Hypoxia-inducible factor 1 promoter-induced JAB1 overexpression enhances chemotherapeutic sensitivity of lung cancer cell line A549 in an anoxic environment

In silico identification of potential key regulatory factors in smoking-induced lung cancer

Background

Lung cancer is a leading cause of cancer-related death worldwide and is the most commonly diagnosed cancer. Like other cancers, it is a complex and highly heterogeneous disease involving multiple signaling pathways. Identifying potential therapeutic targets is critical for the development of effective treatment strategies.

Methods

We used a systems biology approach to identify potential key regulatory factors in smoking-induced lung cancer. We first identified genes that were differentially expressed between smokers with normal lungs and those with cancerous lungs, then integrated these differentially expressed genes (DEGs) with data from a protein-protein interaction database to build a network model with functional modules for pathway analysis. We also carried out a gene set enrichment analysis of DEG lists using the Kinase Enrichment Analysis (KEA), Protein-Protein Interaction (PPI) hubs, and KEGG (Kyoto Encyclopedia of Genes and Genomes) databases.

Results

Twelve transcription factors were identified as having potential significance in lung cancer (CREB1, NUCKS1, HOXB4, MYCN, MYC, PHF8, TRIM28, WT1, CUX1, CRX, GABP, and TCF3); three of these (CRX, GABP, and TCF) have not been previously implicated in lung carcinogenesis. In addition, 11 kinases were found to be potentially related to lung cancer (MAPK1, IGF1R, RPS6KA1, ATR, MAPK14, MAPK3, MAPK4, MAPK8, PRKCZ, and INSR, and PRKAA1). However, PRKAA1 is reported here for the first time. MEPCE, CDK1, PRKCA, COPS5, GSK3B, BRCA1, EP300, and PIN1 were identified as potential hubs in lung cancer-associated signaling. In addition, we found 18 pathways that were potentially related to lung carcinogenesis, of which 12 (mitogen-activated protein kinase, gonadotropin-releasing hormone, Toll-like receptor, ErbB, and insulin signaling; purine and ether lipid metabolism; adherens junctions; regulation of autophagy; snare interactions in vesicular transport; and cell cycle) have been previously identified.

Conclusion

Our systems-based approach identified potential key molecules in lung carcinogenesis and provides a basis for investigations of tumor development as well as novel drug targets for lung cancer treatment.

Knockdown of Med19 suppresses proliferation and enhances chemo-sensitivity to cisplatin in non-small cell lung cancer cells

Mediator 19 (Med19) is a component of the mediator complex which is a coactivator for DNA-binding factors that activate transcription via RNA polymerase II. Accumulating evidence has shown that Med19 plays important roles in cancer cell proliferation and tumorigenesis. The involvement of Med19 in sensitivity to the chemotherapeutic agent cisplatin was here investigated. We employed RNA interference to reduce Med19 expression in human non-small cell lung cancer (NSCLC) cell lines and analyzed their phenotypic changes. The results showed that after Med19 siRNA transfection, expression of Med19 mRNA and protein was dramatically reduced (p<0.05). Meanwhile, impaired growth potential, arrested cell cycle at G0/G1 phase and enhanced sensitivity to cisplatin were exhibited. Apoptosis and caspase-3 activity were increased when cells were exposed to Med19 siRNA and/or cisplatin. The present findings suggest that Med19 facilitates tumorigenic properties of NSCLC cells and knockdown of Med19 may be a rational therapeutic tool for lung cancer cisplatin sensitization.

miR-21 modulates paclitaxel sensitivity and hypoxia-inducible factor-1α expression in human ovarian cancer cells

Drug resistance is a major problem encountered in the treatment of ovarian cancer. Previous studies have demonstrated that in several types of cancer the overexpression of the multidrug resistance 1 (MDR1) gene is mainly associated with drug resistance. The present study aimed to investigate the role of miR-21 in the development of drug resistance in ovarian cancer cells. The expression levels of miR-21 in the ovarian cancer A2780 and A2780/taxol cell lines were detected by stem-loop real-time PCR. A2780 and A2780/taxol cells were transfected with mimics or inhibitors of miR-21 or negative control RNA. The expression levels of P-glycoprotein (P-gp) and hypoxia-inducible factor-1α (HIF-1α) proteins were assessed by western blot analysis. Drug sensitivity was analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The expression levels of miR-21 and P-gp were upregulated to a greater extent in the paclitaxel-resistant ovarian cancer A2780/taxol cell line compared with the parental A2780 cell line. Transfection of A2780/taxol cells with inhibitors of miR-21 decreased the expression levels of the P-gp and HIF-1α proteins, and increased the sensitivity of the A2780/taxol cells to paclitaxel. The expression levels of P-gp were additionally increased; however, the sensitivity of the miR-21 mimic-treated A2780 cells to paclitaxel was decreased. miR-21 may be involved in the development of drug resistance and the regulation of MDR1/P-gp expression, at least in part, by targeting HIF-1α in ovarian cancer cells.