Circ_0061140 knockdown inhibits tumorigenesis and improves PTX sensitivity by regulating miR-136/CBX2 axis in ovarian cancer.

BACKGROUND: Ovarian cancer is an aggressive tumor in women with high mortality. Paclitaxel (PTX) can be used for the chemotherapy of ovarian cancer. Here, the roles of circular_0061140 (circ_0061140) in PTX sensitivity and malignant progression of ovarian cancer are unveiled. METHODS: The expressions of circ_0061140, microRNA-136 (miR-136) and chromobox 2 (CBX2) mRNA were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Protein expression was determined by western blot. The half maximal inhibitory concentration (IC50) of PTX was determined by 3-(4,5-Dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation was investigated by cell counting kit-8 (CCK-8) and colony formation assays. Cell apoptosis was demonstrated by flow cytometry analysis. Cell migration and invasion were evaluated by transwell assay. The binding relationship between miR-136 and circ_0061140 or CBX2 was predicted by interactome or starbase online database, and identified by dual-luciferase reporter assay. The effects of circ_0061140 on tumor formation and PTX sensitivity in vivo were disclosed by tumor formation assay. RESULTS: Circ_0061140 and CBX2 expressions were upregulated, while miR-136 expression was downregulated in PTX-resistant tissues and cells compared with control groups. Circ_0061140 knockdown repressed cell proliferation, migration and invasion, and promoted cell apoptosis and PTX sensitivity; however, these effects were restrained by miR-136 RNAi. Additionally, circ_0061140 was a sponge of miR-136, and miR-136 bound to CBX2. Furthermore, circ_0061140 knockdown inhibited tumor formation and improved PTX sensitivity in vivo. CONCLUSIONS: Circ_0061140 silencing repressed the progression and PTX resistance of ovarian cancer by downregulating CBX2 expression via sponging miR-136, which provided novel insight into studying the therapy of ovarian cancer with PTX.

Involvement of thioredoxin domain-containing 5 in resistance to nitrosative stress.

Living organisms are exposed to nitrosative stress mediated by nitric oxide (NO) and its derivatives. Multiple cellular mechanisms may be needed to cope with nitrosative stress. This work takes advantage of a hypersensitive Escherichia coli genetic system to identify genes involved in resistance to nitrosative stress in mouse lungs. Mouse thioredoxin domain-containing 5 (mTrx 5) was identified as one of the candidate genes. Its ability to complement the hypersensitive phenotype in an E. coli mutant strain was confirmed by genetic analysis. Purified recombinant mouse thioredoxin domain-containing 5 protein reduced DNA damage that is sensitive to cleavage by the deamination repair enzyme endonuclease V, indicating that mTrx 5 may play a role in scavenging the reactive nitrogen species. E. coli thioredoxin 1 and thioredoxin 2 proteins also reduced the DNA damage in a similar manner. Deletion of trxA (encodes thioredoxin 1) or trxC (encodes thioredoxin 2) in E. coli resulted in a slightly higher sensitivity to nitrosative stress. On the other hand, deletion of both trxA and trxC greatly increased its sensitivity to nitrosative stress. Complementation with the mTrx 5 gene rescued the sensitive phenotype of the double deletion mutant. The potential roles that mTrx 5 may play in coping with nitrosative stress are discussed.