2.4 GHz Electromagnetic Field Influences the Response of the Circadian Oscillator in the Colorectal Cancer Cell Line DLD1 to miR-34a-Mediated Regulation

Abstract

2.4 GHz Electromagnetic Field Influences the Response of the Circadian Oscillator in the Colorectal Cancer Cell Line DLD1 to miR-34a-Mediated Regulation Olejárová S, Moravčík R, Herichová I. 2.4 GHz Electromagnetic Field Influences the Response of the Circadian Oscillator in the Colorectal Cancer Cell Line DLD1 to miR-34a-Mediated Regulation. Int J Mol Sci. 2022 Oct 30;23(21):13210. doi: 10.3390/ijms232113210. PMID: 36361993. Abstract Radiofrequency electromagnetic fields (RF-EMF) exert pleiotropic effects on biological processes including circadian rhythms. miR-34a is a small non-coding RNA whose expression is modulated by RF-EMF and has the capacity to regulate clock gene expression. However, interference between RF-EMF and miR-34a-mediated regulation of the circadian oscillator has not yet been elucidated. Therefore, the present study was designed to reveal if 24 h exposure to 2.4 GHz RF-EMF influences miR-34a-induced changes in clock gene expression, migration and proliferation in colorectal cancer cell line DLD1. The effect of up- or downregulation of miR-34a on DLD1 cells was evaluated using real-time PCR, the scratch assay test and the MTS test. Administration of miR- 34a decreased the expression of per2, bmal1, sirtuin1 and survivin and inhibited proliferation and migration of DLD1 cells. When miR-34a-transfected DLD1 cells were exposed to 2.4 GHz RF-EMF, an increase in cry1 mRNA expression was observed. The inhibitory effect of miR-34a on per2 and survivin was weakened and abolished, respectively. The effect of miR-34a on proliferation and migration was eliminated by RF-EMF exposure. In conclusion, RF-EMF strongly influenced regulation mediated by the tumour suppressor miR-34a on the peripheral circadian oscillator in DLD1 cells. Excerpt To test the effect of RF-EMF on gene expression, DLD1 cells were exposed to a pulsed electromagnetic field, generated by a D-Link GO-RT-N150 Wi-Fi router (D-Link, Taipei, Taiwan), during 24 h. The radiofrequency range was 2426 to 2448 MHz (Wi-Fi channel 6), pulse length was 2.76 ms, pulse frequency was 9.7 Hz, pulse risetime was 0.06–0.08 µs, and pulse falltime was 0.067–0.107 µs. Radiofrequency field power flux density at the level of the cell layer was 1 W/m2 (19 V/m) peak, 0.12 W/m2 (6.6 V/m) RMS. Plates with sham-exposed cells were during this time covered by radiofrequency protective foil YSHIELD HNV100 (YSHIELD GmbH & Co. KG, Ruhstorf an der Rott, Germany). Other conditions were identical for both groups: powerline frequency electric field (50 Hz) at the level of cell layer was below 1 V/m, powerline frequency magnetic field at the level of cell layer was 0.3 µT in both control and experimental groups. Conclusions In conclusion, the present study revealed new target genes of miR-34a-5p with key roles in the circadian oscillator functioning– per2, bmal1 and cry1. In the case of per2 and bmal1, miR-34a-5p downregulated gene expression, and this effect was most likely mediated via the 3′UTR region. cry1 mRNA expression was upregulated after miR-34a administration, and this influence is more likely to be mediated by an alternative way of miRNA functioning. Interestingly, exposure to RF-EMF potentiates the capacity of miR-34a to induce the expression of clock genes with oncogenic capacity—cry1 and cry2. Moreover, the functioning of the miR-34a inhibitor was weakened when cells were exposed to RF-EMF, and consequently, the increase in tumour-suppressive per2 mRNA expression induced by the miR-34a inhibitor was less pronounced under RF-EMF conditions compared to the control. Similarly, miR-34a inhibited the expression of anti-apoptotic protein survivin was diminished when cells were exposed to RF-EMF. RF-EMF have been classified by the WHO as possibly carcinogenic for humans. Our data are in line with this conclusion, as the results indicate that RF-EMF can shift the influence of miR-34a in cancer progression manifested by analysed target genes from typical tumour-suppressive to neutral or slightly oncogenic. Open access paper: mdpi.com

AI evidence extraction

Main findings

miR-34a administration decreased per2, bmal1, sirtuin1 and survivin expression and inhibited DLD1 proliferation and migration. In miR-34a-transfected cells, 24 h exposure to 2.4 GHz RF-EMF increased cry1 mRNA expression, weakened/abolished miR-34a effects on per2 and survivin, and eliminated miR-34a-associated inhibition of proliferation and migration.

Outcomes measured

• Clock gene mRNA expression (per2, bmal1, sirtuin1, survivin, cry1)
• Cell proliferation (MTS test)
• Cell migration (scratch assay)

Limitations

• In vitro study in a single colorectal cancer cell line (DLD1)
• Exposure metrics reported as power flux density/field strength; SAR not reported
• Sample size and replication details not provided in the abstract/excerpt

Suggested hubs

• school-wi-fi (0.55)
  Uses a Wi‑Fi router (2.4 GHz) as the RF-EMF source; findings relate to Wi‑Fi-type exposure.

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        "band": "RF",
        "source": "wi-fi",
        "frequency_mhz": 2437,
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    "population": "Colorectal cancer cell line DLD1",
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    "outcomes": [
        "Clock gene mRNA expression (per2, bmal1, sirtuin1, survivin, cry1)",
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    "effect_direction": "harm",
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    "peer_reviewed_likely": "yes",
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        "miR-34a",
        "circadian oscillator",
        "clock genes",
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        "cry1",
        "survivin",
        "proliferation",
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