

The combination of fludarabine, cyclophosphamide, and granulocyte-macrophage colony-stimulating factor in the treatment of patients with relapsed chronic lymphocytic leukemia and low-grade Non-Hodgkin's lymphoma

PURPOSE

The goal of this study was to evaluate the efficacy of the fludarabine/cyclophosphamide combination in patients with relapsed chronic lymphocytic lymphoma (CLL) and low-grade non-Hodgkin's lymphoma (NHL) and to assess the impact of adding granulocyte-macrophage colony-stimulating factor (GM-CSF) to this regimen in a randomized fashion.

PATIENTS AND METHODS

Thirty-four patients (CLL, n=16; low-grade NHL, n=18) were enrolled. The median number of previous treatments was 2. Patients received <or=6 cycles of fludarabine at 30 mg/m2 per day and cyclophosphamide at 300 mg/m2 per day on days 1-3 of a 28-day cycle. Patients were randomized to supportive care or to receive GM-CSF at 250 mg/m2 per day, starting 24 hours after completion of chemotherapy and continuing up to 48 hours before the next cycle. Those who had received >6 months of previous therapy with an alkylating agent or had preexisting cytopenias received a 25% dose reduction. Twenty-two patients (65%) were randomized to receive GM-CSF. Patients completed a median of 5 cycles of treatment (range, 1-6 cycles). Twenty-seven patients (80%) received >or=3 cycles of treatment and were evaluated for response.

RESULTS

Seven patients (26%) exhibited a complete response; 6 of the 7 had low-grade NHL. Fourteen patients (52%) exhibited a partial response, and 6 patients (22%) had stable disease. Notably, 6 of the 7 patients who exhibited complete response and 9 of 14 patients with partial responses were randomized to the GM-CSF arm. The duration of response ranged from 4 months to 26 months. The toxicities were mainly hematologic. Nineteen patients (70%) experienced >or=1 episode of grade 3/4 neutropenia, but only 4 (15%) experienced febrile neutropenia; 3 of those patients were assigned to the GM-CSF arm.

CONCLUSIONS

The combination of fludarabine and cyclophosphamide is a well-tolerated and effective treatment regimen for patients with relapsed CLL and low-grade NHL. A higher percentage of complete responses were noted in patients with low-grade NHL compared with patients with CLL. Granulocyte-macrophage colony-stimulating factor did not seem to decrease the incidence of febrile neutropenia. However, the higher number of complete and partial responses noted on the GM-CSF arm is intriguing and warrants further investigation.

A potential role of macrophage activation in the treatment of cancer

One of the functions of macrophages is to provide a defense mechanism against tumor cells. In the last decades the mechanism of tumor cell killing by macrophages have been studied extensively. The tumor cytotoxic function of macrophages requires stimulation either with bacterial cell wall products such as lipopolysaccharide (LPS) or muramyldipeptide (MDP) or with cytokines such as interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Activated macrophages secrete several substances that are directly involved in tumor cell killing i.e. tumor necrosis factor (TNF) and nitric oxide (NO). On the other hand, substances are secreted that are able to stimulate tumor cell growth, depending on the stage and the nature of the tumor. Several clinical trials have been performed aiming at the activation of macrophages or dendritic cells, a subpopulation of the macrophages. In this review we will summarize and discuss experimental studies and clinical trials based on the activation of macrophages.

Native human blood dendritic cells as potent effectors in antibody-dependent cellular cytotoxicity

Functional studies on native human dendritic cells (DCs) are hampered by technical difficulties in preparing fresh DCs. Recently, with the help of the monoclonal antibody M-DC8, we succeeded in isolating a major subpopulation of human blood DCs by a one-step immunomagnetic separation procedure. These cells strongly express FcγRIII (CD16) and FcγRII (CD32) and are quite efficient in the antigen-specific activation of naive T cells. Because some Fcγ receptor-bearing cell types are known as effector cells in antibody-dependent cellular cytotoxicity (ADCC), we investigated whether M-DC8+ DCs are capable of effectuating ADCC. In this report we show that freshly prepared M-DC8+ DCs efficiently mediate tumor-directed ADCC and that both types of Fcγ receptors as well as tumor necrosis factor α essentially contribute to the cytotoxic activity. The results provide evidence that, in addition to their pivotal role in primary T-cell activation, a subset of blood DCs displays efficient cytotoxicity in ADCC.

Phase II trial of the anti-G(D2) monoclonal antibody 3F8 and granulocyte-macrophage colony-stimulating factor for neuroblastoma

PURPOSE

To describe oncolytic effects of treatment with anti-G(D2) monoclonal antibody 3F8 plus granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with neuroblastoma (NB).

PATIENTS AND METHODS

Patients were eligible for 3F8/GM-CSF if intensive therapy had not eradicated potentially lethal NB. One cycle consisted of GM-CSF (subcutaneous bolus) on days 1 through 5, 11, and 12, and GM-CSF (2-hour intravenous [IV] infusion) followed after a 1-hour interval by 3F8 (1.5-hour IV infusion) on days 6 through 10 and 13 through 17. GM-CSF was dosed at 250 microg/m(2)/d on days 1 through 7 and at 500 microg/m(2)/d on days 8 through 17. 3F8 was dosed at 10 mg/m(2)/d (100 mg/m(2)/cycle). 3F8 was given with an opiate and an antihistamine. Patients without progressive disease (PD) or elevated human antimouse antibody titers could be treated again beginning 3 weeks after completion of a cycle.

RESULTS

Among 19 patients treated for NB resistant to induction therapy, 12 of 15 had complete remission (CR) of bone marrow (BM) disease, and three others who had less than partial responses achieved prolonged progression-free survival (one remains on study at 21+ months, two had PD at 12 and 17 months). Among patients treated for recurrent NB resistant to retrieval therapy, five of 10 had CR in BM. The 15 patients treated for PD fared poorly, although two had scintigraphic findings suggestive of a short-term response. Side effects were limited to readily manageable pain and, less commonly, rash of short duration; hence, patients were treated as outpatients.

CONCLUSION

3F8/GM-CSF is well tolerated and shows promise for treatment of minimal residual NB in BM.

Natural cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) is not impaired in patients suffering from chronic hepatitis C

BACKGROUND/AIMS

Recent observations suggest that natural killer (NK) cell activity might be impaired in chronic hepatitis C. However, to date antibody-dependent cellular cytotoxicity (ADCC) has not been studied in chronic hepatitis C in detail.

METHODS

Therefore, we investigated spontaneous and cytokine-induced (interleukin-2 and interferon-gamma) natural cytotoxicity and ADCC in 29 patients suffering from chronic hepatitis C and 19 healthy controls. Cytotoxicity was determined with a flow-cytometric assay, which can also assess monocyte cytotoxicity. As target cells we used the colorectal tumor cell line HT29 and the lymphoma cell line Raji.

RESULTS

We found no significant differences with respect to spontaneous cytotoxicity (HCV versus healthy controls (32 vs. 46%) and 17-1A specific ADCC (59 vs. 48%), even if isolated monocytes or NK cells were studied. Preincubation and stimulation of effector cells with cytokines increased both natural cytotoxicity and ADCC by 20-30%. However, natural cytotoxicity and ADCC after stimulation did not differ between the two groups.

CONCLUSIONS

Our data obtained with a long-term cytotoxicity assay do not reveal impaired cytolytic capacity of the innate immune system in chronic hepatitis C, even when isolated monocytes and NK cells were studied as effector cells.

Combinations of the cytokines IL-12, IL-2 and IFN-alpha significantly augment whereas the cytokine IL-4 suppresses the cytokine-induced antibody-dependent cellular cytotoxicity of monoclonal antibodies 17-1A and BR55-2

Since some cytokines effectively enhance the cytotoxicity of monoclonal antibodies, we investigated whether a combination of cytokines can augment the antibody-dependent cellular cytotoxicity (ADCC) of monoclonal antibodies 17-1A and BR55-2 against the colorectal carcinoma cell line HT29. Since monocytes/macrophages are important effector cells for ADCC, we used a new flow cytometric cytotoxicity assay, which allows the analysis of long-term-ADCC exerted by these cells. In our previous studies with peripheral blood mononuclear cells from normal donors, we found that IL-2, IL-12 and IFN-alpha increase ADCC. Therefore, we examined whether combination of these three cytokines with IL-2, IL-4, IL-6, IL-10, IL-12, IFN-alpha, IFN-gamma, GM-CSF, M-CSF and TNF-alpha may yield higher ADCC than obtained by the application of single cytokines. Indeed, we found that the combinations IL-2/IFN-alpha, IL-2/IL-12 and IL-12/IFN-alpha potentiated ADCC. Interestingly, the ineffective single cytokines TNF-alpha and GM-CSF in the combinations IL-2/TNF-alpha, IFN-alpha/TNF-alpha and IFN-alpha/GM-CSF also proved to enhance ADCC. In contrast, IL-4 significantly suppressed the IL-2, IL-12 and IFN-alpha-induced ADCC. In addition, the immunosuppressive cytokine IL-10 in higher concentrations significantly suppressed the IL-12-induced-ADCC. Our results may be useful to find combinations of cytokines and mAb for the treatment of cancer.

Combined therapy with anti-P-glycoprotein antibody and macrophage colony-stimulating factor gene transduction for multiorgan metastases of multidrug-resistant human small cell lung cancer in NK cell-depleted SCID mice

Our aim was to determine the antimetastatic potential of anti-P-glycoprotein (P-gp) antibodies (Abs) against multidrug-resistant (MDR) human small cell lung cancer (SCLC) cells expressing P-gp. Human SCLC cells H69 (P-gp negative) and its etoposide-resistant variant H69/YP (P-gp positive) were used. H69 and H69/VP cells injected i.v. metastasized to the liver, kidneys and systemic lymph nodes of NK cell-depleted severe combined immunodeficient (SCID) mice. H69/VP cells, but not H69 cells, were resistant to treatments with vindesine. Treatment with mouse-human chimeric anti-P-gp Ab (MH162) and its mouse counterpart (MRK-16) reduced metastasis of H69/VP cells in various organs and prolonged the survival of tumor-bearing mice, although they were less effective if injected at late times (after 28 days). Treatment with another mouse anti-Pgp Ab, MRK-17, was effective only against liver metastasis. MH162 and MRK-16 efficiently induced Ab-dependent cellular cytotoxicity (ADCC) by peritoneal macrophages against H69/VP cells in vitro, but MRK-17 was less effective, in accordance with their in vivo antimetastatic potential. Gene transfection of macrophage colony-stimulating factor (M-CSF) into H69/VP cells to augment macrophage-mediated ADCC resulted in inhibition of metastasis to the liver and lymph nodes, but not kidneys. Combined treatment with a low dose of MRK-16 completely cured metastasis of M-CSF transfectant, but not of the mock transfectant. Our findings suggest that while anti-P-gp Abs had antimetastatic potential against SCLC cells expressing P-gp, combined treatment with M-CSF gene transduction to augment the therapeutic efficacy of anti-P-gp Abs may be beneficial for eradicating metastatic MDR SCLC in humans.

Transformation of rat glioma cells with the M-CSF gene inhibits tumorigenesis in vivo

Macrophage colony-stimulating factor (M-CSF) is a potent stimulator of the effector cells such as monocytes and macrophages. To evaluate the effect of M-CSF on malignant gliomas, we transfected the rat gliosarcoma cell line (9L) with human M-CSF expression vector (pCEF-MCSF) by a liposome method. Transfectants were selected using G418-containing medium. As a control, 9L cells transfected with pRc/CMV and selected by G418 were used. The effects of M-CSF gene transfection on tumor cell proliferation in vitro and in vivo were examined. All growth rate did not change in vitro. While the control 9L cells formed progressively enlarging masses, 9L cells transfected with the M-CSF gene did not develop into tumors after the injection into rats. On the other hand, in rats receiving anti-asialo GM1 antibody, 9L cells transfected with M-CSF gene developed into tumors, though at a slower rate than control 9L cells. Histologic examination after transplantation of 9L cells transfected with M-CSF gene disclosed intense infiltration of macrophages in the tumor. Thus M-CSF gene transfection into glioma cells stimulates an antitumor effect.

Establishment of an activated macrophage cell line, A-THP-1, and its properties

A new macrophage cell line with activated character and unique morphology was isolated by selecting adherent cells from the human monocytic cell line THP-1. The original THP-1 cells had been cultured for more than 9 years using 25 cm2 flasks, when cells with a different morphology appeared, adhering to the bottoms of the culture flasks. These were selected by discarding floating nonadherent cells at every subculture. Enrichment of adherent THP-1 cells with long processes proceeded during the cultivation. These adherent THP-1 showed remarkable phenotypic changes, not only morphologically, but also functionally. Namely, increased phagocytic activity, HLA-DR expression and MLR stimulator activity were remarkable. This adherent cell line was designated as activated-THP-1 (A-THP-1), since it demonstrated characteristics of activated macrophages continuously without exogenous stimulation. A cloned A-THP-1 cell line (A-THP-1 C1) also showed the same features and contained about 10% multinucleated giant cells probably caused by cell fusion. This A-THP-1 cell line, the first activated macrophage cell line to be established, provides a good model for understanding of activation mechanisms of macrophages and multinucleation. In this paper, morphological, immunological, and biological characters of this cell line are described.

Human macrophages induced in vitro by macrophage colony-stimulating factor are deficient in IL-12 production

IL-12 is important for Th1 differentiation. Myeloid-derived antigen-presenting cells (APC) such as monocytes, macrophages (Mphi) and dendritic cells (DC) are believed to be major sources of IL-12 in vivo. We have compared IL-12 production of fresh monocytes with Mphi differentiated in vitro using macrophage colony-stimulating factor (M-CSF) or human plasma, and in vitro generated dendritic cells, since these differentiated cell types represent APC at sites of antigen challenge. Macrophages stimulated with lipopolysaccharide (LPS) or heat-killed Listeria monocytogenes in the presence or absence of IFN-gamma produced minimal IL-12 p70 by comparison with DC or monocytes, despite comparable production of TNF-alpha. M-CSF-induced Mphi produced low levels of IL-10 constitutively and high levels after stimulation with LPS, but neutralization of IL-10 did not augment Mphi IL-12 production. Exposure of Mphi to TNF-alpha, granulocyte-macrophage CSF or IFN-gamma did not substantially up-regulate IL-12. Therefore M-CSF induces a differentiated Mphi phenotype in which IL-12 production is down-regulated, perhaps irreversibly. This may be the default pathway for monocyte-Mphi development in the absence of inflammation.

Optimal scheduling of interleukin-12 and fractionated radiation therapy in the murine Lewis lung carcinoma

Interleukin-12 (IL-12), a naturally occurring cytokine, has demonstrated antitumor activity in several murine solid tumors. The Lewis lung carcinoma was used to study the most effective scheduling of recombinant murine interleukin-12 (rmIL-12) administration with fractionated radiation therapy. The effect of the schedule of rmIL-12 administration alone or along with a 1- or 2-week fractionated radiation therapy regimen was examined. Beginning rmIL-12 prior to or at the same time as radiation therapy and extending rmIL-12 through the radiation regimen and beyond produced the longest tumor growth delays. Those treatment regimens which were most effective against the primary tumor were also most effective in decreasing the number of lung metastases on day 20. To further assess the immunotherapeutic effects from rmIL-12 administration, the efficacy of rmIL-12 with fractionated radiation therapy delivered to a right hind-limb tumor was measured as tumor growth delay in an unirradiated left hind-limb tumor. There was some difference in the tumor growth delay between the unirradiated tumor in the animals bearing an irradiated tumor in the contralateral leg, and the tumors in animals receiving rmIL-12 only. Recombinant murine granulocyte-macrophage-colony stimulating factor (rmGM-CSF) was also an antitumor agent active against the Lewis lung carcinoma and produced an additive effect in combination with fractionated radiation therapy in this tumor. rmIL-12 was a radiation sensitizer in the Lewis lung carcinoma. When rmIL-12 (45-microg/kg) and rmGM-CSF (45 microg/kg) were administered together with fractionated radiation therapy, a marked increase in tumor growth delay resulted. This treatment combination also nearly ablated lung metastases on day 20 in these animals. These results may serve as a useful guide in developing clinical protocols, including rmIL-12 and fractionated radiation therapy.

Immune therapy with macrophages: present status and critical requirements for implementation

Adoptive transfer of activated macrophages has been validated in animal experimental tumor models; clinical trials are ongoing (70 patients up to now). The mechanisms involved are reviewed as well as improved and standardized procedures for macrophage differentiation and activation. New developments including specific Ag presentation and gene therapy are discussed.

Granulocyte-macrophage colony-stimulating factor dependent monocyte-mediated cytotoxicity post-autologous bone marrow transplantation

We investigated the in vitro antitumor activity of monocytes derived from autologous bone marrow transplanted (ABMT) patients treated in vivo with granulocyte-macrophage colony-stimulating factor (GM-CSF). Thirty-four patients (17 female, 17 male), median age 42 (range 3-57) years, were enrolled in the study. Fourteen patients were diagnosed with non-Hodgkin's lymphoma (NHL), eight with Hodgkin's disease (HD), nine with breast cancer and three with neuroblastoma. Six patients who did not receive GM-CSF post-ABMT served as controls. We assessed cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC), expression of the activation antigen CD16, and cytokine production by an enriched population of monocytes (> 90% CD+14) pre-, during and post-GM-CSF administration. Within the group of patients receiving treatment, ADCC was significantly higher during in vivo GM-CSF administration than post-therapy (P < 0.05) and in 50% of these patients, ADCC increased during in vivo GM-CSF administration over pretreatment values. In addition, in vivo GM-CSF administration caused the monocytes to secrete elevated levels of tumor necrosis factor-alpha (TNF-alpha) and GM-CSF (P < 0.05). We conclude that GM-CSF augments monocyte-mediated cytotoxicity post-ABMT, and therefore may have a role in controlling minimal residual disease post-transplant.

Transduction of the macrophage colony-stimulating factor gene into human multidrug resistant cancer cells: enhanced therapeutic efficacy of monoclonal anti-P-glycoprotein antibody in nude mice

To develop a therapeutic modality for overcoming multidrug-resistant (MDR) cancer with anti-MDR1 antibody, we examined the effect of macrophage colony-stimulating factor (M-CSF) gene transfection into MDR AD10 cells on therapy of MDR cancer with anti-MDR1 antibody (MRK17) in nude mice. MDR human ovarian cancer (AD10) cells were transduced with the human M-CSF gene inserted into an expression vector to establish gene-modified cells capable of producing low (ML-AD10), intermediate (MM-AD10) nd high (MH-AD10) amounts of M-CSF. Systemic administration of MRK17 resulted in significant dose-dependent inhibition of subcutaneous growth of ML-AD10 tumors. In contrast, systemic administration of recombinant M-CSF in combination with MRK17 did not augment the therapeutic efficacy of MRK17 alone, but rather promoted the growth of the parent AD10 cells. To test the efficacy of in vivo M-CSF gene therapy combined with antibody, we mixed the parent AD10 cells with MH-AD10 cells producing a large amount of M-CSF, and inoculated the mixed cells subcutaneously. Treatment with MRK17 inhibited growth of the mixed cells more than that of the parent cells alone. Thus, combined therapy with anti-MDR1 mAb and M-CSF gene modification of MDR cancer cells may provide a new immunotherapeutic modality for overcoming MDR in humans.

Three-dimensional co-culture of human monocytes and macrophages with tumor cells: analysis of macrophage differentiation and activation

Here we report on an experimental system for generating TAM in vitro by culturing human MO and MO-derived macrophages (MAC) within 3-dimensional multicellular tumor spheroids (MCS). MO as well as MO-derived MAC migrate into tumor spheroids and spread throughout the entire spheroid within 16 hr. In contrast, fibroblast-spheroids were not infiltrated. The regular expression of MAC maturation-associated antigens on infiltrating MO was suppressed within MCS of the undifferentiated bladder carcinoma line J82 with regard to carboxypeptidase M (CPM), MAX.3 antigen and CD105. However, MAC within spheroids of highly differentiated papillary RT4 cells failed only the single antigen CD51, whereas MAC expressed the complete maturation-associated phenotype within non-tumorigenic HCV29 spheroids. Interestingly, the suppressive effect of J82 carcinoma cells could only be observed in 3-dimensional but not in monolayer cultures. The J82-MCS induced suppression of CPM and MAX.3 expression was only seen to be operative on infiltrating blood MO: MO first differentiated for 2 days and subsequently co-cultured with J82-MCS showed normal expression of MAX.3 and CPM within the spheroid. Besides the modulation of MAC phenotype, the cytokine response of intraspheroidal MAC was analyzed: upon co-culture MO secreted high IL-1beta and IL-6 but low amounts of TNF-alpha as compared to MAC. This MO typical cytokine pattern remained constant for up to 8 days in culture, again indicating a disturbed MO to MAC maturation within tumor spheroids. In conclusion, a 3-dimensional interaction with tumor cells in vitro results in significant changes in the phenotype and function of the spheroid-associated MO and MAC.