Table 1.
Compilation of studies with cell lines exposed to UV radiation and DNA methylation
| Country, Year [Reference] |
Study Design | Cell Lines | Groups | UV Radiation Treatment | Methylation Type | Technique | Outcome and Conclusion | Other Outcomes |
|---|---|---|---|---|---|---|---|---|
| India, 2006 [36] | Comparison of UVA and UVB-irradiated and non-irradiated cells | HaCaT and A431 (epidermoid carcinoma) | Irradiated group x non-irradiated group | 6 cycles of exposure to UVA (150–200 mJ/cm2) and UVB (15–20 mJ/cm2). Cells were cultured for 1–2 days before re-exposure to the same radiation dosage | Site-specific (p16, MGMT, DAP Kinase, GSTP1) | COBRA | Hypermethylation of p16 was observed on the irradiated group | |
| Germany, 2011 [37] | Comparison of UVA-irradiated and non-irradiated cells | HaCaT | Irradiated group x non-irradiated group | UVA exposure (200 kJ/m2) once a week for 10 to 15 weeks, with a six-day interval between irradiation events | Site-specific (p16) | qMSP | Hypermethylation of p16 (up to 70%) as well as ↓ of its transcripts on the irradiated group | |
| USA, 2013 [38] | Comparison of cells submitted to different doses of radiation, as well as different periods of UV exposure and cell recovery | NHEK | Negative controls (non-irradiated cells); positive low and high-dose controls (one-time radiation); cells exposed to low or high doses of radiation with an 8 or 18-day growth period | 10 cycles of low (130 J/m2) or high-dose (260 J/m2) UVB irradiation with 2–3 days of “cell recovery” between each cycle. After the final irradiation, cells were grown for 8 or 18 days | Global and site-specific (CXXC5, PPP3CB, L17C, CCDC40, C21orf29) | MIRA combined with microarray analysis; COBRA | No differences were detected in the DNA methylation profile of irradiated cells. Further studies are encouraged. | |
| China, 2015 [39] | Evaluation of PCF effect upon DNA methylation in UVB-irradiated cells | HaCaT | Non-irradiated group (control); irradiated group, no treatment x irradiated group + PCF or vitamin C | 20 chronic UVB exposure cycles (10 mJ/cm2 for 15 min per cycle) with 24–48h intervals | Site-specific (p16, RASSF1A) | MS-HRM | Hypermethylation of p16 and RASSF1A, ↓ transcript levels of both genes, and ↑ in transcript and protein levels of DNMT3B in irradiated cells | PCF provoked demethylation on the studied tumor suppressor genes and generated better effects than vitamin C |
| China, 2017 [40] | Comparison of UVB-irradiated and non-irradiated cells | HaCaT | Irradiated x non-irradiated cells | UVB exposure (40 mJ/cm2 or 80 mJ/cm2) for 24h | Global methylation and hydroxymethylation | IHC; IF | ↑ Global hydroxymethylation and ↑ transcript and protein levels of TETs 1, 2 and 3 in irradiated cells | |
| Japan, 2019 [41] | Comparison of UVB irradiated and non-irradiated cells, as well as between UV-exposed and non-exposed human facial regions | HDK1 and cells from human facial biopsies | Exposed group x non-exposed group | Exposure to different doses of UVB (10 or 100mJ/cm2) for two weeks (4× or less per week) for HDK1; regular sun exposure for facial samples | Global and site-specific (WNT1) | IHC; BS | Hypomethylation of WNT1 dose-dependent and ↑ transcript levels of WNT1 in irradiated cells. | Hypomethylation of WTN1; ↓ global methylation; ↓ DNMT1 levels in solar lentigines |
COBRA: Combined bisulfite restriction analysis; qMSP: Quantitative methylation-specific PCR; MIRA: Methylated-CpG island recovery assay; MS-HRM: Methylation specific-high resolution melting analyses; HC: Immunohistochemistry; IF Immunofluorescence; BS: Bisulphite sequencing.