Effects of extremely low-frequency electromagnetic fields (ELF-EMF) exposure on B6C3F1 mice.

OBJECTIVE: Long-term exposure study was conducted to investigate the effects of extremely low-frequency electromagnetic field on the tumor promotion process and fertility. METHODS: Ten pregnant C57BL/6NCrj mice were exposed to 50 Hz field 500 mG for 1 week (12 h per day), and 24 male and 42 female B6C3F1mice born from them were further exposed up to 15.5 months. As a control group, 10 pregnant mice were bred without exposure, and 30 produced male and 32 female mice were observed without exposure for the same period. RESULTS: Mean body weights of exposed groups of male and female mice were decreased significantly than those of the control groups. In exposed mice, there was no increased incidence of liver and lung tumor. In female mice, the incidence of chronic myeloid leukemia [3/42 (7%)] in the exposed group was significantly greater than in the control group. The size of seminiferous tubules in the EMF exposed groups were significantly less than the control group. CONCLUSIONS: These data support the hypothesis that long-term exposure of 50 Hz magnetic fields is a significant risk factor for neoplastic development and fertility in mice.

Intracellular localization of survivin determines biological behavior in colorectal cancer.

Survivin is a bifunctional protein that suppresses apoptosis and regulates cell division and is highly expressed in various human cancers. Recently, the intracellular localization of survivin in tumors has been suggested as a prognostic marker, but the molecular mechanisms are not understood. The aims of the present study were to investigate the different localization of survivin expression in colorectal carcinoma and expression of survivin relationships with clinicopathological factors and patient survival. Immunohistochemical analyses of 142 cases of advanced colorectal cancer showed that 109 (76.8%) cases expressed survivin in the nucleus and 29 cases (20.4%) in the cytoplasm. Cytoplasmic survivin overexpression was associated with a poor prognosis, but nuclear survivin overexpression was associated with a better prognosis. Subcellular distribution of survivin in five cases of cancerous or surrounding normal tissues derived from fresh biopsy of non-fixed samples of colorectal cancer patients was further demonstrated by Western blotting. Survivin was primarily found in the insoluble fraction. Interestingly, regardless of survivin protein levels in the insoluble fraction, patients who had cancerous tissue expressing cytoplasmic and nuclear soluble survivin suffered from lymph nodes metastases. These data suggest that the function of cytoplasmic survivin might be important for malignant progress and the levels of cytoplasmic and nuclear soluble survivin might be more relevant for prognostic factors for colorectal cancer than the total amount of survivin.

Association of clinicopathological features with E-cadherin (CDH1) gene-160 C>A promoter polymorphism in Turkish colorectal cancer patients.

BACKGROUND AND AIM OF STUDY: The role of E-cadherin (CDH1) gene-160 C>A (rs16260) promoter polymorphism in colorectal cancer (CRC) still remains inconclusive. The aim of this study is to investigate the associations between the CDH1-160 C>A polymorphism with the susceptibility and clinicopathological development of CRC in the Turkish patients. To our knowledge, this is the first report examining the role of CDH1 polymorphism in Turkish CRC patients. MATERIALS AND METHODS: A total of 92 colorectal carcinoma cases (including 62 colon and 30 rectal cancer patients) and the corresponding adjacent normal tissues as controls were studied. The polymorphism was genotyped using polymerase chain reaction-restriction fragment length polymorphism analysis. Clinicopathological features including patient's age, gender, tumor stage, and tumor location (colon/rectum) were compared statistically with the polymorphism status. RESULTS: There was no significant difference in both genotype and allele frequencies of the CDH1 polymorphism between colorectal tumor cases and normal samples (P = 0.472 and 0.508, respectively). Furthermore, no significant associations were observed between the CDH1 polymorphism status and age, gender, tumor stage, and tumor location of the colorectal tumor cases (all P > 0.05). CONCLUSIONS: These results indicate that CDH1-160 C>A polymorphism does not contribute to the genetic susceptibility of CRC and the polymorphism may not be a direct effect on the progression of the disease in Turkish CRC patients.

Somatic mutation in mitochondrial DNA and nuclear microsatellite instability in gastric cancer.

It was reported that somatic mutations in the mitochondrial DNA (mtDNA) are associated with high-frequency microsatellite instability (MSI-H) of the nuclear in gastric cancers. However, no correlation between mtDNA mutations and nuclear MSI-H was found in colorectal, breast, and renal cancers. Therefore, the association between mtDNA mutations and nuclear MSI-H in gastric cancers is controversial. We examined mtDNA mutations and nuclear MSI in a large panel of gastric cancers. One-hundred and five gastric cancers were selected. Mutations in the mononucleotide repeat (D310) of mtDNA and nuclear MSI at 5 microsatellite loci were examined by microsatellite assay. Somatic mutations in the mtDNA and nuclear MSI-H were detected in 16 (15%) and 14 (13%) of the gastric cancers, respectively. mtDNA mutations were detected in 2 of the 14 (14%) and 14 of the 91 (15%) tumors with and without nuclear MSI-H, respectively. There was no significant difference between them. These results suggest that somatic mutations in the mtDNA and nuclear MSI-H play important roles in gastric carcinogenesis, and that mtDNA mutations may not be associated with nuclear MSI-H in gastric cancers.

P-selectin expression in a colon tumor model exposed by sinusoidal electromagnetic fields.

P-selectin is mainly involved in the initial process of tumor cell adhesion to platelets. The aim of the present study was to determine the expression level of P-selectin in a colon tumor model affected by sinusoidal electromagnetic fields (SMF). Male Wistar albino rats aged 2-2.5 months were used. The animals were divided into the I [N-Methyl-N-Nitrosurea (MNU)], II (SMF-MNU), III (SMF) and IV (control) groups. The rats were housed five per polycarbonate cage. Sixty milligrams of MNU was dissolved in 6 ml sterile 0.9% NaCl. Prepared solutions were administered intra rectally (i.r.) to the 1st and 3rd groups as 0.2 ml/per animal. The same procedure was applied to the 2nd and 4th groups, although 0.2 ml/per animal sterile isotonic solution was administered instead. This procedure was repeated once a week for 10 weeks. Following the administration of MNU, the 2nd and 3rd groups were exposed to a sinusoidal magnetic field (SMF, 50 Hz, 5 mT) for 6 h/day for 8 months. P-selectin expression of the four groups of rat colon tissues was determined using immunohistochemistry on paraffin sections. The labeled streptavidin biotin method was performed. Fisher's exact test was used for differences between proportions. Results showed that there was no statistically significant (P>0.05) change in the expression level of P-selectin. However, this result should be verified by both in vivo and in vitro experiments to determine the effects of the magnetic fields on P-selectin.

Autologous fascia graft as a biological barrier to silicone application in rabbits.

OBJECTIVE: To determine the cellular effects of providing a fascial interface around subcutaneously-placed silicone implants, in terms of capsule thickness, myofibroblast/fibroblast cell count and inflammatory cell count. STUDY DESIGN: Interventional, comparative study. PLACE AND DURATION OF STUDY: Istanbul University Cerrahpasa Medical Faculty, Laboratory of Experimental Animals, Istanbul, Turkey, from May to September 2008. METHODOLOGY: A total of 16 adult New Zealand male rabbits with mean weight of 2508 ± 360 g were used in the study. Animals were divided into two groups as experiment and control groups with equal number of rabbits in each. Fascia injection was applied on silicone implant in the experiment group and compared with the control group in terms of capsule thickness, myofibroblast/fibroblast cell count and inflammatory cell count. At the end of the experiment, tissue samples were examined macroscopically and microscopically for the above. Statistical analysis of data was performed using student's t-test. RESULTS: A statistically significant difference was found between experiment group and control group in terms of mean capsule thickness, mean myofibroblast and fibroblast cell counts and cell density (p < 0.05, each). CONCLUSION: Fascia tissue barrier prevent silicone rod reaction and foreign body reaction developing against silicone prosthesis in the studied animal model.

PARP6, a mono(ADP-ribosyl) transferase and a negative regulator of cell proliferation, is involved in colorectal cancer development.

Poly(ADP-ribose) polymerase (PARP) is an enzyme that mediates post-translational modification of proteins. Seventeen known members of the PARP superfamily can be grouped into three classes based on catalytic activity: (i) classical poly(ADP-ribose) polymerases, (ii) mono(ADP­ribosyl) transferases and (iii) catalytically inactive members. PARP6 belongs to the mono(ADP-ribosyl) transferase class, and here we have found that PARP6 is a negative regulator of cell proliferation. Forced expression of PARP6 in HeLa cells induced growth suppression, but a PARP6 mutant with a C-terminal deletion lacking the catalytic domain had no effect. The PARP6-expressing cells accumulated in the S-phase, and the magnitude of S-phase accumulation was observed to be greater in cells expressing a PARP6 mutant with an N-terminal deletion, lacking a putative regulatory domain. Immunohistochemical analysis revealed that PARP6 positivity was found at higher frequencies in colorectal cancer tissues with well-differentiated histology compared to those with poorly differentiated histology. Furthermore, PARP6 positivity negatively correlated with the Ki-67 proliferation index. Kaplan-Meier analysis showed that PARP6-positive colorectal cancer had a good prognosis. Based on these results, we propose that PARP6 acts as a tumor suppressor through its role in cell cycle control.

Nuclear Aurora B and cytoplasmic Survivin expression is involved in lymph node metastasis of colorectal cancer.

The chromosomal passenger complex (CPC) is a key regulator of chromosome segregation and cytokinesis, and consists of Aurora B kinase, INCENP, Survivin and Borealin. Aurora B is a member of a family of serine/threonine protein kinases, and Survivin belongs to the inhibitors of apoptosis (IAP) gene family, and is also a member of the CPC family. Aurora B and Survivin have also been reported to be overexpressed in various human cancers; however, as yet no studies have investigated the co-expression of Survivin and Aurora B in colorectal carcinoma. Therefore, in the present study, the correlation between Aurora B and Survivin expression was investigated using immunohistochemistry and the associated pathological features in colorectal carcinoma were analyzed. Our present findings showed that nuclear Aurora B and cytoplasmic Survivin expression are strongly associated with and involved in lymph node metastasis in colorectal cancer. Therefore, we suggest that nuclear Aurora B and cytoplasmic Survivin are useful diagnostic markers and therapeutic targets in colorectal carcinoma.

GSM base station electromagnetic radiation and oxidative stress in rats.

The ever increasing use of cellular phones and the increasing number of associated base stations are becoming a widespread source of nonionizing electromagnetic radiation. Some biological effects are likely to occur even at low-level EM fields. In this study, a gigahertz transverse electromagnetic (GTEM) cell was used as an exposure environment for plane wave conditions of far-field free space EM field propagation at the GSM base transceiver station (BTS) frequency of 945 MHz, and effects on oxidative stress in rats were investigated. When EM fields at a power density of 3.67 W/m2 (specific absorption rate = 11.3 mW/kg), which is well below current exposure limits, were applied, MDA (malondialdehyde) level was found to increase and GSH (reduced glutathione) concentration was found to decrease significantly (p < 0.0001). Additionally, there was a less significant (p = 0.0190) increase in SOD (superoxide dismutase) activity under EM exposure.

Influence of 50 Hz frequency sinusoidal magnetic field on the blood-brain barrier permeability of diabetic rats.

The combined effects of diabetes and a 50 Hz, 5 mT RMS flux density sinusoidal magnetic field for 8 h a day, for 21 consecutive days on the permeation of Evans-blue dye through the blood-brain barrier were studied in male Wistar albino rats. Our results suggest that magnetic field has no effect on the blood-brain barrier permeability in normoglycemic animals, but that diabetic rats are vulnerable to magnetic fields.

Variable E-cadherin expression in a MNU-induced colon tumor model in rats which exposed with 50 Hz frequency sinusoidal magnetic field.

Inactivation of the E-cadherin system by multiple mechanisms, including both genetic and epigenetic events, plays a significant role in multistage carcinogenesis. We have investigated the effects of sinusoidal electromagnetic fields (SMF) on E-cadherin expression in an MNU (N-methyl-N-nitrosurea)-induced colon tumor model. Male wistar albino rats were used for the study. The rats were classified into four groups: I (MNU), II (SMF+MNU), III (SMF) and IV (control). After administered at MNU in 1st and 2nd groups, 2nd and 3rd groups were exposed to a sinusoidal magnetic field (SMF, 50 Hz, 5 mT) for 6 hours/day for 8 months. The expression of E-cadherin were examined in four groups of rat colon tissues by immunohistochemistry on paraffin sections. For immunohistochemical analysis, the labeled streptavidin biotin method was performed using a Vectastain Universal Quick Kit with microwave accentuation. Fisher's exact test was used for statistical analysis between proportions. Immunohistochemical studies of E-cadherin expression in this model demonstrated significant differences for cytoplasmic expression pattern. These results suggest that the electromagnetic fields result in significant alterations in cell adhesion mechanisms. This study has implications for understanding the role of fields in cell detachment in cancer metastasis. Further work is required to determine the relative effect of the magnetic fields on these phenomena.

Prevalence of Helicobacter pylori resistance to clarithromycin and metronidazole determined by 23S ribosomal RNA and rdxA gene analyses in Hiroshima, Japan.

BACKGROUND AND AIMS: Resistance to antibiotics in Helicobacter pylori is increasing and becoming a serious problem in eradication treatment of H. pylori. The prevalence of H. pylori infections that are resistant to clarithromycin, metronidazole, or both were determined in H. pylori isolates in Hiroshima, Japan. METHODS: Sixty Japanese patients with H. pylori infection were collected between 1999 and 2000. To detect the resistance to clarithromycin and metronidazole, mutations of the 23S ribosomal RNA (rRNA) and rdxA genes that are responsible for resistance in H. pylori, were examined by direct sequencing analysis. RESULTS: Resistance to clarithromycin and metronidazole was detected in 12 (20.0%) and nine (15.0%) of the patients, respectively. Dual resistance to clarithromycin and metronidazole was detected in five (8.3%) patients. CONCLUSION: These results indicate that the relatively high prevalence of the dual resistance in H. pylori isolates may need special attention and new therapeutic approaches in Japan.

Chromosomal and microsatellite instability in sporadic gastric cancer.

BACKGROUND: Gastric cancer can progress through two pathways of genomic instability: chromosomal (CIN) and microsatellite instability (MSI). It is hypothesized that these two pathways are not always independent and that some tumors show overlap between these two mechanisms. METHODS: A total of 98 sporadic gastric cancers were classified based on their MSI status, using microsatellite assay with BAT26. Evidence for CIN was investigated by identifying loss of heterozygosity (LOH) events on chromosome arms, 5q, 10p, 17p, 17q, and 18q, which are regions harboring tumor suppressor genes that are significant in gastric cancer development. RESULTS: Twelve tumors (12%) showed high-frequency MSI (MSI-H). Overall, 43 of the tumors (44%) had at least one LOH event, with most frequent chromosomal losses observed on 10p and 18q (30%, respectively), followed by 5q (21%), 17p (14%), and 17q (12%). Interestingly, overlap was observed between CIN and MSI pathways. Of 43 cancers with LOH events, four (9%) were also MSI-H. It was also found that 48% of cancers without MSI-H had no LOH events identified, comprising a subgroup of tumors that were not representative of either of these two pathways of genomic instability. CONCLUSION: These results suggest that molecular mechanisms of genomic instability are not necessarily independent and may not be fully defined by either the MSI or CIN pathways in sporadic gastric cancers.

p53 expression, K-ras gene mutation and microsatellite instability in gastric B-cell lymphomas.

BACKGROUND AND AIMS: Genetic mechanisms involved in the development of gastric B-cell lymphomas remain unclear. The aim of the present study was to clarify the roles of mutations of the p53 and K-ras genes, and microsatellite instability (MSI) in the development of gastric B-cell lymphomas. METHODS: We investigated p53 immunoreactivity, mutations of the K-ras gene, and MSI in 27 gastric marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue type (MZBCL) and 24 diffuse large B-cell lymphomas (DLBCL). p53 immunoreactivity was examined using a monoclonal antibody, DO-7. Mutation of the K-ras gene was detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. MSI was examined at five microsatellite loci with a microsatellite assay. Cases were classified as having high-frequency MSI (MSI-H) (>/= 2 loci showing instability), low-frequency MSI (MSI-L) (only one locus showing instability), or as microsatellite stable. RESULTS: p53 immunoreactivity was detected in 1 of 16 (6%) MZBCL and 8 of 19 (42%) DLBCL. Frequency of p53 immunoreactivity in DLBCL was significantly higher than that in MZBCL (P = 0.018). MSI-H was detected only in 1 of 20 (5%) DLBCL. None of the cases examined showed mutation of the K-ras gene. CONCLUSIONS: These data suggest that mutations of the p53 gene may play an important role in the development of gastric DLBCL, and that mutations of the K-ras gene and MSI may be involved in little part of the development of gastric B-cell lymphomas.