Limits...
MUTYH mediates the toxicity of combined DNA 6-thioguanine and UVA radiation.

Grasso F, Ruggieri V, De Luca G, Leopardi P, Mancuso MT, Casorelli I, Pichierri P, Karran P, Bignami M - Oncotarget (2015)

Bottom Line: Although 6-TG/UVA treatment caused early checkpoint activation irrespective of the MUTYH status, Mutyh- cells failed to arrest in S-phase at late time points.Mutyh-/- mice survived better than wild-type during a 12-month chronicexposure to Aza/UVA treatments that significantly increased levels of skin DNA 8-oxoG.Two squamous cell skin carcinomas arose in Aza/UVA treated Mutyh-/- mice whereas similarly treated wild-type animals remained tumor-free.

View Article: PubMed Central - PubMed

Affiliation: Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Rome, Italy.

ABSTRACT
The therapeutic thiopurines, including the immunosuppressant azathioprine (Aza) cause the accumulation of the UVA photosensitizer 6-thioguanine (6-TG) in the DNA of the patients' cells. DNA 6-TG and UVA are synergistically cytotoxic and their interaction causes oxidative damage. The MUTYH DNA glycosylase participates in the base excision repair of oxidized DNA bases. Using Mutyh-mouse fibroblasts (MEFs) we examined whether MUTYH provides protection against the lethal effects of combined DNA 6-TG/UVA. Surprisingly, Mutyh- MEFs were more resistant than wild-type MEFs, despite accumulating higher levels of DNA 8-oxo-7,8-dihydroguanine (8-oxoG).Their enhanced 6-TG/UVA resistance reflected the absence of the MUTYH protein and MEFs expressing enzymatically-dead human variants were as sensitive as wild-type cells. Consistent with their enhanced resistance, Mutyh- cells sustained fewer DNA strand breaks and lower levels of chromosomal damage after 6-TG/UVA. Although 6-TG/UVA treatment caused early checkpoint activation irrespective of the MUTYH status, Mutyh- cells failed to arrest in S-phase at late time points. MUTYH-dependent toxicity was also apparent in vivo. Mutyh-/- mice survived better than wild-type during a 12-month chronicexposure to Aza/UVA treatments that significantly increased levels of skin DNA 8-oxoG. Two squamous cell skin carcinomas arose in Aza/UVA treated Mutyh-/- mice whereas similarly treated wild-type animals remained tumor-free.

No MeSH data available.


Related in: MedlinePlus

Cell cycle analysis after 6-TG/UVACell cycle progression in WT, Mutyh−/− and G396D-expressing MEFs. Cells were grown for 24h in 0.6μM 6-TG or 6-TG followed by UVA irradiation and sampled for analyses at the indicated time points. The percentage of cells in G1, S and G2 phases of the cell cycle are also indicated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4480694&req=5

Figure 3: Cell cycle analysis after 6-TG/UVACell cycle progression in WT, Mutyh−/− and G396D-expressing MEFs. Cells were grown for 24h in 0.6μM 6-TG or 6-TG followed by UVA irradiation and sampled for analyses at the indicated time points. The percentage of cells in G1, S and G2 phases of the cell cycle are also indicated.

Mentions: The absence of the MUTYH protein had profound effects on cell cycle progression after 6-TG/UVA treatments. In wild-type MEFs, 6-TG/UVA caused a pronounced slowing of progression through the S phase (>75% of the cells were blocked in the S phase at 24h) followed by an accumulation in G2 at 48h (Figure 3). In contrast, the Mutyh−/− cells did not accumulate in S phase, progressed into the G2-M phase at 24h (>34% of the cells) and in G1 at 48h. The behaviour of G396D-expressing MEFs resembled that of wild-type cells, with a similar increase in S-phase arrest and continuing perturbation at 48h post-treatment. Cell cycle progression was not affected by treatment with 6-TG or UVA alone (Figure 3 and data not shown).


MUTYH mediates the toxicity of combined DNA 6-thioguanine and UVA radiation.

Grasso F, Ruggieri V, De Luca G, Leopardi P, Mancuso MT, Casorelli I, Pichierri P, Karran P, Bignami M - Oncotarget (2015)

Cell cycle analysis after 6-TG/UVACell cycle progression in WT, Mutyh−/− and G396D-expressing MEFs. Cells were grown for 24h in 0.6μM 6-TG or 6-TG followed by UVA irradiation and sampled for analyses at the indicated time points. The percentage of cells in G1, S and G2 phases of the cell cycle are also indicated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4480694&req=5

Figure 3: Cell cycle analysis after 6-TG/UVACell cycle progression in WT, Mutyh−/− and G396D-expressing MEFs. Cells were grown for 24h in 0.6μM 6-TG or 6-TG followed by UVA irradiation and sampled for analyses at the indicated time points. The percentage of cells in G1, S and G2 phases of the cell cycle are also indicated.
Mentions: The absence of the MUTYH protein had profound effects on cell cycle progression after 6-TG/UVA treatments. In wild-type MEFs, 6-TG/UVA caused a pronounced slowing of progression through the S phase (>75% of the cells were blocked in the S phase at 24h) followed by an accumulation in G2 at 48h (Figure 3). In contrast, the Mutyh−/− cells did not accumulate in S phase, progressed into the G2-M phase at 24h (>34% of the cells) and in G1 at 48h. The behaviour of G396D-expressing MEFs resembled that of wild-type cells, with a similar increase in S-phase arrest and continuing perturbation at 48h post-treatment. Cell cycle progression was not affected by treatment with 6-TG or UVA alone (Figure 3 and data not shown).

Bottom Line: Although 6-TG/UVA treatment caused early checkpoint activation irrespective of the MUTYH status, Mutyh- cells failed to arrest in S-phase at late time points.Mutyh-/- mice survived better than wild-type during a 12-month chronicexposure to Aza/UVA treatments that significantly increased levels of skin DNA 8-oxoG.Two squamous cell skin carcinomas arose in Aza/UVA treated Mutyh-/- mice whereas similarly treated wild-type animals remained tumor-free.

View Article: PubMed Central - PubMed

Affiliation: Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Rome, Italy.

ABSTRACT
The therapeutic thiopurines, including the immunosuppressant azathioprine (Aza) cause the accumulation of the UVA photosensitizer 6-thioguanine (6-TG) in the DNA of the patients' cells. DNA 6-TG and UVA are synergistically cytotoxic and their interaction causes oxidative damage. The MUTYH DNA glycosylase participates in the base excision repair of oxidized DNA bases. Using Mutyh-mouse fibroblasts (MEFs) we examined whether MUTYH provides protection against the lethal effects of combined DNA 6-TG/UVA. Surprisingly, Mutyh- MEFs were more resistant than wild-type MEFs, despite accumulating higher levels of DNA 8-oxo-7,8-dihydroguanine (8-oxoG).Their enhanced 6-TG/UVA resistance reflected the absence of the MUTYH protein and MEFs expressing enzymatically-dead human variants were as sensitive as wild-type cells. Consistent with their enhanced resistance, Mutyh- cells sustained fewer DNA strand breaks and lower levels of chromosomal damage after 6-TG/UVA. Although 6-TG/UVA treatment caused early checkpoint activation irrespective of the MUTYH status, Mutyh- cells failed to arrest in S-phase at late time points. MUTYH-dependent toxicity was also apparent in vivo. Mutyh-/- mice survived better than wild-type during a 12-month chronicexposure to Aza/UVA treatments that significantly increased levels of skin DNA 8-oxoG. Two squamous cell skin carcinomas arose in Aza/UVA treated Mutyh-/- mice whereas similarly treated wild-type animals remained tumor-free.

No MeSH data available.


Related in: MedlinePlus