Assessment of cardiovascular risk and physical activity: the role of cardiac-specific biomarkers in the general population and athletes.

The first part of this Inter-Society Document describes the mechanisms involved in the development of cardiovascular diseases, particularly arterial hypertension, in adults and the elderly. It will also examine how consistent physical exercise during adolescence and adulthood can help maintain blood pressure levels and prevent progression to symptomatic heart failure. The discussion will include experimental and clinical evidence on the use of specific exercise programs for preventing and controlling cardiovascular diseases in adults and the elderly. In the second part, the clinical relevance of cardiac-specific biomarkers in assessing cardiovascular risk in the general adult population will be examined, with a focus on individuals engaged in sports activities. This section will review recent studies that suggest a significant role of biomarkers in assessing cardiovascular risk, particularly the presence of cardiac damage, in athletes who participate in high-intensity sports. Finally, the document will discuss the potential of using cardiac-specific biomarkers to monitor the effectiveness of personalized physical activity programs (Adapted Physical Activity, APA). These programs are prescribed for specific situations, such as chronic diseases or physical disabilities, including cardiovascular diseases. The purposes of this Inter-Society Document are the following: 1) to discuss the close pathophysiological relationship between physical activity levels (ranging from sedentary behavior to competitive sports), age categories (from adolescence to elderly age), and the development of cardiovascular diseases; 2) to review in detail the experimental and clinical evidences supporting the role of cardiac biomarkers in identifying athletes and individuals of general population at higher cardiovascular risk; 3) to stimulate scientific societies and organizations to develop specific multicenter studies that may take into account the role of cardiac biomarkers in subjects who follow specific exercise programs in order to monitor their cardiovascular risk.

Variability of cardiac troponin levels in normal subjects and in patients with cardiovascular diseases: analytical considerations and clinical relevance.

In accordance with all the most recent international guidelines, the variation of circulating levels of cardiac troponins I and T, measured with high-sensitivity methods (hs-cTnI and hs-cTnT), should be used for the detection of acute myocardial injury. Recent experimental and clinical evidences have demonstrated that the evaluation of hs-cTnI and hs-cTnT variations is particularly relevant: a) for the differential diagnosis of Acute Coronary Syndromes (ACS) in patients admitted to the Emergency Department (ED); b) for the evaluation of cardiovascular risk in patients undergoing major cardiac or non-cardiac surgery, and in asymptomatic subjects of the general population aged >55 years and with co-morbidities; c) for the evaluation of cardiotoxicity caused by administration of some chemotherapy drugs in patients with malignant tumors. The aim of this document is to discuss the fundamental statistical and biological considerations on the intraindividual variability of hs-cTnI and hs-cTnT over time in the same individual. Firstly, it will be discussed in detail as the variations of circulating levels strictly depend not only on the analytical error of the method used but also on the intra-individual variability of the biomarker. Afterwards, the pathophysiological interpretation and the clinical relevance of the determination of the variability of the hs-cTnI and hs-cTnT values ​​ in patients with specific clinical conditions are discussed. Finally, the evaluation over time of the variation in circulating levels of hs-cTnI and hs-cTnT is proposed for a more accurate estimation of cardiovascular risk in asymptomatic subjects from the general population.

Use of high-sensitivity cardiac troponins in the emergency department for the early rule-in and rule-out of acute myocardial infarction without persistent ST-segment elevation (NSTEMI) in Italy.

Serial measurements of cardiac troponin are recommended by international guidelines to diagnose myocardial infarction (MI) since 2000. However, some relevant differences exist between the three different international guidelines published between 2020 and 2021 for the management of patients with chest pain and no ST-segment elevation. In particular, there is no agreement on the cut-offs or absolute change values to diagnose non-ST-segment elevation MI (NSTEMI). Other controversial issues concern the diagnostic accuracy and cost-effectiveness of cut-off values for the most rapid algorithms (0 h/1 h or 0 h/2 h) to rule-in and rule-out NSTEMI. Finally, another important point is the possible differences between demographic and clinical characteristics of patients enrolled in multicenter trials compared to those routinely admitted to the Emergency Department in Italy. The Study Group of Cardiac Biomarkers, supported by the Italian Scientific Societies Società Italiana di Biochimica Clinica, Italian Society of the European Ligand Assay Society, and Società Italiana di Patolgia Clinica e Medicina di Laboratorio decided to revise the document previously published in 2013 about the management of patients with suspected NSTEMI, and to provide some suggestions for the use of these biomarkers in clinical practice, with a particular focus on the Italian setting.

Aqueous Humor Analysis in Overlapping Clinical Diagnosis of Cytomegalovirus and Rubella Virus Anterior Uveitis.

Background and Objectives: A cross-sectional single-center study was conducted to investigate the etiology in hypertensive anterior uveitis whose clinical features are not fully distinctive from cytomegalovirus or from rubella virus and to demonstrate the possible coexistence of both these viruses in causing anterior uveitis. Materials and Methods: The clinical charts of a cohort of patients with hypertensive viral anterior uveitis of uncertain origin consecutively seen in a single center from 2019 to 2022 were retrospectively reviewed; data on the clinical features, aqueous polymerase chain reaction, and antibody response to cytomegalovirus and rubella virus were collected. Results: Forty-three eyes of as many subjects with viral anterior uveitis of uncertain origin were included. Thirty-two patients had an aqueous polymerase chain reaction or antibody index positive to cytomegalovirus only, while 11 cases had an aqueous antibody response to both cytomegalovirus and rubella virus. This latter overlapping group had a statistically significant higher rate of hypochromia and anterior vitritis (p-value: 0.02 and < 0.001, respectively). Conclusions: The simultaneous presence of intraocular antibodies against cytomegalovirus and rubella virus could redefine the differential diagnosis of hypertensive viral anterior uveitis, demonstrating a possible "converged" immune pathway consisting in a variety of stimuli.

Are Individuals with Substance Use Disorders at Higher Risk of SARS-CoV-2 Infection? Population-Based Registry Study in Northern Italy.

BACKGROUND AND AIM: This study assesses whether individuals with substance use disorder are at greater risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than people in the general population. METHODS: A population-based study was conducted including 3,780 individuals, diagnosed with alcohol or other drug dependence and cared for by the addiction service (AS) in the province of Reggio Emilia. Standardised incidence ratios (SIRs) and relative 95% confidence intervals (CIs) of being tested and of being SARS-CoV-2 positive in the population of interest compared with those in the general population of Reggio Emilia were calculated. RESULTS: Both individuals with alcohol and those with other drug use disorders had a lower risk of being SARS-CoV-2 positive (SIR = 0.69; 95% CI 0.32-1.30, SIR = 0.56; 95% CI 0.24-1.10, respectively), despite higher rates of being tested than the general population (SIR = 1.48; 95% CI 1.14-1.89, SIR = 1.51; 95% CI 1.20-1.86, respectively). Among HIV-negative persons, 12.5% were positive to SARS-CoV-2, while none was positive among HIV-positive persons. HCV-infected AS clients had a higher risk of both being tested for SARS-CoV-2 (SIR = 1.99; 95% CI 1.26-2.98) and of resulting positive (SIR = 1.53; 95% CI 0.50-3.58). CONCLUSIONS: Individuals with alcohol and/or other drug use disorders are at higher risk of being tested for SARS-CoV-2 infection but at lower risk of resulting positive than the general population. Further research is warranted in order to support our findings and to address plausible factors underpinning such associations.

Acute-phase reactants during tocilizumab therapy for severe COVID-19 pneumonia.

OBJECTIVES: To identify predictors of clinical improvement and intubation/death in tocilizumab-treated severe COVID19, focusing on IL6 and CRP longitudinal monitoring. METHODS: 173 consecutive patients with severe COVID-19 pneumonia receiving tocilizumab in Reggio Emilia province Hospitals between 11 March and 3 June 2020 were enrolled in a prospective cohort study. Clinical improvement was defined as status improvement on a six-category ordinal scale or discharge from the hospital, whichever came first. A composite outcome of intubation/death was also evaluated. CRP and IL-6 levels were determined before TCZ administration (T0) and after 3 (T3), and 7 (T7) days. RESULTS: At multivariate analysis T0 and T3 CRP levels were negatively associated with clinical improvement (OR 0.13, CI 0.03-0.55 and OR 0.11, CI 0.0-0.46) (p=0.006 and p=0.003) and positively associated with intubation/death (OR 17.66, CI 2.47-126.14 and OR 5.34, CI: 1.49-19.12) (p=0.01 and p=0.004). No significant associations with IL-6 values were observed. General linear model analyses for repeated measures showed significantly different trends for CRP from day 3 to day 7 between patients who improved and those who did not, and between patients who were intubated or died and those who were not (p<0.0001 for both). ROC analysis identified a baseline CRP level of 15.8 mg/dl as the best cut-off to predict intubation/death (AUC = 0.711, sensitivity = 0.67, specificity = 0.71). CONCLUSIONS: CRP serial measurements in the first week of TCZ therapy are useful in identifying patients developing poor outcomes.

The therapeutic potential of tuftsin-phosphorylcholine in giant cell arteritis.

Tuftsin-PhosphorylCholine (TPC) is a novel bi-specific molecule which links tuftsin and phosphorylcholine. TPC has shown immunomodulatory activities in experimental mouse models of autoimmune diseases. We studied herein the effects of TPC ex vivo on both peripheral blood mononuclear cells (PBMCs) and temporal artery biopsies (TABs) obtained from patients with giant cell arteritis (GCA) and age-matched disease controls. GCA is an immune-mediated disease affecting large vessels. Levels of 18 cytokines in supernatants, PBMC viability, T helper (Th) cell differentiation of PBMCs and gene expression in TABs were analyzed. Treatment ex vivo with TPC decreased the production of IL-1ß, IL-2, IL-5, IL-6, IL-9, IL-12(p70), IL-13, IL-17A, IL-18, IL-21, IL-22, IL-23, IFNγ, TNFα, GM-CSF by CD3/CD28 activated PBMCs whereas it negligibly affected cell viability. It reduced Th1 and Th17 differentiation while did not impact Th22 differentiation in PBMCs stimulated by phorbol 12-myristate 13-acetate plus ionomycin. In inflamed TABs, treatment with TPC down-regulated the production of IL-1ß, IL-6, IL-13, IL-17A and CD68 gene expression. The effects of TPC were comparable to the effects of dexamethasone, included as the standard of care, with the exception of a greater reduction of IL-2, IL-18, IFNγ in CD3/CD28 activated PBMCs and CD68 gene in inflamed TABs. In conclusion our results warrant further investigations regarding TPC as an immunotherapeutic agent in GCA and potentially other autoimmune and inflammatory diseases.

Increased expression of interleukin-22 in patients with giant cell arteritis.

Objectives: GCA is characterized by arterial remodelling driven by inflammation. IL-22 is an attractive cytokine which acts at the crosstalk between immune and stromal cells. We hypothesized that IL-22 might be induced in GCA and might be involved in disease pathogenesis. Methods: Patients subjected to temporal artery biopsies (TABs) naïve from therapy were enrolled: 27 biopsy-proven GCA, 8 biopsy-negative GCA, 21 biopsy-negative non-GCA patients. Expression of IL-22 was determined in TABs by immunohystochemistry, in plasma by ELISA, in peripheral blood mononuclear cells by real-time PCR and flow cytometry. Effects of IL-22 on viability and gene expression of primary cultures obtained from TABs were also evaluated. Results: Inflamed TABs from GCA patients showed a higher expression of IL-22 and IL-22 specific receptor subunit (IL-22R1) than non-inflamed TABs. IL-22 was expressed in infiltrating immune cells and spindle shaped cells, IL-22R1 was expressed in endothelial cells. Patients with biopsy-proven GCA showed increased levels of IL-22 in plasma than patients with biopsy-negative GCA, without GCA and healthy subjects. Peripheral blood mononuclear cells from GCA patients expressed higher IL-22 transcript than healthy subjects. After stimulation in vitro with phorbol 12-myristate 13-acetate and ionomycin, the frequencies of Th22 and IL-22+ CD4+ lymphocytes were similar between patients with and without GCA. Treatment with IL-22 of primary cultures obtained from TABs increased cell viability under stress conditions and expression of B-cell activating factor. Conclusion: IL-22 is increased in patients with GCA and affects viability and gene expression of arterial cells, supporting a potential role in disease pathogenesis.

A Black Swan in clinical laboratory practice: the analytical error due to interferences in immunoassay methods.

It is well known that the results of immunoassay methods can be affected by specific or non-specific interferences, ranging from 0.4% to 4.0%. The presence of interference may greatly compromise the accuracy of immunoassay analyses causing an error in the measurement, producing false-positive or false-negative results. From a clinical point of view, these analytical errors may have serious implications for patient care because they can cause misdiagnosis or inappropriate treatment. Unfortunately, it is a very difficult task to identify the irregular analytical errors related to immunoassay methods because they are not detectable by normal laboratory quality control procedures, are reproducible within the test system, may be clinically plausible and are relatively rare. The first line of defense against erroneous results is to use in laboratory practice only immunoassay systems with the highest level of robustness against interference. The second line of defense is always taking into account the possibility of interference in immunoassay results. A correct approach should be addressed on identification of samples at high risk of interference. The attainment of this goal requires a critical review of the test result in relation to patient's clinical conditions and literature data, taking into account the analytical characteristics of the immunoassay system. The experts in immunoassay systems should make every effort to find some specific and reliable quality indicators for irregular analytical errors in order to better detect and monitor erroneous immunoassay results due to specific or non-specific interferences.

Searching for viral antibodies and genome in intraocular fluids of patients with Fuchs uveitis and non-infectious uveitis.

BACKGROUND: To characterise the polyspecific intraocular antibody synthesis in aqueous humor of patients with Fuchs uveitis and other types of non-infectious uveitis. METHODS: Aqueous and serum samples collected from 24 patients with Fuchs uveitis, 21 patients with non-infectious uveitis, and 27 healthy subjects undergoing elective cataract surgery (control group) were analysed. In addition, vitreous samples, collected from seven uveitis patients (five Fuchs and two panuveitis) during retinal surgery, were examined. Specific immunoglobulin G antibodies against cytomegalovirus (CMV), rubella virus, herpes simplex virus (HSV), and varicella zoster virus (VZV) were investigated, and Goldmann-Witmer coefficients (GWCs) were calculated. Real-time PCR was performed to detect viral genome for HSV, VZV, and CMV, while nested PCR was conducted to detect rubella RNA. RESULTS: None of the control samples tested positive for any of the viral antibodies investigated. Intraocular antibody production was found in eight samples of patients affected by Fuchs uveitis (6/8 positive for rubella virus and 2/8 positive for herpes virus). Among patients with non-infectious uveitis, three tested positive for intraocular antibody production (one RV, one HSV and one for VZV). PCR was positive for RV in two patients with Fuchs uveitis, in three patients with non-infectious uveitis (one for RV and two for HSV), and in three control subjects (one for CMV and one for HSV). CONCLUSIONS: Our series confirmed the presence of specific viral antibodies, especially against rubella virus, in the subgroup of patients affected by Fuchs uveitis, suggesting that this virus may be responsible for this chronic inflammatory condition. Rubella virus is probably the main causative agent of Fuchs uveitis, but other viruses may also be involved in the pathogenesis of this disease.

Artificial Intelligence-Assisted Processing of Anterior Segment OCT Images in the Diagnosis of Vitreoretinal Lymphoma.

Anterior segment optical coherence tomography (AS-OCT) allows the explore not only the anterior chamber but also the front part of the vitreous cavity. Our cross-sectional single-centre study investigated whether AS-OCT can distinguish between vitreous involvement due to vitreoretinal lymphoma (VRL) and vitritis in uveitis. We studied AS-OCT images from 28 patients (11 with biopsy-proven VRL and 17 with differential diagnosis uveitis) using publicly available radiomics software written in MATLAB. Patients were divided into two balanced groups: training and testing. Overall, 3260/3705 (88%) AS-OCT images met our defined quality criteria, making them eligible for analysis. We studied five different sets of grey-level samplings (16, 32, 64, 128, and 256 levels), finding that 128 grey levels performed the best. We selected the five most effective radiomic features ranked by the ability to predict the class (VRL or uveitis). We built a classification model using the xgboost python function; through our model, 87% of eyes were correctly diagnosed as VRL or uveitis, regardless of exam technique or lens status. Areas under the receiver operating characteristic curves (AUC) in the 128 grey-level model were 0.95 [CI 0.94, 0.96] and 0.84 for training and testing datasets, respectively. This preliminary retrospective study highlights how AS-OCT can support ophthalmologists when there is clinical suspicion of VRL.

Viral anterior uveitis.

Anterior uveitis has various causes, but the majority of cases are viral induced. The most common viral anterior uveitis etiology includes double-stranded DNA viruses of the Herpesviridae family, including Alpha herpes virinae (herpes simplex 1 and 2 and varicella zoster virus), Beta herpesvirinae (cytomegalovirus), and less frequently, Gamma herpesvirinae (Epstein-Barr virus). In the last few decades, a growing body of evidence has correlated Fuchs uveitis etiology to the rubella virus from the Matonaviridae family, which has a single-stranded RNA genome. The clinical presentation of each of these uveitis is hypertensive granulomatous anterior uveitis; however, the very slight differences between them, which often overlap, make differential diagnosis sometimes difficult. Therefore, diagnostic laboratory tests such as polymerase chain reaction and antibody index or Goldmann-Witmer coefficient analyses on the aqueous humor help to identify the etiology in doubtful cases and thus to plan targeted treatment.

Optimization of Laboratory Diagnostics of Primary Biliary Cholangitis: When Solid-Phase Assays and Immunofluorescence Combine.

The laboratory diagnostics of primary biliary cholangitis (PBC) have substantially improved, thanks to innovative analytical opportunities, such as enzyme-linked immunosorbent assays (ELISA) and multiple immunodot liver profile tests, based on recombinant or purified antigens. This study aimed to identify the best diagnostic test combination to optimize PBC diagnosis. Between January 2014 and March 2017, 164 PBC patients were recruited at the hospitals of Parma, Modena, Reggio-Emilia, and Piacenza. Antinuclear antibodies (ANA) and anti-mitochondrial antibodies (AMA) were assayed by indirect immunofluorescence (IIF), ELISA, and immunodot assays (PBC Screen, MIT3, M2, gp210, and sp100). AMA-IIF resulted in 89.6% positive cases. Using multiple immunodot liver profiles, AMA-M2 sensitivity was 94.5%, while anti-gp210 and anti-sp100 antibodies were positive in 16.5% and 17.7% of patients, respectively. PBC screening yielded positive results in 94.5% of cases; MIT3, sp100, and gp210 were detected by individual ELISA test in 89.0%, 17.1%, and 18.9% of patients, respectively. The association of PBC screening with IIF-AMA improved the diagnostic sensitivity from 89.6% to 98.2% (p < 0.01). When multiple immunodot liver profile testing was integrated with AMA-IIF, the diagnostic sensitivity increased from 89.1% to 98.8% (p < 0.01). The combination of IIF with solid-phase methods significantly improved diagnostic efficacy in PBC patients.

Uveitis and Other Ocular Complications Following COVID-19 Vaccination.

Coronavirus disease 2019 (COVID-19) vaccines can cause transient local and systemic post-vaccination reactions. The aim of this study was to report uveitis and other ocular complications following COVID-19 vaccination. The study included 42 eyes of 34 patients (20 females, 14 males), with a mean age of 49.8 years (range 18-83 years). The cases reported were three herpetic keratitis, two anterior scleritis, five anterior uveitis (AU), three toxoplasma retinochoroiditis, two Vogt-Koyanagi-Harada (VKH) disease reactivations, two pars planitis, two retinal vasculitis, one bilateral panuveitis in new-onset Behçet's disease, three multiple evanescent white dot syndromes (MEWDS), one acute macular neuroretinopathy (AMN), five retinal vein occlusions (RVO), one non-arteritic ischemic optic neuropathy (NAION), three activations of quiescent choroidal neovascularization (CNV) secondary to myopia or uveitis, and one central serous chorioretinopathy (CSCR). Mean time between vaccination and ocular complication onset was 9.4 days (range 1-30 days). Twenty-three cases occurred after Pfizer-BioNTech vaccination (BNT162b2 mRNA), 7 after Oxford-AstraZeneca vaccine (ChAdOx1 nCoV-19), 3 after ModernaTX vaccination (mRNA-1273), and 1 after Janssen Johnson & Johnson vaccine (Ad26.COV2). Uveitis and other ocular complications may develop after the administration of COVID-19 vaccine.

Human Dental Pulp Stem Cells Modulate Cytokine Production in vitro by Peripheral Blood Mononuclear Cells From Coronavirus Disease 2019 Patients.

A subset of patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) developed a condition of hyper-inflammation, which can cause multi-organ damage and the more severe forms of coronavirus disease 2019 (COVID-19). Mesenchymal stem cells (MSCs) can promote tissue regeneration and modulate immune responses and, thus, have the rational requirements to be used to counteract SARS-CoV-2-induced pneumonia and hyper-inflammation. The aim of the present study was to gain insight into possible mechanisms of action of MSCs obtained from human dental pulp [dental pulp stem cells (DPSCs)] in COVID-19 patients. We investigated the concentrations of 18 cytokines in supernatants of peripheral blood mononuclear cells (PBMCs) obtained from COVID-19 patients cultured in vitro alone and in contact with DPSCs. The modulation of cytokines in PBMCs was confirmed by real-time PCR. IL-6 was the sole cytokine detected in supernatants of DPSCs. In resting conditions, co-culture increased IL-1ß, IL-2, IL-5, IL-6, IL-10, IL-18, TNFα, and granulocyte macrophage colony-stimulating factor (GM-CSF) levels. When PBMCs were activated with anti-CD3/CD28 antibody-coated beads, co-culture increased IL-6 and GM-CSF, whereas it decreased IFNγ, TNFα, IL-2, IL-5, IL-9, IL-10, IL-12 (p70), IL-17A, IL-18, IL-21, IL-23, and IL-27 levels. Concentrations of IL-1ß, IL-4, IL-13, and IL-22 were not affected. The comparison of cytokine concentrations in supernatants of PBMCs from COVID-19 patients vs. healthy subjects revealed lower concentrations of IL-10 and higher concentrations of IL-18 in supernatants of CD3/CD28-activated PBMCs from COVID-19 patients. Results are explorative but indicate that DPSCs can modulate the production of cytokines deregulated in COVID-19 patients, supporting their potential use in COVID-19.

Cytokine Profiling in Aqueous Humor Samples From Patients With Non-Infectious Uveitis Associated With Systemic Inflammatory Diseases.

Non-infectious uveitis are intraocular inflammatory conditions caused by dysregulated activation of the immune response without any detectable infectious agents. The aim of this study was to explore potential markers and therapeutic targets for two distinct types of non-infectious uveitis associated with Behçet's disease (BD) and Vogt Koyanagi Harada (VKH) disease. Concentrations of 27 cytokines were investigated in aqueous humor (AH) samples from patients with active uveitis vs. healthy controls (HC) (n = 10 patients with BD-associated uveitis; n = 10 patients with VKH-associated uveitis; n = 10 HC) using the Bio-Plex ProTM human cytokine group I panel. Additionally, leukocytes in AH samples were counted with hemocytometers and characterized by flow cytometry. Eleven cytokines were differentially expressed between patients with uveitis and HC with a median concentration greater than 10 pg/ml. IL-6, IP-10, G-CSF, and IFNγ showed higher concentrations in AH samples from both BD and VKH patients while IL-2, IL-8, IL-13, TNFα, eotaxin, IL-1ra showed statistically significant higher concentrations only in AH samples from BD patients. GM-CSF was the sole cytokine with an opposite profile showing decreased levels in AH samples from BD patients. IL-1ra and IL-6 were detected at higher frequencies in AH samples from BD and VKH patients compared with those from HC while IFNγ and TNFα were not detected in HC. The concentrations of IL-6, IL-8, IP-10, G-CSF, IFNγ, TNFα, eotaxin, IL-1ra positively correlated with the concentrations of leukocytes in AH, suggesting that such cytokines can be produced by immune cells and/or attract and/or promote proliferation and survival of immune cells in these types of uveitis. The correlation matrix of cytokine concentrations in AH samples revealed that IFNγ, TNFα, eotaxin, IL-6, G-CSF highly correlated each other. The ratios of cytokine concentrations between AH and plasma intra-individuals showed that IL-2, IL-6, IP-10, GM-CSF were increased intraocularly. In conclusion, AH sampling followed by multiplex analysis of cytokines should be fostered in non-infectious uveitis to identify cytokines dysregulated intraocularly in each individual laying the groundwork for precision medicine.

Clusterin is a short half-life, poly-ubiquitinated protein, which controls the fate of prostate cancer cells.

The Clusterin (CLU) gene produces different forms of protein products, which vary in their biological properties and distribution within the cell. Both the extra- and intracellular CLU forms regulate cell proliferation and apoptosis. Dis-regulation of CLU expression occurs in many cancer types, including prostate cancer. The role that CLU plays in tumorigenesis is still unclear. We found that CLU over-expression inhibited cell proliferation and induced apoptosis in prostate cancer cells. Here we show that depletion of CLU affects the growth of PC-3 prostate cancer cells. Following siRNA targeting all CLU mRNA variants, all protein products quickly disappeared, inducing cell cycle progression and higher expression of specific proliferation markers (i.e., H3 mRNA, PCNA, and cyclins A, B1, and D) as detected by RT-qPCR and Western blot. Quite surprisingly, we also found that the turnover of CLU protein is very rapid and tightly regulated by ubiquitin-proteasome mediated degradation. Inhibition of protein synthesis by cycloheximide showed that CLU half-life is less than 2 h. CLU protein products were found poly-ubiquitinated by co-immuniprecipitation. Proteasome inhibition by MG132 caused stabilization and accumulation of all CLU protein products, including the nuclear form of CLU (nCLU), and committing cells to caspase-dependent death. In conclusion, proteasome inhibition may induce prostate cancer cell death through accumulation of nCLU, a potential tumor suppressor factor.