A phase 2a open-label clinical trial to determine the effect of famciclovir on EBV activity as measured by EBV shedding in the saliva of patients with multiple sclerosis.

BACKGROUND: Despite increasing evidence that Epstein-Barr virus (EBV) plays a causal role in MS, no treatments have been shown to reduce EBV turnover. We studied the effect of famciclovir on salivary EBV shedding in people with MS (NCT05283551) in a pilot, proof-of-concept study. METHODS: People with MS receiving natalizumab provided weekly saliva samples for 12 weeks before starting famciclovir 500 mg twice daily for 12 weeks. Twelve saliva samples were provided on treatment and 12 following treatment. A real-time qPCR Taqman assay was used to detect EBV DNA in saliva. The proportion of saliva samples containing EBV DNA was compared using the Friedman test. RESULTS: Of 30 participants (19 F; mean age 41 years; median EDSS 3.5), 29 received famciclovir, and 24 completed the 12-week course. Twenty-one participants provided at least one usable saliva sample in all epochs. Ten of the 21 had shedding in at least one sample pre-drug; 7/21 when taking famciclovir (not significant). No difference in EBV DNA copy number was seen. There were no drug-related serious adverse events. CONCLUSION: No significant effect of famciclovir on EBV shedding was seen in this small pilot study. Given the low numbers, a small effect of famciclovir cannot be excluded. Salivary EBV shedding in this natalizumab-treated cohort was lower than in previous studies, which requires replication.

Disease activity 4.5 years after starting cladribine: experience in 264 patients with multiple sclerosis.

Background: Cladribine is an effective immunotherapy for people with multiple sclerosis (pwMS). Whilst most pwMS do not require re-treatment following standard dosing (two treatment courses), disease activity re-emerges in others. The characteristics of pwMS developing re-emerging disease activity remain incompletely understood. Objectives: To explore whether clinical and/or paraclinical baseline characteristics, including the degree of lymphocyte reduction, drug dose and lesions on magnetic resonance imaging (MRI) are associated with re-emerging disease activity. Design: Service evaluation in pwMS undergoing subcutaneous cladribine (SClad) treatment. Methods: Demographics, clinical, laboratory and MRI data of pwMS receiving two courses of SClad were extracted from health records. To assess associations of predictor variables with re-emerging disease activity, a series of Cox proportional hazards models was fitted (one for each predictor variable). Results: Of n = 264 pwMS 236 received two courses of SClad and were included in the analysis. Median follow-up was 4.5 years (3.9, 5.3) from the first, and 3.5 years (2.9, 4.3) from the last SClad administration. Re-emerging disease activity occurred in 57/236 pwMS (24%); 22/236 received further cladribine doses (SClad or cladribine tablets) at 36.7 months [median; interquartile range (IQR): 31.7, 42.1], and 22/236 other immunotherapies 18.9 months (13.0, 30.2) after their second course of SClad, respectively. Eligibility was based on MRI activity in 29, relapse in 5, both in 13, elevated cerebrospinal fluid neurofilament light chain level in 3, deterioration unrelated to relapse in 4 and other in 3. Only 36/57 of those eligible for additional immunotherapy had received a reduced dose of SClad for their second treatment course. Association was detected between re-emerging disease activity and (i) high baseline MRI activity and (ii) low second dose of SClad. Conclusion: Re-emerging disease activity was associated with baseline MRI activity and low dose second course of SClad.

The relationship of cerebrospinal fluid neurofilament levels with magnetic resonance imaging lesion location and disease activity in multiple sclerosis.

BACKGROUND AND PURPOSE: Neurofilament light chain (NfL) is an accepted biomarker of disease activity in multiple sclerosis (MS), but its relationship with magnetic resonance imaging (MRI) activity particularly in reference to lesion location and recurrent activity is not well understood. METHODS: In 139 MS patients who underwent lumbar punctures with follow-up in 25, the relationship between cerebrospinal fluid (CSF) NfL and cranial MRI based on lesion location and lesion number was evaluated. Spearman rank correlation was used to assess the association between CSF NfL and MRI lesion location and lesion counts at baseline and follow-up at 1 year. Multiple linear regression analysis was performed to assess which lesion location was most strongly associated with CSF NfL values. RESULTS: The associations between baseline CSF NfL and lesion location and follow-up lesions were modest, whilst those between baseline MRI and follow-up CSF NfL were greater: periventricular (r = 0.31, p = 0.141), juxtacortical (r = 0.47, p = 0.022), infratentorial (r = 0.71, p ≤ 0.001) and cord lesions (r = 0.60, p = 0.002). All associations, however, improved following adjustment for disease duration and type of MS. Modelling revealed 53% of (log) CSF NfL could be explained by variance in baseline MRI lesion location. CONCLUSIONS: Baseline CSF NfL did not correlate with current or future MRI activity and lesion location. However, baseline MRI activity explained around 53% of the variation in the follow-up CSF NfL, suggesting that the relationship between MRI and CSF NfL is mainly precedent rather than an association, that is one occurring before the other.

Factors contributing to CSF NfL reduction over time in those starting treatment for multiple sclerosis: An observational study.

BACKGROUND: In multiple sclerosis (MS) neurofilament light chain (NfL) is a marker of neuronal damage secondary to inflammation and neurodegeneration. NfL levels drop after commencement of disease-modifying treatment, especially the highly active ones. However, the factors that influence this drop are unknown. OBJECTIVE: To examine the patient and treatment-related factors that influence CSF NfL before and after starting treatment. METHODS: Eligible patients across two centres with two CSF NfL measurements, clinical and MRI data were included as part of an observational cohort study. RESULTS: Data were available in 61 patients, of which 40 were untreated at the first CSF sampling (T1) and treated at the second (T2; mean T1-T2: 19 months). CSF NfL reduction correlated with age (beta = 1.24 95%CI(1.07,1.43); R2 = 0.17; p = 0.005), Expanded Disability Status Scale (EDSS) (beta = 1.12 95%CI(1.00,1.25); R2 = 0.21; p = 0.05) and the type of MS (beta = 0.63 95%CI(0.43, 0.92); R2 = 0.12; p = 0.018; reference=relapsing MS). The treatment effect on a baseline NfL of 702 pg/mL was 451 pg/ml 95%CI(374,509) in a 30-year-old versus 228 pg/ml 95%CI(63,350) in a 60-year-old. There was no association in CSF NfL reduction with BMI, disease duration or sex. In cladribine- and alemtuzumab-treated patients, the CSF NfL T2/T1 ratio did not correlate with lymphocyte depletion rate at 23 weeks. CONCLUSIONS: In this observational study, we found that factors reflecting early disease stage, including a younger age, lower disability and relapsing MS were associated with treatment response in CSF NfL. Other factors were not found to be related, including lymphopaenia in highly-active treatments.

Subcutaneous cladribine to treat multiple sclerosis: experience in 208 patients.

OBJECTIVE: To report on safety and effectiveness of subcutaneous cladribine (Litak®) in multiple sclerosis (MS) patients. METHODS: Litak® was offered to MS-patients irrespective of disease course. Litak® 10 mg was administered for 3-4 days during week 1. Based on lymphocyte count at week 4, patients received another 0-3 doses at week 5. A second course was administered 11 months later. Follow-up included adverse events, relapses, expanded disability status scale (EDSS), 9-hole-peg and Timed-25-foot-walking tests, no-evidence-of-disease-activity (NEDA), no-evidence-of-progression-or-active-disease (NEPAD), MRI, cerebrospinal fluid (CSF) neurofilament light chain (NfL), and lymphocyte counts. RESULTS: In all, 208 patients received at least one course of treatment. Age at baseline was 44 (17-72) years and EDSS 0-8.5. Cladribine was generally well tolerated. One myocardial infarction, one breast cancer, and three severe skin reactions occurred without long-term sequelae. Two patients died (one pneumonia, one encephalitis). Lymphopenia grade 3 occurred in 5% and grade 4 in 0.5%. In 94 out of 116 pwMS with baseline and follow-up (BaFU) data after two treatment courses, EDSS remained stable or improved. At 18 months, 64% of patients with relapsing MS and BaFU data (n = 39) had NEDA. At 19 months, 62% of patients with progressive MS and BaFU data (n = 13) had NEPAD. Of n = 13 patients whose CSF-NfL at baseline was elevated, 77% were normalised within 12 months. CONCLUSIONS: Litak® was well tolerated. Effectiveness in relapsing MS appeared similar to cladribine tablets and was encouraging in progressive MS. Our data suggest cladribine may be safe and effective in MS-patients irrespective of their disease stage.

CSF neurofilament light chain testing as an aid to determine treatment strategies in MS.

OBJECTIVE: To evaluate the use of CSF neurofilament light chain (NfL) measurements in clinical practice as well as their effect on treatment strategies and outcomes in patients with MS. METHODS: This was an observational cohort study of patients with MS who had a CSF NfL measurement between December 2015 and July 2018 as part of their routine clinical care. Treatment strategies were classified as "No Treatment/No Escalation" (no treatment or no escalation of treatment) or "Treatment/Escalation" (first-line injectable/oral disease-modifying therapies (DMTs), highly active DMTs, or treatment escalation). Change in Expanded Disability Status Scale (EDSS) scores was evaluated after 1-year follow-up. RESULTS: Of 203 patients with MS, 117 (58%) had relapsing-remitting MS. Disease activity was most frequently indicated by elevated CSF NfL (n = 85), followed by clinical (n = 81) and MRI activity (n = 65). CSF NfL measurements were independently associated with clinical (p = 0.02) and MRI activity (p < 0.001). Of those with elevated CSF NfL as the only evidence of disease activity (n = 22), 77% had progressive MS (PMS). In patients with PMS, 17 (20%) had elevated CSF NfL as the sole indicator of disease activity. Elevated CSF NfL resulted more frequently in Treatment/Escalation than normal CSF NfL (p < 0.001). Median EDSS change at follow-up was similar between patients receiving No Treatment/No Escalation and Treatment/Escalation decisions (p = 0.81). CONCLUSIONS: CSF NfL measurements informed treatment strategies, alongside clinical and MRI measures. CSF NfL levels were the only indicator of disease activity in a subset of patients, which was more pronounced in patients with PMS. Elevated CSF NfL was associated with more Treatment/Escalation strategies, which had an impact on EDSS outcomes at 1 year.

Serum neurofilament-light concentration and real-world outcome in MS.

BACKGROUND: Prognostication in multiple sclerosis (MS) remains challenging. Biomarkers capable of providing this information at diagnosis would be valuable in shaping therapeutic decisions. Measurement of neurofilament light (NfL) has shown promise in predicting clinical outcomes in established MS, but its ability to predict outcomes in real-world cohorts at diagnosis requires further validation. METHODS: We used linear regression to evaluate the relationship between serum NfL (sNfL), measured at the time of diagnosis with short-term (1-year) and medium-term (5-year) clinical outcomes in 164 people with MS from a real-world, population-based cohort. Cox proportional hazards regression was used to analyse the association between sNfL and subsequent hazard of relapse or sustained accumulation of disability (SAD). Analyses were adjusted for age and disease-modifying treatment (DMT). RESULTS: sNfL concentration at diagnosis was modestly associated with baseline EDSS score (ß = 0.272, 95% CI 0.051 to 0.494, p = 0.016). However, no significant associations were found between baseline sNfL and odds of relapse at 12-months, 5-year EDSS change, or the hazard of relapse or SAD over 5 years follow-up. Dichotomising baseline sNfL according to the median sNfL did not change these findings. CONCLUSIONS: sNfL appears to be of limited clinical utility in predicting future irreversible neurological disability in a largely untreated real-world population, and remains insufficiently validated to shape treatment decisions at the time of diagnosis. Further studies may be needed for sNfL to be considered as a prognostic marker in the MS clinic. However the masking effect of DMTs on the natural disease trajectory will continue to pose challenges.

Medically Unexplained Physical Symptoms in Hospitalized Patients: A 9-Year Retrospective Observational Study.

Introduction: "Medically Unexplained Physical Symptoms" (MUPS) defines a subgroup of patients presenting physical symptoms of unclear origin. The study aims to profile clinical and socio-demographic characteristics of patients with MUPS. Materials and Methods: This 9-years observational retrospective study assesses all patients admitted between 2008 and 2016 in the divisions of neurology and gastroenterology. Socio-demographic and clinical variables were evaluated: gender, age, diagnosis or diagnostic hypothesis, presence of psychiatric comorbidities, psychiatric evaluation, pharmacological treatment, number of admissions/visits. Results: Among 2,479 neurological patients 10.1% presented MUPS. Patients were more frequently women (63.5%), with a mean age of about 50 years. Reported symptoms were headache (22.6%), seizures (8.7%), vertigo (5.9%), fibromyalgia (5.5%), paresthesia (5.1%), visual disturbances (5.1%), amnesia (3.9%). The diagnosis was somatoform disorder in 6.3% of cases, conversion disorder in 2.7%, and somatic symptom disorder in 1.5% only. 2,560 outpatients were evaluated in gastroenterology division. 9.6% (n = 248) of patients had MUPS; 62.1% of them were women. The most affected age group ranged between 15 and 45 years. The most frequent diagnoses were functional abdominal pain (50%), dysmotility-like dyspepsia (26.6%), irritable bowel syndrome (10.4%), meteorism of unknown cause (2.4%), hiccup (1.6%), burning mouth syndrome (1.2%). No patients received a diagnosis of somatic symptom disorder. Discussion: Patients with MUPS are more often women, of middle age, with self-referred specific symptomatology. While neurological patients received a diagnostic-therapeutic approach in line with the literature, gastroenterological patients mainly received antipsychotics. A more comprehensive assessment and a development of psychoeducational interventions are needed to improve patients' quality and quantity of life.

A phase II baseline versus treatment study to determine the efficacy of raltegravir (Isentress) in preventing progression of relapsing remitting multiple sclerosis as determined by gadolinium-enhanced MRI: The INSPIRE study.

BACKGROUND: Although the aetiology of multiple sclerosis (MS) remains elusive, it is clear that Epstein Barr virus (EBV) and possibly other viruses play a role in the pathogenesis of MS. Laboratory evidence suggests that human endogenous retroviruses (HERVs) could also have a role, but no interventional therapy has determined what will happen if HERVs are suppressed. Recent epidemiological evidence indicates patients with HIV infection have a significantly lower risk of developing MS and that HIV antiretroviral therapies may be coincidentally inhibiting HERVs, or other retroelements, that could be implicated in MS. OBJECTIVES: To systematically investigate the effects of an HIV integrase strand inhibitor, raltegravir, on the number of gadolinium (Gd)-enhanced MRI lesions in people with active relapsing MS. METHODS: This is a Phase 2a clinical trial where twenty participants were enrolled in a 3 month baseline phase followed by 3 months of treatment with raltegravir 400 mg twice a day. Patients had monthly Gd-enhanced MRI, saliva collection to test for EBV shedding, blood sampling for safety monitoring, virology (including HERVs), measurement of immunological and inflammatory markers; and physical, neurological and quality-of-life assessments. RESULTS: All patients completed the six months trial period.The primary outcome measure of MS disease activity was the number of Gd-enhancing lesions observed, and raltegravir had no significant effect on the rate of development of Gd-enhancing lesions during the treatment phase compared with the baseline phase. Additionally, there was no change in secondary outcomes of either disability or quality-of-life measures that could reasonably be attributed to the intervention. There was a significant positive between HERV-W/MSRV (multiple sclerosis related virus) Gag Flix (Fluorescence index) B cells and the number of Gd-enhanced lesions at any visit (p = 0.029), which was independent of any potential influence of the trial drug administration. Regarding EBV shedding, there was no significant correlation between the amount of EBV shedding and the number of lesions. No change was detected in inflammatory markers (IL-8, IL-1ß, IL-6, IL-10, TNF, IL-12p70 and HCRP), which were all within normal limits both before and after the intervention. Serum CD163 expression was also unchanged by raltegravir. CONCLUSIONS: Raltegravir did not have any impact on MS disease activity. This could be due to the choice of antiretroviral agent used in this study, the need for a combination of agents, as used in treating HIV infection, the short treatment period or dosing regimen, or the lack of a role of HERV expression in MS once the disease is established. Borderline significance for the association between EBV shedding and the total number of lesions, probably driven by new lesion development, may indicate EBV shedding as a marker of inflammatory disease activity. In conclusion, interesting correlations between HERV-W markers, EBV shedding and new MRI lesions, independent from treatment effects, were found.

Somatosensory innervation of the oral mucosa of adult and aging mice.

Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner's corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.

Efficacy and Tolerability of Two Different Kinds of Titration of Paroxetine Hydrocloride Solution: an Observational Study.

Background: Depressive disorders are expected to be the second highest cause of morbidity in the world until few years. Moreover, patients with depression frequently show many side effects and low compliance to therapy. To find a more tolerated and more efficacy therapy is a growing need. Objective: This observational study investigates the efficacy, safety and tolerability of paroxetine hydrochloride comparing slow versus standard titration in a population affected by Depressive Disoders (according to DSM 5). Methods: 186 outpatients were assessed throught the following scales: Hamilton Depression Rating Scale (HDRS) for depression and World Health Organization Quality of Life Scale Bref for the perceived quality of life (WHOQOL BREF). Treatment-emerged Adverse Events (TEAEs) were recorded throught self-reports. Statystical analysys was performed by GraphPad Prism Version 5.1. Results: The efficacy of paroxetine was confirmed in both titrations by the number of clinical remitters (HDRS ≤ 7 at 12 weeks for 53% of the standard titration group and 58% of the slow titration group), without differences. About safety and tolerability there were more frequent TEAEs among the standard titration group (p < 0.01). Comparing WHOQOL BREF between the two groups at the recruitment and at the twelth week emerged a statistically significant difference (p = 0.003), with highest scores reached in slow titration group. Conclusions: Although the short observation period is an evident limit, this study is consistent to the literature about the efficacy of both titrations of paroxetine to improve depression and shows promising results about the increased tolerability of paroxetine slow titration.

Opportunities for community awareness platforms in personal genomics and bioinformatics education.

Precision and personalized medicine will be increasingly based on the integration of various type of information, particularly electronic health records and genome sequences. The availability of cheap genome sequencing services and the information interoperability will increase the role of online bioinformatics analysis. Being on the Internet poses constant threats to security and privacy. While we are connected and we share information, websites and internet services collect various types of personal data with or without the user consent. It is likely that genomics will merge with the internet culture of connectivity. This process will increase incidental findings, exposure and vulnerability. Here we discuss the social vulnerability owing to the genome and Internet combined security and privacy weaknesses. This urges more efforts in education and social awareness on how biomedical data are analysed and transferred through the internet and how inferential methods could integrate information from different sources. We propose that digital social platforms, used for raising collective awareness in different fields, could be developed for collaborative and bottom-up efforts in education. In this context, bioinformaticians could play a meaningful role in mitigating the future risk of digital-genomic divide.

Cannabis use and genital self-mutilation: an update of case reports.

We reported and compared two case reports of genital self-mutilation with concurrent increasing psychotic symptoms resulting from substance abuse such as cannabis and alcohol.

CACP syndrome: identification of five novel mutations and of the first case of UPD in the largest European cohort.

Camptodactyly-Arthropathy-Coxa vara-Pericarditis (CACP) syndrome is a rare autosomal recessive disorder caused by mutations in PRG4 gene that encodes for proteoglycan 4, a mucin-like glycoprotein that is the major lubricant for joints and tendon surfaces. The molecular studies reported so far have described the identification of 15 mutations associated with this syndrome and the majority of them were found in families of Arabian origin. Here we report the molecular investigation of the largest European cohort that comprises 13 patients, and allowed the identification of 5 novel mutations and of the first case of CACP syndrome resulting from uniparental disomy of chromosome 1.

GLI1 confers profound phenotypic changes upon LNCaP prostate cancer cells that include the acquisition of a hormone independent state.

The GLI (GLI1/GLI2) transcription factors have been implicated in the development and progression of prostate cancer although our understanding of how they actually contribute to the biology of these common tumours is limited. We observed that GLI reporter activity was higher in normal (PNT-2) and tumourigenic (DU145 and PC-3) androgen-independent cells compared to androgen-dependent LNCaP prostate cancer cells and, accordingly, GLI mRNA levels were also elevated. Ectopic expression of GLI1 or the constitutively active ΔNGLI2 mutant induced a distinct cobblestone-like morphology in LNCaP cells that, regarding the former, correlated with increased GLI2 as well as expression of the basal/stem-like markers CD44, ß1-integrin, ΔNp63 and BMI1, and decreased expression of the luminal marker AR (androgen receptor). LNCaP-GLI1 cells were viable in the presence of the AR inhibitor bicalutamide and gene expression profiling revealed that the transcriptome of LNCaP-GLI1 cells was significantly closer to DU145 and PC-3 cells than to control LNCaP-pBP (empty vector) cells, as well as identifying LCN2/NGAL as a highly induced transcript which is associated with hormone independence in breast and prostate cancer. Functionally, LNCaP-GLI1 cells displayed greater clonal growth and were more invasive than control cells but they did not form colonies in soft agar or prostaspheres in suspension suggesting that they do not possess inherent stem cell properties. Moreover, targeted suppression of GLI1 or GLI2 with siRNA did not reverse the transformed phenotype of LNCaP-GLI1 cells nor did double GLI1/GLI2 knockdowns activate AR expression in DU145 or PC-3 cells. As such, early targeting of the GLI oncoproteins may hinder progression to a hormone independent state but a more detailed understanding of the mechanisms that maintain this phenotype is required to determine if their inhibition will enhance the efficacy of anti-hormonal therapy through the induction of a luminal phenotype and increased dependency upon AR function.

Ehlers-Danlos syndrome and neurological features: a review.

Ehlers-Danlos Syndrome is a term that comprises a variety of inherited connective tissue disorders characterized primarily by skin hyperextensibility, joints hypermobility and excessive dislocations, easy bruisability, generalized fragility. If much is known about orthopedic or physiatric features of this syndrome, poor is known about the neurological ones. Thus neurological assessment is very important due to the possible various clinical manifestations in this syndrome.

Myc, Cdk2 and cellular senescence: Old players, new game.

The aberrant activation of oncogenic pathways promotes tumor progression, but concomitantly elicits compensatory tumor-suppressive responses, such as apoptosis or senescence. For example, Ras induces senescence, while Myc generally triggers apoptosis. Myc is in fact viewed as an anti-senescence oncogene, as it is a potent inducer of cell proliferation and immortalization, bypasses growth-inhibitory signals, and cooperates with Ras in cellular transformation. Recent reports prompt re-evaluation of Myc-induced senescence and of its role in tumor progression and therapy. We have shown that the cyclin-dependent kinase Cdk2, although redundant for cell cycle progression, has a unique role in suppressing a Myc-induced senescence program: Myc activation elicited expression of p16(INK4a) and p21(Cip1), and caused senescence in cells lacking Cdk2, but not in Cdk2-proficient cells. We show here that suppression of Myc-induced senescence by Cdk2 does not occur through phosphorylation of its purported substrate residue in Myc (Ser 62). Additional cellular activities have been identified that suppress Myc-induced senescence, including the Wrn helicase, Telomerase and Miz1. These senescencesuppressing activities were critical for tumor progression, as deficiency in either Cdk2, telomerase or Miz1 reduced the onset of Myc-induced lymphoma in transgenic mice. Other gene products like p53, SUV39H1 or TGFß promoted senescence, which together with apoptosis contributed to tumor suppression. Paradoxically, Myc directly counteracted the very same senescence program that it potentially elicited, since it positively regulated Wrn, Telomerase and Cdk2 activity. Furthermore, Cdk2 inhibition re-activated the latent senescence program in Myc expressing cells. Hence, while these molecules are instrumental to the oncogenic action of Myc, they may simultaneously constitute its Achille's heel for therapeutic development.

Cdk2 suppresses cellular senescence induced by the c-myc oncogene.

Activated oncogenes induce compensatory tumour-suppressive responses, such as cellular senescence or apoptosis, but the signals determining the main outcome remain to be fully understood. Here, we uncover a role for Cdk2 (cyclin-dependent kinase 2) in suppressing Myc-induced senescence. Short-term activation of Myc promoted cell-cycle progression in either wild-type or Cdk2 knockout mouse embryo fibroblasts (MEFs). In the knockout MEFs, however, the initial hyper-proliferative response was followed by cellular senescence. Loss of Cdk2 also caused sensitization to Myc-induced senescence in pancreatic beta-cells or splenic B-cells in vivo, correlating with delayed lymphoma onset in the latter. Cdk2-/- MEFs also senesced upon ectopic Wnt signalling or, without an oncogene, upon oxygen-induced culture shock. Myc also causes senescence in cells lacking the DNA repair protein Wrn. However, unlike loss of Wrn, loss of Cdk2 did not enhance Myc-induced replication stress, implying that these proteins suppress senescence through different routes. In MEFs, Myc-induced senescence was genetically dependent on the ARF-p53-p21Cip1 and p16INK4a-pRb pathways, p21Cip1 and p16INK4a being selectively induced in Cdk2-/- cells. Thus, although redundant for cell-cycle progression and development, Cdk2 has a unique role in suppressing oncogene- and/or stress-induced senescence. Pharmacological inhibition of Cdk2 induced Myc-dependent senescence in various cell types, including a p53-null human cancer cell line. Our data warrant re-assessment of Cdk2 as a therapeutic target in Myc- or Wnt-driven tumours.