ascorbic-acid and Chromosomal-Instability

Chromosomal instability (CIN), defined as abnormality in chromosome structure or number, is the hallmark of malignancies. The role of vitamin C in cancer treatment is controversial and its effect on CIN is still an open field of research. In this work, we tried to study the effect of high-dose L-ascorbic acid (L-AA) on CIN-induced (CINhi = CIN high) and non-CIN-induced (CINlo = CIN low) cervical cancer cells.. The aim of this study was to explore the effect of high-dose L-AA on CIN in the cervical cancer cell line (HeLa) cells.. The HeLa cells (CINhi and CINlo) were treated with 2 doses (5 mM and 8 mM) of L-AA for 24 h and 48 h. They were then analyzed by micronucleus (MN) scoring, cell ploidy and flow cytometry, the latter regarding γH2AX expression. Cell viability was assessed by the methylthiazol tetrazolium (MTT) and Annexin V assays.. Treatment of CINhi cells with L-AA led to a decrease in MN score (colchicine - 71.5 ±4.95, 67.5 ±0.71; L-AA (5 mM) - 49 ±7.07, 46.5 ±4.95; L-AA (8 mM) - 42 ±9.89, 41 ±1.41, at 24 h and 48 h, respectively; p < 0.05). Treatment of CINlo cells with L-AA resulted in increased MN score (5 mM - 45 ±7.07, 36 ±4.24; 8 mM - 34.5 ±4.95, 31 ±1.41, at 24 h and 48 h, respectively; control - 15.5 ±0.71, 12.5 ±0.71; p < 0.05) and reduction in cancer cell viability (control - 100%; L-AA (5 mM) - 76.32% ±28.73, 72.74% ±20.30; L-AA (8 mM) - 66.14% ±19.13, 66.99% ±19.99, at 24 h and 48 h, respectively; p < 0.05). The expression of γH2AX was high in both groups at 48 h (mean CINhi = 19.42%, CINlo = 21.14%; control = 1.19% and 1.58%, respectively) with the 8 mM dose of L-AA.. L-ascorbic acid was found to have a differential effect on CINhi and CINlo HeLa cells, which may be due to differences in oxidation status of these 2 categories.

Topics: Ascorbic Acid; Cell Proliferation; Chromosomal Instability; Female; HeLa Cells; Humans; Uterine Cervical Neoplasms

Miazaki, Watanabe, Kumagai and their colleagues reported that induction of HPRT(-) mutants by X-rays in cultured human cells was prevented by ascorbate added 30min after irradiation. They attributed extinction of induced mutation to neutralization by ascorbate of radiation-induced long-lived mutagenic radicals (LLR), found using spectroscopy to have half-lives of minutes or hours. We find that post-irradiation treatment with ascorbate reduces, but does not eliminate, induction of CD59(-) mutants in human-hamster hybrid A(L) cells exposed to high-LET carbon-ions (LET of 100KeV/microm). A(L) cells contain a standard set of Chinese hamster ovary (CHO) chromosomes and a single copy of human chromosome 11 containing the CD59 gene which encodes the CD59 cell surface antigen, a convenient marker for mutation. RibCys [2(R, S)-D-ribo-(1',2',3',4'-tetrahydroxybutyl)thiazolidine-4(R)-carboxylic acid] a 'prodrug' of l-cysteine which also scavenges LLR, had a similar but lesser effect on induced mutation. DMSO, which scavenges classical radicals like H* and OH* but not LLR, also reduced mutation, but only when it was present during irradiation. The lethality of carbon-ions was not altered by ascorbate, RibCys no matter when added. Post-radiation addition of ascorbate and RibCys also affected the quality of CD59(-) mutations induced by carbon-ions. The major change in mutant spectra was a reduction in the prevalence of small, intragenic mutations (mutations not detected by PCR) and in the prevalence of unstable, complicated mutants, which display high levels of persistent chromosomal instability. Thus, ascorbate and RibCys may suppress some kinds of mutations induced by ionizing radiation including those displaying aspects of radiation-induced genomic instability. Countering the effects of both classical radicals and LLR may be important in preventing genetic diseases.

Topics: Animals; Ascorbic Acid; Carbon; CD59 Antigens; Chromosomal Instability; Cricetinae; Cricetulus; Cysteine; Dimethyl Sulfoxide; Humans; Hybrid Cells; Hypoxanthine Phosphoribosyltransferase; Linear Energy Transfer; Mutation; Radiation-Protective Agents; Thiazoles; Thiazolidines