A Tumor Cell-Selective Inhibitor of Mitogen-Activated Protein Kinase Phosphatases Sensitizes Breast Cancer Cells to Lymphokine-Activated Killer Cell Activity.

Dual specificity mitogen-activated protein kinase (MAPK) phosphatases [dual specificity phosphatase/MAP kinase phosphatase (DUSP-MKP)] have been hypothesized to maintain cancer cell survival by buffering excessive MAPK signaling caused by upstream activating oncogenic products. A large and diverse body of literature suggests that genetic depletion of DUSP-MKPs can reduce tumorigenicity, suggesting that hyperactivating MAPK signaling by DUSP-MKP inhibitors could be a novel strategy to selectively affect the transformed phenotype. Through in vivo structure-activity relationship studies in transgenic zebrafish we recently identified a hyperactivator of fibroblast growth factor signaling [(E)-2-benzylidene-5-bromo-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one (BCI-215)] that is devoid of developmental toxicity and restores defective MAPK activity caused by overexpression of DUSP1 and DUSP6 in mammalian cells. Here, we hypothesized that BCI-215 could selectively affect survival of transformed cells. In MDA-MB-231 human breast cancer cells, BCI-215 inhibited cell motility, caused apoptosis but not primary necrosis, and sensitized cells to lymphokine-activated killer cell activity. Mechanistically, BCI-215 induced rapid and sustained phosphorylation of extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK) in the absence of reactive oxygen species, and its toxicity was partially rescued by inhibition of p38 but not JNK or ERK. BCI-215 also hyperactivated MKK4/SEK1, suggesting activation of stress responses. Kinase phosphorylation profiling documented BCI-215 selectively activated MAPKs and their downstream substrates, but not receptor tyrosine kinases, SRC family kinases, AKT, mTOR, or DNA damage pathways. Our findings support the hypothesis that BCI-215 causes selective cancer cell cytotoxicity in part through non-redox-mediated activation of MAPK signaling, and the findings also identify an intersection with immune cell killing that is worthy of further exploration.

A Prospective Observational Study of Adoptive Immunotherapy for Cancer Using Zoledronate-Activated Killer (ZAK) Cells - An Analysis for Patients with Incurable Pancreatic Cancer.

BACKGROUND/AIM: Adoptive immunotherapy (AIT) using autologous zoledronate-activated killer (ZAK) cells has been performed for developing a novel modality of cancer treatment. In this study, data series from incurable pancreatic cancer were analyzed. PATIENTS AND METHODS: Patients were treated with AIT using intravenous administration of ZAK cells every 3 to 4 weeks in combination with standard chemotherapy and possible clinical benefits were examined. RESULTS: Seventy-five patients were treated. A median overall survival (OS) time of 6.7 months was achieved for all patients and 13.1 months for those treated 5 times or more, that increased to 14.6 and 18.3 months, respectively, when the previous treatment period of chemotherapy alone was included in the analysis. The disease control rate was 58.5 %. Multivariate regression analysis showed a significant positive correlation between the survival and baseline value of lymphocyte percentage in white blood cell counts (p=0.031). CONCLUSION: The data suggest that AIT using ZAK cells in combination with chemotherapy is safe and feasible and may be effective in prolonging survival for patients with incurable pancreatic cancer. The lymphocyte percentage at baseline may be a good biomarker for predicting the survival benefit of ZAK cell AIT.

Reversal of epigenetic silencing of MHC class I chain-related protein A and B improves immune recognition of Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is a virally associated cancer characterized by its aggressive behavior and strong immunogenicity. Both viral infection and malignant transformation induce expression of MHC class I chain-related protein (MIC) A and B, which signal stress to cells of the immune system via Natural Killer group 2D (NKG2D) resulting in elimination of target cells. However, despite transformation and the continued presence of virally-encoded proteins, MICs are only expressed in a minority of MCC tumors in situ and are completely absent on MCC cell lines in vitro. This lack of MIC expression was due to epigenetic silencing via MIC promoter hypo-acetylation; indeed, MIC expression was re-induced by pharmacological inhibition of histone deacetylases (HDACs) both in vitro and in vivo. This re-induction of MICs rendered MCC cells more sensitive to immune-mediated lysis. Thus, epigenetic silencing of MICs is an important immune escape mechanism of MCCs.

Anticancer agent pristimerin inhibits IL-2 induced activation of T lymphocytes.

Pristimerin (PM) is a quinonemethide triterpenoid with cytotoxic activity against a wide range of cancer cell lines. However, the effect of PM on IL-2 induced activation of T lymphocytes, which play a major role in antitumor immunity has not been studied. The objective of the present study was to evaluate the effect of PM on IL-2 induced proliferation of T cells, generation of lymphokine activated killer cells (LAK cells) and the signaling pathways involved in activation of T cells by IL-2. PM inhibited the IL-2 induced proliferation of mouse splenic T cells and the generation LAK cells at very low concentrations. The suppression of T cell proliferation by PM was associated with the inhibition of IL-2 induced Janus kinase/signal transducers and activators of transcription (Jak/STAT) and extracellular signal-regulated kinase 1 and 2 (Erk1/2) signaling pathways. PM also inhibited the proliferation and differentiation-related immediate early gene products such as p-c-fos, p-c-jun, c-myc and cyclin D1. In addition, antiapoptotic (prosurvival) NF-кB, p-Akt and p-mTOR were also inhibited by PM. These data demonstrated that PM inhibits IL-2 induced T cell activation and generation of LAK cells by disrupting multiple cell signaling pathways induced by IL-2.

Stimulation of neuronal cells by culture supernatant of T lymphocytes triggered by anti-CD3 mAb followed by propagation in the presence of interleukin-2.

Performance status (PS) frequently improves occurs in cancer patients who have been infused with their own lymphokine-activated killer T cells (LAK-T). In the present study, a culture supernatant of LAK-T (LAK-T sup) administered to 8-week-old rats caused neurogenesis as evidenced by increased 5-ethynyl-2'-deoxyuridine staining of brain tissues. Intravenous injection of granulocyte-macrophage colony stimulating factor (GM-CSF), a major cytokine in LAK-T sup, had a similar effect. Furthermore, LAK-T sup induced Ca(++) increase in rat hippocampal brain slices that was detected in neuronal cells by emission of Fluo-8 NW at 520 nm. The same effect was observed with an rGM-CSF solution. GM-CSF may activate neuronal cells by stimulating the glial cells that surround and attach to them. If so, GM-CSF and LAK-T sup may improve the motor neurons of patients with amyotrophic lateral sclerosis. The neurogenerative effect of GM-CSF in LAK-T sup may also help improve brain function in aged adults including those with dementia such as Alzheimer's disease.

CD16+CD56+ cells are a potential culprit for hematuria in IgA nephropathy.

BACKGROUND: Hematuria is the first manifestation of urinary abnormality in immunoglobulin A nephropathy (IgAN). Hematuria has recently been reported as a risk factor for deterioration of renal function; however, its cause remains unknown. METHODS: We analyzed the surface marker of peripheral blood mononuclear cells before and immediately after tonsillectomy in IgAN patients and controls (chronic tonsillitis or tonsillar hypertrophy) by flow cytometry and investigated the association with hematuria. To prove our hypothesis that NK cells induce hematuria, we administered IL-12, activator of NK cells, to HIGA mice. In addition, we transferred cultured NK cells to nude rats and transferred the CD16(+)CD56(+) cells, including NK cells, that are derived from the peripheral blood of IgAN patients immediately after tonsillectomy to nude rats to assess the hematuria level and renal histology of the recipients. We also performed cytotoxicity assays against glomerular endothelial cells by NK cells. RESULTS: We found that IgAN patients who showed rapid deterioration of hematuria after tonsillectomy also displayed a significant increase in CD16(+)CD56(+) cells in the peripheral blood immediately after tonsillectomy. Exogenous administration of IL-12 to HIGA mice induced hematuria. Adoptive transfer of either cells of an NK cell line, or of CD16(+)CD56(+) cells derived from IgAN patients, into nude rats induced hematuria in the recipients. In vitro analysis showed that NK cells exert cytotoxic activity toward human glomerular endothelial cells in a dose-dependent manner. CONCLUSIONS: CD16(+)CD56(+) cells seem to be responsible for hematuria in IgAN.

Selenium and vitamin E enriched diet increases NK cell cytotoxicity in cattle / Dieta enriquecida com selênio e vitamina E aumenta a citotoxicidade de células NK em bovinos

A number of studies has shown that antioxidants, fatty acids and trace minerals may modulate different immune cell activities, and that their deficiency may be associated with diseases and impaired immune responses. In innate immunity, natural killer (NK) cells have a central role, killing virally infected and cancerous cells, and also secreting cytokines that shape adaptive immune responses. Thus, the aim of this study was to evaluate the effect of enriched diets in selenium plus vitamin E and/or canola oil on complete blood count and on NK cell cytotoxicity from blood lymphocytes of Nellore bulls. Bulls that received selenium plus vitamin E had (P=0.0091) higher NK cell cytotoxicity than control bulls. This result positively correlated with serum selenium levels. To the best of our knowledge, this is the first study that showed immunostimulatory effects of selenium plus vitamin E on NK cell cytotoxicity of Nellore bulls.(AU)

Vários estudos demonstraram que antioxidantes, ácidos graxos e minerais podem modular a atividade de diferentes células do sistema imunológico e que as suas carências podem estar associadas a doenças e a respostas imunes comprometidas. Na imunidade inata, os linfócitos natural killer (NK) têm um papel central matando células infectadas por vírus e células cancerígenas, ao mesmo tempo em que também secretam citocinas que modulam as respostas imunes adaptativas. Assim, o objetivo deste estudo foi avaliar o efeito de dietas enriquecidas em selênio e vitamina E e/ou óleo de canola no hemograma e na citotoxicidade das células NK do sangue de bovinos da raça Nelore. Os animais que receberam selênio e vitamina E tiveram (P = 0,0091) maior citotoxicidade das células NK do que os animais do grupo controle. Este resultado foi positivamente correlacionado com os níveis de selênio no sangue. Para o melhor do nosso conhecimento, este é o primeiro estudo que mostrou efeitos imunoestimulatórios do selênio e vitamina E sobre a citotoxicidade das células NK de bovinos Nelore.(AU)

Cannabinoids increase lung cancer cell lysis by lymphokine-activated killer cells via upregulation of ICAM-1.

Cannabinoids have been shown to promote the expression of the intercellular adhesion molecule 1 (ICAM-1) on lung cancer cells as part of their anti-invasive and antimetastatic action. Using lung cancer cell lines (A549, H460) and metastatic cells derived from a lung cancer patient, the present study addressed the impact of cannabinoid-induced ICAM-1 on cancer cell adhesion to lymphokine-activated killer (LAK) cells and LAK cell-mediated cytotoxicity. Cannabidiol (CBD), a non-psychoactive cannabinoid, enhanced the susceptibility of cancer cells to adhere to and subsequently be lysed by LAK cells, with both effects being reversed by a neutralizing ICAM-1 antibody. Increased cancer cell lysis by CBD was likewise abrogated when CBD-induced ICAM-1 expression was blocked by specific siRNA or by antagonists to cannabinoid receptors (CB1, CB2) and to transient receptor potential vanilloid 1. In addition, enhanced killing of CBD-treated cancer cells was reversed by preincubation of LAK cells with an antibody to lymphocyte function associated antigen-1 (LFA-1) suggesting intercellular ICAM-1/LFA-1 crosslink as crucial event within this process. ICAM-1-dependent pro-killing effects were further confirmed for the phytocannabinoid Δ(9)-tetrahydrocannabinol (THC) and R(+)-methanandamide (MA), a hydrolysis-stable endocannabinoid analogue. Finally, each cannabinoid elicited no significant increase of LAK cell-mediated lysis of non-tumor bronchial epithelial cells, BEAS-2B, associated with a far less pronounced (CBD, THC) or absent (MA) ICAM-1 induction as compared to cancer cells. Altogether, our data demonstrate cannabinoid-induced upregulation of ICAM-1 on lung cancer cells to be responsible for increased cancer cell lysis by LAK cells. These findings provide proof for a novel antitumorigenic mechanism of cannabinoids.

Different immunology mechanisms of Phellinus igniarius in inhibiting growth of liver cancer and melanoma cells.

To assess inhibition mechanisms of a Phellinus igniarius (PI) extract on cancer, C57BL/6 mice were orally treated with PI extractive after or before implanting H22 (hepatocellular carcinoma ) or B16 (melanoma) cells. Mice were orally gavaged with different doses of PI for 36 days 24h after introduction of H22 or B16 cells. Mice in another group were orally treated as above daily for 42 days and implanted with H22 cells on day 7. Then the T lymphocyte, antibody, cytokine, LAK, NK cell activity in spleen, tumor cell apoptosis status and tumor inhibition in related organs, as well as the expression of iNOS and PCNA in tumor tissue were examined. The PI extract could improve animal immunity as well as inhibit cancer cell growth and metastasis with a dose-response relationship. Notably, PI's regulation with the two kinds of tumor appeared to occur in different ways, since the antibody profile and tumor metastasis demonstrated variation between animals implanted with hepatocellular carcinoma and melanoma cells.

Activity of outpatient intravenous interleukin-2 and famotidine in metastatic clear cell kidney cancer.

Outpatient daily intravenous infusions of interleukin-2 (IL-2) have been developed to maintain anticancer activity and decrease toxicity of this agent against kidney cancer. Lymphokine activated killer cell (LAK) numbers are increased with these IL-2 schedules. Famotidine may enhance the LAK activity by increasing IL-2 internalization by the IL-2 receptor on lymphocytes. Fifteen patients with metastatic clear cell kidney cancer received IL-2 18 million IU/M² intravenously over 15-30 minutes preceded by famotidine 20 mg IV daily for 3 days for 6 consecutive weeks as outpatients. Cycles were repeated every 8 weeks. Patient characteristics were seven males/eight females, median age 59 (range: 28-70), median Eastern Cooperative Oncology Group (ECOG) performance status-1; common metastatic sites were lungs (14), lymph nodes (9), liver (4), bone (4), and pancreas (4). Prior systemic therapies were oral tyrosine kinase inhibitor (8), IL-2 (6), and mTor inhibitor (2). Most common toxicities were rigors, arthralgia/myalgia, nausea/emesis, fever, and hypotension. All episodes of hypotension were reversible with intravenous fluid. No patients required hospitalization due to toxicity. One complete response (7%) and four partial responses (26%) were seen (total response rate=33%; 95% confidence interval: 15%-59%). Responses occurred in the lungs, liver, lymph nodes, and bone. Outpatient intravenous IL-2 with famotidine has activity in metastatic clear cell kidney cancer.

Resveratrol prevents endothelial cells injury in high-dose interleukin-2 therapy against melanoma.

Immunotherapy with high-dose interleukin-2 (HDIL-2) is an effective treatment for patients with metastatic melanoma and renal cell carcinoma. However, it is accompanied by severe toxicity involving endothelial cell injury and induction of vascular leak syndrome (VLS). In this study, we found that resveratrol, a plant polyphenol with anti-inflammatory and anti-cancer properties, was able to prevent the endothelial cell injury and inhibit the development of VLS while improving the efficacy of HDIL-2 therapy in the killing of metastasized melanoma. Specifically, C57BL/6 mice were injected with B16F10 cells followed by resveratrol by gavage the next day and continued treatment with resveratrol once a day. On day 9, mice received HDIL-2. On day 12, mice were evaluated for VLS and tumor metastasis. We found that resveratrol significantly inhibited the development of VLS in lung and liver by protecting endothelial cell integrity and preventing endothelial cells from undergoing apoptosis. The metastasis and growth of the tumor in lung were significantly inhibited by HDIL-2 and HDIL-2 + resveratrol treatment. Notably, HDIL-2 + resveratrol co-treatment was more effective in inhibiting tumor metastasis and growth than HDIL-2 treatment alone. We also analyzed the immune status of Gr-1(+)CD11b(+) myeloid-derived suppressor cells (MDSC) and FoxP3(+)CD4(+) regulatory T cells (Treg). We found that resveratrol induced expansion and suppressive function of MDSC which inhibited the development of VLS after adoptive transfer. However, resveratrol suppressed the HDIL-2-induced expansion of Treg cells. We also found that resveratrol enhanced the susceptibility of melanoma to the cytotoxicity of IL-2-activated killer cells, and induced the expression of the tumor suppressor gene FoxO1. Our results suggested the potential use of resveratrol in HDIL-2 treatment against melanoma. We also demonstrated, for the first time, that MDSC is the dominant suppressor cell than regulatory T cell in the development of VLS.

Role of CD44 in lymphokine-activated killer cell-mediated killing of melanoma.

In the current study, we examined the potential significance of CD44 expression on lymphokine-activated killer (LAK) cells in their interaction and killing of melanoma cells. Stimulation of splenocytes with IL-2 led to a significant increase in the expression of CD44 on T cells, NK cells, and NKT cells. Treatment of melanoma-bearing CD44 WT mice with IL-2 led to a significant reduction in the local tumor growth while treatment of melanoma-bearing CD44 KO mice with IL-2 was ineffective at controlling tumor growth. Furthermore, the ability of splenocytes from IL-2-treated CD44 KO mice to kill melanoma tumor targets was significantly reduced when compared to the anti-tumor activity of splenocytes from IL-2-treated CD44 WT mice. The importance of CD44 expression on the LAK cells was further confirmed by the observation that adoptively transferred CD44 WT LAK cells were significantly more effective than CD44 KO LAK cells at controlling tumor growth in vivo. Next, the significance of the increased expression of CD44 in tumor killing was examined and showed that following stimulation with IL-2, distinct populations of cells with low (CD44(lo)) or elevated (CD44(hi)) expression of CD44 are generated and that the CD44(hi) cells are responsible for killing of the melanoma cells. The reduced killing activity of the CD44 KO LAK cells did not result from reduced activation or expression of effector molecules but was due, at least in part, to a reduced ability to adhere to B16F10 tumor cells.

Construction and humanization of a functional bispecific EGFR × CD16 diabody using a refolding system.

We previously reported the construction and activity of a humanized, bispecific diabody (hEx3) that recruited T cells towards an epidermal growth factor receptor (EGFR) positive tumor. Herein, we describe the construction of a second functional, fully humanized, anti-EGFR bispecific diabody that recruits another subset of lymphocyte effectors, the natural killer cells, to EGFR-expressing tumor cells. After we confirmed that an anti-EGFR × anti-CD16 bispecific diabody (Ex16) consisting of a previously humanized anti-EGFR variable fragment (Fv) and a mouse anti-CD16 Fv had growth inhibitory activity, we designed a humanized anti-CD16 Fv to construct the fully humanized Ex16 (hEx16). However, the humanized form had lower activity for inhibition of cancer growth. To restore its growth inhibitory activity, we introduced mutations into the Vernier zone, which is located near the complementarity-determining regions and is involved in their binding activity. We efficiently prepared 15 different hEx16 mutants by expressing each chimeric single-chain component for hEx16 separately. We then used our in vitro refolding system to select the most functional mutant, which had a growth inhibitory effect comparable with that of the commercially available chimeric anti-EGFR antibody, cetuximab. Our refolding system could aid in the efficient optimization of other proteins with heterodimeric structure.

Effect of ziram on natural killer, lymphokine-activated killer, and cytotoxic T lymphocyte activity.

Ziram is a carbamate pesticide, which is widely used throughout the world as a fungicide in agriculture and as an accelerating agent in latex production. In the present study, we investigated the effect of ziram at 0.031-4 µM in vitro on human natural killer (NK) and lymphokine-activated killer (LAK) and murine cytotoxic T lymphocyte (CTL) activity and found that it significantly inhibited all three activities in a concentration-dependent manner. To explore the mechanism of ziram-induced inhibition of NK activity, NK-92MI cells, a human NK cell line, were used. We previously confirmed that NK-92MI cells express CD56, perforin, granzyme (Gr) A, GrB, Gr3/K, and granulysin and are highly cytotoxic to K562 cells in the chromium release assay. NK-92MI cells were treated with ziram at 0.125-4 µM for 4 or 16 h at 37°C in vitro. Then, intracellular levels of perforin, GrA, GrB, Gr3/K, and granulysin were determined by flow cytometry. It was found that ziram significantly reduced Gr3/K, granulysin, perforin, GrA, and GrB levels. The extent of the decrease differed among the proteins, and the order was as follows: Gr3/K > granulysin > perforin, GrA, and GrB. Taken together, these findings suggest the ziram-induced inhibition of NK, LAK, and CTL activities to be at least partially mediated by decreases in the intracellular levels of Gr3/K, granulysin, perforin, GrA, and GrB.

Induction of metastatic cancer stem cells from the NK/LAK-resistant floating, but not adherent, subset of the UP-LN1 carcinoma cell line by IFN-γ.

As an advanced status of cancer stem cells (CSCs), metastatic CSCs (mCSCs) have been proposed to be the essential seeds that initiate tumor metastasis. However, the biology of mCSCs is poorly understood. In this study, we used a lymph node (LN) metastatic CEA-producing carcinoma cell line, UP-LN1, characterized by the persistent appearance of adherent (A) and floating (F) cells in culture, to determine the distribution of CSCs and mechanisms for the induction of mCSCs. F and A cells displayed distinct phenotypes, CD44(high)/CD24(low) and CD44(low)/CD24(high), respectively. The CSC-rich nature of F cells was typified by stronger expression of multiple drug resistance genes and a 7.8-fold higher frequency of tumor-initiating cells in NOD/SCID mice when compared with A cells. F cells showed a greater depression in HLA class I expression and an extreme resistance to NK/LAK-mediated cytolysis. Moreover, the NK/LAK-resistant F cells were highly susceptible to IFN-γ-mediated induction of surface CXCR4, with concomitant downregulation of cytoplasmic CXCL12 expression, whereas these two parameters remained essentially unchanged in NK/LAK-sensitive A cells. Following the induction of surface CXCR4, enhanced migratory/invasive potential of F cells was demonstrated by in vitro assays. Confocal immunofluorescence microscopy showed the two distinct phenotypes of F and A cells could be correspondingly identified in monodispersed and compact tumor cell areas within the patient's LN tumor lesion. In response to IFN-γ or activated NK/LAK cells, the CXCR4(+) mCSCs could be only induced from the CSCs, which were harbored in the highly tumorigenic CD44(high)/CD24(low) F subset. Our results revealed the complexity and heterogeneity of the CSC of this cell line/tumor and the differential immunomodulatory roles of F and A cells. A better understanding of the interactions among different classes of CSCs and their niches may assist us in eradicating the CSCs/mCSCs through targeted immunotherapy, chemotherapy, or both.

Pulse interleukin-2 with famotidine induces CD56+ lymphocytes in the peripheral blood of patients with metastatic melanoma or kidney cancer.

Increased lymphokine-activated killer (LAK) cell numbers and cytotoxicity against tumor cell lines have been seen in patients receiving high-dose continuous and bolus infusion interleukin-2 (IL-2) regimens. LAK are CD56 positive on flow cytometry. Daily intravenous doses of IL-2 of 18-21.6 MIU/m(2) over 15-30 minutes ("pulses") have been developed to attempt to lessen the toxicity of this therapy. It has been previously shown that the patients with metastatic melanoma or kidney cancer may be treated safely with pulse IL-2 daily for 5 days preceded by intravenous famotidine. Cycles were repeated every 21 days. Because LAK numbers have not been previously described with this regimen, the present study has examined CD56 numbers via peripheral blood flow cytometry in 11 patients with samples scheduled at baseline, after two cycles, and after four cycles. Eight (8) patients had melanoma and 3 had kidney cancer. Median CD56 counts after two cycles was significantly higher than baseline (p = 0.001). Similarly, CD56 counts at 2 months later were also greater than baseline (p = 0.009). There was no difference between median values after two cycles versus after four cycles. Patients who were clinical responders had a median CD56 count of 650 after two cycles when compared with nonresponders who had a median CD56 count of 290 (p = 0.005). CD56 counts are significantly elevated in patients treated with pulse IL-2 with famotidine and clinical responders have significantly higher CD56 than nonresponders.

Mycophenolic acid inhibits natural killer cell proliferation and cytotoxic function: a possible disadvantage of including mycophenolate mofetil in the graft-versus-host disease prophylaxis regimen.

To determine how immunosuppressant agents used for graft-versus-host disease (GVHD) prophylaxis affect natural killer (NK) cells, we examined the effects of cyclosporine (CSP), tacrolimus (TAC), mycophenolic acid (MPA, an active form of mycophenolate mofetil), and methotrexate (MTX) on the proliferation and cytotoxicity of NK cells. The proliferation of NK cells from healthy individuals in the presence of interleukin (IL)-2 and IL-15 was suppressed to 51% ± 16% of that of the controls with CSP, to 31% ± 19% with TAC, to 14% ± 6% with MPA, and to 87% ± 18% with MTX. Both CSP and TAC increased the proportion of CD16(-)CD56(bright) cells, a NK cell subset capable of secreting high amount of cytokines, and also enhanced NKp30 expression, whereas MPA markedly decreased the proportion of CD16(-)CD56(bright) cells and reduced the expression of all activating NK cell receptors, including NKG2D, NKp30, NKp44, and NKp46. MPA also reduced the cytotoxicity against K562 cells from 61% ± 15% to 17% ± 7% and that against Daudi cells from 44% ± 4% to 4% ± 4%, whereas the other 3 drugs did not diminish these cytotoxicities. The inhibition of NK cell proliferation and cytotoxicity against leukemic cell lines by MPA was partially abolished by the inclusion of guanosine in the culture. Similar to the effect of MPA on T cells, MPA inhibited the down-regulation of p27 on NK cells induced by the incubation of NK cells in the presence of IL-2. These results suggest that MPA is a potent inhibitor of NK cells, and that its inclusion in the GVHD prophylaxis regimen might diminish the graft-versus-leukemia effect of NK cells.

Zoledronate-activated Vγ9γδ T cell-based immunotherapy is feasible and restores the impairment of γδ T cells in patients with solid tumors.

Gamma/delta (γδ) T cells play a role in innate immunity and exhibit cytotoxicity toward a large range of tumor types. Recent studies have shown that aminobisphosphonates may be applied to a culture in which a large number of γδ T cells are proliferated ex vivo. We carried out a clinical study of 25 patients with various solid tumors to determine further the safety, immunologic effect and feasibility of zoledronate-activated Vγ9γδ T cell-based immunotherapy. No severe toxicity was observed. In the cells used for the first treatment, the total cell number, frequency and number of CD3(+) Vγ9(+) γδ T cells were 409 ± 284 × 10(7) cells, 56 ± 33% and 255 ± 242 × 10(7) cells, respectively. Aminobisphosphonate therapy or chemotherapy resulted in the suppression of CD3(+) Vγ9(+) γδ T-cell proliferation. The numbers of CD3(+) T cells, CD3(+) Vγ9(+) γδ T cells and CD27(-) CD45RA(-) Vγ9(+) subsets in peripheral blood were significantly lower in patients than in healthy subjects (P < 0.05). From such an impaired immunologic condition, the numbers and frequencies of CD3(+) Vγ9(+) γδ T cells and CD27(-) CD45RA(-) subsets significantly increased in patients treated with this immunotherapy. Zoledronate-activated Vγ9γδ T cell-based immunotherapy that restores the number of Vγ9γδ T cells in cancer patients may provide another mode of adoptive immunotherapy.

The proteasome inhibitor bortezomib disrupts tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression and natural killer (NK) cell killing of TRAIL receptor-positive multiple myeloma cells.

Bortezomib, a potent 26S proteasome inhibitor, is approved for the treatment of multiple myeloma (MM) and clinical trials are under way to evaluate its efficacy in other malignant diseases. However, cytotoxic effects of bortezomib on immune-competent cells have also been observed. In this study, we show that bortezomib downregulates cell surface expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on primary human interleukin (IL)-2-activated natural killer (NK) cells. Pharmacological inhibition of the transcription factor, NF-kappaB also profoundly decreased TRAIL expression, suggesting that NF-kappaB is involved in the regulation of TRAIL expression in activated human NK cells. Furthermore, perforin-independent killing of the human MM cell lines RPMI8226 and U266 by NK cells was markedly suppressed following bortezomib treatment. In addition, blocking cell surface-bound TRAIL with a TRAIL antibody impaired NK cell-mediated lysis of the TRAIL-sensitive MM cell line, RPMI8226. In conclusion, the proteasome is likely to be involved in the regulation of TRAIL expression in primary human IL-2-activated NK cells. Proteasome inhibition by bortezomib disrupts TRAIL expression and TRAIL dependent and/or independent pathway-mediated killing of myeloma cells, suggesting that bortezomib may potentially hamper NK-dependent immunosurveillance against tumors in patients treated with this drug.

Highly enhanced cytotoxicity of a dimeric bispecific diabody, the hEx3 tetrabody.

We previously reported the utility for cancer immunotherapy of a humanized bispecific diabody (hEx3) that targets epidermal growth factor receptor and CD3. Here, we used dynamic and static light scattering measurements to show that the multimer fraction observed in hEx3 in solution is a monodisperse tetramer. The multimerization into tetramers increased the inhibition of cancer cell growth by the hEx3 diabody. Furthermore, 1:2 stoichiometric binding for both antigens was observed in a thermodynamic analysis, indicating that the tetramer has bivalent binding activity for each target, and the structure may be in a circular configuration, as is the case for the single-chain Fv tetrabody. In addition to enhanced cytotoxicity, the functional affinity and stability of the hEx3 tetrabody were superior to those of the hEx3 diabody. The increase in molecular weight is also expected to improve the pharmacokinetics of the bispecific diabody, making the hEx3 tetrabody attractive as a therapeutic antibody fragment for cancer immunotherapy.