Divergent Oxidative Stress in Normal Tissues and Inflammatory Cells in Hodgkin and Non-Hodgkin Lymphoma

BACKGROUND

Previous studies reported mitochondrial and endoplasmic reticulum redox stress in peripheral blood mononucleated cells (PBMCs) of treatment-naïve Hodgkin lymphoma (HL) patients. Here, we assessed whether this response also applies to non-HL (NHL) patients, and whether the oxidative damage is a selective feature of PBMCs or, rather, also affects tissues not directly involved in the inflammatory response.

METHODS

Isolated PBMCs of 28 HL, 9 diffuse large B cell lymphoma, 8 less aggressive-NHL, and 45 controls underwent flow cytometry to evaluate redox stress and uptake of the glucose analogue 2-NBDG. This analysis was complemented with the assay of malondialdehyde (MDA) levels and enzymatic activity of glucose-6P-dehydrogenase and hexose-6P-dehydrogenase (H6PD). In all lymphoma patients, ¹⁸F-fluoro-deoxyglucose uptake was estimated in the myocardium and skeletal muscles.

RESULTS

Mitochondrial reactive oxygen species generation and MDA levels were increased only in HL patients as well as H6PD activity and 2-NBDG uptake. Similarly, myocardial FDG retention was higher in HL than in other groups as opposed to a similar tracer uptake in the skeletal muscle.

CONCLUSIONS

Redox stress of PBMCs is more pronounced in HL with respect to both NHL groups. This phenomenon is coherent with an increased activity of H6PD that also extends to the myocardium.

Gene's expression underpinning the divergent predictive value of [18F]F-fluorodeoxyglucose and prostate-specific membrane antigen positron emission tomography in primary prostate cancer: a bioinformatic and experimental study

BACKGROUND

Positron Emission Tomography (PET) imaging with Prostate-Specific Membrane Antigen (PSMA) and Fluorodeoxyglucose (FDG) represent promising biomarkers for risk-stratification of Prostate Cancer (PCa). We verified whether the expression of genes encoding for PSMA and enzymes regulating FDG cellular uptake are independent and additive prognosticators in PCa.

METHODS

mRNA expression of genes involved in glucose metabolism and PSMA regulation obtained from primary PCa specimens were retrieved from open-source databases and analyzed using an integrative bioinformatics approach. Machine Learning (ML) techniques were used to create predictive Progression-Free Survival (PFS) models. Cellular models of primary PCa with different aggressiveness were used to compare [18F]F-PSMA-1007 and [18F]F-FDG uptake kinetics in vitro. Confocal microscopy, immunofluorescence staining, and quantification analyses were performed to assess the intracellular and cellular membrane PSMA expression.

RESULTS

ML analyses identified a predictive functional network involving four glucose metabolism-related genes: ALDOB, CTH, PARP2, and SLC2A4. By contrast, FOLH1 expression (encoding for PSMA) did not provide any additive predictive value to the model. At a cellular level, the increase in proliferation rate and migratory potential by primary PCa cells was associated with enhanced FDG uptake and decreased PSMA retention (paralleled by the preferential intracellular localization).

CONCLUSIONS

The overexpression of a functional network involving four glucose metabolism-related genes identifies a higher risk of disease progression since the earliest phases of PCa, in agreement with the acknowledged prognostic value of FDG PET imaging. By contrast, the prognostic value of PSMA PET imaging is independent of the expression of its encoding gene FOLH1. Instead, it is influenced by the protein docking to the cell membrane, regulating its accessibility to tracer binding.

The Role of Endoplasmic Reticulum in the Differential Endurance against Redox Stress in Cortical and Spinal Astrocytes from the Newborn SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

Recent studies reported that the uptake of [18F]-fluorodeoxyglucose (FDG) is increased in the spinal cord (SC) and decreased in the motor cortex (MC) of patients with ALS, suggesting that the disease might differently affect the two nervous districts with different time sequence or with different mechanisms. Here we show that MC and SC astrocytes harvested from newborn B6SJL-Tg (SOD1^G93A) 1Gur mice could play different roles in the pathogenesis of the disease. Spectrophotometric and cytofluorimetric analyses showed an increase in redox stress, a decrease in antioxidant capacity and a relative mitochondria respiratory uncoupling in MC SOD1^G93A astrocytes. By contrast, SC mutated cells showed a higher endurance against oxidative damage, through the increase in antioxidant defense, and a preserved respiratory function. FDG uptake reproduced the metabolic response observed in ALS patients: SOD1^G93A mutation caused a selective enhancement in tracer retention only in mutated SC astrocytes, matching the activity of the reticular pentose phosphate pathway and, thus, of hexose-6P dehydrogenase. Finally, both MC and SC mutated astrocytes were characterized by an impressive ultrastructural enlargement of the endoplasmic reticulum (ER) and impairment in ER–mitochondria networking, more evident in mutated MC than in SC cells. Thus, SOD1^G93A mutation differently impaired MC and SC astrocyte biology in a very early stage of life.

Metformin and Cancer Glucose Metabolism: At the Bench or at the Bedside?

Several studies reported that metformin, the most widely used drug for type 2 diabetes, might affect cancer aggressiveness. The biguanide seems to directly impair cancer energy asset, with the consequent phosphorylation of AMP-activated protein kinase (AMPK) inhibiting cell proliferation and tumor growth. This action is most often attributed to a well-documented blockage of oxidative phosphorylation (OXPHOS) caused by a direct interference of metformin on Complex I function. Nevertheless, several other pleiotropic actions seem to contribute to the anticancer potential of this biguanide. In particular, in vitro and in vivo experimental studies recently documented that metformin selectively inhibits the uptake of 2-[18F]-Fluoro-2-Deoxy-D-Glucose (FDG), via an impaired catalytic function of the enzyme hexose-6P-dehydrogenase (H6PD). H6PD triggers a still largely uncharacterized pentose-phosphate pathway (PPP) within the endoplasmic reticulum (ER) that has been found to play a pivotal role in feeding the NADPH reductive power for both cellular proliferation and antioxidant responses. Regardless of its exploitability in the clinical setting, this metformin action might configure the ER metabolism as a potential target for innovative therapeutic strategies in patients with solid cancers and potentially modifies the current interpretative model of FDG uptake, attributing PET/CT capability to predict cancer aggressiveness to the activation of H6PD catalytic function.

Increased myocardial 18F-FDG uptake as a marker of Doxorubicin-induced oxidative stress

BACKGROUND

Oxidative stress and its interference on myocardial metabolism play a major role in Doxorubicin (DXR) cardiotoxic cascade.

METHODS

Mice models of neuroblastoma (NB) were treated with 5 mg DXR/kg, either free (Free-DXR) or encapsulated in untargeted (SL[DXR]) or in NB-targeting Stealth Liposomes (pep-SL[DXR] and TP-pep-SL[DXR]). Control mice received saline. FDG-PET was performed at baseline (PET1) and 7 days after therapy (PET2). At PET2 Troponin-I and NT-proBNP were assessed. Explanted hearts underwent biochemical, histological, and immunohistochemical analyses. Finally, FDG uptake and glucose consumption were simultaneously measured in cultured H9c2 in the presence/absence of Free-DXR (1 μM).

RESULTS

Free-DXR significantly enhanced the myocardial oxidative stress. Myocardial-SUV remained relatively stable in controls and mice treated with liposomal formulations, while it significantly increased at PET2 with respect to baseline in Free-DXR. At this timepoint, myocardial-SUV was directly correlated with both myocardial redox stress and hexose-6-phosphate-dehydrogenase (H6PD) enzymatic activity, which selectively sustain cellular anti-oxidant mechanisms. Intriguingly, in vitro, Free-DXR selectively increased FDG extraction fraction without altering the corresponding value for glucose.

CONCLUSION

The direct correlation between cardiac FDG uptake and oxidative stress indexes supports the potential role of FDG-PET as an early biomarker of DXR oxidative damage.

18F-Fluorodeoxyglucose Positron Emission Tomography Tracks the Heterogeneous Brain Susceptibility to the Hyperglycemia-Related Redox Stress

In cognitively normal patients, mild hyperglycemia selectively decreases 18F-Fluorodeoxyglucose (FDG) uptake in the posterior brain, reproducing Alzheimer disease pattern, hampering the diagnostic accuracy of this widely used tool. This phenomenon might involve either a heterogeneous response of glucose metabolism or a different sensitivity to hyperglycemia-related redox stress. Indeed, previous studies reported a close link between FDG uptake and activation of a specific pentose phosphate pathway (PPP), triggered by hexose-6P-dehydrogenase (H6PD) and contributing to fuel NADPH-dependent antioxidant responses in the endoplasmic reticulum (ER). To clarify this issue, dynamic positron emission tomography was performed in 40 BALB/c mice four weeks after administration of saline (n = 17) or 150 mg/kg streptozotocin (n = 23, STZ). Imaging data were compared with biochemical and histological indexes of glucose metabolism and redox balance. Cortical FDG uptake was homogeneous in controls, while it was selectively decreased in the posterior brain of STZ mice. This difference was independent of the activity of enzymes regulating glycolysis and cytosolic PPP, while it was paralleled by a decreased H6PD catalytic function and enhanced indexes of oxidative damage. Thus, the relative decrease in FDG uptake of the posterior brain reflects a lower activation of ER-PPP in response to hyperglycemia-related redox stress in these areas.

Mechanisms underlying the predictive power of high skeletal muscle uptake of FDG in amyotrophic lateral sclerosis

Background

We recently reported that enhanced [18F]-fluorodeoxyglucose (FDG) uptake in skeletal muscles predicts disease aggressiveness in patients with amyotrophic lateral sclerosis (ALS). The present experimental study aimed to assess whether this predictive potential reflects the link between FDG uptake and redox stress that has been previously reported in different tissues and disease models.

Methods

The study included 15 SOD1^G93A mice (as experimental ALS model) and 15 wildtype mice (around 120 days old). Mice were submitted to micro-PET imaging. Enzymatic pathways and response to oxidative stress were evaluated in harvested quadriceps and hearts by biochemical, immunohistochemical, and immunofluorescence analysis. Colocalization between the endoplasmic reticulum (ER) and the fluorescent FDG analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) was performed in fresh skeletal muscle sections. Finally, mitochondrial ultrastructure and bioenergetics were evaluated in harvested quadriceps and hearts.

Results

FDG retention was significantly higher in hindlimb skeletal muscles of symptomatic SOD1^G93A mice with respect to control ones. This difference was not explained by any acceleration in glucose degradation through glycolysis or cytosolic pentose phosphate pathway (PPP). Similarly, it was independent of inflammatory infiltration. Rather, the high FDG retention in SOD1^G93A skeletal muscle was associated with an accelerated generation of reactive oxygen species. This redox stress selectively involved the ER and the local PPP triggered by hexose-6P-dehydrogenase. ER involvement was confirmed by the colocalization of the 2-NBDG with a vital ER tracker. The oxidative damage in transgenic skeletal muscle was associated with a severe impairment in the crosstalk between ER and mitochondria combined with alterations in mitochondrial ultrastructure and fusion/fission balance. The expected respiratory damage was confirmed by a deceleration in ATP synthesis and oxygen consumption rate. These same abnormalities were represented to a markedly lower degree in the myocardium, as a sample of non-voluntary striated muscle.

Conclusion

Skeletal muscle of SOD1^G93A mice reproduces the increased FDG uptake observed in ALS patients. This finding reflects the selective activation of the ER-PPP in response to significant redox stress associated with alterations of mitochondrial ultrastructure, networking, and connection with the ER itself. This scenario is less severe in cardiomyocytes suggesting a relevant role for either communication with synaptic plaque or contraction dynamics.

The Elusive Link Between Cancer FDG Uptake and Glycolytic Flux Explains the Preserved Diagnostic Accuracy of PET/CT in Diabetes

This study aims to verify in experimental models of hyperglycemia induced by streptozotocin (STZ-DM) to what degree the high competition between unlabeled glucose and metformin (MET) treatment might affect the accuracy of cancer FDG imaging. The study included 36 “control” and 36 “STZ-DM” Balb/c mice, undergoing intraperitoneal injection of saline or streptozotocin, respectively. Two-weeks later, mice were subcutaneously implanted with breast (4 T1) or colon (CT26) cancer cells and subdivided in three subgroups for treatment with water or with MET at 10 or 750 mg/Kg/day. Two weeks after, mice were submitted to micro-PET imaging. Enzymatic pathways and response to oxidative stress were evaluated in harvested tumors. Finally, competition by glucose, 2-deoxyglucose (2DG) and the fluorescent analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) on FDG uptake was studied in 4 T1 and CT26 cultured cells. STZ-DM slightly decreased cancer volume and FDG uptake rate (MRF). More importantly, it also abolished MET capability to decelerate lesion growth and MRF. This metabolic reprogramming closely agreed with the activity of hexose-6-phosphate dehydrogenase within the endoplasmic reticulum. Finally, co-incubation with 2DG virtually abolished FDG and 2-NBDG uptake within the endoplasmic reticulum in cultured cells. These data challenge the current dogma linking FDG uptake to glycolytic flux and introduce a new model to explain the relation between glucose analogue uptake and hexoses reticular metabolism. This selective fate of FDG contributes to the preserved sensitivity of PET imaging in oncology even in chronic moderate hyperglycemic conditions.

Insulin-independent stimulation of skeletal muscle glucose uptake by low-dose abscisic acid via AMPK activation

Abscisic acid (ABA) is a plant hormone active also in mammals where it regulates, at nanomolar concentrations, blood glucose homeostasis. Here we investigated the mechanism through which low-dose ABA controls glycemia and glucose fate. ABA stimulated uptake of the fluorescent glucose analog 2-NBDG by L6, and of [¹⁸F]-deoxy-glucose (FDG) by mouse skeletal muscle, in the absence of insulin, and both effects were abrogated by the specific AMPK inhibitor dorsomorphin. In L6, incubation with ABA increased phosphorylation of AMPK and upregulated PGC-1α expression. LANCL2 silencing reduced all these ABA-induced effects. In vivo, low-dose oral ABA stimulated glucose uptake and storage in the skeletal muscle of rats undergoing an oral glucose load, as detected by micro-PET. Chronic treatment with ABA significantly improved the AUC of glycemia and muscle glycogen content in CD1 mice exposed to a high-glucose diet. Finally, both acute and chronic ABA treatment of hypoinsulinemic TRPM2^-/- mice ameliorated the glycemia profile and increased muscle glycogen storage. Altogether, these results suggest that low-dose oral ABA might be beneficial for pre-diabetic and diabetic subjects by increasing insulin-independent skeletal muscle glucose disposal through an AMPK-mediated mechanism.

FDG uptake tracks the oxidative damage in diabetic skeletal muscle: An experimental study

OBJECTIVES

The present study aims to verify the relationship between glucose consumption and uptake of ¹⁸F-2-deoxy-glucose (FDG) in the skeletal muscle (SM) of experimental models of streptozotocin-induced diabetes mellitus (STZ-DM).

METHODS

The study included 36 Balb/c mice. Two weeks after intraperitoneal administration of saline (control group, n = 18) or 150 mg streptozotocin (STZ-DM group, n = 18), the two cohorts were submitted to an oral glucose tolerance test and were further subdivided into three groups (n = 6 each): untreated and treated with metformin (MTF) at low or high doses (10 or 750 mg/kg daily, respectively). Two weeks thereafter, all mice were submitted to dynamic micro-positron emission tomography (PET) imaging after prolonged fasting. After sacrifice, enzymatic pathways and response to oxidative stress were evaluated in harvested SM.

RESULTS

On PET imaging, the FDG uptake rate in hindlimb SM was significantly lower in nondiabetic mice as compared with STZ-DM-untreated mice. MTF had no significant effect on SM FDG uptake in untreated mice; however, its high dose induced a significant decrease in STZ-DM animals. Upon conventional analysis, the SM standard uptake value was higher in STZ-DM mice, while MTF was virtually ineffective in either control or STZ-DM models. This metabolic reprogramming was not explained by any change in cytosolic glucose metabolism. By contrast, it closely agreed with the catalytic function of hexose-6P-dehydrogenase (H6PD; i.e., the trigger of a specific pentose phosphate pathway selectively located within the endoplasmic reticulum). In agreement with this role, the H6PD enzymatic response to both STZ-DM and MTF matched the activation of the NADPH-dependent antioxidant responses to the increased generation of reactive oxygen species caused by chronic hyperglycemia. Ex vivo analysis of tracer kinetics confirmed that the enhanced SM avidity for FDG occurred despite a significant reduction in glucose consumption, while it was associated with increased radioactivity transfer to the endoplasmic reticulum.

CONCLUSIONS

These data challenge the current dogma linking FDG uptake to the glycolytic rate. They instead introduce a new model considering a strict link between the uptake of this glucose analog, H6PD reticular activity, and oxidative damage in diabetes, at least under fasting condition.

The role of CEA, CYFRA21-1 and NSE in monitoring tumor response to Nivolumab in advanced non-small cell lung cancer (NSCLC) patients

Background

CEA, CYFRA21-1 and NSE are tumor markers used for monitoring the response to chemotherapy in advanced adenocarcinoma, squamous cell carcinoma and small-cell lung cancer, respectively. Their role in cancer immunotherapy needs to be elucidated.

Methods

Patients with advanced non-small cell lung cancer (NSCLC) were treated with nivolumab 3 mg/kg every 2 weeks within the Italian Nivolumab Expanded Access Program. Blood samples were collected at baseline, at each cycle up to cycle 5 and then every two cycles until patient’s withdrawn from the study. All patients underwent a CT-scan after every 4 cycles of treatment and responses were classified according to RECIST 1.1. The biomarkers serum levels were measured with a chemiluminescent microparticle immunoassay for CEA and with an immuno radiometric assay for CYFRA21-1 and NSE. The markers values at baseline and after 4 cycles were used to analyze the relationship between their variation over baseline and the tumor response, evaluated as disease control rate (DCR: CR + PR + SD), and survival (PFS and OS).

Results

A total of 70 patients were evaluable for the analysis. Overall, a disease control was obtained in 24 patients (35.8%, 4 PR + 20 SD). After 4 cycles of nivolumab a CEA or CYFRA21-1 reduction ≥ 20% over the baseline was significantly associated with DCR (CEA, p = 0.021; CYFRA21-1, p < 0.001), PFS (CEA, p = 0.028; CYFRA21-1, p < 0.001) and OS (CEA, p = 0.026; CYFRA21-1, p = 0.019). Multivariate analysis confirmed the ability of CYFRA21-1 reduction ≥ 20% to predict DCR (p = 0.002) and PFS (p < 0.001).

Conclusion

The reduction in serum level of CYFRA21-1 or CEA might be a reliable biomarker to predict immunotherapy efficacy in NSCLC patients. NSE was not significant for monitoring the efficacy of nivolumab.

Obligatory role of endoplasmic reticulum in brain FDG uptake

PURPOSE

The endoplasmic reticulum (ER) contains hexose-6P-dehydrogenase (H6PD). This enzyme competes with glucose-6P-phosphatase for processing a variety of phosphorylated hexoses including 2DG-6P. The present study aimed to verify whether this ER glucose-processing machinery contributes to brain FDG uptake.

METHODS

Effect of the H6PD inhibitor metformin on brain 18F-FDG accumulation was studied, in vivo, by microPET imaging. These data were complemented with the in vitro estimation of the lumped constant (LC). Finally, reticular accumulation of the fluorescent 2DG analogue 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2NBDG) and its response to metformin was studied by confocal microscopy in cultured neurons and astrocytes.

RESULTS

Metformin halved brain 18F-FDG accumulation without altering whole body tracer clearance. Ex vivo, this same response faced the doubling of both glucose consumption and lactate release. The consequent fall in LC was not explained by any change in expression or activity of its theoretical determinants (GLUTs, hexokinases, glucose-6P-phosphatase), while it agreed with the drug-induced inhibition of H6PD function. In vitro, 2NBDG accumulation selectively involved the ER lumen and correlated with H6PD activity being higher in neurons than in astrocytes, despite a lower glucose consumption.

CONCLUSIONS

The activity of the reticular enzyme H6PD profoundly contributes to brain 18F-FDG uptake. These data challenge the current dogma linking 2DG/FDG uptake to the glycolytic rate and introduce a new model to explain the link between 18-FDG uptake and neuronal activity.

Functional Activation of Osteoclast Commitment in Chronic Lymphocytic Leukaemia: a Possible Role for RANK/RANKL Pathway

Skeletal erosion has been found to represent an independent prognostic indicator in patients with advanced stages of chronic lymphocytic leukaemia (CLL). Whether this phenomenon also occurs in early CLL phases and its underlying mechanisms have yet to be fully elucidated. In this study, we prospectively enrolled 36 consecutive treatment-naïve patients to analyse skeletal structure and bone marrow distribution using a computational approach to PET/CT images. This evaluation was combined with the analysis of RANK/RANKL loop activation in the leukemic clone, given recent reports on its role in CLL progression. Bone erosion was particularly evident in long bone shafts, progressively increased from Binet stage A to Binet stage C, and was correlated with both local expansion of metabolically active bone marrow documented by FDG uptake and with the number of RANKL + cells present in the circulating blood. In immune-deficient NOD/Shi-scid, γcnull (NSG) mice, administration of CLL cells caused an appreciable compact bone erosion that was prevented by Denosumab. CLL cell proliferation in vitro correlated with RANK expression and was impaired by Denosumab-mediated disruption of the RANK/RANKL loop. This study suggests an interaction between CLL cells and stromal elements able to simultaneously impair bone structure and increase proliferating potential of leukemic clone.

Metformin inhibits cell cycle progression of B-cell chronic lymphocytic leukemia cells

B-cell chronic lymphocytic leukemia (CLL) was believed to result from clonal accumulation of resting apoptosis-resistant malignant B lymphocytes. However, it became increasingly clear that CLL cells undergo, during their life, iterative cycles of re-activation and subsequent clonal expansion. Drugs interfering with CLL cell cycle entry would be greatly beneficial in the treatment of this disease.

1, 1-Dimethylbiguanide hydrochloride (metformin), the most widely prescribed oral hypoglycemic agent, inexpensive and well tolerated, has recently received increased attention for its potential antitumor activity. We wondered whether metformin has apoptotic and anti-proliferative activity on leukemic cells derived from CLL patients.

Metformin was administered in vitro either to quiescent cells or during CLL cell activation stimuli, provided by classical co-culturing with CD40L-expressing fibroblasts.

At doses that were totally ineffective on normal lymphocytes, metformin induced apoptosis of quiescent CLL cells and inhibition of cell cycle entry when CLL were stimulated by CD40-CD40L ligation. This cytostatic effect was accompanied by decreased expression of survival- and proliferation-associated proteins, inhibition of signaling pathways involved in CLL disease progression and decreased intracellular glucose available for glycolysis.

In drug combination experiments, metformin lowered the apoptotic threshold and potentiated the cytotoxic effects of classical and novel antitumor molecules.

Our results indicate that, while CLL cells after stimulation are in the process of building their full survival and cycling armamentarium, the presence of metformin affects this process.

Discovery of a novel glucose metabolism in cancer: The role of endoplasmic reticulum beyond glycolysis and pentose phosphate shunt

Cancer metabolism is characterized by an accelerated glycolytic rate facing reduced activity of oxidative phosphorylation. This “Warburg effect” represents a standard to diagnose and monitor tumor aggressiveness with ¹⁸F-fluorodeoxyglucose whose uptake is currently regarded as an accurate index of total glucose consumption. Studying cancer metabolic response to respiratory chain inhibition by metformin, we repeatedly observed a reduction of tracer uptake facing a marked increase in glucose consumption. This puzzling discordance brought us to discover that ¹⁸F-fluorodeoxyglucose preferentially accumulates within endoplasmic reticulum by exploiting the catalytic function of hexose-6-phosphate-dehydrogenase. Silencing enzyme expression and activity decreased both tracer uptake and glucose consumption, caused severe energy depletion and decreased NADPH content without altering mitochondrial function. These data document the existence of an unknown glucose metabolism triggered by hexose-6-phosphate-dehydrogenase within endoplasmic reticulum of cancer cells. Besides its basic relevance, this finding can improve clinical cancer diagnosis and might represent potential target for therapy.

Interleukin 21 Controls mRNA and MicroRNA Expression in CD40-Activated Chronic Lymphocytic Leukemia Cells

Several factors support CLL cell survival in the microenvironment. Under different experimental conditions, IL21 can either induce apoptosis or promote CLL cell survival. To investigate mechanisms involved in the effects of IL21, we studied the ability of IL21 to modulate gene and miRNA expressions in CD40-activated CLL cells. IL21 was a major regulator of chemokine production in CLL cells and it modulated the expression of genes involved in cell movement, metabolism, survival and apoptosis. In particular, IL21 down-regulated the expression of the chemokine genes CCL4, CCL3, CCL3L1, CCL17, and CCL2, while it up-regulated the Th1-related CXCL9 and CXCL10. In addition, IL21 down-regulated the expression of genes encoding signaling molecules, such as CD40, DDR1 and PIK3CD. IL21 modulated a similar set of genes in CLL and normal B-cells (e.g. chemokine genes), whereas other genes, including MYC, TNF, E2F1, EGR2 and GAS-6, were regulated only in CLL cells. An integrated analysis of the miRNome and gene expression indicated that several miRNAs were under IL21 control and these could, in turn, influence the expression of potential target genes. We focused on hsa-miR-663b predicted to down-regulate several relevant genes. Transfection of hsa-miR-663b or its specific antagonist showed that this miRNA regulated CCL17, DDR1, PIK3CD and CD40 gene expression. Our data indicated that IL21 modulates the expression of genes mediating the crosstalk between CLL cells and their microenvironment and miRNAs may take part in this process.

CD133-Positive Cells from Non-Small Cell Lung Cancer Show Distinct Sensitivity to Cisplatin and Afatinib

The standard of care for advanced non-small cell lung cancer (NSCLC) consists in cisplatin-combination chemotherapy. In patients bearing tumors with activating mutations of the epidermal growth factor receptor (EGFR), the inhibition of the EGFR intracellular tyrosine kinase can induce up to 80 % response rates. However, both therapeutic strategies will eventually lead to recurrent disease due to the development of drug resistance. The identification of rare cancer stem-like cells able to repopulate the tumor, after failure to standard treatment modalities, has led to characterize these cells as potential therapeutic targets. This article will address the role of the CD133/EpCAM stem cell-related markers and explore cell sensitivity to cisplatin and to the EGFR-tyrosine kinase inhibitor, afatinib. Three human NSCLC cell lines, one wild-type (A549) and two harboring EGFR mutations (H1650 and H1975), as well as 20 NSCLC primary cultures, were grown in non-differentiating culture conditions for stem cell enrichment. Flow-cytometry analyses of CD133 and EpCAM and cell sensitivity to cisplatin and afatinib were performed. Moreover, the expression of activated EGFR was assessed by Western blot. The cell lines and primary cultures grown in non-differentiating culture conditions were enriched with CD133/EpCAM-positive cells and were significantly more resistant to cisplatin and more sensitive to afatinib as compared to the differentiated counterpart. In addition, increased EGFR-phosphorylation in non-differentiated cultures was observed. The present findings suggest that afatinib might be beneficial for patients bearing tumors with constitutively activated EGFR, to target chemo-resistant CD133/EpCAM-positive cancer stem cells.

Direct inhibition of hexokinase activity by metformin at least partially impairs glucose metabolism and tumor growth in experimental breast cancer

Emerging evidence suggests that metformin, a widely used anti-diabetic drug, may be useful in the prevention and treatment of different cancers. In the present study, we demonstrate that metformin directly inhibits the enzymatic function of hexokinase (HK) I and II in a cell line of triple-negative breast cancer (MDA-MB-231). The inhibition is selective for these isoforms, as documented by experiments with purified HK I and II as well as with cell lysates. Measurements of ¹⁸F-fluoro-deoxyglycose uptake document that it is dose- and time-dependent and powerful enough to virtually abolish glucose consumption despite unchanged availability of membrane glucose transporters. The profound energetic imbalance activates phosphorylation and is subsequently followed by cell death. More importantly, the “in vivo” relevance of this effect is confirmed by studies of orthotopic xenografts of MDA-MB-231 cells in athymic (nu/nu) mice. Administration of high drug doses after tumor development caused an evident tumor necrosis in a time as short as 48 h. On the other hand, 1 mo metformin treatment markedly reduced cancer glucose consumption and growth. Taken together, our results strongly suggest that HK inhibition contributes to metformin therapeutic and preventive potential in breast cancer.

Recombinant IL-21 and anti-CD4 antibodies cooperate in syngeneic neuroblastoma immunotherapy and mediate long-lasting immunity

IL-21 is an immune-enhancing cytokine, which showed promising results in cancer immunotherapy. We previously observed that the administration of anti-CD4 cell-depleting antibody strongly enhanced the anti-tumor effects of an IL-21-engineered neuroblastoma (NB) cell vaccine. Here, we studied the therapeutic effects of a combination of recombinant (r) IL-21 and anti-CD4 monoclonal antibodies (mAb) in a syngeneic model of disseminated NB. Subcutaneous rIL-21 therapy at 0.5 or 1 μg/dose (at days 2, 6, 9, 13 and 15 after NB induction) had a limited effect on NB development. However, coadministration of rIL-21 at the two dose levels and a cell-depleting anti-CD4 mAb cured 28 and 70 % of mice, respectively. Combined immunotherapy was also effective if started 7 days after NB implant, resulting in a 30 % cure rate. Anti-CD4 antibody treatment efficiently depleted CD4(+) CD25(high) Treg cells, but alone had limited impact on NB. Combination immunotherapy by anti-CD4 mAb and rIL-21 induced a CD8(+) cytotoxic T lymphocyte response, which resulted in tumor eradication and long-lasting immunity. CD4(+) T cells, which re-populated mice after combination immunotherapy, were required for immunity to NB antigens as indicated by CD4(+) T cell depletion and re-challenge experiments. In conclusion, these data support a role for regulatory CD4(+) T cells in a syngeneic NB model and suggest that rIL-21 combined with CD4(+) T cell depletion reprograms CD4(+) T cells from immune regulatory to anti-tumor functions. These observations open new perspectives for the use of IL-21-based immunotherapy in conjunction with transient CD4(+) T cell depletion, in human metastatic NB.

Metformin impairs glucose consumption and survival in Calu-1 cells by direct inhibition of hexokinase-II

The anti-hyperglycaemic drug metformin has important anticancer properties as shown by the direct inhibition of cancer cells proliferation. Tumor cells avidly use glucose as a source for energy production and cell building blocks. Critical to this phenotype is the production of glucose-6-phosphate (G6P), catalysed by hexokinases (HK) I and II, whose role in glucose retention and metabolism is highly advantageous for cell survival and proliferation. Here we show that metformin impairs the enzymatic function of HKI and II in Calu-1 cells. This inhibition virtually abolishes cell glucose uptake and phosphorylation as documented by the reduced entrapment of ¹⁸F-fluorodeoxyglucose. In-silico models indicate that this action is due to metformin capability to mimic G6P features by steadily binding its pocket in HKII. The impairment of this energy source results in mitochondrial depolarization and subsequent cell death. These results could represent a starting point to open effective strategies in cancer prevention and treatment.

The IL-18 antagonist IL-18-binding protein is produced in the human ovarian cancer microenvironment

PURPOSE

Interleukin (IL)-18 is an immune-enhancing cytokine, which induces IFN-γ production, T-helper 1 responses, and antitumor effects. In turn, IFN-γ stimulates IL-18-binding protein production, which blocks IL-18 activity. In view of the potential use of IL-18 in epithelial ovarian cancer (EOC) immunotherapy, here, we studied IL-18BP expression and its regulation by cytokines in EOC cells in vitro and in vivo.

EXPERIMENTAL DESIGN

Expression and production of IL-18BP in EOC cell lines, primary ovarian carcinomas, and the corresponding normal tissues, patients' serum, and ascites were investigated by immunochemistry, ELISA, screening of gene expression profiles, and reverse-transcription PCR.

RESULTS

Analysis of gene expression profiles revealed that IL18BP mRNA is increased in EOC tumors compared with normal ovary cells. Release of IL-18BP was detectable in EOC sera and to a greater extent in the ascites, indicating production at the tumor site. Indeed, immunochemical analyses on cells isolated from the ascites and on tumor sections indicated that IL-18BP is expressed in both tumor cells and tumor-associated leukocytes, which displayed a CD3-CD20-NKp46-CD13+CD14low phenotype. EOC cell lines do not constitutively express IL-18BP. However, its release is inducible both by IFN-γ stimulation in vitro and by xenotransplantation of EOC cells in immune-deficient mice, suggesting a role for the microenvironment. In vitro experiments and immunochemistry indicated that IL-27 is also involved in IL-18BP upregulation in EOC cell lines and primary cells through STAT1 activation. Together, these data indicate that IL-18BP, which is produced in EOC in response to microenvironmental factors, may inhibit endogenous or exogenous IL-18 activity.

Immunotherapeutic applications of IL-15

IL-15 is a member of the IL-2 family of cytokines, which play a fundamental role in innate and adaptive immune responses. IL-15 has pleiotropic immune-enhancing activities, as it stimulates NK, T and NKT cell proliferation, survival and effector functions. In view of these properties, IL-15 is regarded as a good candidate for cancer immunotherapy. This possibility is reinforced by its low toxicity and efficacy in preclinical tumor models. The use of IL-15 to boost the immune response in HIV infection has also been proposed, although further studies are required to establish potential risks and benefits. Clinical trials of IL-15 have been initiated in cancer patients and in HIV vaccination and will elucidate the potential of IL-15-based immunotherapy. The purpose of this review is to provide an update on the potential applications of IL-15 in cancer immunotherapy and HIV infection.

Activated leukocyte cell adhesion molecule soluble form: a potential biomarker of epithelial ovarian cancer is increased in type II tumors

Activated leukocyte cell adhesion molecule (ALCAM) is involved in cell-cell interactions in cancer. Shedding of its ectodomain by the metalloprotease ADAM17/TACE generates a soluble form (sALCAM). Here, we show that serum sALCAM levels were significantly higher in epithelial ovarian cancer (EOC) (p < 0.005) than in controls. The performance of sALCAM as classifier, tested by receiver operating characteristic curve, resulted in an area under the curve (AUC) of 0.8067. Serum sALCAM levels showed direct correlation with Carbohydrate Antigen-125 (CA125/MUC16). Moreover, significantly higher levels were found in type II tumors, even in stage I/II, suggesting that elevated sALCAM is an early feature of aggressive EOC. In addition, sALCAM levels were higher in ascites than in sera, suggesting local processing of ALCAM in the peritoneal cavity. In immunodeficient mice, intraperitoneally implanted with a human EOC cell line, human sALCAM progressively increased in serum and was even higher in the ascites. The biochemical characterization of the sALCAM in EOC sera and ascites, showed two predominant forms of approximately 95 and 65 kDa but no EOC-specific isoform. In addition, full-length transmembrane ALCAM but no soluble form was detected in tumor-derived exosomes found in ascites. Finally, in vitro invasion assays showed that inhibition of ADAM17/TACE activity decreased EOC invasive properties, while opposite effects were mediated by a sALCAM-Fc chimera and by an antibody interfering with ALCAM/ALCAM interactions. Altogether these data suggest that sALCAM is a marker of EOC, which correlates with more aggressive type II tumors, and that ADAM17/TACE activity and sALCAM itself mediate enhanced invasiveness.

Interleukin (IL)-18, a biomarker of human ovarian carcinoma, is predominantly released as biologically inactive precursor

Interleukin (IL)-18 is a proinflammatory and immune-enhancing cytokine, which exerts antitumor effects in vivo, mediated by the induction of interferon (IFN)γ. We previously reported that IL-18 processing is defective in epithelial ovarian carcinoma (EOC) cells, which secrete an inactive precursor (pro-IL-18) in vitro. In addition, IL-18 was reported as a potential biomarker of EOC. Here, we further investigated its role as a serological marker in human EOC and addressed its possible biological activity in vivo. Our data indicate that immunoreactive IL-18 is increased in EOC patients' sera at diagnosis as compared with age-matched healthy women. IL-18 levels were higher in the ascitic fluids than in sera, suggesting a local production in the peritoneal cavity. Indeed, immunohistochemical analysis of tumors showed IL-18 expression in cytokeratine-positive neoplastic cells, although also scattered histiocytes and some lymphoid cells stained for IL-18. The detection of human IL-18 in sera and ascitic fluids of immunodeficient mice, orthotopically implanted with human EOC cells, further suggested that circulating IL-18 is tumor-derived. However, IL-18 is not an EOC specific biomarker, as increased serum levels were found also in some endometrial cancer patients. By means of a new monoclonal antibody, we characterized IL-18 present in the ascitic fluid as pro-IL-18, which is biologically inactive. Accordingly, IFNγ was not increased in EOC patients' sera and ascitic fluids and showed no correlation with IL-18 levels. Altogether these data indicate that IL-18 in EOC fluids is predominantly tumor-derived and that its lack of biological activity may represent a mechanism of tumor-escape.

Transient depletion of CD4(+) T cells augments IL-21-based immunotherapy of disseminated neuroblastoma in syngeneic mice

IL-21 is a member of the IL-2 cytokine family, produced by CD4+ T cells. We previously showed that immunotherapy (IT) with IL-21-transduced neuroblastoma cells (Neuro2a/IL-21) cured 33% of syngeneic mice bearing systemic NB. Here, we studied whether the removal of Treg cells could potentiate the therapeutic efficacy of Neuro2a/IL-21 vaccine. The administration of anti-CD25 mAb, which targets Treg cells, slightly potentiated the effect of vaccine IT (50% cure rate), but anti-CD4 mAb had a more potent effect leading to 80% cure rate. Anti-CD25 mAb, indeed, only partially depleted CD4+CD25+FoxP3+ Treg cells, whereas anti-CD4 mAb was more effective in this respect, leading to 90% depletion of Treg cells. In mice receiving vaccine+anti-CD4 mAb, which developed systemic immunity to NB, CD4+ T cells counts completely recovered in 90 days. Depletion of CD8+ T cells abrogated the effect of the combined IT, indicating a predominant role of these cells in driving the immune response. In addition, CD8+ T cells from cured mice coinjected with Neuro2a/parental cells (pc) in NOD-SCID mice completely inhibited tumor growth. Spleen cells from mice receiving Neuro2a/IL-21 vaccination showed increased expression of IFN-alpha2, -beta1 and -gamma mRNA. Moreover, mice receiving vaccine therapy alone or vaccine+anti-CD4 mAb showed increased IFN-gamma serum levels and IFN-gamma-producing CD8+ T cells were found in spleen cells. In conclusion, anti-CD4 mAb potentiated IL-21-based IT by removing Treg cells and/or their precursors and other potentially immune-suppressive CD4+ cell subsets, thus allowing the development of an IL-21-driven CD8+ T cell response, which mediates NB rejection.

A multi-DNA preventive vaccine for p53/Neu-driven cancer syndrome

The highly aggressive cancer syndrome of female mice carrying a p53 knockout allele and a rat HER-2/neu (Neu) transgene (BALB-p53Neu) can be prevented by a cell vaccine presenting three components: Neu, interleukin (IL)-12 production, and allogeneic major histocompatibility complex (MHC) alleles (Triplex cell vaccine). Here we tested a second-generation Triplex DNA-based vaccine (Tri-DNA), consisting of the combination of three gene components (a transmembrane-extracellular domain fragment of the Neu gene, IL-12 genes, and the H-2D(q) allogeneic MHC gene), carried by separate plasmids. The Tri-DNA vaccine was at least as effective as the Triplex cell vaccine for cancer immunoprevention, giving a similar delay in the onset of mammary cancer and complete protection from salivary cancer. Both vaccines induced anti-Neu antibodies of the murine IgG2a isotype at similar levels. The Tri-DNA vaccine gave more restricted immunostimulation, consisting of a fully helper T cell type 1 (Th1)-polarized response, with effective production of interferon (IFN)-gamma in response to the vaccine but no spontaneous production, and no induction of anti-Neu IgG3 antibodies. On the other hand, the Triplex cell vaccine induced both Th1 and Th2 cytokines, a strong increase in spontaneous IFN-gamma production, and high levels of IgG3 antibodies recognizing Neu-positive syngeneic cells. In conclusion, the Tri-DNA vaccine is as effective as Triplex cell vaccine, exploiting a more restricted immune stimulation.

IL-8 induces exocytosis of arginase 1 by neutrophil polymorphonuclears in nonsmall cell lung cancer

Arginase 1 (ARG1) inhibits T-cell proliferation by degrading extracellular arginine, which results in decreased responsiveness of T cells to CD3/TCR stimulation. In humans, ARG1 is stored in inactive form within granules of polymorphonuclear neutrophils (PMNs) and gets activated on release. We studied the role of PMNs-related ARG1 activity in nonsmall cell lung cancer (NSLC), in which tumor-infiltrating lymphocytes showed reduced proliferation in response to CD3/TCR triggering. Patients with NSCLC had increased ARG1 plasma levels as compared to healthy controls. Furthermore, immunohistochemistry showed that tumor-infiltrating PMNs display reduced intracellular ARG1, in comparison to intravascular or peritumoral PMNs, suggesting a role of tumor microenvironment in ARG1 release. Indeed, supernatants of NSCLC cell lines induced exocytosis of ARG1 from PMNs. All (4/4) NSCLC cell lines and all (7/7) CD14- cell samples from NSCLC expressed interleukin (IL)-8 mRNA, whereas TNFalpha mRNA was expressed by 1 cell line and by 2 tumor specimens. Furthermore, all NSCLC cell lines secreted immunoreactive IL-8, albeit at different levels. IL-8 was as effective as TNFalpha in triggering ARG1 release and the 2 cytokines acted synergistically. Secreted ARG1 was biologically active and catabolized extracellular arginine. The supernatant of IL-8 gene-silenced NSCLC cells did not mediate ARG1 release by PMNs. Altogether these findings demonstrate a role of IL-8 in ARG1 exocytosis by PMNs and indicate that, due at least in part to IL-8 secreted by NSCLC cells, PMNs infiltrating NSCLC release ARG1. This phenomenon could contribute to local immune suppression.

Cancer stem cells: a new paradigm for understanding tumor growth and progression and drug resistance

Normal somatic stem cells (SC) are naturally resistant to chemotherapeutic agents due to their expression of various membrane transporter molecules (such as MDR-1), detoxifying enzymes and DNA repair proteins. In addition, they also have a slow rate of cell turnover and therefore escape from chemotherapeutic agents that target rapidly replicating cells. Cancer stem cells (CSC), being the mutated counterparts of normal SC, also have similar properties, which allow them to survive therapy. These surviving CSC then repopulate the tumor, causing relapse. The purpose of this review is to understand the most current research into the cellular and molecular biology of CSC. Topics that will be explored are the origin of CSC, the CSC niche, the regulation of self-renewal in normal and cancer SC, and CSC as therapeutic targets.

The ALCAM shedding by the metalloprotease ADAM17/TACE is involved in motility of ovarian carcinoma cells

Previous findings indicated that the activated leukocyte cell adhesion molecule (ALCAM) is expressed by tumors and plays a role in tumor biology. In this study, we show that ALCAM is shed from epithelial ovarian cancer (EOC) cells in vitro, leading to the generation of a soluble ALCAM (sALCAM), consisting of most of the extracellular domain. A similar sALCAM molecule was also found in the ascitic fluids and sera from EOC patients, suggesting that this process also occurs in vivo. sALCAM is constitutively produced by EOC cells, and this process can be enhanced by cell treatment with pervanadate, phorbol 12-myristate 13-acetate (PMA), or epidermal growth factor (EGF), a known growth factor for EOC. Pharmacologic inhibitors of matrix metalloproteinases (MMP) and of a disintegrin and metalloproteases (ADAM), and the tissue inhibitor of metalloproteinase-3, significantly inhibited sALCAM release by EOC cells. The ADAM17/TACE molecule was expressed in EOC cell lines and ADAM17/TACE silencing by specific small interfering RNA-reduced ALCAM shedding. In addition, inhibitors of ADAM function blocked EOC cell motility in a wound-healing assay. Conversely, a recombinant antibody blocking ALCAM adhesive functions and inducing ALCAM internalization enhanced EOC cell motility. Altogether, our data suggest that the disruption of ALCAM-mediated adhesion is a relevant step in EOC motility, and ADAM17/TACE takes part in this process, which may be relevant to EOC invasive potential.

Inhibition of prostate carcinogenesis by combined active immunoprophylaxis

The aim of this study is to investigate whether an active immunoprophylactic approach combining specific antigens and adjuvant stimuli would be able to inhibit prostate carcinogenesis in transgenic TRAMP mice. A vaccine consisting of allogeneic large T antigen (TAg)-positive SV40-transformed cells combined with systemic recombinant IL-12 was administered to TRAMP mice, starting from when they were still tumor-free at 5-6 weeks of age. The combined vaccine significantly inhibited prostate carcinogenesis, giving a more than doubled median latency time of prostatic tumors (53 weeks in comparison to 26 weeks in control mice). Vaccination with cells alone or IL-12 treatment alone was poorly effective (median latency of 30 and 39 weeks, respectively). The combined vaccine induced a very high CD4 response biased toward the Th1 pathway, with the induction of a humoral response that included TAg-specific antibodies. Therefore, such active immunoprophylactic approach based on the combination of allogeneic SV40 TAg-positive cells and systemic administration of recombinant IL-12 significantly delayed autochthonous urogenital carcinogenesis driven by SV40 TAg in TRAMP mice.

Glioma immunotherapy by IL-21 gene-modified cells or by recombinant IL-21 involves antibody responses

Most tumors of the central nervous system, especially glioblastoma, are refractory to treatment and invariably lethal. The aim of this study was to assess the ability of different interleukins (IL), IL-2, IL-12 and IL-21, produced by transduced glioma cells to activate an immune response and trigger intracranial tumor rejection. Such experiments were performed by the use of a slow-growing clone of GL261 (GL D2-60) that was used as orthotopic glioma model. Using GL D2-60-transduced cells, all cytokines elicited an immune response against the tumor. Most notably 100% of the animals receiving a primary implant of IL-21-transduced cells rejected the implant, and 76% of these animals survived to a subsequent rechallenge with GL261 parental cells, while the other transduced cytokine genes were not as effective. Rejection responses were also obtained by admixing wild-type tumor cells with IL-21-producing GL D2-60 cells, indicating a local bystander effect of IL-21. More importantly, IL-21-secreting GL D2-60 cells or 1 microg of rIL-21 protein stereotactically injected into established GL D2-60 tumors were able to trigger glioblastoma rejection in 90 and 77% of mice, respectively. Again most of these mice survived to GL261 rechallenge. Immune mice showed antibody responses to glioma antigens, predominantly involving IgG2a and IgG2b isotypes, which mediated complement- or cell-dependent glioma cell lysis. Antibody responses were crucial for glioma immunotherapy by IL-21-secreting GL D2-60 cells, as immunotherapy was uneffective in syngeneic microMT B-cell-deficient mice. These results suggest that IL-21 should be considered as a suitable candidate for glioma immunotherapy by local delivery.

CD25+ Regulatory T Cell Depletion Augments Immunotherapy of Micrometastases by an IL-21-Secreting Cellular Vaccine

IL-21 is an IL-2-like cytokine, signaling through a specific IL-21R and the IL-2R gamma-chain. Because the TS/A mammary adenocarcinoma cells genetically modified to secrete IL-21 (TS/A-IL-21) are strongly immunogenic in syngeneic mice, we analyzed their application as vaccine. In mice bearing TS/A-parental cell (pc) micrometastases, vaccination with irradiated TS/A-IL-21 cells significantly increased the animal life span, but cured only 17% of mice. Spleen cells from cured mice developed CTL activity and produced IFN-gamma in response to stimulation by the AH1 epitope of the gp70env Ag of TS/A-pc. We tested whether the low therapeutic outcome might be due to CD4+CD25+ regulatory T cells (Treg) present in TS/A-pc tumors and draining lymph nodes and whether IL-21 had any effect on these cells. Indeed, CD4+CD25+ cells suppressed IFN-gamma production by splenocytes from immune mice in response to stimulation by the AH1 peptide. Low concentrations of IL-21 (10 ng/ml) failed to reverse the inhibitory activity of CD4+CD25+ cells in an allogeneic MLR, whereas 60 ng/ml rIL-21 partially restored responder T cell proliferation. IL-21R expression on CD25- lymphocytes suggested that IL-21 could be more effective in mice depleted of CD25+ cells. Depletion of Treg cells by a single dose of anti-CD25 mAb combined with TS/A-IL-21 cell vaccine cured >70% of mice bearing micrometastases, whereas anti-CD25 mAb treatment alone had no effect. Successful combined immunotherapy required NK cells, CD8+ T cells, and IFN-gamma. In conclusion, immunotherapy of micrometastases by an IL-21-based cellular vaccine is strongly potentiated by CD25+ cell depletion.

Sequential Immunogene Therapy with Interleukin-12– and Interleukin-15–Engineered Neuroblastoma Cells Cures Metastatic Disease in Syngeneic Mice

Purpose: To investigate the potential synergistic effects of Neuro2a neuroblastoma cells engineered with IL-12 and/or IL-15 genes in improving survival of syngeneic mice bearing neuroblastoma metastatic disease.

Experimental Design: Neuro2a cells engineered with interleukin (IL)-12 (Neuro2a/IL-12), IL-15 (Neuro2a/IL-15), or both cytokines (Neuro2a/IL-12/IL-15) were injected s.c. in syngeneic A/J mice challenged i.v. with Neuro2a parental cells (Neuro2apc) using different schedules of administration in either preventive or therapeutic settings.

Results: A single injection of Neuro2a/IL-12 or Neuro2a/IL-15 cells induced resistance to a subsequent i.v. Neuro2apc challenge in 45% and 28% of mice, respectively. Neuro2a/IL-12/IL-15 cells protected 28% of mice, showing no synergistic effect. However, sequential vaccination with Neuro2a/IL-12 (day −30) followed by Neuro2a/IL-15 (day −15) protected 71% of mice from subsequent challenge with Neuro2apc. A single dose of Neuro2a/IL-12 prolonged the mean survival time of mice bearing established metastatic neuroblastoma from 21 ± 3 to 46 ± 27 days but failed to cure mice, whereas Neuro2a/IL-15 or Neuro2a/IL-12/IL-15 were ineffective. However, sequential vaccination with Neuro2a/IL-12 (day +3) followed by Neuro2a/IL-15 (day +13) cured 43% of mice as assessed by histologic analysis of different organs from long-term surviving mice. CTL activity against Neuro2apc cells was observed in splenocytes from treated mice, and CD8+ T-cell depletion abrogated the therapeutic effect of vaccination.

Conclusions: Sequential vaccination with IL-12- and IL-15-engineered neuroblastoma cells induced optimal preventive and therapeutic effects, which may be related to the Th1 priming effect of IL-12 followed by the enhancement of CD8+ T-cell responses and their maintenance mediated by IL-15.

Sequential immunogene therapy with interleukin-12- and interleukin-15-engineered neuroblastoma cells cures metastatic disease in syngeneic mice

PURPOSE

To investigate the potential synergistic effects of Neuro2a neuroblastoma cells engineered with IL-12 and/or IL-15 genes in improving survival of syngeneic mice bearing neuroblastoma metastatic disease.

EXPERIMENTAL DESIGN

Neuro2a cells engineered with interleukin (IL)-12 (Neuro2a/IL-12), IL-15 (Neuro2a/IL-15), or both cytokines (Neuro2a/IL-12/IL-15) were injected s.c. in syngeneic A/J mice challenged i.v. with Neuro2a parental cells (Neuro2apc) using different schedules of administration in either preventive or therapeutic settings.

RESULTS

A single injection of Neuro2a/IL-12 or Neuro2a/IL-15 cells induced resistance to a subsequent i.v. Neuro2apc challenge in 45% and 28% of mice, respectively. Neuro2a/IL-12/IL-15 cells protected 28% of mice, showing no synergistic effect. However, sequential vaccination with Neuro2a/IL-12 (day -30) followed by Neuro2a/IL-15 (day -15) protected 71% of mice from subsequent challenge with Neuro2apc. A single dose of Neuro2a/IL-12 prolonged the mean survival time of mice bearing established metastatic neuroblastoma from 21 +/- 3 to 46 +/- 27 days but failed to cure mice, whereas Neuro2a/IL-15 or Neuro2a/IL-12/IL-15 were ineffective. However, sequential vaccination with Neuro2a/IL-12 (day +3) followed by Neuro2a/IL-15 (day +13) cured 43% of mice as assessed by histologic analysis of different organs from long-term surviving mice. CTL activity against Neuro2apc cells was observed in splenocytes from treated mice, and CD8(+) T-cell depletion abrogated the therapeutic effect of vaccination.

CONCLUSIONS

Sequential vaccination with IL-12- and IL-15-engineered neuroblastoma cells induced optimal preventive and therapeutic effects, which may be related to the Th1 priming effect of IL-12 followed by the enhancement of CD8(+) T-cell responses and their maintenance mediated by IL-15.

IL-21 induces tumor rejection by specific CTL and IFN-gamma-dependent CXC chemokines in syngeneic mice

IL-21 is an immune-stimulatory four alpha helix cytokine produced by activated T cells. To study the in vivo antitumor activities of IL-21, TS/A murine mammary adenocarcinoma cells were genetically modified to secrete IL-21 (TS/A-IL-21). These cells developed small tumors that were subsequently rejected by 90% of s.c. injected syngeneic mice. Five days after injection, TS/A-IL-21 tumors showed numerous infiltrating granulocytes, NK cells, and to a lesser extent CD8(+) T cells, along with the expression of TNF-alpha, IFN-gamma, and endothelial adhesion molecules ICAM-1 and VCAM-1. At day 7, CD8(+) and CD4(+) T cells increased together with IFN-gamma, and the CXC chemokines IFN-gamma-inducible protein 10, monokine induced by IFN-gamma, and IFN-inducible T cell alpha-chemoattractant. The TS/A-IL-21 tumor displayed a disrupted vascular network with abortive sprouting and signs of endothelial cell damage. In vivo depletion experiments by specific Abs showed that rejection of TS/A-IL-21 cells required CD8(+) T lymphocytes and granulocytes. When injected in IFN-gamma-deficient mice, TS/A-IL-21 cells formed tumors that regressed in only 29% of animals, indicating a role for IFN-gamma in IL-21-mediated antitumor response, but also the existence of IFN-gamma-independent effects. Most immunocompetent mice rejecting TS/A-IL-21 cells developed protective immunity against TS/A-pc (75%) and against the antigenically related C26 colon carcinoma cells (61%), as indicated by rechallenge experiments. A specific CTL response against the gp70-env protein of an endogenous murine retrovirus coexpressed by TS/A and C26 cells was detected in mice rejecting TS/A-IL-21 cells. These data suggest that IL-21 represents a suitable adjuvant in inducing specific CTL responses.

Tumor cells engineered with IL-12 and IL-15 genes induce protective antibody responses in nude mice

IL-12 and IL-15 stimulate T, B, and NK cell functions through independent mechanisms, and cooperative effects of these cytokines have been reported. The human MHC class I-negative small cell lung cancer cell line, N592, genetically engineered to secrete IL-15, N592/IL-15, showed a reduced tumor growth rate, while N592 cells engineered with IL-12, N592/IL-12, grew similarly to the wild-type N592, N592 parental cells (N592pc), in nude mice. However, N592 cells coexpressing both cytokines, N592/IL-12/IL-15 cells, were completely rejected by 100% of nude mice. Here we show that 60% of nude mice rejecting N592/IL-12/IL-15 cells were resistant to N592pc rechallenge. SCID mice rejected N592/IL-12/IL-15 cells, but did not develop resistance to N592pc rechallenge, suggesting a role of Ab responses. Among nude mice rejecting N592/IL-12/IL-15 cells, those developing resistance to N592pc rechallenge had significantly higher titers of anti-N592 IgG2b Abs than nonresistant nude mice. Induction of an Ig class switch in nude mice was related to the expression of IFN-gamma and CD40 ligand in the draining lymph nodes. An IgG2b, anti-N592 mAb, derived from N592/IL-12/IL-15-immunized nude mice splenocytes induced significant protection against N592pc, while an IgM mAb was ineffective. The protective IgG2b mAb, but not the IgM mAb, triggered Ab-dependent cell-mediated cytotoxicity by nude mouse splenocytes against N592pc. These data indicate that IL-12 and IL-15 synergistically trigger innate, immunity-mediated, anti-tumor effects, resulting in cytotoxic IgG Ab responses in T cell-deficient mice. Protective Ab responses may relate to both direct actions of IL-12 and IL-15 on B cells and to the activation of an innate immunity-B cell cross-talk.

Interleukin-2 induces cell cycle perturbations leading to cell growth inhibition and death in malignant mesothelioma cells in vitro

Previous report indicated that Interleukin-2 (IL-2) is able to inhibit the growth of IL-2-receptor-positive cancer cell lines without any involvement of the immune system, through IL-2-induced alterations of the cell cycle kinetics. In this study we provide evidence that IL-2 exerts anti-proliferative effect on three human malignant mesothelioma (MMe) cells in vitro, while no effects were observed on normal human mesothelial cell (HMC) primary cultures. The growth inhibitory effect of IL-2 on neoplastic cells appeared to depend on the baseline proliferative status of these cells. Indeed, in highly proliferating MMe cells, we observed a reduction of malignant cells in the S-phase of the cell cycle, with an accumulation in G0/G1, followed by apotosis for longer incubations or exposure to higher doses. On the contrary, in MMe cells proliferating at lower rate, IL-2 induces only a late cytotoxic effect, leading to apoptosis, without significantly affecting the cell cycle. IL-2Rbeta mRNA was detectable by RT-PCR in all MMe cells, IL-2Ralpha mRNA in one only out the three assayed and IL-2Rgamma mRNA in none. In addition, mRNA specific for the IL-2Rbeta-associated Jak-1 tyrosine kinase was expressed in all MMe cell lines, further suggesting that IL-2Rbeta may play a role in the observed effects. Very low, albeit detectable, levels of IL-2Rbeta chain appeared to be expressed at the cell surface of MMe cells by indirect immunofluorescence and FACS analyses. Finally, Ca(++) fluxes were rapidly induced when MMe cells were exposed to exogenous IL-2.

DNA vaccination against the ovarian carcinoma-associated antigen folate receptor alpha (FRalpha) induces cytotoxic T lymphocyte and antibody responses in mice

Human folate receptor alpha (FRalpha) is a folate-binding protein that is selectively overexpressed in ovarian carcinoma and has been regarded as a suitable target antigen for immunotherapy purposes. To study the possible use of this antigen in DNA vaccination, FRalpha cDNA was ligated into the VR1012 (Vical) expression vector under the transcriptional control of the cytomegalovirus promoter. A total of 100 microg of purified plasmid DNA was injected intramuscularly in BALB/c mice three times at 14-day intervals. At 10 days after the second injection, the sera of the animals (100%) displayed significant antibody titers (by indirect immunofluorescence and fluorescence-activated cell sorter analysis) against syngeneic C26 cells transduced with FRalpha, but not against unmodified C26 cells. Immunoglobulin G2a was the predominant isotype. In addition, specific cytotoxic T lymphocyte activity against FRalpha-transduced C26 cells could be detected in splenocytes from all immunized animals. Coinjection of a plasmid containing interleukin-2 cDNA increased both antibody titers and cytotoxic T lymphocyte activity. Challenge by subcutaneous injection with FRalpha-transduced C26 cells (performed 10 days after the third injection) showed a statistically significant delay in tumor growth. Vaccination with the FRalpha and interleukin-2 cDNA mixture, which was performed after an intravenous injection of FRalpha-transduced cells, enhanced the mean survival time and reduced the number of lung metastases, thus suggesting that such vaccination is effective even against preexisting tumor cells.

Establishment of four new mesothelioma cell lines: characterization by ultrastructural and immunophenotypic analysis

The aim of this study was to assess the biological characteristics of four new malignant mesothelioma (MM) cell lines. Since simian virus (SV)40 sequences have been recently detected in MM, SV40 large T antigen (Tag) expression was also analysed. MM cell lines were characterized by morphological, ultrastructural and cytogenetic analysis. Expression of Tag and of relevant MM markers was studied by immunocytochemistry, surface antigens by indirect immunofluorescence and immunomodulating cytokines by enzyme-linked immunosorbent assay (ELISA). The four MM cell lines, established from pleural effusions, showed a slow proliferation rate and pleomorphic changes during culture. Cell lines expressed vimentin, cytokeratins 8 and 18, and the mesothelial antigen recognized by HBME-1 monoclonal antibody, but not carcinoembryonic antigen. Surface human leukocyte antigen (HLA)-class I and intercellular adhesion molecule (ICAM)-1 molecules were present on all the cell lines. While HLA class II and CD86 were constitutively undetectable, HLA-class II was present after interferon (IFN)-gamma stimulation. All cell lines displayed abnormal karyotypes with chromosome 6 abnormalities. Transforming growth factor (TGF)-beta2 and interleukin (IL)-6 were constitutively secreted, while tumour necrosis factor (TNF)-alpha was secreted only in response to lipopolysaccharide. Intranuclear Tag was expressed in two cell lines. The persistence of large T antigen with human leukocyte antigen class I and intercellular adhesion molecule-1 positivity may point to large T antigen as a target for cytotoxic T-lymphocyte-based immunotherapy in some malignant mesothelioma patients.

Primary human mesothelioma cells express class II MHC, ICAM-1 and B7-2 and can present recall antigens to autologous blood lymphocytes

Mesothelioma cells (MMc) are considered to be weakly immunogenic and the experimental approaches attempting to induce an immune response against these cells have been disappointing. Our aim was to investigate whether MMc possess the surface accessory molecules involved in antigen presentation and whether these cells are capable of presenting recall antigens to autologous blood lymphocytes. Four primary MMc cultures were generated from malignant effusions and examined to assess whether the accessory molecules required for antigen presentation were present on their surfaces. Intercellular adhesion molecule-I (ICAM-I; CD54); class I and class II major histocompatibility complex-DR (MHCI and MHCII-DR); B7-1 (CD80.3); and B7-2 (CD86) expression by MMc was studied by immunocytochemical and/or FACScan analysis. MMc were pulsed with purified protein derivative (PPD), Tetanus toxoid (TT) and Candida albicans (CA) bodies, and incubated with autologous lymphocytes. Lymphocyte proliferation was estimated by radionucleotide incorporation. Phenotypic analysis showed the presence of MHCII-DR, ICAM-I and B7-2 on primary MMc cultures, whereas the phenotypic evaluation of 2 established MMc lines did not show the presence of the B7-1 and B7-2 molecules. In addition, MHCII-DR was detectable only after interferon gamma (IFN-gamma) stimulation. Primary MMc cultures acquired the capability to induce lymphocyte proliferation after pulse with the recall antigens. To achieve characterization of these lymphocytes, we generated a PPD-specific CD4+ T-cell clone. PPD-pulsed MMc were shown to specifically induce T-cell clone proliferation through a MHCII-DR-mediated process. We conclude that primary MMc possess the surface molecules required for antigen presentation and can present recall antigens to CD4+ lymphocytes.

Reciprocal expression of CD70 and of its receptor, CD27, in human long term-activated T and natural killer (NK) cells: inverse regulation by cytokines and role in induction of cytotoxicity

By transfection of COS cells with an expression vector containing CD70 cDNA we demonstrate that two previously described MoAbs (ED6 and LD6) recognize CD70. By means of these MoAbs, we show that the surface expression of CD70 inversely correlates with the expression of its receptor, CD27, on activated T and NK cell populations and clones, although a subpopulation of cells expressing low density of both molecules exists. In addition, culture in the presence of IL-4 significantly enhances CD27 and reduces CD70 surface expression in phytohaemagglutinin (PHA)-activated peripheral blood lymphocytes (PBL), while tumour necrosis factor-alpha (TNF-alpha) displays opposite effects, indicating that receptor and ligand are reciprocally regulated by these cytokines. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of CD27 and CD70 mRNA suggests a transcriptional control of CD27 antigen expression in T cell clones. In addition, we show by the use of a re-directed killing assay that in cytotoxic T cell receptor (TCR) alpha/beta+ T cell clones, CD27 molecule may be involved in the regulation of cytolytic functions and may act synergistically with CD2. Finally, CD70 also acts as a signal-transducing molecule in some activated CD70+ TCR gamma/delta+ T or NK cell clones. In conclusion, our data indicate that CD27 and CD70 molecules are differentially expressed and regulated on long term-activated T and NK cells and are involved in the control of cellular functions.

Analysis of IL-2 receptor expression and of the biological effects of IL-2 gene transfection in small-cell lung cancer

We have analysed the expression of interleukin-2 receptor (IL-2R) on a panel of small-cell lung cancer (SCLC) cell lines. None of the 11 SCLC cell lines studied expressed detectable surface IL-2R alpha or beta chains by indirect immunofluorescence. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses indicated that only one out of 11 cell lines expressed detectable IL-2R beta mRNA while two expressed a weak positivity for IL-2R gamma. Five SCLC cell lines were transfected with the plasmid vector RSV.5 neo containing IL-2 cDNA coding sequence. Stable transfectants secreted biologically active IL-2 (ranging from 25 to 100 U ml-1 in the culture supernatant). IL-2 transfection did not produce significant modifications in the expression of surface molecules such as IL-2R alpha and beta chains, intercellular adhesion molecule-1 (ICAM-1), CD44, HLA class I and II or in IL-2R beta or gamma mRNA. More importantly, IL-2-transfected N592 and NCI H69 cell lines completely lost their tumorigenic potential in nude mice after subcutaneous injection, whereas experimental controls transfected with RSV.5 neo vector only, displayed an in vivo growth pattern identical to that of untransfected cells. In addition, in the N592 model, IL-2-producing N592 inhibited the growth of wild-type N592 injected at the same site, while injection of parental cells on the opposite side did not significantly affect the growth of wild-type tumour cells. Histopathological analysis of the rejection process of IL-2-transfected cells demonstrated the presence of MAC-1+, MAC-3+ macrophages and of RB68C5+ granulocytes, whereas T cells were undetectable and NK cells were scarcely represented. In addition, a reduction of the tumour blood vessels was observed. The possible relevance of these data for the development of vaccination strategies using cytokine-engineered tumour cells in SCLC is discussed.

Identification of a novel interleukin-15 (IL-15) transcript isoform generated by alternative splicing in human small cell lung cancer cell lines

IL-15 is a cytokine promoting growth and differentiation of T, B and NK lymphocytes. By RT-PCR analysis, using primers allowing amplification of the entire IL-15 mRNA coding region, 9/11 small cell lung cancer (SCLC) cell lines displayed detectable IL-15 gene expression. In addition to the expected band sizing 524 bp, a larger band was also observed. Cloning and sequence analysis of the larger cDNA from two SCLC cell lines revealed a size of 643 hp due to the presence of additional 119 hp within the previously reported IL-15 cDNA sequence. The 119 hp sequence matched with an IL-15 genomic sequence downstream the IL-15 second coding exon and may represent a previously unreported alternative exon (exon A). The SCLC-associated IL-15 mRNA isoform has a shorter open reading frame (ORF) due to stop codons in exon A, followed by a new AUG codon. The predicted IL-15 precursor protein displays a shorter signal peptide but shares the same aminoacidic composition of mature IL-15 protein. A possible functional role of IL-15, different from 'IL-2-like' activity, in human tumours, is suggested.

The natural killer-related receptor for HLA-C expressed on T cells from CD3+ lymphoproliferative disease of granular lymphocytes displays either inhibitory or stimulatory function

Four patients with lymphoproliferative disease of granular lymphocytes (LDGL) coexpressing CD3 and the natural killer (NK)-related "p58" receptor for HLA-C alleles were studied. These CD3+p58+ LDGLs have been detected among a series of 44 CD3+ LDGLs analyzed. Two patients with LDGL (GI and BA) expressed only the p58 molecule defined by the GL-183 and CH-L monoclonal antibodies (MoAbs), while the cases of patients PU and MA also coexpressed the molecular form identified by EB6 anti-p58 MoAb. Three LDGL cases (GI, MA, and PU) displayed the CD8+4-CD16+ T-cell receptor (TCR)alpha/beta+ phenotype, while one patient (BA) was CD8+4+CD16+ TCRalpha/beta+. Freshly isolated granular lymphocytes (GL) from these cases displayed cytolytic activity in an anti-CD3 MoAb-triggered redirected killing assay against the Fcgamma-receptor+ (Fcgamma-R+) P815 target cell line. Lysis of P815 target cells, triggered by an anti-CD3 or by anti-CD16 MoAb, could be inhibited by the addition of anti-p58 MoAb in three fresh or interleukin (IL)-2-cultured GL tested (GI, MA, and PU). Triggering of cytotoxicity against the HLA-DR+ Fcgamma-R+ Daudi cell line induced by appropriate superantigens could also be inhibited by anti-p58 MoAb in patients PU and GI with LDGL. These data indicate that activation through the CD16, CD3, and TCR molecules can be modulated by p58 receptors in these LDGLs. On the contrary, IL-2-expanded cells of patient BA were induced to lyse P815 target cells by anti-p58 MoAb. In addition, anti-p58 MoAB enhanced anti-CD16 MoAb triggered lysis and did not inhibit activation via CD3. These data indicate that, in this particular patient with LDGL, p58 displays a stimulatory effect on cell triggering, rather than the typical inhibitory effect previously observed in p58+ T-cell clones derived from healthy donors. The anti-p58 MoAb did not induce CA++ mobilization in p58+ LDGLs and in a p58+CD3+ normal T-cell clone equipped with inhibitory p58 molecules, while Ca++ mobilization could be observed in cultured GL from patient BA, which could be activated by anti-58 MoAb. These findings suggest that stimulatory and inhibitory p58 molecules are equipped with different signal transducing properties, thus contributing to a better knowledge of the normal counterpart.

Functional ambivalence of the Kp43 (CD94) NK cell-associated surface antigen

We originally characterized the Kp43 (CD94) surface Ag, whose expression is restricted to human NK cells and a minor T lymphocyte subset. As shown in the present study, anti-Kp43 mAbs but not their F(ab')2 fragments markedly inhibited the cytolytic activity of polyclonal-activated NK cells in a redirected lysis assay against the murine P815 cell line. Furthermore, anti-Kp43 mAbs also down-regulated the CD16-dependent redirected killing and PHA-induced lectin-dependent cellular cytotoxicity. However, the intensity of the inhibitory effect was variable and no significant down-regulation of cytotoxicity was substantiated in NK cell populations from some individuals. A similar variability in the responsiveness to anti-Kp43 mAb was noticed when fresh CD3- lymphocyte populations were tested: in some donors we observed the induction of redirected lysis, whereas in other samples the Kp43-specific mAb inhibited cytotoxicity. The analysis of single cell-derived microcultures provided a clue to interpret the variable responsiveness of polyclonal cell populations; remarkably, the cytolytic activity of some NK clones was inhibited, whereas that of others was either stimulated or unaffected. The pattern of responsiveness in the cytolytic assay correlated with TNF production upon stimulation with solid phase-bound anti-Kp43 mAbs. The different types of clones could be derived from the same individual, although their relative proportions varied from donor to donor. Moreover, Kp43 appeared to be coupled differently to signal transduction pathways, because (Ca2+)i mobilization in the presence of the Kp43-specific mAbs was substantiated only in clones that were activated in the redirected lysis assay.

Functional ambivalence of the Kp43 (CD94) NK cell-associated surface antigen

We originally characterized the Kp43 (CD94) surface Ag, whose expression is restricted to human NK cells and a minor T lymphocyte subset. As shown in the present study, anti-Kp43 mAbs but not their F(ab')2 fragments markedly inhibited the cytolytic activity of polyclonal-activated NK cells in a redirected lysis assay against the murine P815 cell line. Furthermore, anti-Kp43 mAbs also down-regulated the CD16-dependent redirected killing and PHA-induced lectin-dependent cellular cytotoxicity. However, the intensity of the inhibitory effect was variable and no significant down-regulation of cytotoxicity was substantiated in NK cell populations from some individuals. A similar variability in the responsiveness to anti-Kp43 mAb was noticed when fresh CD3- lymphocyte populations were tested: in some donors we observed the induction of redirected lysis, whereas in other samples the Kp43-specific mAb inhibited cytotoxicity. The analysis of single cell-derived microcultures provided a clue to interpret the variable responsiveness of polyclonal cell populations; remarkably, the cytolytic activity of some NK clones was inhibited, whereas that of others was either stimulated or unaffected. The pattern of responsiveness in the cytolytic assay correlated with TNF production upon stimulation with solid phase-bound anti-Kp43 mAbs. The different types of clones could be derived from the same individual, although their relative proportions varied from donor to donor. Moreover, Kp43 appeared to be coupled differently to signal transduction pathways, because (Ca2+)i mobilization in the presence of the Kp43-specific mAbs was substantiated only in clones that were activated in the redirected lysis assay.

Analysis of natural killer (NK) cell subsets defined by the expression of two novel surface antigens (EB6 and GL183) in AIDS and AIDS-related conditions

In this study we analyzed the expression of EB6 and GL183, which are part of P58 molecular family that represents the putative NK receptor for MHC class I molecules, in peripheral blood lymphocytes of 60 patients with HIV infection (20 asymptomatic HIV-seropositive individuals, 20 patients with constitutional symptoms, and 20 AIDS patients) and correlated it with the level of CD4+, CD56+ cells, and the NK cell activity in order to determine a possible relation with disease progression. The absolute number (but not the percentage) of CD56+, EB6+, and GL183+ cells was significantly reduced only in AIDS patients but not in the other AIDS-related clinical conditions. On the contrary, NK cell activity was reduced in all HIV-infected patients. In a 6-month follow-up, patients with constant clinical conditions and stable CD4+ cells level showed no significant difference, either in the percentage or absolute number of EB6+ and GL183+ cells. Interestingly, dual-color fluorescence indicates that GL183 and EB6 molecules (that in normal individuals are virtually absent on CD3- NK cells) are expressed in HIV-infected individuals not only in CD56+ cells but also in CD3+ cells. This may reflect a depletion of other T cell subsets or alternatively (less likely) a specific immune response. Our data indicate that the expression of EB6 and GL183 in T and NK cells from HIV-infected patients might be relevant in the course of the disease and for the disease-associated functional defect of NK cell activity.