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Quinone-induced DNA single strand breaks in a human colon carcinoma cell line
A D'Odorico1, G C Sturniolo, R F Bilton
1Division of Gastroenterology, Padua University, Italy.
Abstract:
It has been demonstrated that synthetic quinones, such as menadione, cause DNA damage in different cell systems, possibly being mediated by free radicals generated during redox cycling. It has been suggested that the damage caused could be related to tumor induction in different sites. To our knowledge it has not yet been demonstrated that the natural quinones, vitamin K1 and K2, exert the same activity. Using a colon carcinoma cell line, HT-29, we examined the extent of DNA damage induced by menadione, vitamin K1 and K2. Menadione caused significant DNA damage at low concentrations (25-200 microM) with a linear correlation of r = 0.95. In the presence of dicoumarol, a DT-diaphorase inhibitor, the damage was detected at concentrations five times lower indicating that free radicals generated during the redox cycling play a key role. Neither vitamin K1, incorporated in micelles, nor K2 caused detectable single strand breaks with respect to the controls either in the presence or in absence of dicoumarol. Our results demonstrate that, despite their redox cycling properties, the natural forms of vitamin K do not cause DNA damage in HT-29 cells as menadione does in the experimental conditions used.
Insights
Synthetic menadione causes DNA damage via free radicals, but natural vitamins K1 and K2 do not damage DNA in colon cancer cells. This suggests natural vitamin K forms are safer than synthetic menadione in this context.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Synthetic quinones like menadione can induce DNA damage, potentially linked to tumor induction.
- The genotoxicity of natural quinones, vitamins K1 and K2, remains largely uncharacterized.
- Redox cycling and free radical generation are implicated in menadione-induced DNA damage.
Purpose of the Study:
- To investigate and compare the DNA-damaging potential of menadione, vitamin K1, and vitamin K2.
- To determine if natural vitamin K forms induce DNA damage in a colon carcinoma cell line.
- To elucidate the role of free radicals and DT-diaphorase in menadione-induced genotoxicity.
Main Methods:
- Utilized the HT-29 colon carcinoma cell line for experimental assays.
- Administered menadione, vitamin K1 (in micelles), and vitamin K2 to cell cultures.
- Assessed DNA single-strand breaks in the presence and absence of dicoumarol, a DT-diaphorase inhibitor.
Main Results:
- Menadione induced significant DNA damage in HT-29 cells, showing a linear correlation (r=0.95) with concentration.
- Inhibition of DT-diaphorase by dicoumarol potentiated menadione's DNA damaging effects, confirming the role of free radicals.
- Neither vitamin K1 nor K2 caused detectable DNA damage under the tested conditions, irrespective of dicoumarol presence.
Conclusions:
- Natural forms of vitamin K (K1 and K2) do not induce DNA damage in HT-29 colon cancer cells.
- Menadione, a synthetic quinone, is genotoxic to HT-29 cells, mediated by free radical generation during redox cycling.
- The findings differentiate the genotoxic profiles of synthetic menadione and natural vitamin K forms.