Profiles of alternative splicing landscape in breast cancer and their clinical significance: an integrative analysis based on large-sequencing data.

BACKGROUND: Alternative splicing (AS) is closely correlated with the initiation and progression of carcinoma. The systematic analysis of its biological and clinical significance in breast cancer (BRCA) is, however, lacking. METHODS: Clinical data and RNA-seq were obtained from the TCGA dataset and differentially expressed AS (DEAS) events between tumor and paired normal BRCA tissues were identified. Enrichment analysis was then used to reveal the potential biological functions of DEAS events. We performed protein-protein interaction (PPI) analysis of DEAS events by using STRING and the correlation network between splicing factors (SFs) and AS events was constructed. The LASSO Cox model, Kaplan-Meier and log-rank tests were used to construct and evaluate DEAS-related risk signature, and the association between DEAS events and clinicopathological features were then analyzed. RESULTS: After strict filtering, 35,367 AS events and 973 DEAS events were detected. DEAS corresponding genes were significantly enriched in pivotal pathways including cell adhesion, cytoskeleton organization, and extracellular matrix organization. A total of 103 DEAS events were correlated with disease free survival. The DEAS-related risk signature stratified BRCA patients into two groups and the area under curve (AUC) was 0.754. Moreover, patients in the high-risk group had enriched basel-like subtype, advanced clinical stages, proliferation, and metastasis potency. CONCLUSIONS: Collectively, the profile of DEAS landscape in BRCA revealed the potential biological function and prognostic value of DEAS events.

Anticancer bioactive peptide (ACBP) inhibits gastric cancer cells by upregulating growth arrest and DNA damage-inducible gene 45A (GADD45A).

Recently, we reported that anticancer bioactive peptide (ACBP), purified from goat spleens immunized with human gastric cancer extracts, significantly inhibited gastric cancer cells in vitro and gastric tumors in vivo via repressing cell growth and promoting apoptosis, making it a promising potential biological anticancer drug. However, it is not known what genes are functionally required for the ACBP effects. Here, we first found that two tumor suppressor genes, cyclin-dependent kinase inhibitor 2B (CDKN2B) and growth arrest and DNA damage-inducible alpha (GADD45A), were upregulated significantly in the cells with ACBP treatment by microarray screening and the findings were validated by real-time RT-PCR. Next, GADD45A mRNA and protein expressions were downregulated in the gastric cancer cells by lentivirus-mediated RNAi; then, cell viability, cell cycle, and apoptosis were assayed by MTT and flow cytometry. Interestingly, our results indicated that cell viability was not dependent on GADD45A without ACBP treatment; however, cell sensitivity to ACBP was significantly decreased in ACBP-treated gastric cancer cells with GADD45A downregulation. Therefore, we demonstrate that GADD45A was functionally required for ACBP to inhibit gastric cancer cells, suggesting that GADD45A may become a biomarker for ACBP sensitivity. Our findings have significant implications on the molecular mechanism understanding, biomarker development, and anticancer drug development of ACBP.

Use of a dietary exposure system for screening of insecticidal compounds for their toxicity to the planthopper Laodelphax striatellus.

We developed a dietary exposure assay for screening insecticidal compounds for their toxicity and for assessing the side effects of insecticidal proteins produced by genetically engineered (GE) plants on the planthopper Laodelphax striatellus Fallén. The fitness bioassay confirmed that the diet fulfills the requirements to be used in the dietary exposure system. To validate the efficacy of the dietary exposure system, nymphs of L. striatellus were fed diets treated with different concentrations of an inorganic stomach poison, potassium arsenate (PA), or a cysteine protease inhibitor, E-64. The results showed that with increasing concentrations of E-64, the larval development time was prolonged, the adult weight was reduced and the survival rate of L. striatellus was decreased. Similarly the survival rates of L. striatellus consistently decreased with increasing PA content in the diet. The data indicate that the dietary exposure assay is able to detect the effects of insecticidal compounds on L. striatellus. Subsequently, this assay was successfully used for assessing the potential toxicity of Cry2Aa. The results showed that L. striatellus larvae were not negatively affected when fed the artificial diet containing purified Cry2Aa at 300 µg/g diet. In the assay, the stability and bioactivity of crystal (Cry) proteins in the food sources were confirmed by enzyme-linked immunosorbent assay and sensitive-insect bioassays. These results show that L. striatellus is not sensitive to Cry2Aa. We conclude that the dietary exposure system is valid and useful for assessing the toxicity of insecticidal compounds produced by GE plants on planthoppers.

[Molecular imaging of epidermal growth factor receptor in glioma-bearing rats].

OBJECTIVE: To investigate the value of 11C-PD153035 as an EGFR imaging agent in C6 tumor-bearing rat. METHODS: The tumor-bearing rats were generated by subcutaneous injection of glioma C6 cells. Positron emission tomography/computer tomography (PET/CT) scans started as soon as intravenous injection of 11C-PD153035 (15-20 MBq/0.3 ml) was completed, images were collected continuously. The region of interest (ROI) was used to study the percentage of radioactivity in major organs and implanted tumors in the rats. The accumulation and blocking study in vitro was completed. RESULTS: There were significant differences in 11C-PD153035 uptake among major organs. The maximum uptake in the organs ranked in the following order: liver > gastrointestinal tract > kidney > lung > brain > muscle. Radioactivity could be also observed in the tumors. The radioactivity ratio (T/NT, target/non-target) peaked (4.15) at 40 - 50 min post injection. The in vitro blocking study showed that 11C-PD153035 uptaken by C6 cells could be blocked by PD153035. CONCLUSION: The results of this study show that 11C-PD153035 can be uptaken by EGFR-expressing tumors. 11C-PD153035 has a potential as a bioprobe to yield useful information for both diagnosis and therapy of tumors. However, the high concentration of 11C-PD153035 in the gastrointestinal tract is unfavorably affecting the tumor detection in these organs.

[Down-regulation of TopI by RNA interference reduces the drug-sensitivity of small cell lung cancer cell lines to topotecan].

OBJECTIVE: To investigate the expressions of TopI gene in small cell lung cancer cell line H446, and explore the influence of TopI on the chemosensitivity of the cell line to topotecan (TPT). METHODS: Western blot was performed to detect the TopI expression in H446 cells. Lipofectamine 2000 was used for the transient transfection of H446 cells by siRNA, and the transfection efficacy was detected. TopI mRNA was analyzed by quantitative RT-PCR and TopI protein was detected by Western blot to selected effective siRNA. The drug-sensitivity to topotecan (TPT) was evaluated by MTT assay. RESULTS: TopI gene was expressed in H446 cells. Lipofectamine 2000 mediated the siRNA effectively (88.67%). Compared with its parental cells, RT-PCR results showed that TopI mRNAs in transfected cells were reduced by (95.7 +/- 1.6)%, (90.8 +/- 1.6)%, (96.1 +/- 2.7)% and (96.3 +/- 1.8)%, respectively, and decreased significantly at protein level. By MTT assay, the inhibition rate of TPT to H446 cells transfected by siRNA was lower than that of control group at same concentrations (P < 0.01). CONCLUSION: siRNAs can silence the expression of TopI and decrease the drug-sensitivity of H446 cells to TPT.

[Prolonged hypoxia induces GST-pi expression and drug resistance in lung adenocarcinoma cell line SPCA1].

OBJECTIVE: To investigate the association of hypoxia with GST-pi expression in lung adenocarcinoma cells SPCA1 and the drug resistance in hypoxic condition. METHODS: RNA and protein in SPCA1 cells treated with hypoxia (0.5% O(2)) for 16 h were isolated. HIF-1alpha and GST-pi mRNA expression was detected by real time RT-PCR, and HIF-1alpha protein was detected by Western blotting analysis. GST-pi protein was finally analyzed on a FACScan flow cytometer using Cellquest software. Sensitivity of Doxorubicin and Mitomycin in hypoxic SPCA1 cells was detected using cell clonogenic assay. RESULTS: HIF-1alpha expression was up-regulated on mRNA and protein levels in hypoxic SPCA1 cells, so as was GST-pi expression. Doxorubicin resistance was increased, but hypoxia had no significant influence on Mitomycin resistance. GST-pi expression had no significant change after HIF-1alpha was down-regulated by RNA interfering. CONCLUSION: Though prolonged hypoxia can induce GST-pi expression and increase drug resistance such as to Doxorubicin, HIF-1alpha expression has no correlation with GST-pi expression.

Regulation of the chemokine receptor CXCR4 and metastasis by hypoxia-inducible factor in non small cell lung cancer cell lines.

Hypoxia promotes metastatic potential of tumor cells by largely unknown mechanisms. Hypoxia inducible factor (HIF) is a heterodimeric transcription factor consisting of alpha and beta (ARNT) subunits and plays an important role in tumor microenvironment. CXCR4 is a cell surface receptor that has been shown to mediate the metastasis of various tumors. CXCR4 induction by hypoxia is dependent on both activation of HIF and transcript stabilization. To investigate the mechanisms involved in hypoxia-induced metastasis and hypoxia-mediated chemokine receptor CXCR4 expression, we used lentiviral vector mediated RNA interfering (RNAi) to knock down expression of HIF-1alpha or HIF-2alpha in two NSCLC cell lines to investigate HIF-dependent invasion, migration and adhesion. Here we show that: (1) hypoxia is an important factor in regulating CXCR4 mediated metastasis and the cells exhibited reducing invasion, adhesion and migration in response to CXCL12 after knocking down HIF. (2) HIF-1alpha and HIF-2alpha are essential for hypoxic cellular response to cancer invasion and adhesion through upregulation of CXCR4. HIF-1alpha and HIF-2alpha are playing important roles in tumor metastasis, which may offer for future intervention strategies. We also show that the lentivirus mediated RNAi technology is very effective on knocking down gene expression.