ABSTRACT
Hypermethylation in the promoter region is an important epigenetic mechanism for the transcriptional repression of a number of cancer-associated genes, and over-expression and/or increased activity of DNA methyltransferases are considered to be the main cause of promoter hypermethylation. In order to explore the roles of two methyltransferase members (DNMT1 and DNMT3b) in the cholangiocarcinoma tumorigenesis, antisense eukaryotic expression plasmid of DNMT1 and DNMT3b gene was constructed respectively, and were co-transfected into the human cholangiocarcinoma cell line QBC-939 to observe their biological effects on the cell growth and proliferation ability, apoptosis, cell cycle alteration, and the tumorigenesis ability in the subcutaneous tissue of nude mouse. The results demonstrated that co-transfection with antisense eukaryotic expression plasmid of DNMT1 and DNMT3b gene and single transfection with antisense eukaryotic expression plasmid of DNMT1 gene can suppress the growth and proliferation of QBC-939, block the cell cycle at G1 phase, increase the apoptosis rate, minimize the tumor size in the subcutaneous tissue of nude mouse. The suppressing biological effect of co-transfection is stronger than single transfection with antisense DNMT1. Meanwhile, single transfection with antisense eukaryotic expression plasmid of DNMT3b gene has no effects on the biological characteristics of QBC-939. This study suggests that DNMT1 gene plays a key role in DNA methylation and DNMT3b gene may act as an accessory to support its function in inactivation of tumor suppressor genes. Combination DNMT1 and DNMT3b will inhere their biological effects and have the synergistic effect on suppressing the growth of human cholangiocarcinoma cell line QBC-939.
ABSTRACT
The effect of targeted magnetic nanoparticles on hepatoma and the underlying mechanism were examined. Nude mice transplanted with a human hepatoma cell line (HepG2 cells) were randomized into 5 groups, including: (1) group A, receiving normal saline, (2) group B, receiving5-fluorouracil (5-Fu), (3) group C, receiving magnetic nanoparticles containing 5-Fu, (4) group D,consisting of treatment with magnetic nanoparticles containing 5-Fu and inside magnetic field and (5)group E, receiving pure magnetic nanoparticles and inside magnetic field. Morphological features of transplanted tumors in mice in each group were observed under transmission electron microscope(TEM). The expression of bcl-2/bax protein was immunohistochemically detected by SABC method.The results showed that a large number of apoptotic tumor cells were found in group B and group D under TEM. The expression of bcl-2 protein was significantly decreased and the expression of bax protein increased significantly in both group B and D as compared with those in group A, C and E(P＜0.01 for all). The decrease in bcl-2 and the increase in bax were more in group D as compared with group B (P＜0.01). It is concluded that the targeted magnetic nanoparticles containing 5-Fu can improve the chemotherapeutic effect of 5-Fu by decreasing bcl-2 expression, increasing bax expression and inducing apoptosis of the liver cancer cells.