Anti-HIPK2 monoclonal antibody, clone 2G20

AIM To explore novel therapeutic target of cisplatin resistance in human gastric cancer. METHODS The sensitivity of SGC7901 cells and cisplatin-resistant SGC7901 cells (SGC7901/DDP) for cisplatin were detected by 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay. High-quality total RNA which isolated from SGC7901/DDP cells and SGC7901 cells were used for mRNA microarray analysis. Results were analyzed bioinformatically to predict their roles in the development of cisplatin resistance and the expression of 13 dysregulated mRNAs we selected were validated by quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS SGC7901/DDP cells highly resistant to cisplatin demonstrated by MTT assay. A total of 1308 mRNAs ( 578 upregulated and 730 downregulated) were differentially expressed ( fold change >= 2 and P-value < 0.05) in the SGC7901/DDP cells compared with SGC7901 cells. The expression of mRNAs detected by qRT-PCR were consistent with the microarray results. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes pathway and protein-protein interaction analysis demonstrated that the differentially expressed mRNAs were enriched in PI3K-Akt, Notch, MAPK, ErbB, Jak-STAT, NF-kappaB signaling pathways which may be involved in cisplatin resistance. Several genes such as PDE3B, VEGFC, IGFBP3, TLR4, HIPK2 and EGF may associated with drug resistance of gastric cancer cells to cisplatin. CONCLUSION Exploration of those altered mRNAs may provide more promising strategy in diagnosis and therapy for gastric cancer with cisplatin resistance.

Homeodomain-interacting protein kinase 2 (HIPK2) is a nuclear serine/threonine kinase of the subfamily of dual-specificity Yak1-related kinase proteins. HIPK2 was first described as a homeodomain-interacting protein kinase acting as a corepressor for homeodomain transcription factors. More recently, it was reported that HIPK2 plays a role in p53-mediated cellular apoptosis and could also participate in the regulation of the cell cycle. US11 protein of herpes simplex virus type 1 is a multifunctional protein involved in the regulation of several processes related to the survival of cells submitted to environmental stresses by mechanisms that are not fully elucidated. In an attempt to better understand the multiple functions of US11, we identified cellular binding partners of this protein by using the yeast two-hybrid system. We report that US11 interacts with HIPK2 through the PEST domain of HIPK2 and that this interaction occurs also in human cells. This interaction modifies the subcellular distribution of HIPK2 and protects the cell against the HIPK2-induced cell growth arrest.