Dynamic genomic changes in methotrexate-resistant human cancer cell lines beyond DHFR amplification suggest potential new targets for preventing drug resistance.

BACKGROUND: Although DHFR gene amplification has long been known as a major mechanism for methotrexate (MTX) resistance in cancer, the early changes and detailed development of the resistance are not yet fully understood. METHODS: We performed genomic, transcriptional and proteomic analyses of human colon cancer cells with sequentially increasing levels of MTX-resistance. RESULTS: The genomic amplification evolved in three phases (pre-amplification, homogenously staining region (HSR) and extrachromosomal DNA (ecDNA)). We confirm that genomic amplification and increased expression of DHFR, with formation of HSRs and especially ecDNAs, is the major driver of resistance. However, DHFR did not play a detectable role in the early phase. In the late phase (ecDNA), increase in FAM151B protein level may also have an important role by decreasing sensitivity to MTX. In addition, although MSH3 and ZFYVE16 may be subject to different posttranscriptional regulations and therefore protein expressions are decreased in ecDNA stages compared to HSR stages, they still play important roles in MTX resistance. CONCLUSION: The study provides a detailed evolutionary trajectory of MTX-resistance and identifies new targets, especially ecDNAs, which could help to prevent drug resistance. It also presents a proof-of-principal approach which could be applied to other cancer drug resistance studies.

RPL22L1, a novel candidate oncogene promotes temozolomide resistance by activating STAT3 in glioblastoma.

Aggressiveness and drug resistance are major challenges in the clinical treatment of glioblastoma (GBM). Our previously research reported a novel candidate oncogene ribosomal protein L22 like 1 (RPL22L1). The aim of this study was to elucidate the potential role and mechanism of RPL22L1 in progression and temozolomide (TMZ) resistance of GBM. Online database, tissue microarrays and clinical tissue specimens were used to evaluate the expression and clinical implication of RPL22L1 in GBM. We performed cell function assays, orthotopic and subcutaneous xenograft tumor models to evaluate the effects and molecular mechanisms of RPL22L1 on GBM. RPL22L1 expression was significantly upregulated in GBM and associated with poorer prognosis. RPL22L1 overexpression enhanced GBM cell proliferation, migration, invasion, TMZ resistance and tumorigenicity, which could be reduced by RPL22L1 knockdown. Further, we found RPL22L1 promoted mesenchymal phenotype of GBM and the impact of these effects was closely related to EGFR/STAT3 pathway. Importantly, we observed that STAT3 specific inhibitor (Stattic) significantly inhibited the malignant functions of RPL22L1, especially on TMZ resistance. RPL22L1 overexpressed increased combination drug sensitive of Stattic and TMZ both in vitro and in vivo. Moreover, Stattic effectively restored the sensitive of RPL22L1 induced TMZ resistance in vitro and in vivo. Our study identified a novel candidate oncogene RPL22L1 which promoted the GBM malignancy through STAT3 pathway. And we highlighted that Stattic combined with TMZ therapy might be an effective treatment strategy in RPL22L1 high-expressed GBM patients.

Novel insights into the ecDNA formation mechanism involving MSH3 in methotrexate­resistant human colorectal cancer cells.

Extrachromosomal DNAs (ecDNAs), also known as double minutes (DMs), can induce a fast increase in gene copy numbers and promote the development of cancer, including drug resistance. MutS homolog 3 (MSH3), a key protein in mismatch repair, has been indicated to participate in the regulation of DNA double­strand break (DSB) repair, which has been reported to be associated with the formation of ecDNAs. However, it remains unclear whether MSH3 can influence drug resistance via ecDNAs in cancer. In the present study, high MSH3 expression was observed in methotrexate (MTX)­resistant HT29 cells [DM­ and homogeneously staining region (HSR)­containing cells] compared with parental HT29 cells. Additionally, decreased amounts of ecDNAs, HSRs and amplified genes locating on ecDNAs and HSRs were detected following depletion of MSH3 and this could be reversed by overexpressing MSH3 in DM­containing cells. No corresponding changes were found in HSR­containing cells. The present study further verified the involvement of MSH3­regulated DNA DSB repair pathways in the formation of ecDNAs by detecting the expression of core proteins and pathway activity. Furthermore, expulsion of ecDNAs/HSRs was detected and increased frequencies of micronuclei/nuclear buds with dihydrofolate reductase (DHFR) signals were observed in MSH3­depleted DM­containing cells. Finally, changes in MSH3 expression could affect DHFR amplification­derived DHFR expression and cell sensitivity to MTX, suggesting that MSH3 may influence cancer drug resistance by altering the amount of ecDNAs. In conclusion, the present study revealed a novel mechanism involving MSH3 in the regulation of ecDNAs by DSB repair, which will have clinical value in the treatment of ecDNA­based drug resistance in cancer.

The effect of SNPs in lncRNA as ceRNA on the risk and prognosis of hepatocellular carcinoma.

BACKGROUND: Most susceptible loci of hepatocellular carcinoma (HCC) identified by genome-wide association studies (GWAS) are located in non-coding regions, and the mechanism of action remains unclear. The objective of this study was to explore the association of single nucleotide polymorphisms (SNPs) on long non-coding RNAs (lncRNAs) that affect competing endogenous RNAs (ceRNA) regulation mechanism with the risk and prognosis of HCC. METHODS: Based on a set of bioinformatics strategies, eight lncRNA genes that affect HCC through the mechanism of lncRNA-mediated ceRNA were systematically screened, and 15 SNPs that affect microRNA (miRNA) binding in these lncRNA genes were annotated. Genotyping was performed in 800 HCC cases and 801 healthy controls to examine associations of these SNPs with HCC in a northeastern Chinese Han population. RESULTS: The GG, GC and GG + GC genotypes of HOTAIR rs7958904 were associated with a 0.65, 0.59 and 0.63-fold decreased HCC risk, respectively. In addition, HCC patients with PVT1 rs3931282 AA + GA genotypes were less prone to develop late-stage cancers in a stratified analysis of clinical characteristics. When stratified by clinical biochemical indexes, rs1134492 and rs10589312 in PVT1 and rs84557 in EGFR-AS1 showed significant associations with aspartate aminotransferase (AST), alanine aminotransferase (ALT) or AST/ALT ratio in HCC patients. Furthermore, we constructed potential ceRNA regulatory axes that might be affected by five positive SNPs to explain the causes of these genetic associations. CONCLUSIONS: HOTAIR rs7958904, PVT1 rs3931282, rs1134492 and rs10589312, and EGFR-AS1 rs84557 might be predictors for HCC risk or prognosis. Our results provide new insights into how SNPs on lncRNA-mediated ceRNAs confer interindividual differences to occurrence and progression of HCC.

Ribosomal protein L22-like1 (RPL22L1) mediates sorafenib sensitivity via ERK in hepatocellular carcinoma.

Precision medicine in hepatocellular carcinoma (HCC) relies on validated biomarkers that help subgroup patients for targeted treatment. Here, we identified a novel candidate oncogene, ribosomal protein L22-like1 (RPL22L1), which was markedly elevated in HCC, contributed to HCC malignancy and adverse patient survival. Functional studies indicated RPL22L1 overexpression accelerated cell proliferation, migration, invasion and sorafenib resistance. Mechanism studies revealed that RPL22L1 activated ERK to induce atypical epithelial-to-mesenchymal transition (EMT) progress. Importantly, the ERK inhibitor (ERKi) could potentiate sorafenib efficiency in RPL22L1-high HCC cells. In summary, these data uncover RPL22L1 is a potential marker to guide precision therapy for utilizing ERKi to enhance the sorafenib efficacy in RPL22L1-high HCC patients.

The Impacts of Non-coding RNAs and N6-Methyladenosine on Cancer: Past, Present and Future.

N6-methyladenosine (m6A) modifications control multifaceted RNA metabolism and are one of the most extensively distributed modifications on the human transcriptome, including non-coding RNAs (ncRNAs). Previous concepts of ncRNAs as "junk" transcriptional products have evolved to the concept that ncRNAs are functional regulatory molecules that determine specific biological processes and cell fates. The dysregulation of m6A modifications and ncRNAs have been implicated in the development of human carcinogenesis. Certain types of ncRNAs have been reported to exert regulatory effects on m6A machinery. However, a better understanding of the relationship between m6A modifications and ncRNAs in cancer is still needed. This review discusses mutual interactions between m6A modifications and ncRNAs and their impacts on the development of human cancer. We summarize the clinical significance of m6A-ncRNA networks for cancer diagnosis and treatment, and we ask challenging questions that remain unanswered in this field of research. Understanding the complex coordination between m6A modifications and ncRNAs will be useful for guiding the development of therapeutic interventions.

Molecular structure and evolution mechanism of two populations of double minutes in human colorectal cancer cells.

Gene amplification chiefly manifests as homogeneously stained regions (HSRs) or double minutes (DMs) in cytogenetically and extrachromosomal DNA (ecDNA) in molecular genetics. Evidence suggests that gene amplification is becoming a hotspot for cancer research, which may be a new treatment strategy for cancer. DMs usually carry oncogenes or chemoresistant genes that are associated with cancer progression, occurrence and prognosis. Defining the molecular structure of DMs will facilitate understanding of the molecular mechanism of tumorigenesis. In this study, we re-identified the origin and integral sequence of DMs in human colorectal adenocarcinoma cell line NCI-H716 by genetic mapping and sequencing strategy, employing high-resolution array-based comparative genomic hybridization, high-throughput sequencing, multiplex-fluorescence in situ hybridization and chromosome walking techniques. We identified two distinct populations of DMs in NCI-H716, confirming their heterogeneity in cancer cells, and managed to construct their molecular structure, which were not investigated before. Research evidence of amplicons distribution in two different populations of DMs suggested that a multi-step evolutionary model could fit the module of DM genesis better in NCI-H716 cell line. In conclusion, our data implicated that DMs play a very important role in cancer progression and further investigation is necessary to uncover the role of the DMs.

Disease causing property analyzation of variants in 12 Chinese families with polycystic kidney disease.

BACKGROUND: Polycystic kidney disease (PKD) is an inherited disease that is life-threatening. Multiple cysts are present in the bilateral kidneys of PKD patients. The progressively enlarged cysts cause structural damage and loss of kidney function. METHODS: This study examined and analyzed 12 families with polycystic kidney disease. Whole exome sequencing (WES) or whole genome sequencing (WGS) of the probands was performed to detect the pathogenic genes. The candidate gene segments for lineal consanguinity in the family were amplified by the nest PCR followed by Sanger sequencing. The variants were assessed by pathogenic and conservational property prediction analysis and interpreted according to the American College of Medical Genetics and Genomics. RESULTS: Nine of the 12 pedigrees were identified the disease causing variants. Among them, four novel variants in PKD1, c.6930delG:p.C2311Vfs*3, c.1216T>C:p.C406R, c.8548T>C:p.S2850P, and c.3865G>A:p.V1289M (NM_001009944.2) were detected. After assessment, the four novel variants were considered to be pathogenic variants and cause autosomal dominant polycystic kidney disease in family. The detected variants were interpreted. CONCLUSION: The four novel variants in PKD1, c.6930delG:p.C2311Vfs*3, c.1216T>C:p.C406R, c.8548T>C:p.S2850P, and c.3865G>A:p.V1289M (NM_001009944.2) are pathogenic variants and cause autosomal dominant polycystic kidney disease in family.

Physiological Acclimatization of the Liver to 180-Day Isolation and the Mars Solar Day.

Physiological changes in humans are evident under environmental conditions similar to those on a Mars mission involving both a space factor (long-term isolation) and a time factor (the Mars solar day). However, very few studies have investigated the response of the liver to those conditions. Serum protein levels, bilirubin levels, aminotransferase activities, blood alkaline phosphatase, gamma-glutamyltransferase, lipid levels, and serum cytokines interleukin-6 and interferon-γ levels were analyzed 30 days before the mock mission; on days 2, 30, 60, 75, 90, 105, 120, 150, and 175 of the mission; and 30 days after the mission, in four subjects in 4-person 180-day Controlled Ecological Life Support System Experiment. Serum protein levels (total protein and globulin) decreased and bilirubin increased under the isolation environment from day 2 and exhibited chronic acclimatization from days 30 to 175. Effects of the Mars solar day were evident on day 75. Blood lipid levels were somewhat affected. No obvious peak in any enzyme level was detected during the mission. The change tendency of these results indicated that future studies should explore whether protein parameters especially globulin could serve as indicators of immunological function exposure to the stress of a Mars mission.

Analysis of miRNA expression profiles in the liver of Clock Δ19 mutant mice.

The circadian clock controls the physiological functions of many tissues including the liver via an autoregulatory transcriptional-translational feedback loop, of which CLOCK is a core positive component. In addition, many studies have indicated that microRNAs (miRNAs) regulate liver function. However, how CLOCK-regulated miRNAs are linked to liver function remains largely unknown. In this study, miRNAs expression profiles were performed in the liver of Clock Δ19 mutant mice. Compared to wild type mice, totals of 61 and 57 putative CLOCK-regulated miRNAs were differentially expressed (fold change absolute value ≥2) at zeitgeber time 2 and zeitgeber time 14, respectively. According to the pathway analyses, the target genes of differentially expressed miRNAs were mainly involved in pathways in cancer, the PI3K-Akt signaling pathway and the MAPK signaling pathway. Protein-protein interaction analyses revealed that the hub genes were primarily associated with pathway in cancer and circadian rhythms. Expression validation showed that while the expression levels of miR-195 and miR-340 were up-regulated, the rhythms of these two miRNAs were always maintained. The expression level of nr1d2 mRNA was down-regulated. We identified a number of prospective CLOCK-regulated miRNAs that play roles in the various physiological processes of the liver, providing a reference to better understanding the potential regulatory mechanisms in the liver.

Hydrogen peroxide modulates clock gene expression via PRX2-STAT3-REV-ERBα/ß pathway.

The circadian rhythm is a widespread physiological phenomenon present in almost all forms of life and is constituted by a system of interlocked transcriptional/translational feedback loops (TTFLs). External zeitgebers regulate biological rhythms through the direct or indirect regulation of circadian genes. Oxidative stress is involved in many diseases and injuries, such as ageing, diabetes, Alzheimer's disease, and cancer. Despite an increasing number of studies on circadian rhythm disorders caused by oxidative stress, little is known about the effects of oxidants on clock gene expression and the underlying mechanism. In this study, we found that the protein expression of circadian genes Clock, Bmal1, Per1/2, and Cry1/2 in NIH3T3 cells was upregulated by hydrogen peroxide (H2O2), an important mediator of oxidative stress. In addition, H2O2 modulated the circadian rhythm of Bmal1-luciferase via RORα, REV-ERBα (NR1D1), and REV-ERBß (NR1D2). Further studies showed that H2O2 regulated biological rhythm by PRX2-STAT3-REV-ERBα/ß pathway. These findings provide an accessory loop-related mechanism by which non-transcriptional oscillation interplays with TTFLs.

TSPAN12 Precedes Tumor Proliferation by Cell Cycle Control in Ovarian Cancer.

TSPAN12, a member of the tetraspanin family, has been highly connected with the pathogenesis of cancer. Its biological function, however, especially in ovarian cancer (OC), has not been well elucidated. In this study, The Cancer Genome Atlas (TCGA) dataset analysis revealed that upregulation of TSPAN12 gene expression was significantly correlated with patient survival, suggesting that TSPAN12 might be a potential prognostic marker for OC. Further exploration showed that TSPAN12 overexpression accelerated proliferation and colony formation of OVCAR3 and SKOV3 OC cells. Knockdown of TSPAN12 expression in A2780 and SKOV3 cells decreased both proliferation and colony formation. Western blot analysis showed that several cyclins and cyclin-dependent kinases (CDK) (e.g., Cyclin A2, Cyclin D1, Cyclin E2, CDK2, and CDK4) were significantly involved in the regulation of cell cycle downstream of TSPAN12. Moreover, TSPAN12 accelerated mitotic progression by controlling cell cycle. Thus, our data demonstrated that TSPAN12 could be a novel molecular target for the treatment of OC.

Identification of a pathogenic mutation in a Chinese pedigree with polycystic kidney disease.

Polycystic kidney disease (PKD) is a life­threatening inherited disease with a morbidity of 1:500­1,000 worldwide. Numerous progressively enlarging cysts are observed in the bilateral kidneys of patients with PKD, inducing structural damage and loss of kidney function. The present study analyzed one family with PKD. Whole exome sequencing of the proband was performed to detect the pathogenic gene present in the family. Candidate gene segments for lineal consanguinity in the family were amplified by nest polymerase chain reaction, followed by Sanger sequencing. One novel duplication variant (NM_001009944.2:c.9359dupA:p.Y3120_E3121delinsX) and one missense mutation (c.G9022A:p.V3008M) were detected in PKD1. Additionally, the pathogenic substitutions in PKD1 published from the dataset were analyzed. Following analysis and confirmation, the duplication variant NM_001009944.2:c.9359dupA:p.Y3120_E3121delinsX in PKD1, within the polycystin­1, lipoxygenase, α­toxin domain, was considered to be the pathogenic factor in the examined family with autosomal dominant PKD. Additionally, based on the analysis of 4,805 pathogenic substitutions in PKD1 within various regions, the presence of the missense mutation in the N­terminal domain of polycystin­1 may present high pathogenicity in ADPKD.

Expression profiles and functional annotation analysis of mRNAs in suprachiasmatic nucleus of Clock mutant mice.

The core circadian clock gene, Clock, is a positive component of the transcription/translation feedback loop in the master pacemaker suprachiasmatic nucleus (SCN) in mammals. The robust daytime peak of some clock genes in the wild-type SCN is absent in Clock mutant mice. However, very little is known about the impact of Clock mutation on the expression of other functional genes in SCN. Here, we performed cDNA microarray and found 799 differentially expressed genes (DEGs) at zeitgeber time 2 (ZT2) and 1289 DEGs at ZT14 in SCN of Clock△19/△19 mutant mice. KEGG pathway analysis showed that the changed mRNAs were highly associated with hedgehog signaling pathway, retinol metabolism, allograft rejection, drug metabolism, hematopoietic cell lineage and neuroactive ligand-receptor interaction. The top 14 and 71 hub genes were identified from the protein-protein interaction (PPI) network at ZT2 and ZT14, respectively. The sub-networks revealed hub genes were involved in olfactory transduction and neuroactive ligand-receptor interaction pathways. These results demonstrate the Clock△19/△19 mutation alters the expression of various genes involved in a wide spectrum of biological function in mouse SCN, which are helpful for better understanding the function of Clock and potential regulatory mechanisms.

Overexpression of RCC2 Enhances Cell Motility and Promotes Tumor Metastasis in Lung Adenocarcinoma by Inducing Epithelial-Mesenchymal Transition.

Purpose: Investigate the role of regulator of chromosome condensation 2 (RCC2) on lung adenocarcinoma (LUAD) metastasis.Experimental Design: Clinical specimens were used to assess the impact of RCC2 on LUAD metastasis. Mouse models, cytobiology, and molecular biology assays were performed to elucidate the function and underlying mechanisms of RCC2 in LUAD.Results: RCC2 expression was frequently increased in LUADs (88/122, 72.13%). It was confirmed by analysis of a larger cohort of TCGA RNA-seq data containing 488 LUADs and 58 normal lung tissues (P < 0.001). Importantly, increased level of RCC2 was significantly associated with T status of tumor (P = 0.002), lymph node metastasis (P = 0.004), and advanced clinical stage (P = 0.001). Patients with LUAD with higher expression of RCC2 had shorter overall survival. Cox regression analysis demonstrated that RCC2 was an independent poorer prognostic factor for patients with LUAD. Moreover, forced expression of RCC2 promoted intrapulmonary metastasis in vivo and significantly enhanced LUAD cell migration, invasion, and proliferation in vitro Further study found that RCC2 induced epithelial-mesenchymal transition (EMT) and also stimulated the expression of MMP-2 and MMP-9. In addition, RCC2 was able to activate JNK, while inhibition of JNK suppressed the effect of RCC2 on LUAD cell migration, invasion, EMT, and the expression of MMP-2 and MMP-9.Conclusions: RCC2 plays a pivotal role in LUAD metastasis by inducing EMT via activation of MAPK-JNK signaling. Clin Cancer Res; 23(18); 5598-610. ©2017 AACR.

Activation of HIF-1α and its downstream targets in rat hippocampus after long-term simulated microgravity exposure.

Microgravity has many detrimental impact on brain functions, however the underlying mechanism remain unclear. In present study, 28 days of tail-suspension (30°) was used to simulate microgravity in rats. We showed that oxidative stress in hippocampus was increased after 28 days of simulated microgravity in consideration of the decreased expression of NF-E2-related factor 2 (Nrf2) and the declined activities of total superoxide dismutase (T-SOD), CuZn-SOD, glutathione peroxidase (GSH-PX) and total antioxidant capacity (T-AOC). Using RNA-seq, we further investigated the effect of simulated microgravity on the expression of genes in hippocampus, and 849 genes were found to be differentially expressed. According to pathway analysis, the differentially expressed genes involved in cytoskeleton, metabolism, immunity, transcription regulation, etc. It is interesting to note that the differentially expressed genes were involved in hypoxia-associated pathway. In agreement with this, the expression of hypoxia induced factor-1α (HIF-1α), the master regulator of oxygen homeostasis, was significantly increased. Meanwhile, HIF-2α, a HIF-1α paralog, was elevated compared with the control group. The expression of pyruvate dehydrogenase kinase 1 (PDK1), lactate dehydrogenase A (LDHA) and vascular endothelial growth factor (VEGF), three well-defined downstream targets of HIF-1α, were up-regulated in hippocampus after 28 days of simulated microgravity exposure. Additionally, brain oxygen saturation (SO2) and blood flow analyzed by the tissue oxygen analysis system were also significantly reduced. These findings indicate that simulated microgravity might cause an alteration in oxygen homeostasis, providing novel insight into better understanding of how simulated microgravity affects the function of hippocampus and a new direction to the development of countermeasure for brain dysfunction during spaceflight (actual microgravity).

Intramuscular injection of mechano growth factor E domain peptide regulated expression of memory-related sod, miR-134 and miR-125b-3p in rat hippocampus under simulated weightlessness.

OBJECTIVE: To investigate the expression of memory-related antioxidant genes and miRNAs under simulated weightlessness and the regulation of mechano growth factor (MGF) E domain, the peptide preventing nerve damage. RESULTS: Igf-iea and mgf mRNA levels, expression of antioxidant genes sod1 and sod2 and levels of miR-134 and miR-125b-3p increased in rat hippocampus after 14 days tail suspension to simulate weightlessness which was inhibited with intramuscular injection of E domain peptide. Therefore, administration of MGF E domain peptide could reverse increased expressions of memory-related igf-iea, mgf, sod1, sod2, miR-134 and miR-125b-3p in rat hippocampus under simulated weightlessness. CONCLUSIONS: MGF may regulate the redox state and miRNA-targeted NR-CREB signaling, and intramuscular injection may be the alternative administration because of its safety, convenience and ability to pass through the blood brain barrier.

Met promotes the formation of double minute chromosomes induced by Sei-1 in NIH-3T3 murine fibroblasts.

BACKGROUND: Sei-1 is an oncogene capable of inducing double minute chromosomes (DMs) formation. DMs are hallmarks of amplification and contribute to oncogenesis. However, the mechanism of Sei-1 inducing DMs formation remains unelucidated. RESULTS: DMs formation significantly increased during serial passage in vivo and gradually decreased following culture in vitro. micro nuclei (MN) was found to be responsible for the reduction. Of the DMs-carrying genes, Met was found to be markedly amplified, overexpressed and highly correlated with DMs formation. Inhibition of Met signaling decreased the number of DMs and reduced the amplification of the DMs-carrying genes. We identified a 3.57Mb DMs representing the majority population, which consists of the 1.21 Mb AMP1 from locus 6qA2 and the 2.36 Mb AMP2 from locus 6qA2-3. MATERIALS AND METHODS: We employed NIH-3T3 cell line with Sei-1 overexpression to monitor and characterize DMs in vivo and in vitro. Array comparative genome hybridization (aCGH) and fluorescence in situ hybridization (FISH) were performed to reveal amplification regions and DMs-carrying genes. Metaphase spread was prepared to count the DMs. Western blot and Met inhibition rescue experiments were performed to examine for involvement of altered Met signaling in Sei-1 induced DMs. Genomic walking and PCR were adopted to reveal DMs structure. CONCLUSIONS: Met is an important promotor of DMs formation.

A new method of detecting pulmonary nodules with PET/CT based on an improved watershed algorithm.

BACKGROUND: Integrated 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is widely performed for staging solitary pulmonary nodules (SPNs). However, the diagnostic efficacy of SPNs based on PET/CT is not optimal. Here, we propose a method of detection based on PET/CT that can differentiate malignant and benign SPNs with few false-positives. METHOD: Our proposed method combines the features of positron-emission tomography (PET) and computed tomography (CT). A dynamic threshold segmentation method was used to identify lung parenchyma in CT images and suspicious areas in PET images. Then, an improved watershed method was used to mark suspicious areas on the CT image. Next, the support vector machine (SVM) method was used to classify SPNs based on textural features of CT images and metabolic features of PET images to validate the proposed method. RESULTS: Our proposed method was more efficient than traditional methods and methods based on the CT or PET features alone (sensitivity 95.6%; average of 2.9 false positives per scan).

MiR-146a regulates SOD2 expression in H2O2 stimulated PC12 cells.

SOD2 (superoxide dismutase 2) is one of the endogenous antioxidant enzymes that protect against reactive oxygen species. While explorations of SOD2 expression regulation are mainly focused on transcriptional and post-translational activation, there are few reports about the post-transcriptional regulation of SOD2. MicroRNAs (miRNAs) are 21nt-25nt (nucleotide) small noncoding RNAs that have emerged as indispensable regulators of gene expression. Here we show that miR-146a, a widely expressed miRNA, is up-regulated by H2O2-induced stress. By sequence analysis we found a binding site for miR-146a in the sod2 mRNA 3'UTR, and a luciferase reporter assay confirmed that miR-146a can interact with this sod2 regulatory region. Our results further show that miR-146a could down-regulate the SOD2 protein expression, and antisense-miR-146a could reverse the decrease of both the SOD2 level and cell viability in H2O2 treated PC12 cells. In conclusion, here we have identified a novel function of miR-146a in the post-transcriptional regulation of SOD2 expression.