To study whether 916 MHz microwave exposure with different intensities and durations could induce cellular neoplastic transformation in NIH3T3 cells.
NIH3T3 cells were used due to their sensitivity to carcinogens or cancer promoter in environment. Cell morphology and cell proliferation were examined in vitro.
Furthermore, an carcinogenesis assay with immunodeficiency mice was carried out to determine the neoplastic promotion. 10 mice were used for carcinogenesis assay and divided into five groups: one control group, three exposure groups and a positive control (injected a nasopharyngeal carcinoma cell line). Exposed and sham exposed cells were injected subcutaneously into the back of the mice. After tumor development, the mice were killed, the tumor was dissected and divided into two parts: one part was fixed and the other one was mashed and injected into two additional mice in order to study whether the developed tumor was able to grow in vivo.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
916 MHz
Exposure duration:
continuous for 2 h/day every day, until cells lost their contact inhibition (up to 8 weeks)
|
|
Cells were exposed in four groups: 1) control group 2) exposure at 90 W/cm² 3) exposure at 50 W/cm² 4) exposure at 10 W/cm²
| Frequency | 916 MHz |
|---|---|
| Type | |
| Exposure duration | continuous for 2 h/day every day, until cells lost their contact inhibition (up to 8 weeks) |
| Exposure source |
|
|---|---|
| Chamber | culture flasks and antenna were placed in a bench |
| Setup | cells were exposed in flasks at three different distances from the antenna (for the different power densities) |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 90 W/m² | maximum | measured | - | close contact to the antenna |
| power density | 50 W/m² | maximum | measured | - | middle distance to the antenna |
| power density | 10 W/m² | maximum | measured | - | furthest away from the antenna |
The data showed that cell morphology (loss of contact inhibition) and cell proliferation were changed after 5-8 weeks of exposure: The cells of the exposed groups formed colonies in the soft agar plates, whereas the control cells did not.
In the carcinogenesis assay, tumors developed on the back of mice inoculated with the exposed cells after 5-7 weeks. Tumors also developed in the additional two mice injected with the mashed tumor tissue (after 4 weeks).
All effects were time and dose dependent. In conclusion, the results indicate that microwave exposure can promote neoplastic transformation of NIH3T3 cells.
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