Effect of busulphan treatment and elevated temperature on the expression of the beta-pol gene in rat testis

Daily Intravenous Infusion of Busulfan Impurity 5 for 4 Days Is Not Associated With Toxic Effects in the Rat

The alkylating agent busulfan is used in conditioning treatment of chronic myelogenous or granulocytic leukemia prior to stem cell transplantations. Its cytotoxic activity results in primary damage or destruction of hematopoietic cells. While the toxicity of busulfan is well investigated, little is known about the toxic effects of its impurities. In this study, the effect of 4-day intravenous infusion (3 h/d) of 4.8 mg/kg/d busulfan and 0.49, 4.9, and 49 mg/kg/d busulfan impurity 5 (4-((methylsulfonyl)oxy)butyl acetate) was investigated in rats. Whereas busulfan elicited myelotoxic and hepatotoxic effects, no toxic effects were observed in animals receiving the impurity at dosages up to 10 times higher than busulfan. The highest impurity dose of 49 mg/kg/d is therefore considered the no-observed-adverse-effect level of busulfan impurity 5.

Low expression of DNA polymerase beta in human testicular germ cell tumours--impact on foetal gonocytic origin theory

Different models of pathogenesis of adult testicular germ cell tumours (TGCTs) are presented. Analysis of telomeric length and DNA polymerase beta expression suggests that seminoma and nonseminoma, two main histological types of TGCTs, derive independently from transformed foetal primordial cells.

Characteristics of DNA repair induced by DNA polymerase β in hepatoma cells after γ-ray irradiation

AIM: To investigate the effects of DNA repair induced by DNA polymerase β in hepatoma cells after γ-ray irradiation.

METHODS: Cell nuclei were prepared from mouse model (SMMC LTNM), in which human hepatoma cells are transplanted on nude mice. The nuclei were then irradiated with ⁶⁰Co-γ rays at different dose levels or dose rates. A selective inhibitor test was then used to detect the effects of the radiation on DNA repair using N-ethylmaleimide (NEM) and ddTTP as selective inhibitors to DNA polymerases γ and β respectively.

RESULTS: ³H-TTP incorporation into irradiated nuclei or calf thymus DNA was significantly higher than that the rate at which it is incorporated into non-irradiated nuclei when either DNA polymerase β or γ was inhibited. When both NEM and ddTTP are present, the ³H-TTP incorporation in irradiated DNA was not significantly different from the non-irradiated nuclei. Furthermore, ³H-TTP incorporation into DNA of SMMC-LTNM hepatoma nuclei was higher than that of normal hepatocyte nuclei (P < 0.01). This suggests that DNA repair induced by DNA polymerase β was more active in hepatoma cell nuclei than in normal hepatocyte nuclei.

CONCLUSION: DNA polymerase β may be more responsive to DNA damage in some tumor cells than that in normal cells, which may facilitate the cells to repair DNA damages from radiation more efficiently.

Alternative splicing of DNA polymerase beta mRNA is not tumor-specific

Mammalian DNA polymerase beta is a crucial enzyme in cell genomic maintenance. Its structure is highly conserved. Some splice variants of beta-pol mRNA were observed. One alternative splice DNA polymerase beta mRNA, generated by 87 nt deletion (exon 11) in the catalytic domain of this enzyme, was suggested to be responsible for genomic instability in tumorigenesis and in genetic disorder (Werner syndrome). Here, we show that exon-11-deleted beta-pol mRNA is present in all examined normal and tumor tissues as well as in resting or PHA-stimulated peripheral-blood mononuclear cells. This finding proves that the presence of the exon-11 alternative splicing variant of beta-pol mRNA is not tumor-specific.