Effect of brachytherapy on NF-κB and VEGF in gastric carcinoma xenografts.

Iodine-125 (125I) seed irradiation can be used as an important supplementary treatment for unresectable advanced gastric cancer. However, the radiobiological mechanism underlying brachytherapy remains unclear. Therefore, we investigated the influence of continuous and low-energy 125I irradiation on the cell cycle distribution, apoptosis, expression of NF-κB and VEGF and tumor growth in a human gastric cancer xenograft model. To create an animal model of gastric cancer, SGC-7901 cells were surgically implanted into mice. The 60 mice bearing SGC-7901 gastric cancer xenografts were randomly separated into 2 groups. Sham seeds (0 mCi) were implanted into the control group (n=30); 125I seeds (0.6 mCi) were implanted into the treatment group (n=30). At 28 days after irradiation, apoptosis was detected by flow cytometry. fluorescence micrograph detected intense VEGF and NF-κB immunofluorescence in the tumor samples, and changes in NF-κB and VEGF mRNA and protein expression were assessed by real-time PCR and western blot analysis, respectively. The tumor volume and weight were measured 0-28 days after 125I seed implantation. 125I seed irradiation induced significant apoptosis and G2/M phase arrest. Reduction in the intensities of VEGF and NF-κB immunofluorescence in tumor vessels was observed after treatment. NF-κB and VEGF mRNA and protein expression levels were substantially lower in the implantation treatment group than in the control group. Consequently, 125I seed implantation inhibited cancer growth and reduced cancer volume. The present study revealed that 125I seed irradiation significantly induced apoptosis and cell cycle arrest in the human gastric cancer xenografts. 125I-induced changes in NF-κB and VEGF expression are suggested as potential mechanisms underlying effective brachytherapy.

125I seed irradiation induces up-regulation of the genes associated with apoptosis and cell cycle arrest and inhibits growth of gastric cancer xenografts.

BACKGROUND: Iodine 125 (125I) seed irradiation can be used as an important supplementary treatment for unresectable advanced gastric cancer. Here, we aim to comprehensively elucidate the biological effects induced by 125I seed irradiation in human gastric cancer xenograft model by using global expression and DNA methylation analyses. METHODS: The 48 mice bearing NCI-N87 gastric cancer xenografts were randomly separated into 2 groups: sham seeds (O mCi) were implanted into the control group (n = 24); 125 l seeds (0.9 mCi) were implanted into the treatment group (n = 24). The mitotic index and apoptotic index were evaluated by quantitative morphometric analysis of the expression of proliferating cell nuclear antigen (PCNA) and in situ terminal transferase-mediated fluorescein deoxy- UTP nick end labeling (TUNEL), respectively. Global gene expression changes induced by 125I seed irradiation were analyzed by using Nimblegen Human gene expression array. DNA methylation profile in the tumors from control group was investigated with methylated DNA immunoprecipitation (MeDIP) and Nimblegen CpG promoter microarrays. The changes in the methylation status of selected genes were further investigated by using MeDIP-PCR. RESULTS: 125I seed irradiation suppresses the growth of gastric cancer xenografts in nude mice. PCNA staining and tissue TUNEL assays showed that both inhibition of cell proliferation and induction of apoptosis contribute to the 125I-induced tumor suppression in nude mouse model. Gene expression profiles revealed that the expression levels of several hundred genes, many of which are associated with apoptosis or cell cycle arrest, including BMF, MAPK8, BNIP3, RFWD3, CDKN2B and WNT9A, were upregulated following 125I seed irradiation. Furthermore, the up-regulation of some of these genes, such as BNIP3 and WNT9A, was found to be associated with irradiation-induced DNA demethylation. CONCLUSIONS: This study revealed that 125I seed irradiation could significantly induce the up-regulation of apoptosis- and cell cycle-related genes in human gastric cancer xenografts. And some of the up-regulation might be attributed to 125I-irradiation induced demethylation in gene promoter regions. Collectively, these findings provided evidence for the efficacy of this modality for the treatment of gastric cancer.

[125I seed implantation in sphincter preservation for treatment of low rectal cancer].

OBJECTIVE: To evaluate the effects of (125)I seed implantation in sphincter preservation for treatment of low rectal cancer. METHODS: Seventy-six patients with low rectal cancer were randomly divided into 2 group: group A, 17 males and 13 females, aged 48.5 +/- 2.4, receiving rectostomy and anal sphincter preservation and group B, 24 males and 22 females, aged 49.4 +/- 2.6, receiving modified TME and anal sphincter preservation combined with brachytherapy by (125)I seed implantation. Two to four weeks after operation chemotherapy with 5-FU/CF were performed. Follow-up was carried out 6, 12, 24, and 36 months after operation. RESULTS: The local recurrence rates 6, 12, 24, and 36 months after operation were 0%, 11.1%, 14.3%, and 23% respectively in the group A, and all 0% in the group B (P < 0.05 for the rate 36 months later). The survival rates 6, 12, 24, and 36 months after operation were 100%, 100%, 85.7%, and 76.7% respectively in the group A, and were 100%, 100%, 97.1%, and 93% respectively in the group B (P < 0.05 for the rate 36 months later). The functions of defecation and erection were better in the group B and the symptom of pain was improved better in the group A too (all P < 0.05). CONCLUSIONS: Safe, simple, and effective, surgery with sphincter preservation combined with brachytherapy in low rectal cancer is one of the ideal methods for treatment of low rectal cancer.