GAPDH facilitates homologous recombination repair by stabilizing RAD51 in an HDAC1-dependent manner.

Homologous recombination (HR), a form of error-free DNA double-strand break (DSB) repair, is important for the maintenance of genomic integrity. Here, we identify a moonlighting protein, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), as a regulator of HR repair, which is mediated through HDAC1-dependent regulation of RAD51 stability. Mechanistically, in response to DSBs, Src signaling is activated and mediates GAPDH nuclear translocation. Then, GAPDH directly binds with HDAC1, releasing it from its suppressor. Subsequently, activated HDAC1 deacetylates RAD51 and prevents it from undergoing proteasomal degradation. GAPDH knockdown decreases RAD51 protein levels and inhibits HR, which is re-established by overexpression of HDAC1 but not SIRT1. Notably, K40 is an important acetylation site of RAD51, which facilitates stability maintenance. Collectively, our findings provide new insights into the importance of GAPDH in HR repair, in addition to its glycolytic activity, and they show that GAPDH stabilizes RAD51 by interacting with HDAC1 and promoting HDAC1 deacetylation of RAD51.

The relationship of serum gastrin-17 and oral mucositis in head and neck carcinoma patients receiving radiotherapy.

OBJECTIVE: The aim of this study was to analyze the relationship of serum gastrin-17 (G-17) and oral mucositis in head and neck carcinoma (HNC) patients receiving radiotherapy. METHODS: Serum G-17 were detected in patients before and after radiotherapy. Patients were divided into high G-17 group (baseline serum G-17 ≥ 5pmol/L) and low G-17 group (baseline serum G-17 < 5pmol/L). The severity of oral mucositis was analyzed between the two groups. Other complications such as dysphagia, salivary gland, mandible, thyroid function, larynx, pain, and weight loss were also investigated. RESULTS: Forty-two patients were analyzed in this study. The level of serum G-17 had a significant decrease after radiotherapy (7.29 ± 5.70pmol/L versus 4.93 ± 4.46pmol/L, P = 0.038). In low serum G-17 group, the incidences of grade 0, 1-2 and 3-4 of oral mucositis were 0%, 30.4%, and 69.6%, respectively. In high serum G-17 group, the incidences of grade 0, 1-2 and 3-4 of oral mucositis were 0%, 63.2%, and 36.8%, respectively. Pearson correlation analysis showed that serum G-17 was negatively correlated with oral mucositis (r=-0.595, P < 0.01). Weight loss of low G-17 group was more serious than that of high G-17 group. CONCLUSION: Serum G-17 has a close relationship with oral mucositis. Baseline serum G-17 may be a potential predictor for the severity of oral mucositis in HNC patients receiving radiotherapy.

FEN1 inhibitor synergizes with low-dose camptothecin to induce increased cell killing via the mitochondria mediated apoptotic pathway.

Camptothecin has been used in tumor therapy for a long time but its antitumor effect is rather limited due to the side effect and the drug resistance. FEN1, a major component of DNA repair systems, plays important roles in maintaining genomic stability via DNA replication and repair. Here we found that FEN1 inhibitor greatly sensitizes cancer cells to low-dose camptothecin. The combinative treatment of FEN1 inhibitor and 1 nM camptothecin induced a synthetic lethal effect, which synergistically suppressed cancer cell proliferation and significantly mediated apoptosis both in vitro and in vivo. Our study suggested that targeting FEN1 could be a potent strategy for tumor-targeting cancer therapy.

Symmetrical dimethylation of H4R3: A bridge linking DNA damage and repair upon oxidative stress.

The DNA lesions caused by oxidative damage are principally repaired by the base excision repair (BER) pathway. 8-oxoguanine DNA glycosylase 1 (OGG1) initiates BER through recognizing and cleaving the oxidatively damaged nucleobase 8-oxo-7,8-dihydroguanine (8-oxoG). How the BER machinery detects and accesses lesions within the context of chromatin is largely unknown. Here, we found that the symmetrical dimethylarginine of histone H4 (producing H4R3me2s) serves as a bridge between DNA damage and subsequent repair. Intracellular H4R3me2s was significantly increased after treatment with the DNA oxidant reagent H2O2, and this increase was regulated by OGG1, which could directly interact with the specific arginine methyltransferase, PRMT5. Arginine-methylated H4R3 could associate with flap endonuclease 1 (FEN1) and enhance its nuclease activity and BER efficiency. Furthermore, cells with a decreased level of H4R3me2s were more susceptible to DNA-damaging agents and accumulated more DNA damage lesions in their genome. Taken together, these results demonstrate that H4R3me2s can be recognized as a reader protein that senses DNA damage and a writer protein that promotes DNA repair.

Src-mediated phosphorylation of GAPDH regulates its nuclear localization and cellular response to DNA damage.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme involved in energy metabolism. Recently, GAPDH has been suggested to have extraglycolytic functions in DNA repair, but the underlying mechanism for the GAPDH response to DNA damage remains unclear. Here, we demonstrate that the tyrosine kinase Src is activated under DNA damage stress and phosphorylates GAPDH at Tyr41. This phosphorylation of GAPDH is essential for its nuclear translocation and DNA repair function. Blocking the nuclear import of GAPDH by suppressing Src signaling or through a GAPDH Tyr41 mutation impairs its response to DNA damage. Nuclear GAPDH is recruited to DNA lesions and associates with DNA polymerase ß (Pol ß) to function in DNA repair. Nuclear GAPDH promotes Pol ß polymerase activity and increases base excision repair (BER) efficiency. Furthermore, GAPDH knockdown dramatically decreases BER efficiency and sensitizes cells to DNA damaging agents. Importantly, the knockdown of GAPDH in colon cancer SW480 cells and xenograft models effectively enhances their sensitivity to the chemotherapeutic drug 5-FU. In summary, our findings provide mechanistic insight into the new function of GAPDH in DNA repair and suggest a potential therapeutic target in chemotherapy.

Inhibition of AKT Sensitizes Cancer Cells to Antineoplastic Drugs by Downregulating Flap Endonuclease 1.

DNA repair mechanisms are crucial for cell survival. It increases the cancer cell's ability to resist DNA damage. FEN1 is involved in DNA replication and repair, specifically long-patch base excision repair. Although the gene function and post-translational modification of FEN1 are well studied, the regulatory mechanism of FEN1 by upstream signal pathways remains unclear. In this article, we have identified AKT as a regulator of FEN1 activity in lung cancer cells. Sustained activation of AKT can phosphorylate nuclear transcription factor NF-κB/p65. NF-κB/p65 directly binds to FEN1 promoter to promote a high transcription level of FEN1, revealing the contribution of the AKT signaling pathway to drug resistance of cancer cells. The combination of an AKT inhibitor and cisplatin efficiently suppressed lung cancer cell growth both in vitro and in vivo Our study illustrated an upstream regulatory mechanism of FEN1, which will contribute to the development of effective lung cancer therapies.These findings identified AKT as a regulator of FEN1 activity and revealed the AKT signaling pathway's contribution to drug resistance, which will contribute to the development of effective lung cancer therapy.

Polymorphism rs2682818 in miR-618 is associated with colorectal cancer susceptibility in a Han Chinese population.

MicroRNAs (miRNAs), endogenous small noncoding RNAs (ncRNAs), play crucial roles in cancer development. Many studies have demonstrated that miRNAs can serve as diagnostic and therapeutic biomarkers for malignancies. Additionally, single nucleotide polymorphisms (SNPs) located in miRNA functional regions have been reported to be involved in cancer susceptibility. In this study, we investigated the associations between SNPs located in miRNA functional regions and colorectal cancer (CRC) susceptibility. We systematically screened all candidate miRNAs and their SNPs and then evaluated the relationships between the SNPs and CRC susceptibility in a Han Chinese population including 878 patients with CRC and 884 controls. Genotyping was performed by TaqMan assay. After comprehensively screening the miRNAs and SNPs, we elected to evaluate the association between SNP rs2682818 in miR-618 and CRC susceptibility. We found that the AA and AC/AA genotypes of rs2682818 were associated with a decreased risk of CRC compared with the CC genotype (odds ratio (OR) = 0.54, 95% confidence interval (CI) = 0.37-0.79 for AA vs. CC in codominant model; OR = 0.82, 95% CI = 0.68-0.99 for AC/AA vs. CC in dominant model). However, we obtained no statically significant results in our subgroup analyses. SNP rs2682818 in miR-618 has potential as a biomarker for individuals with high CRC susceptibility. Our findings need to be verified in studies including larger samples. Moreover, molecular functional studies of miR-681 must be performed to confirm its relationship with CRC.

The role of hypertriglyceridemia for acute kidney injury in the course of acute pancreatitis and an animal model.

OBJECTIVE: The aim of this study was to investigate the role of hypertriglyceridemia for acute kidney injury (AKI) in the course of acute pancreatitis. METHODS: Patients with acute pancreatitis were retrospectively divided into four groups according to admission triglyceride: normal group, mild HTG group, moderate HTG group and severe HTG group. Clinical characteristics were compared among these groups. Wild type (WT) mice and Human ApoC III transgenic (ApoCIIItg) mice were used in the next animal experiments. Severe acute pancreatitis (SAP) model was established by retrograde injection of 0.5% sodium taurocholate (0.1 ml/100 g) from duodenum to pancreatic duct. Histological scores, serum amylase, creatinine, usea nitrogen were compared between WT mice and ApoCIIItg mice. RESULTS: Two hundred and sixty-two patients were classified into 4 groups: normal TG (104, 39.7%), mild HTG (72, 27.5%), moderate HTG (47, 17.9%), and severe HTG (39, 14.9%) groups. The proportions of AKI were 13.5% (14/104, normal), 13.9% (10/72, mild), 21.3% (10/47, moderate), and 38.5% (15/39, severe), respectively. After establishing SAP model, the levels of serum amylase (P < 0.05) and pancreatic histological score (P < 0.05) of ApoCIII-SAP-9h group were significantly higher than that of WT-SAP-9h group, respectively. ApoCIII-SAP-9h group had significantly higher levels of serum creatinine (P < 0.001), usea nitrogen (P < 0.001), and kidney histological score (P < 0.05) than that of WT-SAP-9h group, respectively. CONCLUSIONS: Mild HTG has little adverse impact on disease severity of acute pancreatitis; severe HTG can aggravate kidney injury in the course of acute pancreatitis. ApoCIII-SAP mice have more serious pancreatic damage and kidney injury than WT-SAP mice.

SEW2871 Alleviates the Severity of Caerulein-Induced Acute Pancreatitis in Mice.

Sphingosine-1-phosphate type-1 receptor (S1P1) agonists have the potential to inhibit the egress of lymphocytes, and have been demonstrated to provide protective effects on some acute inflammatory diseases. However, the value of S1P1 agonists on acute pancreatitis (AP) remains unclear. The aim of this study was to explore the effect of SEW2871, a S1P1-selective agonist, on caerulein-induced AP in mice. AP was induced by giving eight intraperitoneal injections of caerulein (50 µg/kg/h) at hourly intervals. SEW2871 was administered by gavage, at a dose of 20 mg/kg, at 0 h and 12 h after the first intraperitoneal injection of caerulein. The mice were sacrificed at 24 h. Severity of AP, serum amylase and lipase activity, levels of serum cytokines, pancreatic myeloperoxidase (MPO) activity, CD45+CD4+ T lymphocytes in blood, CD4+ T cell infiltration in the pancreas, and proinflammatory cytokine production were assessed. Furthermore, the expression of signal transducer and activator of transcription (STAT) 3 and phospho-STAT3 (p-STAT3) in the pancreas was also evaluated. The results revealed that the administration of SEW2871 ameliorated the severity of AP, by a reduction of serum pancreatic enzyme activity and levels of cytokines, decreased pancreatic MPO activity, depletion of CD4+CD45+ T lymphocytes in the blood and a reduction of CD4+ T cell infiltration in the pancreas. Furthermore, the expression of proinflammatory cytokines mRNA and p-STAT3 were also suppressed by SEW2871 treatment. These results suggest that SEW2871 treatment attenuates the severity of caerulein-induced AP in mice, which may provide a new therapeutic approach for AP therapy.

Predictors of critical acute pancreatitis: a prospective cohort study.

Critical acute pancreatitis (CAP) has recently emerged as the most ominous severity category of acute pancreatitis (AP). As such there have been no studies specifically designed to evaluate predictors of CAP. In this study, we aimed to evaluate the accuracy of 4 parameters (Acute Physiology and Chronic Health Evaluation [APACHE] II score, C-reactive protein [CRP], D-dimer, and intra-abdominal pressure [IAP]) for predicting CAP early after hospital admission. During the study period, data on patients with AP were prospectively collected and D-dimer, CRP, and IAP levels were measured using standard methods at admission whereas the APACHE II score was calculated within 24 hours of hospital admission. The receiver-operating characteristic (ROC) curve analysis was applied and the likelihood ratios were calculated to evaluate the predictive accuracy. A total of 173 consecutive patients were included in the analysis and 47 (27%) of them developed CAP. The overall hospital mortality was 11% (19 of 173). APACHE II score ≥11 and IAP ≥13 mm Hg showed significantly better overall predictive accuracy than D-dimer and CRP (area under the ROC curve-0.94 and 0.92 vs. 0.815 and 0.667, correspondingly). The positive likelihood ratio of APACHE II score is excellent (9.9) but of IAP is moderate (4.2). The latter can be improved by adding CRP (5.8). In conclusion, of the parameters studied, APACHE II score and IAP are the best available predictors of CAP within 24 hours of hospital admission. Given that APACHE II score is rather cumbersome, the combination of IAP and CRP appears to be the most practical way to predict critical course of AP early after hospital admission.

Hypertriglyceridemia is a risk factor for acute kidney injury in the early phase of acute pancreatitis.

OBJECTIVE: The aim of this study was to investigate the risk factors for acute kidney injury (AKI) in patients with acute pancreatitis (AP). METHODS: Patients with AP were retrospectively divided into AKI group and non-AKI group. To investigate the risk factors for AKI, logistic regression analysis was performed with demography, etiologies, and comorbidities. Mortalities of patients with different body mass indexes were compared. RESULTS: There were 43 patients with AKI and 202 patients without AKI. The risk factor for AKI in AP was hypertriglyceridemia (odds ratio, 2.964; 95% confidence interval, 1.485-5.915; P = 0.007). Forty-two patients developed AKI within the first 48 hours. The mortalities of normal weight, overweight, and obese groups in patients with AKI were 16.7%, 17.4%, and 62.5%, respectively. All the 4 patients who died in the non-AKI group were of normal weight. CONCLUSIONS: Hypertriglyceridemia is an independent risk factor for AKI in the early phase of AP. Obesity does not increase mortality of patients without AKI. We hypothesize that the role of pancreatic enzymes on triglyceride accumulated in renal may be an explanation for AKI in the early phase of AP.

Acute cholecystitis in the late phase of severe acute pancreatitis: a neglected problem.

OBJECTIVE: This study aimed to evaluate the incidence and risk factors for acute cholecystitis (AC) in the late phase of severe acute pancreatitis (SAP). METHODS: A review of patients with SAP from January 2008 to December 2009 was performed. Clinical characteristics were compared between patients with AC in the late phase and those without. Risk factors for AC were analyzed using a logistic regression analysis. Receiver operating characteristic curve was used to estimate the predictive value of the risk factors. RESULTS: A total of 269 cases were included. Twenty-seven episodes of AC in the late phase were identified. Patients with AC had higher computed tomography severity index and Acute Physiology and Chronic Health Evaluation (APACHE) II score, as well as higher rate of intraabdominal hypertension, infective pancreatic necrosis (IPN) of the pancreas head, fistula, abdominal bleeding, mechanical ventilation, and prolonged enteral nutrition (EN) via jejunal tube. Independent risk factors for AC, based on the results of logistic regression analysis, included higher APACHE II score, prolonged EN via jejunal tube, and IPN of the pancreas head. CONCLUSIONS: Approximately 10% of patients with SAP will develop AC in the late phase. Risk factors include higher APACHE II score, prolonged EN via jejunal tube, and IPN of the pancreas head.