Antitumor Antibodies in the Treatment of Cancer: Fc Receptors Link Opsonic Antibody with Cellular Immunity

Cyclophosphamide Enhances Cancer Antibody Immunotherapy in the Resistant Bone Marrow Niche by Modulating Macrophage FcγR Expression

Therapy-resistant microenvironments represent a major barrier toward effective elimination of disseminated cancer. Many hematologic and solid tumors are resistant to therapeutic antibodies in the bone marrow (BM), but not in the periphery (e.g., spleen). We previously showed that cyclophosphamide (CTX) sensitizes the BM niche to antibody therapeutics. Here, we show that (i) BM resistance was induced not only by the tumor but also by the intrinsic BM microenvironment; (ii) CTX treatment overcame both intrinsic and extrinsic resistance mechanisms by augmenting macrophage activation and phagocytosis, including significant upregulation of activating Fcγ receptors (FcγRIII and FcγRIV) and downregulation of the inhibitory receptor, FcγRIIB; and (iii) CTX synergized with cetuximab (anti-EGFR) and trastuzumab (anti-Her2) in eliminating metastatic breast cancer in the BM of humanized mice. These findings provide insights into the mechanisms by which CTX synergizes with antibody therapeutics in resistant niche-specific organs and its applicability in treating BM-resident tumors.

Infiltration by myeloperoxidase-positive neutrophils is an independent prognostic factor in breast cancer

PURPOSE

Myeloperoxidase (MPO) is an enzyme secreted by neutrophil granulocytes as a result of phagocytosis during inflammation. In colorectal cancer, tumour infiltration by MPO expressing cells has been shown to be independently associated with a favourable prognosis. In this study, we explored the role of MPO-positive cell infiltration and its prognostic significance in invasive breast cancer.

METHODS

We performed immunohistochemical staining for MPO on multiple tissue microarrays comprising a total of 928 human breast cancer samples with detailed clinical-pathological annotation and outcome data.

RESULTS

MPO-positive cell infiltration (≥ 5 cells/tissue punch) was found in 150 (16%) of the 928 evaluable breast cancer cases. In univariate survival analyses, infiltration by MPO-positive cells was associated with a significantly better overall survival (p < 0.001). In subset univariate analyses, the infiltration by MPO-positive cells was associated with significantly better overall survival in the Luminal B/HER2-negative subtype (p = 0.005), the HER2 enriched subtype (p = 0.011), and the Triple Negative subtype (p < 0.001). In multivariate analysis, MPO expression proved to be an independent prognostic factor for improved overall survival (p < 0.001).

CONCLUSIONS

This is the first study to show that infiltration of MPO-positive cells is an independent prognostic biomarker for improved overall survival in human breast cancer.

Immune-relevant aspects of murine models of head and neck cancer

Head and neck cancers (HNCs) cause significant mortality and morbidity. There have been few advances in therapeutic management of HNC in the past 4 to 5 decades, which support the need for studies focusing on HNC biology. In recent years, increased recognition of the relevance of the host response in cancer progression has led to novel therapeutic strategies and putative biomarkers of tumor aggressiveness. However, tumor-immune interactions are highly complex and vary with cancer type. Pre-clinical, in vivo models represent an important and necessary step in understanding biological processes involved in development, progression and treatment of HNC. Rodents (mice, rats, hamsters) are the most frequently used animal models in HNC research. The relevance and utility of information generated by studies in murine models is unquestionable, but it is also limited in application to tumor-immune interactions. In this review, we present information regarding the immune-specific characteristics of the murine models most commonly used in HNC research, including immunocompromised and immunocompetent animals. The particular characteristics of xenograft, chemically induced, syngeneic, transgenic, and humanized models are discussed in order to provide context and insight for researchers interested in the in vivo study of tumor-immune interactions in HNC.

Role of FcγRs in Antibody-Based Cancer Therapy

Monoclonal antibodies can mediate antitumor activity by multiple mechanisms. They can bind directly to tumor receptors resulting in tumor cell death, or can bind to soluble growth factors, angiogenic factors, or their cognate receptors blocking signals required for tumor cell growth or survival. Monoclonal antibodies, upon binding to tumor cell, can also engage the host's immune system to mediate immune-mediated destruction of the tumor. The Fc portion of the antibody is essential in engaging the host immune system by fixing complement resulting in complement-mediated cytotoxicity (CDC) of the tumor, or by engaging Fc receptors for IgG (FcγR) expressed by leukocytes leading to antibody-dependent cellular cytotoxicity (ADCC) or antibody-dependent cellular phagocytosis (ADCP) of tumor cells. Antibodies whose Fc portion preferentially engage activating FcγRs have shown greater inhibition of tumor growth and metastasis. Monoclonal antibodies can also stimulate the immune system by binding to targets expressed on immune cells. These antibodies may stimulate antitumor immunity by antagonizing a negative regulatory signal, agonizing a costimulatory signal, or depleting immune cells that are inhibitory. The importance of Fc:FcγR interactions in antitumor therapy for each of these mechanisms have been demonstrated in both mouse models and clinical trials and will be the focus of this chapter.

Fc-γ Receptor Polymorphisms, Cetuximab Therapy, and Survival in the NCIC CTG CO.17 Trial of Colorectal Cancer

PURPOSE

Two germline Fc-γ receptor (FCGR) polymorphisms, rs1801274 [FCGR2A;His(H)131Arg(R)] and rs396991 [FCGR3A;Phe(F)158Val(V)] produce altered proteins through amino acid substitutions; both are reported to be associated with cetuximab-related outcomes. We performed a validation of these polymorphisms in NCIC CTG CO.17, a randomized trial of cetuximab monotherapy in refractory, metastatic colorectal cancer expressing EGFR.

EXPERIMENTAL DESIGN

DNA extracted from formalin-fixed paraffin-embedded tissue was genotyped. In addition to log-rank tests, Cox proportional hazard models assessed their relationships with overall (OS) and progression-free survival (PFS), adjusting for clinically important prognostic factors, along with a polymorphism-treatment arm interaction term.

RESULTS

Somatic KRAS status was wild-type for exon 2 in 153 (52%) of 293 patients, from whom tumor DNA was available. For FCGR2A H/H, a genotype-treatment interaction for KRAS wild-type patients was observed for OS (P = 0.03). In KRAS wild-type patients carrying FCGR2A H/H, cetuximab (vs. no cetuximab) improved survival substantially, with adjusted HRs (aHR) of 0.36 (OS) and 0.19 (PFS) and absolute benefits of 5.5 months (OS; P = 0.003) and 3.7 months (PFS; P = 0.02). In contrast, patients carrying FCGR2A R alleles (H/R or R/R) had aHRs of only 0.78 (OS; 2.8-month benefit) and 0.53 (PFS; 1.6-month benefit). No relationships were found for rs396991 (FCGR3A).

CONCLUSIONS

In the CO.17 trial, cetuximab worked best for patients with KRAS wild-type colorectal cancers carrying FCGR2A H/H genotypes. Significantly lower benefits were observed in patients carrying germline FCGR2A R alleles. Clin Cancer Res; 22(10); 2435-44. ©2016 AACR.

Interplay between Natural Killer Cells and Anti-HER2 Antibodies: Perspectives for Breast Cancer Immunotherapy

Overexpression of the human epidermal growth factor receptor 2 (HER2) defines a subgroup of breast tumors with aggressive behavior. The addition of HER2-targeted antibodies (i.e., trastuzumab, pertuzumab) to chemotherapy significantly improves relapse-free and overall survival in patients with early-stage and advanced disease. Nonetheless, considerable proportions of patients develop resistance to treatment, highlighting the need for additional and co-adjuvant therapeutic strategies. HER2-specific antibodies can trigger natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity and indirectly enhance the development of tumor-specific T cell immunity; both mechanisms contributing to their antitumor efficacy in preclinical models. Antibody-dependent NK cell activation results in the release of cytotoxic granules as well as the secretion of pro-inflammatory cytokines (i.e., IFNγ and TNFα) and chemokines. Hence, NK cell tumor suppressive functions include direct cytolytic killing of tumor cells as well as the regulation of subsequent antitumor adaptive immunity. Albeit tumors with gene expression signatures associated to the presence of cytotoxic lymphocyte infiltrates benefit from trastuzumab-based treatment, NK cell-related biomarkers of response/resistance to HER2-specific therapeutic antibodies in breast cancer patients remain elusive. Several variables, including (i) the configuration of the patient NK cell repertoire; (ii) tumor molecular features (i.e., estrogen receptor expression); (iii) concomitant therapeutic regimens (i.e., chemotherapeutic agents, tyrosine kinase inhibitors); and (iv) evasion mechanisms developed by progressive breast tumors, have been shown to quantitatively and qualitatively influence antibody-triggered NK cell responses. In this review, we discuss possible interventions for restoring/enhancing the therapeutic activity of HER2 therapeutic antibodies by harnessing NK cell antitumor potential through combinatorial approaches, including immune checkpoint blocking/stimulatory antibodies, cytokines and toll-like receptor agonists.

The influence of FCGR2A and FCGR3A polymorphisms on the survival of patients with recurrent or metastatic squamous cell head and neck cancer treated with cetuximab

FCGR2A-H131R and FCGR3A-V157F are single-nucleotide polymorphisms known to influence the outcome of patients treated with rituximab, cetuximab and trastuzumab. We investigated the impact of these polymorphisms on the clinical outcome of 103 patients with recurrent or metastatic squamous cell carcinoma of the head and neck treated with a platinum compound, fluorouracil and cetuximab as palliative first-line therapy. The survival of patients with FCGR2A-131H/H and/or FCGR3A-157V/V genotypes was significantly longer compared with patients carrying 131R and 157F alleles (median progression-free survival (PFS): 5.5 vs 4.1 months, P=0.02; median overall survival: 10.2 vs 7.2 months, P=0.04). In multivariate analysis, the FCGR2A and 3A genotypes as well as the time between initial diagnosis and relapse of disease not amenable to curative therapy remained the only independent prognostic factors for PFS. The results are in line with previous reports in colorectal cancer patients and confirm the possible value of genetic polymorphisms of immunocompetent cells for the success of cetuximab treatment.

Tailoring polymeric hybrid micelles with lymph node targeting ability to improve the potency of cancer vaccines

It has been widely accepted that lymph nodes (LNs) are critical targets of cancer vaccines and particles sized between 10 and 100 nm with a neutral or negative surface charge are preferred for lymphatic transfer after subcutaneous or intradermal injection. However their limited uptake by antigen presenting cells (APCs) and inadequate retention within LNs undoubtedly restrains their strength on activating T cell immunity. Here, we address this issue by tailoring the physicochemical properties of polymeric hybrid micelles (HMs), which are self-assembled from two amphiphilic diblock copolymers, poly-(ethylene glycol) phosphorethanolamine (PEG-PE) and polyethylenimine-stearic acid conjugate (PSA) via hydrophobic and electrostatic interactions. We successfully encapsulate melanoma antigen peptide Trp2 and Toll-like receptor-9 (TLR-9) agonist CpG ODN into HMs with a size of sub-30 nm. Their surface characteristics which are found closely related to their in vivo kinetics can be modulated by simply adjusting the molar ratio of PEG-PE and PSA. Our results demonstrated the optimized HMs with an equal mol of PEG-PE and PSA can potently target proximal LNs where their cargos are efficiently internalized by DCs. Furthermore, HMs mediated Trp2/CpG delivery system greatly expands antigen specific cytotoxic T lymphocytes (CTLs) and offers a strong anti-tumor effect in a lung metastatic melanoma model.

Mouse and human FcR effector functions

Mouse and human FcRs have been a major focus of attention not only of the scientific community, through the cloning and characterization of novel receptors, and of the medical community, through the identification of polymorphisms and linkage to disease but also of the pharmaceutical community, through the identification of FcRs as targets for therapy or engineering of Fc domains for the generation of enhanced therapeutic antibodies. The availability of knockout mouse lines for every single mouse FcR, of multiple or cell-specific--'à la carte'--FcR knockouts and the increasing generation of hFcR transgenics enable powerful in vivo approaches for the study of mouse and human FcR biology. This review will present the landscape of the current FcR family, their effector functions and the in vivo models at hand to study them. These in vivo models were recently instrumental in re-defining the properties and effector functions of FcRs that had been overlooked or discarded from previous analyses. A particular focus will be made on the (mis)concepts on the role of high-affinity IgG receptors in vivo and on results from antibody engineering to enhance or abrogate antibody effector functions mediated by FcRs.

Neutrophils in Cancer: Two Sides of the Same Coin

Neutrophils are the most abundant leukocytes in blood and are considered to be the first line of defense during inflammation and infections. In addition, neutrophils are also found infiltrating many types of tumors. Tumor-associated neutrophils (TANs) have relevant roles in malignant disease. Indeed neutrophils may be potent antitumor effector cells. However, increasing clinical evidence shows TANs correlate with poor prognosis. The tumor microenvironment controls neutrophil recruitment and in turn TANs help tumor progression. Hence, TANs can be beneficial or detrimental to the host. It is the purpose of this review to highlight these two sides of the neutrophil coin in cancer and to describe recent studies that provide some light on the mechanisms for neutrophil recruitment to the tumor, for neutrophils supporting tumor progression, and for neutrophil activation to enhance their antitumor functions.

Hep88 mAb-initiated paraptosis-like PCD pathway in hepatocellular carcinoma cell line through the binding of mortalin (HSPA9) and alpha-enolase

Background

Hepatocellular carcinoma (HCC) is the most prevalent hepatic cancer worldwide. Currently, a targeted therapy via monoclonal antibodies (mAbs) specific to tumor-associated antigen is undergoing continual development in HCC treatment.

Methods

In this regard, after establishing and consequently exploring Hep88 mAb’s tumoricidal effect on hepatocellular carcinoma cell line (HepG2 cell line), the Hep88 mAb’s specific antigens from both membrane and cytoplasmic fractions of HepG2 cell line were identified by 2-D gel electrophoresis and western blot analysis. After in-gel digestion and subsequent analysis by liquid chromatography-mass spectrometry (LC-MS), mortalin (HSPA9) and alpha-enolase were identified. The recombinant proteins specific to Hep88 mAb were cloned and expressed in E. coli BL21(DE3). Moreover, alteration of HepG2 and Chang liver cell line after being induced by Hep88 mAb for 1–3 days was investigated using a transmission electron microscope.

Results

The result demonstrated that Hep88 mAb can bind to the recombinant mortalin (HSPA9) and alpha-enolase. In addition, the gradual appearing of mitochondria vacuolization and endoplasmic reticulum dilatation were observed. Those characteristics might be explained by the paraptosis-like program cell death (PCD), which is induced by the binding of Hep88 mAb to mortalin (HSPA9). Mortalin depletion resulting from the formation of Hep88 mAb-mortalin (HSPA9) complex might initiate transcription-independence of p53-mediated apoptosis. Additionally, Hep88mAb-alpha-enolase complex might initiate HepG2 cells energy exhaustion by glycolysis pathway obstruction.

Conclusion

These fascinating results imply that Hep88 mAb might be a promising tool for the development of an effective treatment of HCC in the next decade.

Detection of chondroitin sulfate proteoglycan 4 (CSPG4) in melanoma

The tumor antigen chondroitin sulfate proteoglycan 4 (CSPG4) appears to be a useful biomarker to identify melanoma cells and an attractive target to apply antibody-based immunotherapy for the treatment of melanoma. Here we described the reverse transcription-polymerase chain reaction (RT-PCR) method and the immunohistochemical (IHC) staining method to detect the expression of CSPG4 in melanoma cells and tissues.

Neutrophils mediate antibody-induced antitumor effects in mice

Tumor engraftment followed by monoclonal antibody (mAb) therapy targeting tumor antigens represents a gold standard for assessing the efficiency of mAbs to eliminate tumor cells. Mouse models have demonstrated that receptors for the Fc portion of immunoglobulin G (FcγRs) are critical determinants of mAb therapeutic efficacy, but the FcγR-expressing cell populations responsible remain elusive. We show that neutrophils are responsible for mAb-induced therapy of both subcutaneous syngeneic melanoma and human breast cancer xenografts. mAb-induced tumor reduction, abolished in neutropenic mice, could be restored in FcγR-deficient hosts upon transfer of FcγR+ neutrophils or upon human FcγRIIA/CD32A transgenic expression. Finally, conditional knockout mice unable to perform FcγR-mediated activation and phagocytosis specifically in neutrophils were resistant to mAb-induced therapy. Our work suggests that neutrophils are necessary and sufficient for mAb-induced therapy of subcutaneous tumors, and represent a new and critical focal point for optimizing mAb-induced immunotherapies that will impact on human cancer treatment.

A critical review of the role of Fc gamma receptor polymorphisms in the response to monoclonal antibodies in cancer

Antibody-dependent cellular cytotoxicity (ADCC) is a major mechanism of action of therapeutic monoclonal antibodies (mAbs) such as cetuximab, rituximab and trastuzumab. Fc gamma receptors (FcgR) on human white blood cells are an integral part of the ADCC pathway. Differential response to therapeutic mAbs has been reported to correlate with specific polymorphisms in two of these genes: FCGR2A (H131R) and FCGR3A (V158F). These polymorphisms are associated with differential affinity of the receptors for mAbs. This review critically examines the current evidence for genotyping the corresponding single nucleotide polymorphisms (SNPs) to predict response to mAbs in patients with cancer.

The use of epidermal growth factor receptor monoclonal antibodies in squamous cell carcinoma of the head and neck

Targeting of the EGF receptor (EGFR) has become a standard of care in several tumor types. In squamous cell carcinoma of the head and neck, monoclonal antibodies directed against EGFR have become a regular component of therapy for curative as well as palliative treatment strategies. These agents have anti-tumor efficacy as a single modality and have demonstrated synergistic tumor killing when combined with radiation and/or chemotherapy. While cetuximab has been the primary anti-EGFR monoclonal antibody used in the US, variant anti-EGFR monoclonal antibodies have been used in several clinical studies and shown benefit with improved toxicity profiles. Next generation anti-EGFR monoclonal antibodies may demonstrate multi-target epitope recognition, enhanced immune cell stimulation, or conjugation with radioisotopes in order to improve clinical outcomes. Identification of the specific patient subset that would optimally benefit from anti-EGFR monoclonal antibodies remains an elusive goal.

Properties of mouse and human IgG receptors and their contribution to disease models

Impressive advances in defining the properties of receptors for the Fc portion of immunoglobulins (FcR) have been made over the past several years. Ligand specificities were systematically analyzed for both human and mouse FcRs that revealed novel receptors for specific IgG subclasses. Expression patterns were redefined using novel specific anti-FcR mAbs that revealed major differences between human and mouse systems. The in vivo roles of IgG receptors have been addressed using specific FcR knockout mice or in mice expressing a single FcR, and have demonstrated a predominant contribution of mouse activating IgG receptors FcγRIII and FcγRIV to models of autoimmunity (eg, arthritis) and allergy (eg, anaphylaxis). Novel blocking mAbs specific for these activating IgG receptors have enabled, for the first time, the investigation of their roles in vivo in wild-type mice. In parallel, the in vivo properties of human FcRs have been reported using transgenic mice and models of inflammatory and allergic reactions, in particular those of human activating IgG receptor FcγRIIA (CD32A). Importantly, these studies led to the identification of specific cell populations responsible for the induction of various inflammatory diseases and have revealed, in particular, the unexpected contribution of neutrophils and monocytes to the induction of anaphylactic shock.

A recombinant triplebody with specificity for CD19 and HLA-DR mediates preferential binding to antigen double-positive cells by dual-targeting

To test the hypothesis that dual-targeting confers the novel ability of selective binding to antigen double-positive over antigen single-positive cells, a single-chain triplebody (sctb), HLA-ds16-hu19, was produced and characterized. The molecule carries three single-chain Fv (scFv) antibody fragments in a single polypeptide chain, the two distal ones specific for the human histocompatibility protein HLA-DR and the B-lymphoid cell surface protein CD19, the central one for CD16, the human low affinity Fc-receptor FcγRIII. For comparison, the bispecific scFvs (bsscFv) hu19-ds16 and HLA-ds16 were also produced. All CD16 binding modules are disulfide-stabilized (ds). The sctb bound simultaneously to both CD19 and HLA-DR on the same cancer cell and, thus, showed functional dual-targeting. In a mixing-experiment with HLA-DR single-positive HUT-78 cells and (HLA-DR plus CD19) double-positive SEM cells, the triplebody showed preferential binding to the double-positive cells, even when the single-positive cells were present in a numerical excess of up to 20-fold. In antibody-dependent cellular cytotoxicity experiments with mononuclear cells as effector cells, the sctb promoted equal lysis of Raji cells, an antigen double-positive cell line, at 130-fold lower concentrations than the bsscFv hu19-ds16, indicating that both distal scFvs of the sctb contributed to tumor cell lysis. A panel of stably-transfected HEK293 cell lines was generated that included CD19- and HLA-DR single-positive and (HLA-DR plus CD19) double-positive lines with antigen-surface densities varying over a broad range. Using a pair of cell lines with matching densities, the sctb eliminated double-positive target cells preferentially single-positive cells. This ability of preferential or selective targeting of antigen double-positive over single-positive cells opens attractive new perspectives for the use of dual-targeting sctbs in cancer therapy.

Immunoglobulin Fc fragment tagging allows strong activation of endogenous CD4 T cells to reshape the tumor milieu and enhance the antitumor effect of lentivector immunization

A major problem with current cancer vaccines is that the induction of CD8 immune responses is rarely associated with antitumor benefits, mainly owing to multiple immune suppressions in established tumor lesions. In this study, we investigated if and how activation of endogenous CD4 T cells could be achieved to influence the suppressive tumor milieu and antitumor effect. We engineered a lentivector (lv) to express a nominal fusion Ag composed of hepatitis B surface protein and IgG2a Fc fragment (HBS-Fc-lv) to increase the magnitude of CD8 response but, more importantly, to induce effective coactivation of CD4 T cells. We found that, remarkably, immunization with HBS-Fc-lv caused significant regression of established tumors. Immunologic analysis revealed that, compared with HBS-lv without Fc fragment, immunization with HBS-Fc-lv markedly increased the number of functional CD8 and CD4 T cells and the level of Th1/Tc1-like cytokines in the tumor while substantially decreasing the regulatory T cell ratio. The favorable immunologic changes in tumor lesions and the improvement of antitumor effects from HBS-Fc-lv immunization were dependent on the CD4 activation, which was Fc receptor mediated. Adoptive transfer of CD4 T cells from the HBS-Fc-lv-immunized mice could activate endogenous CD8 T cells in an IFN-γ-dependent manner. We conclude that endogenous CD4 T cells can be activated by lv expressing Fc-tagged Ag to provide another layer of help--that is, creating a Th1/Tc1-like proinflammatory milieu within the tumor lesion to boost the effector phase of immune responses in enhancing the antitumor effect.

Using monoclonal antibodies to stimulate antitumor cellular immunity

Monoclonal antibodies (mAbs) have an established role in current cancer therapy with seven approved for the treatment of a wide variety of tumors. The approved mAbs directly target tumor cells; however, it is becoming increasingly clear that as well as their direct effects, these mAbs can present antigens to the immune system. This stimulates long-lasting T-cell immunity, which may correlate with long-term survival. A more direct approach is to use mAbs to target antigens directly to antigen-presenting cells. One approach, ImmunoBody, which has just entered the clinic, stimulates antitumor immunity using mAbs genetically engineered to express tumor-specific T-cell epitopes. T cells not only respond via their T-cell receptors recognizing T-cell epitopes presented on MHC but are also influenced by stimulation of a wide variety of costimulatory molecules. mAbs targeting these molecules can also influence antitumor immunity. The main protagonist in this class of mAbs is ipilimumab, which has recently been shown to improve survival at 2 years in 23% of advanced melanoma patients. Combinations of mAbs targeting tumor antigens to activated antigen-presenting cells and mAbs targeting costimulatory receptors may provide effective therapy for a broad range of tumors.

Cetuximab ± chemotherapy enhances dendritic cell-mediated phagocytosis of colon cancer cells and ignites a highly efficient colon cancer antigen-specific cytotoxic T-cell response in vitro

Cetuximab is a human/mouse chimeric IgG1 monoclonal antibody (mAb) to epidermal growth factor receptor, approved for colorectal carcinoma treatment in combination with chemotherapy. The immune-mediated effects elicited by its human fraction of crystallization moiety might critically contribute to the overall anti-tumor effectiveness of the antibody. We therefore investigated cetuximab ability to promote colon cancer cell opsonization and phagocytosis by human dendritic cells (DCs) that are subsequently engaged in antigen-cross presentation to cytotoxic T-lymphocyte (CTL) precursors. Human colon cancer cell lines were evaluated for susceptibility to DC-mediated phagocytosis before and after treatment with chemotherapy ± cetuximab in vitro. Human DCs loaded with control or drug-treated cetuximab-coated colon cancer cells were used to in vitro generate cytotoxic T cell clones from peripheral blood mononuclear cells of human leucocyte antigen-A(*)02.01(+) donors. T-cell cultures were characterized for immune-phenotype and tumor-antigen specific CTL activity. The results confirmed that treatment of tumor cells with irinotecan + L-folinate + 5-flurouracil (ILF) or with gemcitabine + ILF increased tumor antigen expression. Moreover, malignant cells exposed to chemotherapy and cetuximab were highly susceptible to phagocytosis by human DCs and were able to promote their activation. The consequent DC-mediated cross-priming of antigens derived from mAb-covered/drug-treated cancer cells elicited a robust CTL anti-tumor response. On the basis of our data, we suggest a possible involvement of CTL-dependent immunity in cetuximab anti-cancer effects.

Tumor antigen-targeted, monoclonal antibody-based immunotherapy: clinical response, cellular immunity, and immunoescape

PURPOSE

Tumor antigen (TA) -targeted monoclonal antibodies (mAb), rituximab, trastuzumab, and cetuximab, are clinically effective for some advanced malignancies, especially in conjunction with chemotherapy and/or radiotherapy. However, these results are only seen in a subset (20% to 30%) of patients. We discuss the immunologic mechanism(s) underlying these clinical findings and their potential role in the variability in patients' clinical response.

METHODS

We reviewed the evidence indicating that the effects of TA-targeted mAb-based immunotherapy are mediated not only by inhibition of signaling pathways, but also by cell-mediated cytotoxicity triggered by the infused TA-targeted mAb. We analyzed the immunologic variables that can influence the outcome of antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro and in animal model systems. We also analyzed the correlation reported between these variables and the clinical response to mAb-based immunotherapy.

RESULTS

Of the variables that influence ADCC mediated by TA-targeted mAb, only polymorphisms of Fcγ receptors (FcγR) expressed by patients' lymphocytes were correlated with clinical efficacy. However, this correlation is not absolute and is not observed in all malignancies. Thus other variables may be responsible for the antitumor effects seen in mAb-treated patients. We discuss the evidence that triggering of TA-specific cellular immunity by TA-targeted mAb, in conjunction with immune escape mechanisms used by tumor cells, may contribute to the differential clinical responses to mAb-based immunotherapy.

CONCLUSION

Identification of the mechanism(s) underlying the clinical response of patients with cancer treated with TA-targeted mAb is crucial to optimizing their application in the clinic and to selecting the patients most likely to benefit from their use.

Humanised IgG1 antibody variants targeting membrane-bound carcinoembryonic antigen by antibody-dependent cellular cytotoxicity and phagocytosis

BACKGROUND

The effect of glycoengineering a membrane specific anti-carcinoembryonic antigen (CEA) (this paper uses the original term CEA for the formally designated CEACAM5) antibody (PR1A3) on its ability to enhance killing of colorectal cancer (CRC) cell lines by human immune effector cells was assessed. In vivo efficacy of the antibody was also tested.

METHODS

The antibody was modified using EBNA cells cotransfected with beta-1,4-N-acetylglucosaminyltransferase III and the humanised hPR1A3 antibody genes.

RESULTS

The resulting alteration of the Fc segment glycosylation pattern enhances the antibody's binding affinity to the FcgammaRIIIa receptor on human immune effector cells but does not alter the antibody's binding capacity. Antibody-dependent cellular cytotoxicity (ADCC) is inhibited in the presence of anti-FcgammaRIII blocking antibodies. This glycovariant of hPR1A3 enhances ADCC 10-fold relative to the parent unmodified antibody using either unfractionated peripheral blood mononuclear or natural killer (NK) cells and CEA-positive CRC cells as targets. NK cells are far more potent in eliciting ADCC than either freshly isolated monocytes or granulocytes. Flow cytometry and automated fluorescent microscopy have been used to show that both versions of hPR1A3 can induce antibody-dependent cellular phagocytosis (ADCP) by monocyte-derived macrophages. However, the glycovariant antibody did not mediate enhanced ADCP. This may be explained by the relatively low expression of FcgammaRIIIa on cultured macrophages. In vivo studies show the efficacy of glycoengineered humanised IgG1 PR1A3 in significantly improving survival in a CRC metastatic murine model.

CONCLUSION

The greatly enhanced in vitro ADCC activity of the glycoengineered version of hPR1A3 is likely to be clinically beneficial.

Specificity and affinity of human Fcγ receptors and their polymorphic variants for human IgG subclasses

Distinct genes encode 6 human receptors for IgG (hFcγRs), 3 of which have 2 or 3 polymorphic variants. The specificity and affinity of individual hFcγRs for the 4 human IgG subclasses is unknown. This information is critical for antibody-based immunotherapy which has been increasingly used in the clinics. We investigated the binding of polyclonal and monoclonal IgG1, IgG2, IgG3, and IgG4 to FcγRI; FcγRIIA, IIB, and IIC; FcγRIIIA and IIIB; and all known polymorphic variants. Wild-type and low-fucosylated IgG1 anti-CD20 and anti-RhD mAbs were also examined. We found that (1) IgG1 and IgG3 bind to all hFcγRs; (2) IgG2 bind not only to FcγRIIAH131, but also, with a lower affinity, to FcγRIIAR131 and FcγRIIIAV158; (3) IgG4 bind to FcγRI, FcγRIIA, IIB and IIC and FcγRIIIAV158; and (4) the inhibitory receptor FcγRIIB has a lower affinity for IgG1, IgG2, and IgG3 than all other hFcγRs. We also identified parameters that determine the specificity and affinity of hFcγRs for IgG subclasses. These results document how hFcγR specificity and affinity may account for the biological activities of antibodies. They therefore highlight the role of specific hFcγRs in the therapeutic and pathogenic effects of antibodies in disease.

Combinatorial treatments including vaccines, chemotherapy and monoclonal antibodies for cancer therapy

Accumulating evidence suggests that despite the potency of cytotoxic anticancer agents, and the great specificity that can be achieved with immunotherapy, neither of these two types of treatment by itself has been sufficient to eradicate the disease. Still, the combination of these two different modalities holds enormous potential for eliciting therapeutic results. Indeed, certain chemotherapeutic agents have shown immunomodulatory activities, and several combined approaches have already been attempted. For instance, chemotherapy has been proven to enhance the efficacy of tumor cell vaccines, and to favor the activity of adoptively transferred tumor-specific T cells. A number of mechanisms have been proposed for the chemotherapy-triggered enhancement of immunotherapy response. Thus, chemotherapy may favor tumor cell death, and by that enhance tumor-antigen cross-presentation in vivo. Drug-induced myelosuppression may induce the production of cytokines favoring homeostatic proliferation, and/or ablate immunosuppression mechanisms. Furthermore, the recently reported synergy between monoclonal antibodies and chemotherapy or peptide vaccination is based upon the induction of endogenous humoral and cellular immune responses. This would suggest that monoclonal antibodies may not only provide passive immunotherapy but can also promote tumor-specific active immunity. This article will review several strategies in which immunotherapy can be exploited in preclinical and clinical studies in combination with other agents and therapeutic modalities that are quite unique when compared with "conventional" combination therapies (ie, treatments with chemotherapeutic drugs or chemotherapy and radiotherapy based protocols). The results from these studies may have significant implications for the development of new protocols based on combinatorial treatments including vaccines, chemotherapy and monoclonal antibodies, suggesting an exciting potential for therapeutic synergy with general applicability to various cancer types. Given the complicity of immune-based therapies and cancer pharmacology, it will be necessary to bring together cancer immunologists and clinicians, so as to provide a robust stimulus for realizing the successful management of cancer in the near future.

Induction of long-lasting antitumor immunity by concomitant cell therapy with allogeneic lymphocytes and trifunctional bispecific antibody

OBJECTIVE

Use of a trifunctional bispecific antibody (trAb) given concomitantly with allogeneic cell therapy to achieve an anti tumor effect without graft-vs-host disease (GVHD).

MATERIALS AND METHODS

A trAb-directed against murine CD3 and human epithelial cell adhesion molecule (EpCAM) (BiLu), was given alone or concomitantly with interleukin (IL)-2-activated (LAK) H-2(b) donor splenocytes to H-2(d/b) mice inoculated with murine melanoma cells transfected with human EpCAM.

RESULTS

A total of 32/38 mice treated with BiLu and LAK splenocytes, were tumor-free survivors without GVHD for >200 days following inoculation of a 100% lethal tumor dose (5 x 10(4)). Of 28 disease-free surviving mice previously treated with LAK splenocytes and BiLu, 24 mice proved resistance to a second tumor challenge of 10(4) cells given >210 days following the first tumor inoculation with no evidence of disease for >150 days. In contrast, only 4 of 13 disease-free survivor mice treated with naïve splenocytes and BiLu, and 5 of 10 disease-free survivor controls treated with BiLu only, resisted the second tumor challenge. Induction of antitumor immunity was more efficient and long-lasting (>150 days) in mice previously injected with a lethal tumor cell dose of 5 x 10(4) cells than in mice previously inoculated with 5 x 10(3) tumor cells.

CONCLUSION

Concomitantly treatment of allogeneic LAK cells and trAb-induced an efficient long-lasting antitumor immunity. Considering the documented efficacy of anti-EpCAM bispecific antibody in various metastatic cancers, clinical application of our approach may be justified in patients with minimal residual disease at high risk for tumor recurrence.

Antibody-based cancer therapy

BACKGROUND

The clinical efficacy of mAbs is generally ascribed to interference with signaling pathways leading to arrest of cell-cycle progression and inhibition of tumor growth. Furthermore, mAbs also have the capacity to activate effector functions of the innate immune system and facilitate the destruction of malignant cells.

OBJECTIVES

The induction of tumor-specific immunity is a desired outcome in cancer immunotherapy. The prevailing situation raises one major question that has to be addressed. This is the clear need for the induction of tumor-specific immunity by combining mAb treatment with other modalities of cancer immunotherapy.

METHODS

Through mAb treatment, recent efforts focus at initiating or enhancing active antitumor immune responses by i) potentiating co-stimulation and blocking co-inhibition; and ii) rendering tumors more immunogenic through increased tumor peptide expression.

RESULTS/CONCLUSIONS

In this review, the functional characteristics of mAbs, together with their mechanisms of action and clinical application, is summarized as is the potential of combination immunotherapies using mAbs for the augmentation of adaptive antitumor immunity. The results from preclinical and clinical studies demonstrate that mAbs can also promote tumor-specific active immunity.

Targeted killing of colorectal cancer cell lines by a humanised IgG1 monoclonal antibody that binds to membrane-bound carcinoembryonic antigen

The distribution of carcinoembryonic antigen (CEA) in colorectal cancer (CRC) differs from that in normal colorectal tissue, being found on all borders of the cell membrane and hence enabling access to intravenous antibody, making CEA a good target for antibody-based therapy. The distinctive anti-CEA antibody, PR1A3, binds only membrane-bound CEA. Humanised PR1A3 (hPR1A3) was assessed both in vitro cytotoxicity and binding assays with colorectal cancer cell lines expressing varying levels of CEA. Human peripheral blood mononuclear cells (PBMCs) and purified natural killer (NK) cells were used as effectors. The in vitro assays demonstrated hPR1A3 CEA-specific binding and antibody-dependent and CEA-specific killing of human colorectal cancer cell lines by human PBMCs. The effect increased with increasing concentration of antibody and surface CEA, and was lost by using the parent murine IgG1 PR1A3. Killing was also blocked by antibody to the Fc-γIIIA receptor. Purified human NK cells were effective at much lower effector:target ratios than unfractionated PBMCs, indicating that NK cells were the main mediators of hPR1A3-based CEA-specific killing. The results support the development of hPR1A3 for therapy of colorectal cancer.

A mechanistic perspective of monoclonal antibodies in cancer therapy beyond target-related effects

Several monoclonal antibodies are now in clinical use for cancer therapy, and many others are currently undergoing clinical evaluation. These agents offer unique specificity against key molecular targets on tumor cells or in the tumor microenvironment. The clinical efficacy of monoclonal antibodies is generally attributed to target-specific mechanisms resulting from neutralizing or inhibiting a growth factor or receptor that drives cell proliferation and tumor growth. Several targets, including CD20, human epidermal growth factor receptor 2, vascular endothelial growth factor, and epidermal growth factor receptor, have been validated in specific malignancies on the basis of monoclonal antibody efficacy. However, monoclonal antibodies also have the potential to activate immune-mediated effector functions, including antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. These functions result from interactions involving the Fc domain of the antibody, and, consequently, may vary by antibody, isotype, and Fc modification, such as changes in glycosylation. Accordingly, all monoclonal antibodies directed against a given target should not be considered equivalent in their ability to stimulate immune-mediated effector functions.

Interactions of tumor cells with dendritic cells: balancing immunity and tolerance

Dendritic cells (DCs) are antigen-presenting cells specialized to initiate and maintain immunity and tolerance. DCs initiate immune responses in a manner that depends on signals they receive from pathogens, surrounding cells and their products. Most tumors are infiltrated by DCs. Thus, interactions between DCs and dying tumor cells may determine the balance between immunity and tolerance to tumor cells. In addition, DCs also display non-immunologic effects on tumors and the tumor microenvironment. Therefore, improved understanding of the cross talk between tumor cells and DCs may suggest new approaches to improve cancer therapy.