Natural killer cells produce T cell-recruiting chemokines in response to antibody-coated tumor cells

Are natural killer cells protecting the metabolically healthy obese patient?

With the emerging obesity pandemic, identifying those who appear to be protected from adverse consequences such as type 2 diabetes and certain malignancies will become important. We propose that the circulating immune system plays a role in the development of these comorbidities. Clinical data and blood samples were collected from 52 patients with severe obesity attending a hospital weight-management clinic and 11 lean healthy controls. Patients were classified into metabolically "healthy obese" (n = 26; mean age 42.6 years, mean BMI 46.8 kg/m(2)) or "unhealthy obese" (n = 26; mean age 45 years, mean BMI 47.5 kg/m(2)) groups, based upon standard cutoff points for blood pressure, lipid profile, and fasting glucose. Circulating lymphoid populations and phenotypes were assessed by flow cytometry. Obese patients had significantly less circulating natural killer (NK) and cytotoxic T lymphocytes (CTL) compared to lean controls. There were significantly higher levels of NK cells and CTLs in the healthy obese group compared to the unhealthy obese group (NK: 11.7% vs. 6.5%, P < 0.0001, CD8 13.4% vs. 9.3%, P = 0.04), independent of age and BMI and these NK cells were also less activated in the healthy compared to the unhealthy group (CD69, 4.1% vs. 11.8%, P = 0.03). This is the first time that quantitative differences in the circulating immune system of obese patients with similar BMI but different metabolic profiles have been described. The significantly higher levels of CTLs and NK cells, which express fewer inhibitory molecules, could protect against malignancy, infection, and metabolic disease seen in obesity.

Differential upregulation of chemokine receptors on CD56 NK cells and their transmigration to the site of infection in tuberculous pleurisy

Chemokines and their receptors orchestrate leukocyte recruitment and confer immunity during Mycobacterium tuberculosis infection. The immunoregulatory and cytotoxic activities of natural killer (NK) cells are essential at the site of infection during tuberculous pleurisy. The frequency, subtypes, and expression of phenotype markers and chemokine receptors on NK cells were assessed by flow cytometry in tuberculous (TB) and nontuberculous (NTB) pleural fluid (PF). Chemotaxis was also shown in response to chemokines. A significant decrease in CD56(dim) with no change in CD56(bright) NK cells was observed, while a significant increase in activation markers and Toll-like receptors (TLRs) was observed on TB-PF CD56(bright) NK cells. Significantly increased expression of chemokine receptors CCR1, CCR2 and CCR7 on CD56(bright) and CCR5 on CD56(dim) NK cells was observed in the TB group. Transmigration of TB-PF NK cells was significantly high in response to IL-8, IP-10, MCP-1 and SLC. Transmigrated TB-NK cells showed a significant increase in CXCR2, CCR2 and CCR7 expression. The study suggests that CD56(bright) NK cells may recognize M. tuberculosis directly using TLRs, HLA-DR and express CD69 as an early activation marker. In addition, CC chemokines induce activation signals in chemokine receptors mediating differential NK cell migration to the site. Thus, NK cells act as first direct sensors and effectors in mycobacterial infection.

A phase II trial of trastuzumab in combination with low-dose interleukin-2 (IL-2) in patients (PTS) with metastatic breast cancer (MBC) who have previously failed trastuzumab

Trastuzumab mediates the lysis of HER2-expressing breast cancer cell lines by interleukin-2 (IL-2) primed natural killer (NK) cells. We hypothesized that IL-2 would augment the anti-tumor effects of trastuzumab in MBC in patients who had progressed on or within 12 months of receiving a trastuzumab-containing regimen. Secondary objectives were to measure antibody-directed cellular cytotoxicity (ADCC) against HER2 over-expressing target cells, and to measure serum cytokines. Patients received trastuzumab (4 mg/kg intravenously (IV)) every 2 weeks in combination with daily low-dose IL-2 (1 million IU/m(2) subcutaneously (SC)) and pulsed intermediate-dose IL-2 (12 million IU/m(2) SC). Samples were analyzed for NK cell expansion and ADCC against a HER2-positive breast cancer cell line. In addition, interferon-gamma (IFN-gamma), mRNA expression in peripheral blood mononuclear cells (PBMC) and the following serum cytokines were measured: IFN-gamma, monokine-induced by IFN-gamma (MIG), and interferon-inducible protein ten (IP-10). The median number of treatment cycles was four (range 1-23) and the treatment was well tolerated. There were no objective responses. NK cells were not expanded and ADCC was not enhanced. Eight (62%) patients had a twofold or higher increase in mRNA transcript for IFN-gamma, two (15%) patients had elevated serum levels of IFN-gamma and 12 (92%) had increases angiogenic MIG and IP-10. In trastuzumab-refractory patients adding IL-2 did not produce responses and did not result in NK cell expansion. However, these patients had the ability to respond to IL-2 as evidenced by increases in IFN-gamma transcripts and chemokines. The lack of NK cell expansion may explain the absence of clinical benefit.

TGF-beta utilizes SMAD3 to inhibit CD16-mediated IFN-gamma production and antibody-dependent cellular cytotoxicity in human NK cells

TGF-beta can be a potent suppressor of lymphocyte effector cell functions and can mediate these effects via distinct molecular pathways. The role of TGF-beta in regulating CD16-mediated NK cell IFN-gamma production and antibody-dependent cellular cytotoxicity (ADCC) is unclear, as are the signaling pathways that may be utilized. Treatment of primary human NK cells with TGF-beta inhibited IFN-gamma production induced by CD16 activation with or without IL-12 or IL-2, and it did so without affecting the phosphorylation/activation of MAP kinases ERK and p38, as well as STAT4. TGF-beta treatment induced SMAD3 phosphorylation, and ectopic overexpression of SMAD3 resulted in a significant decrease in IFN-gamma gene expression following CD16 activation with or without IL-12 or IL-2. Likewise, NK cells obtained from smad3(-/-) mice produced more IFN-gamma in response to CD16 activation plus IL-12 when compared with NK cells obtained from wild-type mice. Coactivation of human NK cells via CD16 and IL-12 induced expression of T-BET, the positive regulator of IFN-gamma, and T-BET was suppressed by TGF-beta and by SMAD3 overexpression. An extended treatment of primary NK cells with TGF-beta was required to inhibit ADCC, and it did so by inhibiting granzyme A and granzyme B expression. This effect was accentuated in cells overexpressing SMAD3. Collectively, our results indicate that TGF-beta inhibits CD16-mediated human NK cell IFN-gamma production and ADCC, and these effects are mediated via SMAD3.

lenalidomide enhances natural killer cell and monocyte-mediated antibody-dependent cellular cytotoxicity of rituximab-treated CD20+ tumor cells

PURPOSE

Lenalidomide has significant activity in myelodysplastic syndromes, multiple myeloma, and non-Hodgkin's lymphoma (NHL). In previous studies, natural killer (NK) cell expansion by lenalidomide was shown to enhance the cytotoxic effect of rituximab. This study assessed the ability of lenalidomide to enhance antibody-dependent cellular cytotoxicity (ADCC) in rituximab-treated NHL cell lines and primary tumor cells from patients with B-cell chronic lymphocytic leukemia (B-CLL) in vitro.

EXPERIMENTAL DESIGN

An in vitro ADCC system was used to assess the ability of lenalidomide to enhance human NK cell and monocyte function in response to rituximab.

RESULTS

Lenalidomide directly enhanced IFN-gamma production via Fc-gamma receptor-mediated signaling in response to IgG. It was also a potent enhancer of NK cell-mediated and monocyte-mediated tumor cell ADCC for a variety of rituximab-treated NHL cell lines in vitro, an effect that was dependent on the presence of antibody and either interleukin-2 or interleukin-12. Lenalidomide also enhanced the ability of NK cells to kill primary tumor cells derived from three patients with B-CLL who have been treated previously with fludarabine plus cyclophosphamide. Enhanced NK cell ADCC was associated with enhanced granzyme B and Fas ligand expression and could be inhibited by a granzyme B inhibitor and partially inhibited by antibody to FasL. Enhanced NK cell Fc-gamma receptor signaling is associated with enhanced phosphorylated extracellular signal-related kinase levels leading to enhanced effector function.

CONCLUSIONS

These findings suggest that lenalidomide has the potential to enhance the rituximab-induced killing of NHL cell lines and primary B-cell chronic lymphocytic leukemia cells via a NK cell-mediated and monocyte-mediated ADCC mechanism in vitro, providing a strong rationale for the combination of lenalidomide with IgG1 antibodies to target tumor-specific antigens in patients with cancer.

Microglia and myeloperoxidase: a deadly partnership in neurodegenerative disease

The role of inflammation in Alzheimer's disease, Parkinson's disease, and multiple sclerosis has recently come under increased scrutiny. Associated with these inflammatory responses are tumor necrosis factor-alpha (TNF-alpha) and reactive oxygen species (ROS), both believed to be derived from brain microglia. In addition to the above, the presence of myeloperoxidase (MPO) in these diseased brains has been reported by a number of investigators. However, the possible role of MPO and enzymatically inactive MPO (iMPO) as the "choreographers" of the destruction done by TNF-alpha and ROS is not generally recognized. Previously, our laboratory has reported that MPO/iMPO enhance macrophage generation of ROS and expression of proinflammatory cytokine genes as well as gene products. Recent studies in our laboratory indicate that the same response occurs with microglia. A paradigm is presented for the perpetuation of inflammation associated with neurodegenerative diseases. This model describes the unrecognized consequences of the stimulation of microglia by MPO or iMPO. Both MPO and iMPO and/or its receptor may represent new therapeutic targets for the treatment of these diseases.

alpha-Galactosylceramide-loaded, antigen-expressing B cells prime a wide spectrum of antitumor immunity

Most of the current tumor vaccines successfully elicit strong protection against tumor but offer little therapeutic effect against existing tumors, highlighting the need for a more effective vaccine strategy. Vaccination with tumor antigen-presenting cells can induce antitumor immune responses. We have previously shown that NKT-licensed B cells prime cytotoxic T lymphocytes (CTLs) with epitope peptide and generate prophylactic/therapeutic antitumor effects. To extend our B cell vaccine approach to the whole antigen, and to overcome the MHC restriction, we used a nonreplicating adenovirus to transduce B cells with antigenic gene. Primary B cells transduced with an adenovirus-encoding truncated Her-2/neu (AdHM) efficiently expressed Her-2/neu. Compared with the moderate antitumor activity induced by vaccination with adenovirus-transduced B cells (B/AdHM), vaccination with alpha-galactosylceramide-loaded B/AdHM (B/AdHM/alpha GalCer) induced significantly stronger antitumor immunity, especially in the tumor-bearing mice. The depletion study showed that CD4(+), CD8(+) and NK cells were all necessary for the therapeutic immunity. Confirming the results of the depletion study, B/AdHM/alpha GalCer vaccination induced cytotoxic NK cell responses but B/AdHM did not. Vaccination with B/AdHM/alpha GalCer generated Her-2/neu-specific antibodies more efficiently than B/AdHM immunization. More importantly, B/AdHM/alpha GalCer could prime Her-2/neu-specific cytotoxic T cells more efficiently and durably than B/AdHM. CD4(+) cells appeared to be necessary for the induction of antibody and CTL responses. Our results demonstrate that, with the help of NKT cells, antigen-transduced B cells efficiently induce innate immunity as well as a wide range of adaptive immunity against the tumor, suggesting that they could be used to develop a novel cellular vaccine.

Interleukin-2 potentiation of cetuximab antitumor activity for epidermal growth factor receptor-overexpressing gastric cancer xenografts through antibody-dependent cellular cytotoxicity

Cetuximab, a chimeric monoclonal antibody to epidermal growth factor receptor (EGFR), has been proved to have clinically significant antitumor activity against advanced colorectal cancers, but its therapeutic activity for gastric cancers remains unclear. In the present study, we investigated the antitumor effect and action mechanism of cetuximab using EGFR high-expressing (MKN-28) and EGFR low-expressing (GLM-1) gastric cancer cell lines without gene amplification. Cetuximab showed neither significant growth inhibition nor induction of apoptosis in either cell line in vitro, and only slightly inhibited ligand-induced phosphorylation of protein kinase B and extracellular signal-regulated kinase in MKN-28 cells. In contrast, cetuximab significantly inhibited subcutaneous and intraperitoneal tumor growth of MKN-28 cells, but not GLM-1 cells, in nude mice. This antitumor activity was significantly enhanced and diminished in nude mice by treatment with interleukin-2 (IL-2) and antiasialo GM1 antibody, which can expand and deplete natural killer (NK) cells, respectively. Antibody-dependent cellular cytotoxicity (ADCC) of cetuximab, as measured by (51)Cr release assay, was significantly higher in MKN-28 than in GLM-1 cells. This ADCC activity was enhanced by IL-2 and reduced by heat-aggregate of human immunoglobulin G, an inhibitor for FcR-III of NK cells. These results suggest that cetuximab in combination with IL-2 shows significant antitumor activity against EGFR high-expressing gastric cancer mainly through NK cell-mediated ADCC. Combination therapy with cetuximab and IL-2 would thus offer a new potential therapeutic approach for a subset of EGFR-overexpressing gastric cancers.

Transient activation of tumor-associated T-effector/memory cells promotes tumor eradication via NK-cell recruitment: minimal role for long-term T-cell immunity in cure of metastatic disease

Local delivery of IL-12 and GM-CSF to advanced primary tumors results in T- and NK-cell-dependent cure of disseminated disease in a murine spontaneous lung metastasis model. Post-therapy functional dynamics of cytotoxic T- and NK-cells were analyzed in primary and metastatic tumors to determine the specific roles of each subset in tumor eradication. Time-dependent depletion of CD8+ T and NK-cells demonstrated that CD8+ T-cells were critical to eradication of metastatic tumors within 3 days of treatment, but not later. In contrast, NK-cells were found to be essential to tumor regression for at least 10 days after cytokine delivery. Analysis of tumor-infiltrating lymphocyte populations in post-therapy primary tumors demonstrated that treatment resulted in the activation of tumor-associated CD8+ T-cells within 24 h as determined by IFNgamma and perforin production. T-cell activity peaked between days 1 and 3 and subsided rapidly thereafter. Activation was not accompanied with an increase in cell numbers suggesting that treatment mobilized pre-existing T-effector/memory cells without inducing proliferation. In contrast, therapy resulted in a > or = 3-fold enhancement of both the quantity and the cytotoxic activity of NK-cells in primary and metastatic tumors on day 3 post-therapy. NK-cell activity was also transient and subsided to pre-therapy levels by day 5. Depletion of CD4+ and CD8+ T-cells prior to treatment completely abrogated NK-cell infiltration into primary and metastatic tumors demonstrating the strict dependence of NK-cell recruitment on pre-existing T-effector/memory cells. Treatment failed to induce significant NK-cell infiltration in IFNgamma-knockout mice establishing the central role of IFNgamma in NK-cell chemotaxis to tumors. These data show that transient activation of tumor-associated T-effector/memory and NK-cells, but not long-term CD8+ T-cell responses, are critical to suppression of metastatic disease in this model; and reveal a novel role for preexisting adaptive T-cell immunity in the recruitment of innate effectors to tumors.

Chemokines as therapeutic targets in renal cell carcinoma

Targeting novel pathways associated with tumor angiogenesis, invasion and immunity, may lead to improvement in patient outcomes for renal cell carcinoma. Chemokines potentiate tumor growth, metastasis, angiogenesis and immune evasion through interactions with stromal cells and neoplastic cells. Further understanding of the mechanisms involved in chemokine-mediated angiogenesis and metastasis may lead to improved therapeutic strategies in this disease. Interactions between chemokine expression and signaling, and the VEGF and hypoxia-inducible factor pathways offer important opportunities to intervene in the process of renal cell carcinoma proliferation, angiogenesis and invasion. Modulation of the CXCR3/CXCR3-ligand or the CXCR4/CXCL12 biologic axis may be potential therapeutic targets for the treatment of renal cell carcinoma. Furthermore, combination treatment with agents targeting chemokine signaling with therapies directed at angiogenesis and tumor immunity may lead to improved outcomes in this disease.

Correlation between NK function and response to trastuzumab in metastatic breast cancer patients

BACKGROUND

Trastuzumab is a monoclonal antibody selectively directed against Her2 and approved for the treatment of Her2 overexpressing breast cancer patients. Its proposed mechanisms of action include mediation of antibody-dependent cellular cytotoxicity (ADCC) by triggering FcgammaRIII on natural killer (NK) cells. This study addresses the correlation between overall NK function and trastuzumab's clinical activity.

SUBJECTS AND METHODS

Clinical and immunological responses were assessed in 26 patients receiving trastuzumab monotherapy as maintenance management after chemotherapy (8 mg/kg load and then standard doses of 6 mg/kg every 3 weeks). Cytotoxic activity against the MHC class I-negative standard NK target K562 cell line and HER2-specific ADCC against a trastuzumab-coated Her2-positive SKBR3 cell line were assessed in peripheral blood mononuclear cells (PBMC) harvested after the first standard dose. After six months, seventeen patients were scored as responders and nine as non-responders according to the RECIST criteria, while Progression-Free Survival (PFS) was calculated during a 12 months follow-up.

RESULTS

The responders had significantly higher levels of both NK and ADCC activities (p < 0.05) that were not different from those of eleven normal controls. The NK activity of the non-responders was significantly (p < 0.05) lower than that of the normal controls. At twelve months, there was a marked correlation between PFS and NK activity only. PFS was significantly longer in patients with high levels of NK activity, whereas its pattern was unrelated to high or low ADCC activity.

CONCLUSION

One of the mechanisms of action of trastuzumab is NK cell-mediated ADCC lysis of the Her2-positve target cell. We show here that its potency is correlated with the short-term response to treatment, whereas longer protection against tumor expansion seems to be mediated by pure NK activity.

RANTES-403 polymorphism is associated with reduced risk of gastric cancer in women

BACKGROUND

Men are more susceptible to gastric cancer (GC) than women. However, the genetic factors associated with the sex difference are not well understood. Chemokines have been shown to modulate tumor behavior, and the sex-specific effect of the chemokine polymorphisms on the host susceptibility to several diseases has been reported. We aimed to determine the role of chemokine polymorphisms on host susceptibility to GC, with special interest on their sex-specific effect.

METHODS

A hospital-based case-control study, including 177 patients with GC and 217 age-matched unaffected healthy controls, was performed in three major tertiary care hospitals. Genotyping for regulated upon activation, normal T-cell expressed and secreted (RANTES) -403 A/G and -28 C/G, CC chemokine receptor 5 (CCR5) deletion, and CCR2-V64I was performed using peripheral blood DNA.

RESULTS

The RANTES -403 GA and AA genotypes were independently associated with a 2.3-fold reduced risk of developing GC (OR=0.44, 95% CI 0.22-0.90, P=0.025) compared with GG genotype in women, but not in men. The RANTES -28C/G and CCR2-V64I polymorphisms were not associated with different risk of developing GC. The tumor stage, histological features, and survival rate were not different when stratified by RANTES -403 and -28 and CCR2-V64I genotypes.

CONCLUSIONS

Our data indicate that women who inherit A allele at RANTES -403 may be at reduced risk of GC.

V gamma 9 V delta 2 T cell cytotoxicity against tumor cells is enhanced by monoclonal antibody drugs--rituximab and trastuzumab

V gamma 9 V delta 2 T cells exert potent cytotoxicity toward various tumor cells and adoptive transfer of V gamma 9 V delta 2 T cells is an attractive proposition for cell based immunotherapy. V gamma 9 V delta 2 T cells expanded in the presence of Zoledronate and IL-2 express CD16 (Fc gamma RIII), which raises the possibility that V gamma 9 V delta 2 T cells could be used in conjunction with tumor targeting monoclonal antibody drugs to increase antitumor cytotoxicity by antibody dependent cellular cytotoxicity (ADCC). Cytotoxic activity against CD20-positive B lineage lymphoma or chronic lymphocytic leukemia (CLL) and HER2-positive breast cancer cells was assessed in the presence of rituximab and trastuzumab, respectively. Cytotoxicity of V gamma 9 V delta 2 T cells against CD20-positive targets was higher when used in combination with rituximab. Similarly, V gamma 9 V delta 2 T cells used in combination with trastuzumab resulted in greater cytotoxicity against HER2-positive cells in comparison with either agent alone and this effect was restricted to the CD16(+)V gamma 9 V delta 2 T cell population. Our results show that CD16(+)V gamma 9 V delta 2 T cells recognize monoclonal antibody coated tumor cells via CD16 and exert ADCC similar to that observed with NK cells, even when target cells are relatively resistant to monoclonal antibodies or V gamma 9 V delta 2 T cells alone. Combination therapy involving ex vivo expanded CD16(+)V gamma 9 V delta 2 T cells and monoclonal antibodies may enhance the clinical outcomes for patients treated with monoclonal antibody therapy.

The inflammatory chemokines CCL2 and CCL5 in breast cancer

A causal role was recently attributed to inflammation in many malignant diseases, including breast cancer. The different inflammatory mediators that are involved in this disease include cells, cytokines and chemokines. Of these, many studies have addressed the involvement and roles of the inflammatory chemokines CCL2 (MCP-1) and CCL5 (RANTES) in breast malignancy. While minimally expressed by normal breast epithelial duct cells, both chemokines are highly expressed by breast tumor cells at primary tumor sites, indicating that CCL2 and CCL5 expression is acquired in the course of malignant transformation, and suggesting that the two chemokines play a role in breast cancer development and/or progression. Supporting this possibility are findings showing significant associations between CCL2 and CCL5 and more advanced disease course and progression. Furthermore, studies in animal model systems have shown active and causative roles for the two chemokines in this disease. In line with the tumor-promoting roles of CCL2 and CCL5 in breast cancer, the two chemokines were shown to mediate many types of tumor-promoting cross-talks between the tumor cells and cells of the tumor microenvironment: (1) they shift the balance at the tumor site between different leukocyte cell types by increasing the presence of deleterious tumor-associated macrophages (TAM) and inhibiting potential anti-tumor T cell activities; (2) of the two chemokines, mainly CCL2 promotes angiogenesis; (3) CCL2 and CCL5 which are expressed by cells of the tumor microenvironment osteoblasts and mesenchymal stem cells play a role in breast metastatic processes. In addition, both chemokines act directly on the tumor cells to promote their pro-malignancy phenotype, by increasing their migratory and invasion-related properties. Together, the overall current information suggests that CCL2 and CCL5 are inflammatory mediators with pro-malignancy activities in breast cancer, and that they should be considered as potential therapeutic targets for the limitation of this disease.

Elements related to heterogeneity of antibody-dependent cell cytotoxicity in patients under trastuzumab therapy for primary operable breast cancer overexpressing Her2

Preliminary results from a pilot trial on trastuzumab's mechanism of action against operable breast tumors overexpressing Her2 suggested a role for antibody-dependent cell cytotoxicity (ADCC). To examine factors affecting ADCC intensity and variability, we extended this study to the phenotypic and functional analysis of circulating mononuclear cells in 18 patients. ADCC was induced by trastuzumab therapy in 15 of 18 patients (83%). Inability to develop ADCC in three patients did not depend on inadequate levels of trastuzumab because further increase in its concentration in vitro was ineffective. Rather, susceptibility to develop ADCC was fairly predicted by test with trastuzumab before therapy and was correlated to the number of lymphocytes coexpressing CD16 and CD56. Phenotypic analysis at the end of ADCC evaluating down-regulation of CD16, and up-regulation of CD69 and CD107a, confirmed that natural killer (NK) cells and CD56(+) T cells were involved in productive engagement of trastuzumab. Also, the killing efficiency of CD16(+) lymphocytes was influenced by 158 V/F polymorphism of Fc gamma RIII (CD16), whereas variations of CD247 on NK cells were consistent with trends between ADCC before and after therapy. Complete pathologic response was observed in one patient showing ADCC of outstanding intensity, whereas four cases of partial response showed intermediate ADCC; none of the three patients unable to mount ADCC had significant tumor regression. These data indicate that quantity and lytic efficiency of CD16(+) lymphocytes are major factors for ADCC induction by trastuzumab, and confirm that breast cancer responses to short-term trastuzumab monotherapy may depend on involvement of the ADCC mechanism.

The activation of natural killer cell effector functions by cetuximab-coated, epidermal growth factor receptor positive tumor cells is enhanced by cytokines

PURPOSE

Natural killer (NK) cells express an activating Fc receptor (FcgammaRIIIa) that mediates antibody-dependent cellular cytotoxicity (ADCC) and production of immune modulatory cytokines in response to antibody-coated targets. Cetuximab is a therapeutic monoclonal antibody directed against the HER1 antigen. We hypothesized that the NK cell response to cetuximab-coated tumor cells could be enhanced by the administration of NK cell-stimulatory cytokines.

EXPERIMENTAL DESIGN

Human NK cells stimulated with cetuximab-coated tumor cells and interleukin-2 (IL-2), IL-12, or IL-21 were assessed for ADCC and secretion of IFN-gamma and T cell-recruiting chemokines. IL-21 and cetuximab were given to nude mice bearing HER1-positive xenografts.

RESULTS

Stimulation of human NK cells with cetuximab-coated tumor cells and IL-2, IL-12, or IL-21 resulted in 3-fold to 10-fold higher IFN-gamma production than was observed with either agent alone. NK cell-derived IFN-gamma significantly enhanced monocyte ADCC against cetuximab-coated tumor cells. Costimulated NK cells also secreted elevated levels of chemokines (IL-8, macrophage inflammatory protein-1alpha, and RANTES) that could direct the migration of naive and activated T cells. IL-2, IL-12, and IL-21 enhanced NK cell ADCC against tumor cells treated with cetuximab. The combination of cetuximab, trastuzumab (an anti-HER2 monoclonal antibody), and IL-21 mediated greater NK cell cytokine secretion and ADCC than any agent alone. Furthermore, administration of IL-21 enhanced the effects of cetuximab in a murine tumor model.

CONCLUSIONS

These results show that cetuximab-mediated NK cell activity can be significantly enhanced in the presence of NK cell-stimulatory cytokines. These factors, therefore, may be effective adjuvants to administer, in combination with cetuximab, to patients with HER1-positive malignancies.

Induction of protective immune responses against NXS2 neuroblastoma challenge in mice by immunotherapy with GD2 mimotope vaccine and IL-15 and IL-21 gene delivery

The GD2 ganglioside expressed on neuroectodermal tumor cells is weakly immunogenic in tumor-bearing patients and induces predominantly IgM antibody responses in the immunized host. Using a syngeneic mouse challenge model with GD2-expressing NXS2 neuroblastoma, we investigated novel strategies for augmenting the effector function of GD2-specific antibody responses induced by a mimotope vaccine. We demonstrated that immunization of A/J mice with DNA vaccine expressing the 47-LDA mimotope of GD2 in combination with IL-15 and IL-21 genes enhanced the induction of GD2 cross-reactive IgG2 antibody responses that exhibited cytolytic activity against NXS2 cells. The combined immunization regimen delivered 1 day after tumor challenge inhibited subcutaneous (s.c.) growth of NXS2 neuroblastoma in A/J mice. The vaccine efficacy was reduced after depletion of NK cells as well as CD4(+) and CD8(+) T lymphocytes suggesting involvement of innate and adaptive immune responses in mediating the antitumor activity in vivo. CD8(+) T cells isolated from the immunized and cured mice were cytotoxic against syngeneic neuroblastoma cells but not against allogeneic EL4 lymphoma, and exhibited antitumor activity after adoptive transfer in NXS2-challenged mice. We also demonstrated that coimmunization of NXS2-challenged mice with the IL-15 and IL-21 gene combination resulted in enhanced CD8(+) T cell function that was partially independent of CD4(+) T cell help in inhibiting tumor growth. This study is the first demonstration that the mimotope vaccine of a weakly immunogenic carbohydrate antigen in combination with plasmid-derived IL-15 and IL-21 cytokines induces both innate and adaptive arms of the immune system leading to the generation of effective protection against neuroblastoma challenge.

The CCL3 Family of Chemokines and Innate Immunity Cooperate In Vivo in the Eradication of an Established Lymphoma Xenograft by Rituximab

The therapeutic mAb rituximab induced the expression of the CCL3 and CCL4 chemokines in the human lymphoma line BJAB following binding to the CD20 Ag. Induction of CCL3/4 in vitro was specific, was observed in several cell lines and freshly isolated lymphoma samples and also took place at the protein level in vitro and in vivo. To investigate the role of these beta-chemokines in the mechanism of action of rituximab, we synthesized a N-terminally truncated CCL3 molecule CCL3(11-70), which had antagonist activity on chemotaxis mediated by either CCL3 or BJAB supernatant. We also set up an established s.c. BJAB tumor model in athymic mice. Rituximab, given weekly after tumors had reached 250 mm2, led to complete disappearance of the lymphoma within 2-3 wk. Treatment of mice with cobra venom factor showed that complement was required for rituximab therapeutic activity. Treatment of BJAB tumor bearing mice every 2 days with the CCL3(11-70) antagonist, starting 1 wk before rituximab treatment, had no effect on tumor growth by itself, but completely inhibited the therapeutic activity of the Ab. To determine whether CCL3 acts through recruitment/activation of immune cells, we specifically depleted NK cells, polymorphonuclear cells, and macrophages using mAbs, clodronate treatment, or Rag2-/-cgamma-/- mice. The data demonstrated that these different cell populations are involved in BJAB tumor eradication. We propose that rituximab rapidly activates complement and induces beta-chemokines in vivo, which in turn activate the innate immunity network required for efficient eradication of the bulky BJAB tumor.

Activation, coactivation, and costimulation of resting human natural killer cells

Natural killer (NK) cells possess potent perforin- and interferon-gamma-dependent effector functions that are tightly regulated. Inhibitory receptors for major histocompatibility complex class I display variegated expression among NK cells, which confers specificity to individual NK cells. Specificity is also provided by engagement of an array of NK cell activation receptors. Target cells may express ligands for a multitude of activation receptors, many of which signal through different pathways. How inhibitory receptors intersect different signaling cascades is not fully understood. This review focuses on advances in understanding how activation receptors cooperate to induce cytotoxicity in resting NK cells. The role of activating receptors in determining specificity and providing redundancy of target cell recognition is discussed. Using Drosophila insect cells as targets, we have examined the contribution of individual receptors. Interestingly, the strength of activation is not determined simply by additive effects of parallel activation pathways. Combinations of signals from different receptors can have different outcomes: synergy, no enhancement over individual signals, or additive effects. Cytotoxicity requires combined signals for granule polarization and degranulation. The integrin leukocyte function-associated antigen-1 contributes a signal for polarization but not for degranulation. Conversely, CD16 alone or in synergistic combinations, such as NKG2D and 2B4, signals for phospholipase-C-gamma- and phosphatidylinositol-3-kinase-dependent degranulation.

The chemokine network: a target in cancer biology?

Chemokine gradients are central to the movement of cells in both homeostatic and pathological processes. Most cancers express a complex array of chemokines that influence the local microenvironment through recruitment of stromal cells and by stimulating angiogenesis. Recently, the discovery of chemokine receptors on tumor cells has led to speculation that the chemokine system may be involved in cancer cell growth and survival, and possibly the development of site-specific spread. Understanding the networks of chemokines and their receptors in cancer will enable manipulation of this system. Both chemokines and their receptors represent targets for therapeutic intervention either with antibodies or small molecule antagonists. However, due to the complexity of the system, and the number of chemokines and receptors that are also expressed by normal cells, issues remain concerning whether systemic or local drug delivery are preferable and whether the redundancy of the system will compensate if one chemokine or receptor is targeted. Nevertheless, efficacy has been demonstrated in a number of experimental models. By targeting this network, it may be possible to generate anti-tumor immune responses by altering the chemokine and/or leukocyte balance in tumors; alternatively, chemokine/chemokine receptor-expressing cancer cells could be directly targeted.

Interleukin-21 enhances NK cell activation in response to antibody-coated targets

NK cells express an activating FcR (FcgammaRIIIa) that mediates Ab-dependent cellular cytotoxicity and the production of immune modulatory cytokines in response to Ab-coated targets. IL-21 has antitumor activity in murine models that depends in part on its ability to promote NK cell cytotoxicity and IFN-gamma secretion. We hypothesized that the NK cell response to FcR stimulation would be enhanced by the administration of IL-21. Human NK cells cultured with IL-21 and immobilized IgG or human breast cancer cells coated with a therapeutic mAb (trastuzumab) secreted large amounts of IFN-gamma. Increased secretion of TNF-alpha and the chemokines IL-8, MIP-1alpha, and RANTES was also observed under these conditions. NK cell IFN-gamma production was dependent on distinct signals mediated by the IL-21R and the FcR and was abrogated in STAT1-deficient NK cells. Supernatants derived from NK cells that had been stimulated with IL-21 and mAb-coated breast cancer cells were able to drive the migration of naive and activated T cells in an in vitro chemotaxis assay. IL-21 also enhanced NK cell lytic activity against Ab-coated tumor cells. Coadministration of IL-21 and Ab-coated tumor cells to immunocompetent mice led to synergistic production of IFN-gamma by NK cells. Furthermore, the administration of IL-21 augmented the effects of an anti-HER2/neu mAb in a murine tumor model, an effect that required IFN-gamma. These findings demonstrate that IL-21 significantly enhances the NK cell response to Ab-coated targets and suggest that IL-21 would be an effective adjuvant to administer in combination with therapeutic mAbs.