The expression of DNMT3a mRNA did not change

regardless of the ��-Nicotinamide purchase 125I irradiation dose. The similar DNMT expression patterns were confirmed by immunohistochemical staining in 125I seed implanted pancreatic cancer. Most importantly, the 2 Gy 125I seed implantation limited the growth of the pancreatic tumor, while 4 Gy 125I seed implantation substantially decreased pancreatic tumor volume. Our results demonstrated that apoptosis may have an important role in the therapeutic effects when pancreatic cancer is exposed to continuous low-energy 125I irradiation. The apoptosis in the 4 Gy group was more obvious than in the 2 Gy group, which is in agreement with the fact that cancer treatment is more effective at 4 Gy than at 2 Gy. Similar irradiation-induced apoptosis patterns were also observed in the other cancer cell

lines [22]. The 125I irradiation induced apoptosis was the primary mechanism of CL187 colonic cancer cell-killing under low dose treatment [22]. Ionizing radiation can generate the reactive oxygen species (ROS), which induce apoptosis [23]. The ROS damages critical cellular components such as DNA, proteins, and lipids, eventually causing cellular apoptosis [24]. Therefore, the 125I irradiation-induced apoptosis is a key mechanism underlying the therapeutic effect of 125I seed implantation in pancreatic cancer. Our results demonstrated that altered DNA methylation patterns might have a pivotal role in Cediranib concentration tumor inhibition resulting

from consecutive low-energy irradiation. The 2 Gy irradiation caused a significant increase in DNMTs expression, whereas 4 Gy irradiation was associated with decreased DNMTs expression. However, a substantial reduction in tumor volume was only observed in 4 Gy irradiation group rather than in 2 Gy group at 28 d after 125I seed implantation. There are a strong and positive correlation between DNA methylation and expression of DNMTs, because DNMTs maintain DNA methylation patterns [25]. Therefore, it is reasonable to speculate that DNA hypomethylation Isotretinoin significantly inhibits cancer cell proliferation or impairs cell survival potentially to an even greater extent than DNA hypermethylation. X- and γ-radiation induce DNA hypomethylation paralleled by decreased DNMTs expression in somatic cells [25–28]. Actually, low-dose irradiation (2Gy) predominantly resulted in reversible DNA damage, which was associated with DNA repair. The DNMTs are the key enzyme for DNA repair. As a result, the increase in reactive DNMTs expression reflects active DNA repair. Thus, 125I irradiation-induced DNA hypomethylation could be the key mechanism by which 125I seed implantation lead to tumor growth inhibition. Aberrant de novo DNA methylation is commonly associated with cancer, and DNA methylation in mammalian cells largely occurs on cytosine residues at CpG dinucleotides in genomic DNA.