Characteristic element of matrix attachment region mediates vector attachment and enhances nerve growth factor expression in Chinese hamster ovary cells.

Preliminary studies have suggested that a characteristic element of the matrix attachment region (MAR) in human interferon-ß mediates the adhesion of vectors to Chinese hamster ovary (CHO) cells. In this study, we investigated if vector adhesion increased nerve growth factor (NGF) expression in CHO cells. The MAR characteristic element sequence of human interferon-ß was inserted into the multiple-cloning site of the pEGFP-C1 vector. The target NGF gene was inserted upstream of the MAR characteristic element sequence to construct the MAR/NGF expression vector. The recombinant plasmid was transfected into CHO cells and stable monoclonal cells were selected using G418. NGF mRNA and protein expression was detected by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Plasmid reduction experiments were used to determine the state of transfected plasmid in mammalian cells. The insertion of MAR into the vector increased NGF expression levels in CHO cells (1.93- fold) compared to the control. The recombinant plasmid expressing the MAR sequence was digested into a linear space vector. The inserted MAR and NGF sequences were consistent with those inserted into the plasmid before recombination. Therefore, we concluded that the MAR characteristic element mediates vector adhesion to CHO cells and enhances the stability and efficiency of the target gene expression.

Lapatinib, a dual inhibitor of epidermal growth factor receptor and human epidermal growth factor receptor 2, potentiates the antitumor effects of cisplatin on esophageal carcinoma.

Epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) overexpression occurs in over 30% of esophageal carcinomas. Combination therapies of EGFR- and HER2-targeting agents with cytotoxic agents are considered a potential therapeutic strategy for esophageal cancer. The antitumor effects of lapatinib, a dual tyrosine kinase inhibitor of EGFR and HER2, cisplatin alone, and the combination of the two drugs on esophageal cancer cells were evaluated. The growth inhibition activity of lapatinib, cisplatin, and lapatinib plus cisplatin was measured by 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assays, and the combination index values were calculated. Additionally, cell cycle distribution and cell apoptosis treated with lapatinib or cisplatin alone and the combination of the two drugs were detected by flow cytometry analysis. The activation of EGFR and HER2 signaling pathways was monitored by Western blot analysis. These experimental data showed that the combination of lapatinib and cisplatin synergistically inhibited cell proliferation and exhibited an enhanced pro-apoptotic effect on esophageal cancer cells. The underlying mechanisms of potentiated effects of combined treatment were associated with reduced phosphorylation of EGFR and HER2, and the downstream signaling molecules AKT and extracellular regulated protein kinases (ERK). Our findings indicated that the combination of lapatinib and cisplatin is one of the promising treatment strategies for esophageal carcinomas with EGFR and HER2 overexpression.