Histone methyltransferase SETDB1 promotes colorectal cancer proliferation through the STAT1-CCND1/CDK6 axis.

Upregulation of histone methyltransferase SET domain bifurcated 1 (SETDB1) is associated with poor prognosis in cancer patients. However, the mechanism of oncogenicity of SETDB1 in cancer is hitherto unknown. Here, we show that SETDB1 is upregulated in human colorectal cancer (CRC) where its level correlates with poor clinical outcome. Ectopic SETDB1 promotes CRC cell proliferation, whereas SETDB1 attenuation inhibits this process. Flow cytometry reveals that SETDB1 promotes proliferation by driving the CRC cell cycle from G0/G1 phase to S phase. Mechanistically, SETDB1 binds directly to the STAT1 promoter region resulting in increased STAT1 expression. Functional characterization reveals that STAT1-CCND1/CDK6 axis is a downstream effector of SETDB1-mediated CRC cell proliferation. Furthermore, SETDB1 upregulation is sufficient to accelerate in vivo proliferation in xenograft animal model. Taken together, our results provide insight into the upregulation of SETDB1 within CRC and can lead to novel treatment strategies targeting this cell proliferation-promoting gene.

Camptothecin inhibits the progression of NPC by regulating TGF-ß-induced activation of the PI3K/AKT signaling pathway.

Nasopharyngeal carcinoma (NPC) is a type of cancer that is characterized by increased invasiveness, metastatic potential and tumor recurrence. Camptothecin has been demonstrated to exhibit anticancer activity. However, the potential underlying molecular mechanisms mediated by camptothecin in NPC cells remain elusive. In the present study, the efficacy of camptothecin for NPC was investigated in vitro and in vivo. Additionally, the potential signaling pathway mediated by camptothecin in NPC cells was also examined. The results indicated that the viability and aggressiveness of NPC cells were suppressed by camptothecin treatment in a dose-dependent manner. Camptothecin administration downregulated the expression levels of cell-cycle-associated proteins including cyclin 1, cyclin-dependent kinase (CDK)1 and CDK2 in NPC cells. Expression levels of migration-associated proteins including vimentin, fibronectin and epithelial cadherin were regulated by camptothecin treatment in NPC cells. Additionally, camptothecin inhibited the expression of transforming growth factor-ß (TGF-ß), phosphoinositide 3-kinase (PI3K) and protein kinase B (AKT), whereas TGF-ß overexpression abrogated camptothecin-mediated inhibition of PI3K and AKT expression and camptothecin-mediated inhibition of the viability and aggressiveness of NPC cells. Camptothecin significantly inhibited tumor growth and increased survival times in a mouse model of cancer. In conclusion, these results indicate that camptothecin treatment may inhibit the viability of NPC cells and aggressiveness by regulating the TGF-ß-induced PI3K/AKT signaling pathways, which in turn may be a potential molecular target for the treatment of NPC.

Reduced miR-433 expression is associated with advanced stages and early relapse of colorectal cancer and restored miR-433 expression suppresses the migration, invasion and proliferation of tumor cells in vitro and in nude mice.

The expression of microRNA (miR-433) is altered in various types of human cancer. The present study analyzed the prognostic and biological value of miR-433 expression in colorectal cancer using reverse transcription-quantitative polymerase chain reaction in 125 colorectal tissue specimens (including a test cohort of 40 cases of paired colorectal cancer and adjacent normal mucosae and a confirmation cohort of 85 cases of stage I-III colorectal cancer). In vitro and nude mouse xenograft experiments were subsequently used to assess the effects of miR-433 expression on the regulation of colorectal cancer cell proliferation, adhesion, migration, and invasion. The data indicated that miR-433 expression was significantly downregulated in colorectal cancer tissues in the test and confirmation patient cohorts and that low miR-433 expression was associated with advanced tumor stage and early relapse. Furthermore, the restoration of miR-433 expression was able to significantly inhibit the proliferation of tumor cells by inducing G1-S cell cycle arrest, suppressing cyclinD1 and CDK4 expression, and markedly inhibited the migratory and invasive capacities of tumor cells in vitro. The restoration of miR-433 expression or liposome-based delivery of miR-433 mimics suppressed the growth of colorectal cancer cell xenografts in nude mice. In conclusion, miR-433 may be a putative tumor suppressor in colorectal cancer, and the detection of low miR-433 expression will be investigated in further studies as a putative biomarker for the detection of early relapse in patients with colorectal cancer.

Histone Methyltransferase SETDB1 Promotes the Progression of Colorectal Cancer by Inhibiting the Expression of TP53.

SETDB1 is a novel histone methyltransferase associated with the functional tri-methylation of histone H3K9. Although aberrant high expression of SETDB1 was experimentally obversed in a variety of solid tumors, its underlying mechanisms in human carcinogenesis are not well known. In this study, we investigated the expression of SETDB1 in a large cohort of colorectal cancer (CRC) samples and cell lines for the first time. Our findings showed that SETDB1 was highly expressed in majority CRC tissues and cell lines; moreover, up-regulation of SETDB1 was negatively correlated with the survival rate of CRC patients. Functionally, over-expression of SETDB1 significantly promoted the proliferation and migration of CRC cells in vitro and in vivo, while knocking down SETDB1 suppressed their growth. Mechanistically, we showed that over-expression of SETDB1 significantly inhibited the apoptosis induced by 5-Fluorouracil in CRC cells, which was closely related to the inhibition of TP53 and BAX expression. Furthermore, we confirmed that SETDB1 could be recruited to the promoter region of TP53, which might contribute its inhibition of apoptosis. For conclusion, our study indicated that SETDB1 is essential for colorectal carcinogenesis, and may be a newly target for treatment and prognostic evaluation in CRC.

Diagnostic value of serum squamous cell carcinoma antigen for hepatocellular carcinoma: a systematic review and meta-analysis.

The aim of this study was to ascertain the diagnostic value of serum squamous cell carcinoma antigen (SCCA) and SCCA-IgM for hepatocellular carcinoma (HCC). After a comprehensive search of PubMed and Web of Science databases, we identified eligible studies on the diagnostic value serum SCCAs for HCC. The quality of the eligible studies was assessed using the revised Quality Assessment for Studies of Diagnostic Accuracy (QUADAS-2) tool. The overall diagnostic value of SCCAs for HCC was pooled using a bivariate model. Twelve studies were included in this systematic review and meta-analysis. The pooled sensitivities for SCCA and SCCA-IgM were 0.61 (95% confidence interval [CI], 0.37-0.81) and 0.70 (95% CI, 0.55-0.82), respectively. The corresponding specificities were 0.80 (95% CI, 0.52-0.94) and 0.62 (95% CI, 0.51-0.72), respectively. The areas under summary receiver operating characteristic (sROC) curves for SCCA and SCCA-IgM were 0.76 (95% CI, 0.72-0.80) and 0.70 (95% CI, 0.66-0.74), respectively. Major design deficiencies of the included studies were two-gate design and partial verification bias. Therefore, we concluded that both serum SCCA and SCCA-IgM have a fair diagnostic value for HCC.

[miR-124 regulates radiosensitivity of colorectal cancer cells by targeting PRRX1].

OBJECTIVE: To detect the expression of miR-124 in colorectal carcinoma (CRC) cells and tissue specimens and analyze its association with the radiosensitivity of the cells. METHODS: The expression of miR-124 in CRC cell lines and tissues were detected using qRT-PCR. The effect of miR-124 in modulating cell radiosensitivity was assessed in CRC cells with miRNA-124 overexpression and miRNA-124 knockdown, and bioinformatics prediction and dual luciferase reporter system were employed to identify the direct target of miR-124. RESULTS: s miR-124 expression was down-regulated in CRC cell lines and tissues. CRC cells over-expressing miR-124 showed an obviously enhanced radiosensitivity, whereas miR-124 knockdown resulted in a reduced radiosensitivity of the cells. Bioinformatics prediction and dual luciferase reporter system verified PRRX1 as a direct target of miR-124, which regulated the radiosensitivity of CRC cells by directly inhibiting PRRX1. CONCLUSION: miR-124 can enhance the radiosensitivity of CRC cells by directly targeting PRRX1, which provides a target for improving the therapeutic effect of radiotherapy of CRC.

KRAS Mutation as a Biomarker for Survival in Patients with Non-Small Cell Lung Cancer, A Meta-Analysis of 12 Randomized Trials.

BACKGROUND: Because there is no clear consensus for the prognostic implication of KRAS mutations in patients with non-small cell lung cancer (NSCLC), we conducted a meta-analysis based on 12 randomized trials to draw a more accurate conclusion. MATERIALS AND METHODS: A systematic computer search of articles from inception to May 1, 2014 using the PubMed, EMBASE, and Cochrane databases was conducted. The enrollment of articles and extraction of data were independently performed by two authors. RESULTS: Our analysis was based on the endpoints overall survival (OS) and progression-free survival (PFS). Nine records (All for OS, 7 for PFS) comprising 12 randomized trials were identified with 3701 patients who underwent a test for KRAS mutations. In the analysis of the pooled hazard ratios (HRs) for OS (HR: 1.39; 95% confidence interval [CI] 1.23-1.56) and PFS (HR: 1.33; 95% CI 1.17-1.51), we found that KRAS mutations are related to poor survival benefit for NSCLC. According to a subgroup analysis stratified by disease stage and line of therapy, the combined HRs for OS and PFS coincided with the finding that the presence of a KRAS mutation is a dismal prognostic factor. However, the prognostic role of KRAS mutations are not statistically significant in a subgroup analysis of patients treated with chemotherapy in combination with cetuximab based on the endpoints OS (P=0.141) and PFS (P=0.643). CONCLUSIONS: Our results indicate that KRAS mutations are associated with inferior survival benefits for NSCLC but not for those treated with chemotherapies integrating cetuximab.

1H-MRS evaluation of breast lesions by using total choline signal-to-noise ratio as an indicator of malignancy: a meta-analysis.

The aim of this study was to evaluate the diagnostic performance of the use of total choline signal-to-noise ratio (tCho SNR) criteria in MRS studies for benign/malignant discrimination of focal breast lesions. We conducted (1) a meta-analysis based on 10 studies including 480 malignant breast lesions and 312 benign breast lesions and (2) a subgroup meta-analysis of tCho SNR ≥ 2 as cutoff for malignancy based on 7 studies including 371 malignant breast lesions and 239 benign breast lesions. (1) The pooled sensitivity and specificity of proton MRS with tCho SNR were 0.74 (95 % CI 0.69-0.77) and 0.76 (95 % CI 0.71-0.81), respectively. The PLR and NLR were 3.67 (95 % CI 2.30-5.83) and 0.25 (95 % CI 0.14-0.42), respectively. From the fitted SROC, the AUC and Q* index were 0.89 and 0.82. Publication bias was present (t = 2.46, P = 0.039). (2) Meta-regression analysis suggested that neither threshold effect nor evaluated covariates including strength of field, pulse sequence, TR and TE were sources of heterogeneity (all P value >0.05). (3) Subgroup meta-analysis: The pooled sensitivity and specificity were 0.79 and 0.72, respectively. The PLR and NLR were 3.49 and 0.20, respectively. The AUC and Q* index were 0.92 and 0.85. The use of tCho SNR criteria in MRS studies was helpful for differentiation between malignant and benign breast lesions. However, pooled diagnostic measures might be overestimated due to publication bias. A tCho SNR ≥ 2 as cutoff for malignancy resulted in higher diagnostic accuracy.

Correlation between expression of thymidylate synthase and clinical outcome of advanced gastric cancer treated with capecitabine alone chemotherapy.

Thymidylate synthase (TS) is a prognostic marker in various tumors. However, the results of previous investigations in gastric cancer (GC) were controversial. The objective of this article is to investigate whether TS expression is associated with clinical outcome in advanced GC receiving capecitabine alone chemotherapy. The study reviewed 58 cases of advanced GC in patients aged ≥65 years between December 2008 and June 2012. All patients were treated with capecitabine alone chemotherapy. Immunohistochemical staining for TS protein expression was performed. The relationships between TS expression and clinicopathological characteristics (included age, gender, number of metastatic sites, Eastern Cooperative Oncology Group (ECOG) score, differentiation, and lymph node metastatic status), chemotherapy response, progression-free survival (PFS), and overall survival (OS) were evaluated. There was no association between TS expression and age, gender, number of metastatic sites, ECOG score, differentiation, and lymph node metastatic status (P > 0.05). The chemotherapy response rates among patients with low- and high-level expression of TS protein were 52.0 % (13/25) and 21.2 % (7/33), respectively (χ (2) = 5.968, P = 0.015). The median PFS and OS in patients with low-level TS expression were significantly longer than those with high-level TS expression (PFS 8.0 vs 2.8 m, P = 0.001; OS 13.3 vs 7.9 m, P = 0.002, respectively). Multivariate Cox regression analysis revealed that TS expression was independent risk factor for OS (hazard ratio (HR) 0.237; 95 % confidence interval (CI) 0.108 to 0.520; P = 0.000). The present study demonstrates that TS expression is associated with chemotherapy response, PFS, and OS in advanced GC patients treated with capecitabine alone chemotherapy.

Overexpression of DcR3 and its significance on tumor cell differentiation and proliferation in glioma.

BACKGROUND: Overexpression of decoy receptor 3 (DcR3) have been reported in various classes of malignancies. However, its expression and clinicopathological contribution in gliomas has not been fully elucidated. OBJECTIVE: To explore the expression and clinical significance of DcR3 protein in relation to tumor cell differentiation and proliferation in glioma cell lines and tissues. METHODS: One hundred and twenty-five samples of glioma patients and 18 cases of normal brain tissues were recruited. The expression of DcR3 protein was detected using immunohistochemistry. Tumor differentiation was assessed by histologic characters and the status of glial fibrillary acidic protein (GFAP). Tumor cell labeling indexes (LIs) of Ki-67 and PCNA were also obtained. The relationship between the DcR3 level and clinicopathological features was investigated, including tumor differentiation, LIs, and survival. Meanwhile, the expression of DcR3 protein was also measured in the supernatants of 8 glioma cell lines and glioma cells freshly prepared from 8 human glioblastoma specimens by using western blot. RESULTS: The level of DcR3 protein in gliomas was significantly higher than that in normal brain tissues (P < 0.01). DcR3 expression showed positive correlations with tumor pathological grade (r = 0.621, P < 0.01) and negative with GFAP expression (r = -0.489, P < 0.01). Furthermore, there were positive correlations between DcR3 expression and Ki-67, PCNA LIs (r = 0.529, P < 0.01; r = 0.556, P < 0.01). The survival in the DcR3 negative group was 50 ± 1.79 months, longer than that of the DcR3 positive group (48.36 ± 2.90), however, without significance (P = 0.149). Different levels of DcR3 could also be detected in the culturing supernatants of all the 8 glioma cell lines and glioma cells freshly obtained from 8 human glioblastoma specimens. CONCLUSIONS: The overexpression of DcR3 might play a crucial role in the tumorigenesis, differentiation, and proliferation of glioma.

Role of an MDM4 polymorphism in the early age of onset of nasopharyngeal carcinoma.

Mouse double minute 4 (MDM4) is a critical negative regulator of the tumor suppressor p53. The results of studies have revealed that an MDM4 polymorphism (rs1563828) may contribute to the earlier onset of several malignant diseases. However, the correlation between this polymorphism and nasopharyngeal carcinoma (NPC) susceptibility has not been explored. We performed a case-control study with 210 NPC patients and 200 healthy controls. Significant associations were found when comparing the age of onset of NPC according to the rs1563828 genotype (P=0.01). The average age of onset of NPC in patients with the TT, CC and CT genotypes was 39.3, 48.2 and 45.5 years, respectively. Homozygous variant (TT) carriers developed NPC at an earlier age than homozygous (CC) carriers, such that the age of onset was accelerated by 8.9 years (P=0.002). Our data suggest that rs1563828 is a modifier of the age of onset of NPC in the population studied. The age of onset for NPC with TT homozygotes was earlier than CC carriers.

Activation of AKT is associated with metastasis of nasopharyngeal carcinoma.

Although radiotherapy results of nasopharyngeal carcinoma (NPC) at an early stage are better than other tumors, there is still a portion of patients with NPC who die before 5 years after the treatment; the underlying mechanism remains to be further understood. This study aims to investigate the mechanism by which NPC cells escape from irradiation. Patients with NPC at stage I was included in this study. All the patients were treated with irradiation. NPC biopsies were obtained from each patient before and 1 week after the start of radiotherapy. Expression of AKT in NPC tissue was assessed by Western blotting. NPC cell line, SUNE-1 cells, was treated with irradiation. The levels of AKT in SUNE-1 cells were also assessed. The frequency of apoptotic SUNE-1 cells was evaluated by flow cytometry. The levels of AKT were markedly increased in NPC tissue after treatment with irradiation, which was significantly correlated with NPC metastasis and mortality. After irradiation, NPC cell line, SUNE-1 cells, expressed higher levels of AKT than control cells. The knockdown of AKT in SUNE-1 cells markedly increased apoptotic cell rate. Radiotherapy can increase the levels of AKT in NPC cells that are associated with NPC metastasis and increase in mortality.

[B-mode ultrasound for defining planning target volume in intensity-modulated radiotherapy for prostate cancer].

OBJECTIVE: To define the planning target volume (PTV) margins in intensity-modulated radiotherapy (IMRT) for prostate cancer without imaging guidance using B-mode acquisition and targeting (BAT) ultrasound-based prostate localization. METHODS: Ten patients with prostate cancer underwent BAT ultrasound alignment before each IMRT session. The set-up deviations, each consisting of isocenter displacements in 3 directions (anterior-posterior, right-left lateral, and superior-inferior), were recorded for a total of 225 times and analyzed with Kolmogorov-Smimov (K-S) method. RESULTS: The isocenter shift in each direction, which represented an average from all the patients, was 3.56∓2.71 mm, 4.08∓3.99 mm, and 3.20∓2.92 mm in the lateral (RL), anteroposterior (AP), and superior-inferior (SI) dimensions, respectively, and the deviations in each direction conformed to a normal distribution (P=0.806, P=0.061, and P=0.106, respectively). In the absence of imaging guidance for IMRT for prostate cancer, the PTV margin should expand by 8.97 mm in the right, 1.87 mm in the left, 12.05 mm in the anterior, 3.91 mm in the posterior, 9.06 mm in the superior and 2.66 mm in the inferior to allow 95% isodose curve to cover 90% of the clinical target volume. CONCLUSION: The ultrasound imagining guided localization, with simple operation, nonirradiation and small systemic error, can be real-time corrected.

[Effect of gemcitabine in enhancing the radiosensitivity of HepG2 hepatoma cells and the possible mechanism].

OBJECTIVE: To evaluate the effect of gemcitabine in enhancing the radiosensitivity of hepatoma cell line HepG2 and explore its mechanisms. METHODS: Clonogenic survival assay is employed to calculate the ratios of L-Q model radiation biology parameters and radiosensitization after different doses of irradiation. Flow cytometry was used to detect the changes in HepG2 cell cycle and apoptosis rate after gemcitabine treatment and radiation exposure. RESULTS: The survival fraction at 2 Gy of HepG2 cells treated with gemcitabine was significantly lower, and the value of alpha was significantly higher than those of untreated cells. GEM treatment increased the percentage of radiation-induced G0/G1 phase cells and cell apoptosis. CONCLUSION: Gemcitabine can significantly enhance the radiosensitivity of HepG2 cells by enhancing radiation-induced cell cycle arrest in G0/G1 phase and cell apoptosis.

A functional variant in microRNA-196a2 is associated with susceptibility of colorectal cancer in a Chinese population.

BACKGROUND AND AIMS: MicroRNAs (miRNA) can act as oncogenes or tumor suppressors. Polymorphisms present in pri-, pre- and mature miRNAs can potentially modulate the expression of hundreds of genes, broadly affecting miRNA function. Notably, the rs11614913 SNP in miR-196a2 has been implicated in carcinogenesis, but its association with colorectal cancer (CRC) remains unexplored. We performed a case-control study to investigate the genetic association between this functional SNP and CRC susceptibility and progression. METHODS: We genotyped the rs11614913 SNP in 252 CRC patients and 543 healthy controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In addition, we examined miR-196a expression level in colorectal cancer tissues (n = 50) obtained from the studied CRC patients. RESULTS: Frequency of the CC genotype was higher in CRC patients than controls, implying that the subjects with the CC genotype or C allele containing genotypes (CT and CC) have a higher risk of CRC. However, no significant association between this polymorphism and CRC progression was observed. Expression analysis revealed that rs11614913 CC or carrying at least one C allele was associated with a significantly increased level of mature miR-196a (p = 0.010 or = 0.022). CONCLUSIONS: The present study provides the first evidence that miR-196a2 polymorphism may contribute to CRC susceptibility in a Chinese population through modulating mature miR-196a expression.

Pharmacological inhibition of AKT sensitizes MCF-7 human breast cancer-initiating cells to radiation.

BACKGROUND: Caner-initiating cells (CICs or cancer stem cells) have been shown both experimentally and clinically to be resistant to radiation. The mechanism underlying radioresistance remains unclear. METHODS: In the present study, we screened 51 genes which are potentially important in mediating radioresistance of breast CICs. RESULTS: The expression of AKT1 and AKT2 at protein and mRNA levels was dramatically increased among the screened genes by 8 Gy radiation treatment in MCF-7 mammosphere cells (predominantly CD24(-/low)/CD44(+) CICs), but not in the bulk population of MCF-7 cells (predominantly CD24(+)/CD44(+)). Using apoptosis and clonogenic survival assays, we found pharmacological inhibition of AKT with selective inhibitors of AKT sensitized MCF-7 mammosphere cells, but not MCF-7 monolayer cells to radiation. CONCLUSION: The present findings suggest that treatment with AKT inhibitors prior to ionizing radiation treatment may be a potential benefit to patients with breast cancer, in particular to eradiate breast CICs.

STAT1 promotes radioresistance of CD44(+)/CD24(-/low) cells in breast cancer.

Breast cancer-initiating cells are a relatively radioresistant subpopulation of breast cancer cells. However, the mechanism of this radioresistance is still unclear. This study aimed to investigate the effect of radiation on the levels of signal transducer and activator of transcription 1 (STAT1) in mammospheres of cancer-initiating cells and monolayer cultures of MCF-7 cells. We isolated CD44(+)/CD24(-/low) cancer-initiating cells from MCF-7 cells and propagated them as mammospheres. Next we used realtime quantitative reverse-transcriptase polymerase chain reaction to examine the mRNA level of STAT1 in mammospheres of breast cancer-initiating cells and monolayer cultures of MCF-7 cells. The apoptosis rate and surviving fraction using clonogenic assays was observed after treating the cells with a STAT1 inhibitor. After irradiation, the STAT1 level in the mammospheres was higher than that in the monolayer cultures. STAT1 inhibitor treatment did not cause significant changes in the apoptosis rate and surviving fraction in the MCF-7 monolayer cultures. However, the inhibitor treatment caused significant differences in the apoptosis rate and surviving fraction in mammospheres. Our study provides the first evidence that STAT1 signaling contributes to radioresistance in breast cancer-initiating cells and reveals STAT1 as a promising target to reduce radioresistance and enhance the efficacy of radiotherapy for breast cancer.

Impact of prolonged fraction delivery times simulating IMRT on cultured nasopharyngeal carcinoma cell killing.

PURPOSE: To determine the impact of prolonged fraction delivery times (FDTs) simulating intensity-modulated radiotherapy (IMRT) on cultured nasopharyngeal carcinoma (NPC) cell killing. METHODS AND MATERIAL: Cultured NPC cell lines CNE1 and CNE2 were used in this study. The biological effectiveness of fractionated irradiation protocols simulating conventional external beam radiotherapy and IMRT (FDT of 15, 36, and 50 minutes) was estimated with standard colony assay, and the differences in cell surviving fractions after irradiation with different protocols were tested by use of the paired t test. The impact degree of prolonged FDTs (from 8 to 50 minutes) on cell killing was also assessed by the dose-modifying factors, which were estimated by comparing the effectiveness of intermittently delivered 2 Gy with that of continuously delivered 1.5 to 2 Gy. RESULTS: The cell surviving fractions of both CNE1 and CNE2 after fractionated irradiation simulating IMRT were higher than those simulating conventional external beam radiotherapy (p < 0.05). The dose-modifying factors for a fraction dose of 2 Gy increased from 1.05 to 1.18 for CNE1 and from 1.05 to 1.11 for CNE2 with the FDT being prolonged from 15 to 50 minutes. CONCLUSIONS: This study showed that the prolonged FDTs simulating IMRT significantly decreased the cell killing in both CNE1 and CNE2 cell lines, and these negative effects increased with the FDT being prolonged from 15 to 50 minutes. These effects, if confirmed by in vivo and clinical studies, need to be considered in designing IMRT treatments for NPC.

[Effect of NAD+ against radiation injury and its dose-effect relationship].

OBJECTIVE: To explore the effect of NAD+ against radiation injury and its dose-effect relationship. METHODS: L02 liver cells cultured in RPMI 1640 medium containing 10% fetal calf serum were exposed to X-ray irradiation followed by immediate application of NAD+. The cellular viability was analyzed by MTT assay and the apoptotic cells were detected by TUNEL methods to observe the damages of L02 liver cells induced by X-ray exposure and analyze the dose-effect relationship of NAD+. RESULTS: The viability of L02 liver cells was decreased with increasing dose of X-ray irradiation. The most obvious growth inhibition of L02 cells occurred 24 h after the irradiation. NAD+ significantly increased the cell survival rate after irradiation, and this effect was gradually increased within the concentration range of 100-1000 microg/ml; at higher concentrations, the survival rate of the irradiated L02 cells showed no significant increase. CONCLUSION: NAD+ provides partial protection of the liver cells against radiation injury, and the effect is positively correlated to NAD+ concentration within a certain range.

[Effects of radiosensitivity and X-ray dose on miR-7 expression in nasopharyngeal carcinoma].

OBJECTIVE: To investigate the effects of radiosensitivity and X-ray dose on the expression of miR-7 in nasopharyngeal carcinoma (NPC) cells. METHODS: Low radiosensitive NPC cells CNE-1 and high radiosensitive NPC cells CNE-2 were exposed to 0, 2 and 8 Gy X-ray. The total RNAs of the cell lines were extracted 10 h after radiation for reverse transcription of miR-7 and 18S rRNA by stem-loop primer and random hexamers, respectively. The non-irradiated CNE-1 cells served as the control sample and the relative quantity of the expression level was calculated after real-time PCR using SyBR green. RESULTS: miR-7 expression differed significantly between CNE-1 and CNE-2 cells (4.49-/+3.62 vs 1.29-/+1.10, F=135.483, P<0.001). The radiation dose also significantly affected the expression of miR-7 in NPC cells (F=39.565, P<0.001). CNE-1 cells with a 2 Gy exposure had the highest expression level of miR-7, while the non-irradiated CNE-1 cells had the lowest expression. CNE-2 cells exposed to 2 Gy X-ray had the lowest expression level of miR-7 and the non-irradiated CNE-2 cells had the highest. CONCLUSION: Radiosensitivity and radiation dose of X-ray have significant effect on the expression of miR-7 in NPC cells, indicating that miR-7 plays an important role in radioresistance of NPC cells to X-ray, and suppressed miR-7 expression may elevate the radiosensitivity of NPC cells.