| Nowadays, human living environment was surrounded by power frequencyelectromagnetic field (PF-EMF) and radio-frequency electromagnetic fields (RF) mainlygenerated by household appliance and wireless communication equipments respectively.As intensity of PF-EMF and RF becomes more and more high, and exposure time ofhuman beings increases, the potential harmful effects of PF-EMF and RF on health havebeen paid much attention. Epidemiological studies showed that long-term exposure toPF-EMF could enhance the incidence of leukemia、brain tumors and breast cancer, inaddition, long-term exposure to RF would increase risks of acoustic neuroma and brainglioma. Therefore, International Agency for Research on Cancer （IARC） has classifiedthem as potential human carcinogens (2B) in2002and2011respectively. At present,there is not adequate experimental evidence to support this viewpoint. It is well knownthat changes of cell morphology, cell cycle, proliferation and apoptosis have closerelationships with cell malignant transformation. To explore the association of long-termexposure of PF-EMF (or RF) and tumorigenesis, SRA01/04and Balb/c3T3cells were used in this study, and cell morphology, cell cycle, proliferation, apoptosis or celltransformation were observed after11weeks PF-EMF exposure or4weeks RF exposure.MethodsSRA01/04and Balb/c3T3cells in exponentially growing phase were sham-exposed orcontinuously exposed to50Hz PF-EMF at2.3mT for2h one day,5days every week;SRA01/04cells and Balb/c3T3cells in exponentially growing phase were sham-exposedor exposed to1950MHz RF at a specific absorption rate (SAR) of2.79W/kg for1h a day,5days every week. After11weeks exposure to PF-EMF or4weeks exposure to RF, cellswere collected instantly.1. Cell viability was detected by MTT assay2. Cell cycle、apoptosis was detected by flow cytometry3. Protein expression was detected by Western Blot4. Cell migration rate was detected by scratch adhesion test5. Cell transformation was detected by soft agar colony assay and plate clone forming testResults1. Compared with sham group, the shape of SRA01/04cells, but not Balb/c3T3cellsbecame round, and heterochromatin gathered at the edge of some cells after10,11weeks exposure to PF-EMF. In addition, Both SRA01/04and Balb/c3T3cells did notshow any change in cell morphology after4weeks exposure to RF.2. MTT assay results showed that compared with sham group, the viability of SRA01/04cells significantly decreased after4weeks exposure to PF-EMF (p<0.05), and there wasno obvious change between sham and exposure group after6,8and10weeks exposureto PF-EMF (p>0.05). However, the viability of SRA01/04cells significantly increasedafter11weeks exposure to PF-EMF (p<0.05). In addition, compared with sham group,the viability of Balb/c cells significantly decreased after4,8,10and11weeks exposureto PF-EMF (p<0.05).4weeks exposure to RF did not change the viability of bothSRA01/04and Balb/c3T3cells (p>0.05).3. Cell cycle distribution assay results showed, compared with sham group, SRA01/04cells in S and G1phase significantly decreased and increased respectively after4weeks exposure to PF-EMF (p<0.05), and the cell cycle distribution has no obvious changeafter6,8and10weeks exposure to PF-EMF (p>0.05). SRA01/04cells in S and G1phase significantly increased and decreased respectively after11weeks exposure toPF-EMF (p<0.05). Compared with sham group, Balb/c3T3cells in S phasesignificantly decreased after4,8,10and11weeks exposure to PF-EMF (p<0.05).4weeks exposure to RF did not change the cell cycle distribution in both SRA01/04andBalb/c3T3cells (p>0.05).4. Western-blot results showed the protein levels of PCNA and CyclinD1significantlyincreased in SRA01/04cells after11weeks exposure to PF-EMF (p<0.05). The proteinlevels of PCNA and CyclinD1significantly decreased after11weeks exposure toPF-EMF (p<0.05).5. In case of apoptosis, it was found that compared with sham group,11weeks exposure toPF-EMF and4weeks exposure to RF did not change the apoptosis rate in SRA01/04cells and Balb/c3T3cells (p>0.05).6. In scratch adhesion test,11weeks exposure to PF-EMF did not change cell migrationrate of SRA01/04cells and Balb/c3T3cells (p>0.05).7. In soft agar colony assay, no colony was found in SRA01/04and Balb/c3T3cells after11weeks exposure to PF-EMF.8. In plate clone forming test, no malignant transformation focus was found in SRA01/04and Balb/c3T3after11weeks exposure to PF-EMF cells.Conclusions1.11weeks of PF-EMF exposure could have some biological effects in SRA01/04andBalb/c3T3cells, and different cell lines have different sensitivity to PF-EMF2. PCNA and CyclinD1were involved in PF-EMF induced cell proliferation and cellcycle distribution change.3.11weeks of PF-EMF exposure could not induce cell transformation in SRA01/04andBalb/c3T3cells.4.4weeks of RF exposure could not have obvious effects on cell proliferation, cell cycledistribution and apoptosis in SRA01/04and Balb/c3T3cells. |
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