Effect of Exposure to 900 MHz GSM Mobile Phone Radiofrequency Radiation on Estrogen Receptor Methylation Status in Colon Cells of Male Sprague Dawley Rats

BACKGROUND

Over the past several years, the rapidly increasing use of mobile phones has raised global concerns about the biological effects of exposure to radiofrequency (RF) radiation. Numerous studies have shown that exposure to electromagnetic fields (EMFs) can be associated with effects on the nervous, endocrine, immune, cardiovascular, hematopoietic and ocular systems. In spite of genetic diversity, the onset and progression of cancer can be controlled by epigenetic mechanisms such as gene promoter methylation. There are extensive studies on the epigenetic changes of the tumor suppressor genes as well as the identification of methylation biomarkers in colorectal cancer. Some studies have revealed that genetic changes can be induced by exposure to RF radiation. However, whether or not RF radiation is capable of inducing epigenetic alteration has not been clarified yet. To date, no study has been conducted on the effect of radiation on epigenetic alterations in colorectal cancer (CRC). Several studies have also shown that methylation of estrogen receptor α (ERα), MYOD, MGMT, SFRP2 and P16 play an important role in CRC. It can be hypothesized that RF exposure can be a reason for the high incidence of CRC in Iran. This study aimed to investigate whether epigenetic pattern of ERα is susceptible to RF radiation and if RF radiation can induce radioadaptive response as epigenetic changes after receiving the challenge dose (γ-ray).

MATERIAL AND METHOD

40 male Sprague-Dawley rats were divided into 4 equal groups (Group I: exposure to RF radiation of a GSM cell phone for 4 hours and sacrificed after 24 hours; Group II: RF exposure for 4 hours, exposure to Co-60 gamma radiation (3 Gy) after 24 hours and sacrificed after 72 hrs; Group III: only 3Gy gamma radiation; Group 4: control group). DNA from colon tissues was extracted to evaluate the methylation status by methylation specific PCR.

RESULTS

Our finding showed that exposure to GSM cell phone RF radiation was capable of altering the pattern of ERα gene methylation compared to that of non-exposed controls. Furthermore, no adaptive response phenomenon was induced in the pattern of ERα gene methylation after exposure to the challenging dose of Co-60 γ-rays.

CONCLUSION

It can be concluded that exposure to RF radiation emitted by GSM mobile phones can lead to epigenetic detrimental changes in ERα promoter methylation pattern.

Sensitive and Noninvasive Detection of Aberrant SFRP2 and MGMT-B Methylation in Iranian Patients with Colon Polyps

BACKGROUND

The pathogenesis of sporadic colorectal cancer (CRC) is influenced by the patient genetic background and environmental factors. Based on prior understanding, these are classified in two major pathways of genetic instability. Microsatellite instability (MSI) and CPG island methylator phenotype (CIMP) are categorized as features of the hypermethylated prototype, and chromosomal instability (CIN) is known to be indicative of the non-hypermethylated category. Secreted frizzled related protein 2 (SFRP2), APC1A in WNT signaling pathway and the DNA repair gene, O6-methylguanine-DNA methyltransferase (MGMT), are frequently hypermethylated in colorectal cancer. Detection of methylated DNA as a biomarker by easy and inexpensive methods might improve the quality of life of patients with CRC via early detection of cancer or a precancerous condition.

AIM

To evaluate the rate of SFRP2 and MGMT hypermethylation in both polyp tissue and serum of patients in south Iran as compared with matched control normal population corresponding samples.

MATERIALS AND METHODS

Methylation-specific PCR was used to detect hypermethylation in DNA extracted from 48 polypoid tissue samples and 25 healthy individuals.

RESULTS

Of total polyp samples, 89.5% had at least one promoter gene hypermethylation. The most frequent methylated locus was SFRP2 followed by MGMT-B (81.2 and 66.6 percent respectively). Serologic detection of hypermethylation was 95% sensitive as compared with polyp tissue. No hypermethylation was detected in normal tissue and serum and its detection in patients with polyps, especially of serrated type, was specific.

CONCLUSIONS

Serologic investigation for detection of MGMT-B, SFRP2 hypermethylation could facilitate prioritization of high risk patients for colonoscopic polyp detection and excision.

Different patterns of DNA methylation of the two distinct O6-methylguanine-DNA methyltransferase (O6-MGMT) promoter regions in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer worldwide. Colorectal cancer incidence differs widely among different geographic regions. In addition to mutational changes, epigenetic mechanisms also play important roles in the pathogenesis of CRCs. O6-methylguanine-DNA methyltransferase (O(6)-MGMT) is a DNA repair protein and in the absence of MGMT activity, G-to-A transition may accumulate in the specific genes such as K-ras and p53. To identify which CpG sites are critical for its downregulation, we analyzed the methylation status of the MGMT gene promoter in two sites in CRC patients. Then we compared the frequency of their methylation changes with the results of our previously reported K-ras gene mutation, APC2 and p16 methylation. MGMT methylation was examined in 92 tumor samples. A methylation specific PCR (MSP) method was performed for two loci of MGMT gene which described as MGMT-A and MGMT-B. The prevalence of MGMT-A, and MGMT-B methylation was 49/91 (53.8%), and 83/92 (90.2%), respectively. We detected high frequency of MGMT-B but not MGMT-A methylation in tumor tissues with APC2 methylation. Our results showed that MGMT-B methylation is significantly associated with K-ras gene mutation rather than MGMT-A (p = 0.04). Simultaneously, an inverse correlation was found between p16 and MGMT-B methylation simultaneously (p = 0.02). Our study indicated that hypermethylation of the specific locus near the MGMT start codon is critical for cancer progression. MGMT-B assessment that is associated with K-ras mutation can have a prognostic value in patients with CRC.

HER-2/neu and E-cadherin Expression and Microsatellite Instability in Gastric Dysplasia

BACKGROUND Gastric dysplasia (GD) is a precursor lesion of gastric adenocarcinoma. Intestinal type gastric carcinoma commonly shows microsatellite instability (MSI) and the diffuse type is associated with down regulation of E-cadherin. HER-2/neu is over-expressed in some cases of gastric cancer. In this study, MSI and expression rates of HER-2/neu and E-cadherin in GD were evaluated. METHODS Paraffin blocks of 21 cases of low grade dysplasia (LD), 11 cases of high grade dysplasia (HD) and 25 cases of indefinite for dysplasia (ID) were collected. After deparaffinization and antigen retrieval, the sections were incubated with antibodies against E-cadherin, hMLH1, hMSH2 and HER-2/neu. The streptavidin-biotin complex method was used followed by peroxidase enzyme development with diaminobenzidine. RESULTS HER-2/neu was positive in six cases of HD (50%), four LD (21%) and two ID (9%). E-cadherin was absent in two cases of LD and showed normal expression in all HD and ID cases. hMLH1 expression was absent or markedly decreased only in the zones of dysplasia in HD (3/11), LD (3/21) and ID (4/25). Absence or diminished expression of hMSH2 was seen in HD (3/11), LD (2/21) and ID (3/25) cases. HER-2/neu expression showed close association with diminished expression of hMLH1 or hMSH2 (p < 0.05). CONCLUSION Stepwise increase in the expression rate of HER-2/neu was seen in ID, LD and HD cases implying its role in cancer evolution. The absence of hMLH1 and hMSH2 in GD may predispose individuals to over-expression of other oncogenes such as HER-2/neu. Abnormal expression of E-cadherin is not a frequent finding in GD.

Competition of tamoxifen with thyroxine for TBG binding: ligand binding assay and computational data

OBJECTIVE

Tamoxifen, a nonesteroidal antiesterogen, is widely used in the treatment of breast cancer. Recently, the effect of tamoxifen on thyroid function has caused considerable concern, yet the results of different studies are controversial and the precise mechanism of such influence is obscure. In view of the fact that some drugs such as furosemide, diclofenac and mefenamic acid, based on the structural similarities to thyroxine could compete for binding to thyroxine binding globulin (TBG) and appears that there are some structural similarities between tamoxifen and thyroxine, one can hypothesize that tamoxifen is also able to compete for TBG binding and thereby affecting thyroid function tests.

DESIGN AND METHODS

In this study, we designed an in vitro binding assay as well as computational methods using MOPAC 7 package for evaluation of competitive potency of tamoxifen for TBG binding in comparison with well-known TBG competitors (including furosemide, mefenamic acid and diclofenac).

RESULTS

The result of competition assay and Scatchard analysis revealed that tamoxifen does not bind to TBG at the T4 binding site, thus it is not a thyroxine competitor. Computational results also indicated that structural characteristics of tamoxifen are significantly different from those of T4 and its well-known competitors.

CONCLUSION

In conclusion, the probability of competition between tamoxifen and T4 is ruled out by these results.