Impact of immune checkpoint inhibitors on atherosclerosis progression in patients with lung cancer

BACKGROUND

Patients with lung cancer face a heightened risk of atherosclerosis-related cardiovascular events. Despite the strong scientific rationale, there is currently a lack of clinical evidence examining the impact of immune checkpoint inhibitors (ICIs) on the advancement of atherosclerosis in patients with lung cancer. The objective of our study was to investigate whether there is a correlation between ICIs and the accelerated progression of atherosclerosis among individuals with lung cancer.

METHODS

In this case-control (2:1 matched by age and gender) study, total, non-calcified, and calcified plaque volumes were measured in the thoracic aorta using sequential contrast-enhanced chest CT scans. Univariate and multivariate rank-based estimation regression models were developed to estimate the effect of ICI therapy on plaque progression in 40 cases (ICI) and 20 controls (non-ICI).

RESULTS

The patients had a median age of 66 years (IQR: 58-69), with 50% of them being women. At baseline, there were no significant differences in plaque volumes between the groups, and their cardiovascular risk profiles were similar. However, the annual progression rate for non-calcified plaque volume was 7 times higher in the ICI group compared with the controls (11.2% vs 1.6% per year, p=0.001). Conversely, the controls showed a greater progression in calcified plaque volume compared with the ICI group (25% vs 2% per year, p=0.017). In a multivariate model that considered cardiovascular risk factors, the use of an ICI was associated with a more substantial progression of non-calcified plaque volume. Additionally, individuals treated with combination ICI therapy exhibited greater plaque progression.

CONCLUSIONS

ICI therapy was associated with more non-calcified plaque progression. These findings underscore the importance of conducting studies aimed at identifying the underlying mechanisms responsible for plaque advancement in patients undergoing ICI treatment.

TRIAL REGISTRATION NUMBER

NCT04430712.

Imaging subclinical coronary atherosclerosis to guide lipid management, are we there yet?

Atherosclerotic cardiovascular disease risk (ASCVD) is an ongoing epidemic, and lipid abnormalities are its primordial cause. Most individuals suffering a first ASCVD event are previously asymptomatic and often do not receive preventative therapies. The cornerstone of primary prevention has been the identification of individuals at risk through risk calculators based on clinical and laboratory traditional risk factors plus risk enhancers. However, it is well accepted that a clinical risk calculator misclassifies a significant proportion of individuals leading to the prescription of a lipid-lowering medication with very little yield or a missed opportunity for lipid-lowering agents with a potentially preventable event. The development of coronary artery calcium scoring (CAC) and CT coronary angiography (CCTA) provide complementary tools to directly visualize coronary plaque and other risk-modifying imaging components that can potentially provide individualized lipid management. Understanding patient selection for CAC or potentially CCTA and the risk implications of the different parameters provided, such as CAC score, coronary stenosis, plaque characteristics and burden, epicardial adipose tissue, and pericoronary adipose tissue, have grown more complex as technologies evolve. These parameters directly affect the shared decision with patients to start or withhold lipid-lowering therapies, to adjust statin intensity or LDL cholesterol goals. Emerging lipid lowering studies with non-invasive imaging as a guide to patient selection and treatment efficacy, plus the evolution of lipid lowering therapies from statins to a diverse armament of newer high-cost agents have pushed these two fields forward with a complex interaction. This review will discuss existing risk estimators, and non-invasive imaging techniques for subclinical coronary atherosclerosis, traditionally studied using CAC and more recently CCTA with qualitative and quantitative measurements. We will also explore the current data, gaps of knowledge and future directions on the use of these techniques in the risk-stratification and guidance of lipid management.

Global Circumferential and Radial Strain Among Patients With Immune Checkpoint Inhibitor Myocarditis

BACKGROUND

Global circumferential strain (GCS) and global radial strain (GRS) are reduced with cytotoxic chemotherapy. There are limited data on the effect of immune checkpoint inhibitor (ICI) myocarditis on GCS and GRS.

OBJECTIVES

This study aimed to detail the role of GCS and GRS in ICI myocarditis.

METHODS

In this retrospective study, GCS and GRS from 75 cases of patients with ICI myocarditis and 50 ICI-treated patients without myocarditis (controls) were compared. Pre-ICI GCS and GRS were available for 12 cases and 50 controls. Measurements were performed in a core laboratory blinded to group and time. Major adverse cardiovascular events (MACEs) were defined as a composite of cardiogenic shock, cardiac arrest, complete heart block, and cardiac death.

RESULTS

Cases and controls were similar in age (66 ± 15 years vs 63 ± 12 years; P = 0.20), sex (male: 73% vs 61%; P = 0.20) and cancer type (P = 0.08). Pre-ICI GCS and GRS were also similar (GCS: 22.6% ± 3.4% vs 23.5% ± 3.8%; P = 0.14; GRS: 45.5% ± 6.2% vs 43.6% ± 8.8%; P = 0.24). Overall, 56% (n = 42) of patients with myocarditis presented with preserved left ventricular ejection fraction (LVEF). GCS and GRS were lower in myocarditis compared with on-ICI controls (GCS: 17.5% ± 4.2% vs 23.6% ± 3.0%; P < 0.001; GRS: 28.6% ± 6.7% vs 47.0% ± 7.4%; P < 0.001). Over a median follow-up of 30 days, 28 cardiovascular events occurred. A GCS (HR: 4.9 [95% CI: 1.6-15.0]; P = 0.005) and GRS (HR: 3.9 [95% CI: 1.4-10.8]; P = 0.008) below the median was associated with an increased event rate. In receiver-operating characteristic (ROC) curves, GCS (AUC: 0.80 [95% CI: 0.70-0.91]) and GRS (AUC: 0.76 [95% CI: 0.64-0.88]) showed better performance than cardiac troponin T (cTnT) (AUC: 0.70 [95% CI: 0.58-0.82]), LVEF (AUC: 0.69 [95% CI: 0.56-0.81]), and age (AUC: 0.54 [95% CI: 0.40-0.68]). Net reclassification index and integrated discrimination improvement demonstrated incremental prognostic utility of GRS over LVEF (P = 0.04) and GCS over cTnT (P = 0.002).

CONCLUSIONS

GCS and GRS are lower in ICI myocarditis, and the magnitude of reduction has prognostic significance.

Association between immune checkpoint inhibitors and vascular endothelial growth factor targeted therapy with cardiovascular events

Background

The use of immune checkpoint inhibitors (ICI) has been associated with a 3-fold higher risk for cardiovascular events as compared to cancer patients who did not receive ICI. Therapies targeting vascular endothelial growth factor (VEGF) have also been associated with a wide range of cardiovascular events. The combination use of ICIs and VEGF inhibitors is currently approved as a treatment for patients with renal-cell carcinoma, hepatocellular carcinoma, non-small cell lung cancer, and endometrial cancer. Data are lacking whether the combination of ICIs and VEGF-targeted therapy is associated with an additional increase in cardiovascular events.

Purpose

To evaluate whether the combination use of ICI and VEGF targeted therapies are associated with a higher risk of cardiovascular events as compared to ICI therapy alone, we performed a retrospective matched case-control study.

Methods

Cases received both ICI and VEGF-targeted therapy (n=157), and control patients (n=157) only received ICI therapy. The primary outcome was a composite of cardiovascular events (myocardial infarction, coronary revascularization, ischemic stroke, deep venous thrombosis, and pulmonary embolism). Patients were censored at time of first event or at last date of follow up. Cox proportional hazard regression analysis was performed to calculate hazard ratio (HR) with 95% confidence interval (CI), counting only the first cardiovascular event.

Results

Baseline characteristics for the cases and controls are shown in Table 1. Overall cases (combination ICI and VEGF inhibitor) and controls (ICI alone) were not different with respect to age, type of cancer, and a prior history of any cardiovascular event. Cases received more ICI cycles as compared to controls (median of 7 [4–17] cycles vs. 4 [2–10] cycles, P&lt;0.001). Cases also had a longer follow-up time (334 [127–663] days vs. 201 [60–564] days, P=0.008) as compared to the control group. As compared to ICI alone, a similar risk for a composite cardiovascular event was observed in those who received both ICI and VEGF-targeted therapy (HR, 0.70 [95% CI, 0.39–1.25]; P=0.23, Table 1). In total, 21/157 patients had a composite cardiovascular event among the cases, who received the combination of ICI and VEGF inhibitor (9 DVT, one MI, 9 PE, two ischemic strokes) as compared to 25/157 among the controls, who received ICI alone (14 DVT, 3 MI, 7 PE, one ischemic stroke). The median time to event was not different between the two groups (126 [98–260] days vs. 145 [28–205] days, P=0.47).

Conclusion

We found that among 157 patients who received a combination of ICI and VEGF-targeted therapy and 157 matched control patients who only received ICI therapy, the risk for cardiovascular events was not different between the two groups.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding.

Pericardial disease in patients treated with immune checkpoint inhibitors

Background

There are limited data on the occurrence, associations and outcomes of pericardial effusions and pericarditis after treatment with immune checkpoint inhibitors (ICIs).

Purpose

To evaluate incidence of pericardial disease in patients treated with an ICI.

Methods

This was a retrospective study at a single academic center that compared 2842 consecutive patients who received ICIs with 2699 age- and cancer-type matched patients with metastatic disease who did not receive ICI (design 1). A pericardial event was defined as a composite outcome of pericarditis and new or worsening moderate or large pericardial effusion. The endpoints were obtained through chart review and were blindly adjudicated. To identify risk factors associated with a pericardial event, in a second analysis, we also compared patients who developed an event on an ICI to patients treated with an ICI who did not develop a pericardial event (design 2). Cox proportional hazard model and logistical regression analysis were performed to study the association between ICI use and pericardial disease as well as pericardial disease and mortality. An additional 6-week landmark analysis was performed to account for lead-time bias.

Results

There were 42 pericardial events in the patients treated with ICI (n=2842) over 193 days (interquartile range 64 to 411) with an incidence rate of 1.57 events per 100 person-years. There was a 4-fold increase in the risk for pericarditis or a pericardial effusion among patients on an ICI compared to controls not treated with ICI after adjusting for potential confounders (hazard ratio [HR] 4.37, 95% confidence interval [CI] 2.09–9.14, p&lt;0.001). Patients who developed pericardial disease while on an ICI had a trend for increased all-cause mortality (HR 1.53, 95% CI 0.99–2.36, p=0.05) compared to those who did not develop pericardial disease. When comparing those who developed pericardial disease after ICI treatment to those who did not, a higher dose of corticosteroid pre-ICI (&gt;0.7 mg/kg prednisone) was associated with increased risk of pericardial disease (HR 2.56, 95% CI 1.00–6.57, p=0.049).

Conclusions

ICI use was associated with an increased risk for development of pericardial disease among cancer patients and a pericardial event on an ICI was associated with a trend towards increased mortality.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): National Institutes of Health/National Heart, Lung, and Blood Institute; a gift from A. Curt Greer and Pamela Kohlberg

Pericardial disease in patients treated with immune checkpoint inhibitors

BACKGROUND

There are limited data on the occurrence, associations and outcomes of pericardial effusions and pericarditis on or after treatment with immune checkpoint inhibitors (ICIs).

METHODS

This was a retrospective study at a single academic center that compared 2842 consecutive patients who received ICIs with 2699 age- and cancer-type matched patients with metastatic disease who did not receive ICI. A pericardial event was defined as a composite outcome of pericarditis and new or worsening moderate or large pericardial effusion. The endpoints were obtained through chart review and were blindly adjudicated. To identify risk factors associated with a pericardial event, we compared patients who developed an event on an ICI with patients treated with an ICI who did not develop a pericardial event. Cox proportional-hazard model and logistical regression analysis were performed to study the association between ICI use and pericardial disease as well as pericardial disease and mortality. An additional 6-week landmark analysis was performed to account for lead-time bias.

RESULTS

There were 42 pericardial events in the patients treated with ICI (n=2842) over 193 days (IQR: 64-411), yielding an incidence rate of 1.57 events per 100 person-years. There was a more than fourfold increase in risk of pericarditis or a pericardial effusion among patients on an ICI compared with controls not treated with ICI after adjusting for potential confounders (HR 4.37, 95% CI 2.09 to 9.14, p<0.001). Patients who developed pericardial disease while on an ICI had a trend for increased all-cause mortality compared with patients who did not develop a pericardial event (HR 1.53, 95% CI 0.99 to 2.36, p=0.05). When comparing those who developed pericardial disease after ICI treatment with those who did not, a higher dose of corticosteroid pre-ICI (>0.7 mg/kg prednisone) was associated with increased risk of pericardial disease (HR 2.56, 95% CI 1.00 to 6.57, p=0.049).

CONCLUSIONS

ICI use was associated with an increased risk of development of pericardial disease among patients with cancer and a pericardial event on an ICI was associated with a trend towards increase in mortality.

Use of physiological information based on grayscale images to improve mass spectrometry imaging data analysis from biological tissues

The characterization of cancer tissues by matrix-assisted laser desorption ionization-mass spectrometry images (MALDI-MSI) is of great interest because of the power of MALDI-MS to understand the composition of biological samples and the imaging side that allows for setting spatial boundaries among tissues of different nature based on their compositional differences. In tissue-based cancer research, information on the spatial location of necrotic/tumoral cell populations can be approximately known from grayscale images of the scanned tissue slices. This study proposes as a major novelty the introduction of this physiologically-based information to help in the performance of unmixing methods, oriented to extract the MS signatures and distribution maps of the different tissues present in biological samples. Specifically, the information gathered from grayscale images will be used as a local rank constraint in Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) for the analysis of MALDI-MSI of cancer tissues. The use of this constraint, setting absence of certain kind of tissues only in clear zones of the image, will help to improve the performance of MCR-ALS and to provide a more reliable definition of the chemical MS fingerprint and location of the tissues of interest. The general strategy to address the analysis of MALDI-MSI of cancer tissues will involve the study of the MCR-ALS results and the posterior use of MCR-ALS scores as dimensionality reduction for image segmentation based on K-means clustering. The resolution method will provide the MS signatures and their distribution maps for each tissue in the sample. Then, the resolved distribution maps for each biological component (MCR scores) will be submitted as initial information to K-means clustering for image segmentation to obtain information on the boundaries of the different tissular regions in the samples studied. MCR-ALS prior to K-means not only provides the desired dimensionality reduction, but additionally resolved non-biological signal contributions are not used and the weight given to the different biological components in the segmentation process can be modulated by suitable preprocessing methods.

Clinical Outcomes After Treatment of Cocaine-Induced Chest Pain with Beta-Blockers: A Systematic Review and Meta-Analysis

BACKGROUND

Recent guidelines have suggested avoiding beta-blockers in the setting of cocaine-associated acute coronary syndrome. However, the available evidence is both scarce and conflicted. The purpose of this systematic review and meta-analysis is to investigate the evidence pertaining to the use of beta-blockers in the setting of acute cocaine-related chest pain and its implication on clinical outcomes.

METHODS

Electronic databases were systematically searched to identify literature relevant to patients with cocaine-associated chest pain who were treated with or without beta-blockers. We examined the end-points of in-hospital all-cause mortality and myocardial infarction. Pooled risk ratios (RR) and their 95% confidence intervals (CI) were calculated for all outcomes using a random-effects model.

RESULTS

Five studies with a total of 1447 patients were included. Our analyses found no differences between patients treated with or without beta-blockers for either myocardial infarction (RR 1.08; 95% CI, 0.61-1.91) or all-cause mortality (RR 0.75; 95% CI, 0.46-1.24). Heterogeneity among included studies was low to moderate.

CONCLUSION

This systematic review and meta-analysis suggests that beta-blocker use is not associated with adverse clinical outcomes in patients presenting with acute chest pain related to cocaine use.

Antibody targeting of claudin-1 as a potential colorectal cancer therapy

BACKGROUND

Metastatic colorectal cancer (mCRC) is one of the major causes of cancer-related death. Despite the substantial progress in mCRC management, it remains important to identify new therapeutic options and biological markers for personalized medicine. Here, we investigated the expression of claudin-1 (CLDN1), a major tight junction transmembrane protein, in the different colorectal cancer (CRC) molecular subtypes and then assessed the anti-tumor effect of a new anti-CLDN1 monoclonal antibody (mAb).

METHODS

Gene expression profiling and immunochemistry analysis of normal and tumor tissue samples from patients with stage IV CRC were used to determine CLDN1 gene expression. Then, the 6F6 mAb against CLDN1 extracellular part was generated. Its effect on CRC cell cycle, proliferation, survival and migration was assessed in vitro, using a 3D cell culture system, flow cytometry, clonogenic and migration assays. In vivo, 6 F6 mAb efficacy was evaluated in nude mice after subcutaneous xenografts or intrasplenic injection of CRC cells.

RESULTS

Compared with normal mucosa where it was almost exclusively cytoplasmic, in CRC samples CLDN1 was overexpressed (p < 0.001) and mainly localized at the membrane. Moreover, it was differentially expressed in the various CRC molecular subtypes. The strongest expressions were found in the consensus molecular subtype CMS2 (p < 0.001), the transit-ampliflying (p < 0.001) and the C5 subtypes (p < 0.001). Lower CLDN1 expression predicted a better outcome in the molecular subtypes C3 and C5 (p = 0.012 and p = 0.004, respectively). CLDN1 targeting with the 6 F6 mAb led to reduction of survival, growth and migration of CLDN1-positive cells. In preclinical mouse models, the 6F6 mAb decreased tumor growth and liver metastasis formation.

CONCLUSION

Our data indicate that CLDN1 targeting with an anti-CLDN1 mAb results in decreased growth and survival of CRC cells. This suggests that CLDN1 could be a new potential therapeutic target.

Molecular subtypes of metastatic colorectal cancer are associated with patient response to irinotecan-based therapies

BACKGROUND

Currently, metastatic colorectal cancer is treated as a homogeneous disease and only RAS mutational status has been approved as a negative predictive factor in patients treated with cetuximab. The aim of this study was to evaluate if recently identified molecular subtypes of colon cancer are associated with response of metastatic patients to first-line therapy.

PATIENTS AND METHODS

We collected and analysed 143 samples of human colorectal tumours with complete clinical annotations, including the response to treatment. Gene expression profiling was used to classify patients in three to six classes using four different molecular classifications. Correlations between molecular subtypes, response to treatment, progression-free and overall survival were analysed.

RESULTS

We first demonstrated that the four previously described molecular classifications of colorectal cancer defined in non-metastatic patients also correctly classify stage IV patients. One of the classifications is strongly associated with response to FOLFIRI (P=0.003), but not to FOLFOX (P=0.911) and FOLFIRI + Bevacizumab (P=0.190). In particular, we identify a molecular subtype representing 28% of the patients that shows an exceptionally high response rate to FOLFIRI (87.5%). These patients have a two-fold longer overall survival (40.1 months) when treated with FOLFIRI, as first-line regimen, instead of FOLFOX (18.6 months).

CONCLUSIONS

Our results demonstrate the interest of molecular classifications to develop tailored therapies for patients with metastatic colorectal cancer and a strong impact of the first-line regimen on the overall survival of some patients. This however remains to be confirmed in a large prospective clinical trial.

Meta-Analysis of Randomized Trials on the Efficacy and Safety of Angiotensin-Converting Enzyme Inhibitors in Patients ≥65 Years of Age

The comparative efficacy and safety of angiotensin-converting enzyme inhibitors (ACEIs) with other agents in patients ≥65 years of age with cardiovascular diseases or at-risk are unknown. Electronic databases were systematically searched to identify all randomized controlled trials that compared ACEIs with control (placebo or active) and reported long-term cardiovascular outcomes. We required the mean age of patients in the studies to be ≥65 years. Random-effects model was used to pool study results. Sixteen trials with 104,321 patients and a mean follow-up of 2.9 years were included. Compared with placebo, ACEIs significantly reduced all outcomes except stroke. Compared with active controls, ACEIs had similar effect on all-cause mortality (relative risk [RR] 0.99, 95% confidence interval [CI] 0.95 to 1.03), cardiovascular mortality (RR 0.99, 95% CI 0.93 to 1.04), heart failure (RR 0.97, 95% CI 0.91 to 1.03), myocardial infarction (RR 0.94, 95% CI 0.88 to 1.00), and stroke (RR 1.07, 95% CI 0.99 to 1.15). ACEIs were associated with an increased risk of angioedema (RR 2.79, 95% CI 1.05 to 7.42), whereas risk for hypotension and renal insufficiency was similar compared with active controls. Meta-regression analysis showed that the effect of ACEIs on outcomes remained consistent with age increasing ≥65 years. Sensitivity analysis excluding trials comparing ACEIs with angiotensin receptor blockers and heart failure trials yielded similar results, except for reduction in myocardial infarction. In conclusion, the efficacy of ACEIs was similar to active controls for mortality outcomes. Compared with placebo, there was evidence for reduction in cardiovascular outcomes; however, ACEIs failed to prevent stroke and increased the risk of angioedema, hypotension, and renal failure.

Mice knock out for the histone acetyltransferase p300/CREB binding protein-associated factor develop a resistance to amyloid toxicity

p300/CREB binding protein-associated factor (PCAF) regulates gene expression by acting through histone acetylation and as a transcription coactivator. Although histone acetyltransferases were involved in the toxicity induced by amyloid-beta (Abeta) peptides, nothing is known about PCAF. We here analyzed the sensitivity of PCAF knockout (KO) mice to the toxic effects induced by i.c.v. injection of Abeta(25-35) peptide, a nontransgenic model of Alzheimer's disease. PCAF wild-type (WT) and KO mice received Abeta(25-35) (1, 3 or 9 nmol) or scrambled Abeta(25-35) (9 nmol) as control. After 7 days, Abeta(25-35) toxicity was measured in the hippocampus of WT mice by a decrease in CA1 pyramidal cells and increases in oxidative stress, endoplasmic reticulum stress and induction of apoptosis. Memory deficits were observed using spontaneous alternation, water-maze learning and passive avoidance. Non-treated PCAF KO mice showed a decrease in CA1 cells and learning alterations. However, Abeta(25-35) injection failed to induce toxicity or worsen the deficits. This resistance to Abeta(25-35) toxicity did not involve changes in glutamate or acetylcholine systems. Examination of enzymes involved in Abeta generation or degradation revealed changes in transcription of presenilins, activity of neprilysin (NEP) and an absence of Abeta(25-35)-induced regulation of NEP activity in PCAF KO mice, partly due to an altered expression of somatostatin (SRIH). We conclude that PCAF regulates the expression of proteins involved in Abeta generation and degradation, thus rendering PCAF KO insensitive to amyloid toxicity. Modulating acetyltransferase activity may offer a new way to develop anti-amyloid therapies.

The interferon-inducible Staf50 gene is downregulated during T cell costimulation by CD2 and CD28

It is well established that interferons (IFN) exert potent regulatory effects on the immune system. We have recently isolated a new IFN-induced human cDNA coding for a member of the Ring finger B-box/B30.2 subfamily that localizes to the chromosome band 11p15. We have named it Staf50. We show in this report that Staf50 is expressed in resting T cells in the absence of exogenous IFN treatment and is strongly repressed during T cell activation by anti-CD28 and anti-CD2 monoclonal antibodies (mAb) at both messenger and protein levels. In addition, we show that several members of the Ring finger B-box/B30.2 subfamily, including the 52-kDa SSA/Ro autoantigen, localize to the same chromosome band, 11p15, and are upregulated by IFN. These data led us to define a family of IFN-induced genes clustered on chromosome 11p15 that may be involved in T cell regulatory processes.

A unique ISRE, in the TATA-less human Isg20 promoter, confers IRF-1-mediated responsiveness to both interferon type I and type II

Interferons (IFNs) encode a family of secreted proteins involved in a number of regulatory functions such as control of cell proliferation, differentiation and regulation of the immune system. Their diverse biological actions are thought to be mediated by the products of specific but usually overlapping sets of cellular genes induced in the target cells. We have recently isolated a human cDNA encoding a new nuclear bodies-associated protein (PML-NBs), which we have termed Isg20. In this report, we describe the cloning and functional characterization of the Isg20 promoter region and the identification of sequence elements and trans-acting factors implicated in its regulation. In the absence of any recognizable TATA or CAAT elements, Isg20 promoter basal activity is dependent upon the positive transcription factors Sp-1 and USF-1. Interestingly, we demonstrate that a unique interferon stimulated response element (ISRE) mediates both IFN type I and type II Isg20 induction in the absence of functional gamma-activated sequence. These inductions are strictly dependent upon of the IFN regulatory factor 1 (IRF-1). In addition, we show that the ISRE is also implicated in the constitutive transcriptional activity of Isg20 gene.

[Interferon signaling pathways]

Interferons (IFNs) encode a large family of multifonctional secreted proteins that are involved in antiviral defense, the regulation of cell growth and modulation of the immune response. They are subdivided into two types that activate transduction pathways via different cell surface receptors. Binding of both IFN type I and II results in the differential activation of JAK (Janus kinases) that phosphorylate latent cytoplasmic transcription factors termed STATs (signal transducer and activator of transcription). Phosphorylated STATs translocate to the nucleus, bind specific DNA elements and direct transcription. Type I IFN induces the phosphorylation of STAT1 and STAT2 proteins by tyrosine phosphorylation involving the type I IFN receptor-associated tyrosine kinases TYK2 and JAK1. Following phosphorylation, STAT1 and STAT2 form the transcriptionally active IFN-stimulated gene factor 3 (ISGF3) by association with a protein of the IFN regulatory factor (IRF) family, p48. The specificity of the transcriptional activation by ISGF3 is mediated by specific elements termed IFN-stimulatory response element (ISRE) located in the promoter region of IFN-inducible genes. ISREs drive the expression of most IFN type I-regulated genes and a few IFN type II-regulated genes. Gene induction by type II IFN involves the phosphorylation of only STAT1 by JAK1 and Jak2 kinases. This phosphorylation generates a homodimer of STAT1 which is able to bind the IFNgamma-activated site (GAS) to activate transcription. This signaling is rapid and direct. Molecules involved in the IFN signaling pathways have been shown to be used by other polypeptide ligands in their own signal transduction pathways. Pathways other than JAK/STAT are also involved in IFN signaling, but their mechanisms are less clear. The best documented are the mitogen-activated protein kinase (MAPK) cascade, the components of the TCR (T cell receptor) signaling cascade and the Pi3 kinase pathway.

Molecular cloning of a new interferon-induced PML nuclear body-associated protein

Transcriptional induction of genes is an essential part of the cellular response to interferons. We have established a cDNA library from human lymphoblastoid Daudi cells treated for 16 h with human alpha/beta-interferon (IFN) and made use of differential screening to search for as yet unidentified IFN-regulated genes. In the course of this study, we have isolated a human cDNA that codes for a 20-kDa protein sharing striking homology with the product of the Xenopus laevis XPMC2 gene. This new gene is induced by both type I and II IFNs in various cell lines and will be referred to as ISG20 for interferon-stimulated gene product of 20 kDa. Confocal immunofluorescence analysis of the subcellular localization of ISG20 protein reveals that it is closely associated with PML and SP100 gene products within the large nuclear matrix-associated multiprotein complexes termed the PML nuclear bodies.

Quantitative analysis of the expression of the HLA-DRB genes at the transcriptional level by competitive polymerase chain reaction

In addition to polymorphism of the peptide-binding site, the density of the MHC class II molecules expressed on the membrane of APC could well play a significant role in the MHC-peptide-TCR interaction during the immune response. We therefore investigated the regulation of the expression of the HLA-DRB genes at the transcriptional level. A competitive PCR approach was used to estimate the quantities of the HLA-DRB transcripts in peripheral blood B cells. When comparing the amounts of steady-state mRNAs among the different DRB1 alleles, the DRB1 transcripts in the DR52 haplotype group were found to be 2.5 to 3.5 times more abundant than the DRB1*01 transcripts, 1.5 to 2 times more abundant than the DRB1*04 transcripts, and 7 times more abundant than the DRB1*08 transcripts. Within the DR52 haplotype group, the DRB1 and DRB3 transcripts had the same abundance. Taken together, these results are in good agreement with the previously reported transcriptional activities of the DRB promoters except for DRB1*04, thus suggesting a differential post-transcriptional regulation among the DRB1 mRNAs.

Quantitative analysis of the expression of the HLA-DRB genes at the transcriptional level by competitive polymerase chain reaction

In addition to polymorphism of the peptide-binding site, the density of the MHC class II molecules expressed on the membrane of APC could well play a significant role in the MHC-peptide-TCR interaction during the immune response. We therefore investigated the regulation of the expression of the HLA-DRB genes at the transcriptional level. A competitive PCR approach was used to estimate the quantities of the HLA-DRB transcripts in peripheral blood B cells. When comparing the amounts of steady-state mRNAs among the different DRB1 alleles, the DRB1 transcripts in the DR52 haplotype group were found to be 2.5 to 3.5 times more abundant than the DRB1*01 transcripts, 1.5 to 2 times more abundant than the DRB1*04 transcripts, and 7 times more abundant than the DRB1*08 transcripts. Within the DR52 haplotype group, the DRB1 and DRB3 transcripts had the same abundance. Taken together, these results are in good agreement with the previously reported transcriptional activities of the DRB promoters except for DRB1*04, thus suggesting a differential post-transcriptional regulation among the DRB1 mRNAs.