VRK1 Regulates Sensitivity to Oxidative Stress by Altering Histone Epigenetic Modifications and the Nuclear Phosphoproteome in Tumor Cells.

The chromatin organization and its dynamic remodeling determine its accessibility and sensitivity to DNA damage oxidative stress, the main source of endogenous DNA damage. We studied the role of the VRK1 chromatin kinase in the response to oxidative stress. which alters the nuclear pattern of histone epigenetic modifications and phosphoproteome pathways. The early effect of oxidative stress on chromatin was studied by determining the levels of 8-oxoG lesions and the alteration of the epigenetic modification of histones. Oxidative stress caused an accumulation of 8-oxoG DNA lesions that were increased by VRK1 depletion, causing a significant accumulation of DNA strand breaks detected by labeling free 3'-DNA ends. In addition, oxidative stress altered the pattern of chromatin epigenetic marks and the nuclear phosphoproteome pathways that were impaired by VRK1 depletion. Oxidative stress induced the acetylation of H4K16ac and H3K9 and the loss of H3K4me3. The depletion of VRK1 altered all these modifications induced by oxidative stress and resulted in losses of H4K16ac and H3K9ac and increases in the H3K9me3 and H3K4me3 levels. All these changes were induced by the oxidative stress in the epigenetic pattern of histones and impaired by VRK1 depletion, indicating that VRK1 plays a major role in the functional reorganization of chromatin in the response to oxidative stress. The analysis of the nuclear phosphoproteome in response to oxidative stress detected an enrichment of the phosphorylated proteins associated with the chromosome organization and chromatin remodeling pathways, which were significantly decreased by VRK1 depletion. VRK1 depletion alters the histone epigenetic pattern and nuclear phosphoproteome pathways in response to oxidative stress. The enzymes performing post-translational epigenetic modifications are potential targets in synthetic lethality strategies for cancer therapies.

Loss of VRK1 alters the nuclear phosphoproteome in the DNA damage response to doxorubicin.

Dynamic chromatin remodeling requires regulatory mechanisms for its adaptation to different nuclear function, which are likely to be mediated by signaling proteins. In this context, VRK1 is a nuclear Ser-Thr kinase that regulates pathways associated with transcription, replication, recombination, and DNA repair. Therefore, VRK1 is a potential regulatory, or coordinator, molecule in these processes. In this work we studied the effect that VRK1 depletion has on the basal nuclear and chromatin phosphoproteome, and their associated pathways. VRK1 depletion caused an alteration in the pattern of the nuclear phosphoproteome, which is mainly associated with nucleoproteins, ribonucleoproteins, RNA splicing and processing. Next, it was determined the changes in proteins associated with DNA damage that was induced by doxorubicin treatment. Doxorubicin alters the nuclear phosphoproteome affecting proteins implicated in DDR, including DSB repair proteins NBN and 53BP1, cellular response to stress and chromatin organization proteins. In VRK1-depleted cells, the effect of doxorubicin on protein phosphorylation was reverted to basal levels. The nuclear phosphoproteome patterns induced by doxorubicin are altered by VRK1 depletion, and is enriched in histone modification proteins and chromatin associated proteins. These results indicate that VRK1 plays a major role in processes requiring chromatin remodeling in its adaptation to different biological contexts.

The pattern of histone H3 epigenetic posttranslational modifications is regulated by the VRK1 chromatin kinase.

BACKGROUND: Dynamic chromatin remodeling is associated with changes in the epigenetic pattern of histone acetylations and methylations required for processes based on dynamic chromatin remodeling and implicated in different nuclear functions. These histone epigenetic modifications need to be coordinated, a role that may be mediated by chromatin kinases such as VRK1, which phosphorylates histones H3 and H2A. METHODS: The effect of VRK1 depletion and VRK1 inhibitor, VRK-IN-1, on the acetylation and methylation of histone H3 in K4, K9 and K27 was determined under different conditions, arrested or proliferating cells, in A549 lung adenocarcinoma and U2OS osteosarcoma cells. RESULTS: Chromatin organization is determined by the phosphorylation pattern of histones mediated by different types of enzymes. We have studied how the VRK1 chromatin kinase can alter the epigenetic posttranslational modifications of histones by using siRNA, a specific inhibitor of this kinase (VRK-IN-1), and of histone acetyl and methyl transferases, as well as histone deacetylase and demethylase. Loss of VRK1 implicated a switch in the state of H3K9 posttranslational modifications. VRK1 depletion/inhibition causes a loss of H3K9 acetylation and facilitates its methylation. This effect is similar to that of the KAT inhibitor C646, and to KDM inhibitors as iadademstat (ORY-1001) or JMJD2 inhibitor. Alternatively, HDAC inhibitors (selisistat, panobinostat, vorinostat) and KMT inhibitors (tazemetostat, chaetocin) have the opposite effect of VRK1 depletion or inhibition, and cause increase of H3K9ac and a decrease of H3K9me3. VRK1 stably interacts with members of these four enzyme families. However, VRK1 can only play a role on these epigenetic modifications by indirect mechanisms in which these epigenetic enzymes are likely targets to be regulated and coordinated by VRK1. CONCLUSIONS: The chromatin kinase VRK1 regulates the epigenetic patterns of histone H3 acetylation and methylation in lysines 4, 9 and 27. VRK1 is a master regulator of chromatin organization associated with its specific functions, such as transcription or DNA repair.

VRK1 Kinase Activity Modulating Histone H4K16 Acetylation Inhibited by SIRT2 and VRK-IN-1.

The accessibility of DNA to different cellular functions requires a dynamic regulation of chromatin organization that is mediated by different epigenetic modifications, which regulate chromatin accessibility and degree of compaction. These epigenetic modifications, particularly the acetylation of histone H4 in lysine 14 (H4K16ac), determine the degree of chromatin accessibility to different nuclear functions, as well as to DNA damage drugs. H4K16ac is regulated by the balance between two alternative histone modifications, acetylation and deacetylation, which are mediated by acetylases and deacetylases. Tip60/KAT5 acetylates, and SIRT2 deacetylates histone H4K16. However, the balance between these two epigenetic enzymes is unknown. VRK1 regulates the level of H4K16 acetylation by activating Tip60. We have shown that the VRK1 and SIRT2 are able to form a stable protein complex. For this work, we used in vitro interaction, pull-down and in vitro kinase assays. In cells, their interaction and colocalization were detected by immunoprecipitation and immunofluorescence. The kinase activity of VRK1 is inhibited by a direct interaction of its N-terminal kinase domain with SIRT2 in vitro. This interaction causes a loss of H4K16ac similarly to the effect of a novel VRK1 inhibitor (VRK-IN-1) or VRK1 depletion. The use of specific SIRT2 inhibitors in lung adenocarcinoma cells induces H4K16ac, contrary to the novel VRK-IN-1 inhibitor, which prevents H4K16ac and a correct DNA damage response. Therefore, the inhibition of SIRT2 can cooperate with VRK1 in the accessibility of drugs to chromatin in response to DNA damage caused by doxorubicin.

Diagnosis of a cystic pancreatic neuroendocrine tumor: is cystic fluid chromogranin A useful?

Cystic pancreatic neuroendocrine tumors (cP-NET) are a diagnostic challenge for clinic, since sometimes nor imaging features, cytology, or the study of biological markers in pancreatic cyst fluid (PCF), are able to provide the nature of the lesion, and therefore the definitive diagnostic is often made in the surgical piece. Is not infrequent that the lesions are wrongly defined as benign, in special when the cytology is negative for malignancy and the PCL is not mucinous and has a high glucose and a low CEA. We could incorporate new markers to improve the diagnostic performance of PCF samples, like chromogranin A, as in our case may be the only specific finding to detect a cP-TNE.

Duodenal pyogenic granuloma: An unusual cause of chronic anemia.

We present the endoscopic finding of a juxtapapillary duodenal pyogenic granuloma in a patient under study for chronic recurrent anemia. The images show the presence of an enlarged papilla, with an exophytic growth of erythematous and friable tissue at its lower border. Although this is a very rare entity, it is necessary to take it into account in the differential diagnosis of refractory anemia because there is an effective endoscopic treatment for it.

The VRK1 chromatin kinase regulates the acetyltransferase activity of Tip60/KAT5 by sequential phosphorylations in response to DNA damage.

The regulation of histone epigenetic modifications mediates the adaptation of chromatin to different biological processes. DNA damage causes a local relaxation of chromatin associated to histone H4 acetylation in K16, mediated by Tip60/KAT5. In this work, we have studied the role that the VRK1 chromatin kinase plays on the activation of Tip60 during this process. In the DNA damage response induced by doxorubicin, VRK1 directly phosphorylates Tip60. However, the phosphorylated Tip60 residues and their functional roles are unknown. In DDR, we have identified these two Tip60 phosphorylated residues and the cooperation of the participating kinases. The T158 phosphorylation, mediated by VRK1, is early and transient, preceding that of S199, which is more sustained in time, and mediated by DNA-PK. The role of each phosphorylated residues was determined by using phosphomimetic and phosphonull mutants and their combination. T158 phosphorylation protects Tip60 from ubiquitin-mediated degradation, promotes its recruitment to chromatin from the nucleoplasm, and is necessary for its full trans-acetylase activity. The phosphorylation in S199 by DNA-PK directly facilitates Tip60 autoacetylation, but it is not enough for trans-acetylation of two of its targets, histone H4 and ATM, which requires a double phosphorylation of Tip60 in T158 and S199. DNA-PK inhibitors block the phosphorylation of S199. We propose a model in which the cooperation between VRK1 and DNA-PK mediates the sequential phosphorylation of Tip60/KAT5, and contributes to the recruitment of this protein to initiate the sequential remodeling of chromatin in DDR. Both proteins are candidates for novel synthetic lethality strategies in cancer treatment.

Lysine Methyltransferase Inhibitors Impair H4K20me2 and 53BP1 Foci in Response to DNA Damage in Sarcomas, a Synthetic Lethality Strategy.

BACKGROUND: Chromatin is dynamically remodeled to adapt to all DNA-related processes, including DNA damage responses (DDR). This adaptation requires DNA and histone epigenetic modifications, which are mediated by several types of enzymes; among them are lysine methyltransferases (KMTs). METHODS: KMT inhibitors, chaetocin and tazemetostat (TZM), were used to study their role in the DDR induced by ionizing radiation or doxorubicin in two human sarcoma cells lines. The effect of these KMT inhibitors was tested by the analysis of chromatin epigenetic modifications, H4K16ac and H4K20me2. DDR was monitored by the formation of γH2AX, MDC1, NBS1 and 53BP1 foci, and the induction of apoptosis. RESULTS: Chaetocin and tazemetostat treatments caused a significant increase of H4K16 acetylation, associated with chromatin relaxation, and increased DNA damage, detected by the labeling of free DNA-ends. These inhibitors significantly reduced H4K20 dimethylation levels in response to DNA damage and impaired the recruitment of 53BP1, but not of MDC1 and NBS1, at DNA damaged sites. This modification of epigenetic marks prevents DNA repair by the NHEJ pathway and leads to cell death. CONCLUSION: KMT inhibitors could function as sensitizers to DNA damage-based therapies and be used in novel synthetic lethality strategies for sarcoma treatment.

Effects of Somatic Methylation in Colonic Polyps on Risk of Developing Metachronous Advanced Colorectal Lesions.

The utility of molecular markers for predicting the risk of metachronous advanced colorectal lesions (MACLs) remains poorly investigated. We examined the relationship between somatic hypermethylation in polyps at baseline and the risk of developing MACL. This retrospective cohort study included 281 consecutive patients with colonic polyps who were enrolled between 2007 and 2009 and followed-up until 2014. MACLs were defined as adenomas of ≥10 mm, high-grade dysplasia, or with a villous component; and serrated lesions of ≥10 mm or with dysplasia. In total, 595 polyps were removed at baseline colonoscopy and analyzed for pathological characteristics and CpG island methylator phenotype (CIMP) using the MS-MLPA (Methylation-Specific -- Multiplex Ligation-dependent Probe Amplification) technique. Forty-five patients (16.0%) showed at least one CIMP+ polyp. MACL risk was higher in patients with CIMP+ polyps (odds ratio (OR), 4.50; 95% CI, 1.78-11.4; p = 0.002). Patients with CIMP+ polyps also exhibited shorter time to MACL development (33.8 months vs. 50.1 months; p < 0.001), even with adjustment for polyp size and number (OR, 2.40; 95% CI, 1.33-4.34). Adding CIMP analysis improved the sensitivity (57.0% to 70.9%), negative predictive value (71.1% to 77.3%), and overall accuracy (49.8% to 52.0%) for MACL risk estimation. These results highlight that CIMP may be a useful marker for endoscopic surveillance.

Intraductal papillary neoplasm of the bile duct: a recurring disease.

Intraductal papillary neoplasm of the bile duct (IPNB) is a premalignant disease characterized by a low incidence, a high risk of malignant transformation, and an uncertain prognosis. We hereby present the case of an 8-mm IPNB in the left liver lobe detected by endosonography in a 76-year-old woman followed for a dissociated asymptomatic cholestasis who was treated with a left hepatectomy. The resected IPNB had low-grade dysplasia and no nodal involvement in the surgical piece; however, signs of recurrence of the disease were observed in the right liver lobe a year and a half later. Therefore, given that it can be multifocal and recurrent, IPNB is a disease that requires close follow-up.

The role of clonal communication and heterogeneity in breast cancer.

BACKGROUND: Cancer is a rapidly evolving, multifactorial disease that accumulates numerous genetic and epigenetic alterations. This results in molecular and phenotypic heterogeneity within the tumor, the complexity of which is further amplified through specific interactions between cancer cells. We aimed to dissect the molecular mechanisms underlying the cooperation between different clones. METHODS: We produced clonal cell lines derived from the MDA-MB-231 breast cancer cell line, using the UbC-StarTrack system, which allowed tracking of multiple clones by color: GFP C3, mKO E10 and Sapphire D7. Characterization of these clones was performed by growth rate, cell metabolic activity, wound healing, invasion assays and genetic and epigenetic arrays. Tumorigenicity was tested by orthotopic and intravenous injections. Clonal cooperation was evaluated by medium complementation, co-culture and co-injection assays. RESULTS: Characterization of these clones in vitro revealed clear genetic and epigenetic differences that affected growth rate, cell metabolic activity, morphology and cytokine expression among cell lines. In vivo, all clonal cell lines were able to form tumors; however, injection of an equal mix of the different clones led to tumors with very few mKO E10 cells. Additionally, the mKO E10 clonal cell line showed a significant inability to form lung metastases. These results confirm that even in stable cell lines heterogeneity is present. In vitro, the complementation of growth medium with medium or exosomes from parental or clonal cell lines increased the growth rate of the other clones. Complementation assays, co-growth and co-injection of mKO E10 and GFP C3 clonal cell lines increased the efficiency of invasion and migration. CONCLUSIONS: These findings support a model where interplay between clones confers aggressiveness, and which may allow identification of the factors involved in cellular communication that could play a role in clonal cooperation and thus represent new targets for preventing tumor progression.

Sometimes things are what they seem.

Accessory spleen is a frequent congenital abnormality (10-20%) resulting in the fusion failure of splenunculi. We present a case report of a 74 year-old man with a nodule identified in the tail of the pancreas of 1.8 cm x 1.5 cm in size. The CT scan showed soft tissue attenuation and arterial hyperenhancement with a lower uptake in the central area, low 18-FDG affinity and no evidence of 111-In-octretide uptake. A solid, round and well-circumscribed nodule was defined as an intrapancreatic accessory spleen (IPAS) by endoscopic ultrasound (EUS), due to shared ultrasonographic characteristics and a pattern of contrast enhancement with the spleen. The material obtained by EUS guided puncture was consistent with a lymph node. A distal pancreatectomy confirmed the presence of an IPAS.

Use of abdominal ultrasound in the diagnosis of hepatic sinusoidal obstruction syndrome (SOS) in a patient receiving a hematopoietic-cell transplant.

The sinusoidal obstruction syndrome (SOS) is an uncommon form of portal hypertension that occurs in hematopoietic-cell transplant recipients who receive intense conditioning treatments. The diagnosis is clinical and it is usually delayed, because in these patients there are many causes that can damage the liver and can delay its detection. We present the case of a 47-year-old man, whose diagnosis was made with clinical and analytical data supported by ultrasound signs that showed hepatic congestion. After treatment with defibrotide the patient improved clinically and analytically. Hepatic vascularization and perfusion also improved. Therefore, abdominal doppler ultrasound is shown as a noninvasive exploration useful for the clinical management of SOS and as an early marker of good clinical evolution.

[Splenic lymphangioma. A rare tumour. Presentation of 3 cases and a literature review]. / Linfangioma esplénico. Un tumor raro. Presentación de 3 casos y revisión de la bibliografía.

BACKGROUND: Lymphangiomas are benign tumours, considered to be congenital malformations of the lymphatic system that predominately affect children, with only a few cases reported in adults. The most common sites of these lesions are the neck (75%) and axillary region (20%), but rarely found in the spleen. OBJECTIVE: A description is presented of 3 cases of incidentally detected splenic lymphangioma, one in a child and in 2 adults, respectively, as well as a literature review. CLINICAL CASES: After a clinical and physical examination, all patients had an abdominal ultrasound, CT scan and a complete splenectomy, followed by a histopathological study on the removed spleen. Two patients were asymptomatic, and the paediatric patient referred to intermittent abdominal pain without other symptoms. The clinical and physical examinations related to the mass were negative. The final diagnosis was based on a combination of radiological and histopathological findings. Total splenectomy was undertaken in all cases without complications. CONCLUSIONS: Splenic lymphangioma is very rare, and more so in adults. This condition is often asymptomatic and is incidentally detected by imagenology due to any other differet cause. The final diagnosis should be based on a combination of clinical, radiological, and histopathological findings. Splenectomy is the treatment of choice and the prognosis is good.

[Signet ring cell carcinoma of the ampulla of Vater]. / Carcinoma de células en anillo de sello de la ampolla de Vater.

INTRODUCTION: Signet ring cell carcinoma of the ampulla of Vater is a rare entity and less than 20 cases have been described in the literature. We report the cases of two patients with this disease and provide a literature review of previous studies. CASE REPORT: We describe two patients with obstructive jaundice. Abdominal ultrasonography and abdominal computed tomography showed dilatation of the intrahepatic and common bile duct. Duodenoscopy indicated a protruding mass on the ampulla of Vater. Histopathological examination showed round cells and their nuclei were located on one side with prominent signet-ring features. One patient underwent a cephalic pancreatoduodenectomy with lymphadenectomy and the other a total pancreatectomy. DISCUSSION: Signet ring cell carcinoma of the ampulla of Vater has only been described in isolated cases in the literature. Therefore, the clinicopathological features and prognosis of this disease have not yet been well defined.

[Cronkhite-Canada syndrome: an acquired, potentially reversible polyposis]. / Síndrome de Cronkhite-Canada: una poliposis adquirida y potencialmente reversible.

Cronkhite-Canada syndrome is an infrequent, nonadenomatous, acquired polyposis that is associated with ectodermic alterations. The etiopathogenesis and optimal therapeutic management are unknown. We present a case of Cronkhite-Canada syndrome in a 58-year-old man who, after combined treatment with corticosteroids, disodium cromoglycate, loratadine, ciprofloxacin, and zinc, showed complete clinical and partial endoscopic remission. The polypoid lesions of Cronkhite-Canada syndrome can be reversed with medical treatment. Consequently, the natural history of the disease can be modified and its prognosis improved.