Adriamycin-induced DNA strand breaks in HeLa and in P388 leukaemia cells detected using in situ nick translation

Demonstration of DNA damage/repair in individual cells using in situ end labelling: association of p53 with sites of DNA damage

We describe the development and application of in situ end labelling (ISEL) to identity sites of damaged DNA in the nuclei of individual cells. In cell culture, exposure to a variety of genotoxic agents induced a dose and time-dependent increase in nuclear labelling. In addition, examination of histological sections of human skin exposed to solar-stimulated UV light showed ISEL in both keratinocytes and superficial dermal cells, with the same spatial and temporal distribution as that of a marker of DNA repair, PCNA (proliferating cell nuclear antigen). Using co-localization techniques and confocal microscopy, we found increased levels of p53 in many ISEL-positive cells in vitro, with a similar distribution of labelling in the nucleus. This observation provides further evidence for a direct role of p53 in the recognition of damaged DNA. Thus, ISEL should prove a convenient method for demonstrating genotoxic insult in individual cells and in histological material, and may have value in toxicological screening. This high-resolution microscopy technique can also be used to compare the spatial distribution of various proteins implicated in the response to DNA damage with the sites of the lesion.

Adriamycin induces large deletions as a major type of mutation in CHO cells

Adriamycin (ADR), a commonly used cancer chemotherapy antibiotic, exhibits a variety of genotoxicities. In this study, we have examined the mutagenicity of ADR at the hypoxanthine-guanine phosphoribosyltransferase gene (hprt) in Chinese hamster ovary (CHO) cells and the xanthine-guanine phosphoribosyltransferase locus (gpt) in a pSV2gpt-transformed CHO cell line, AS52. Although ADR induced a dose-dependent increase of mutant frequency at both loci, it was more mutagenic to the gpt gene than to the hprt locus. Multiplex PCR analysis revealed that 35% of the 103 independent ADR-induced HPRT-deficient mutants carried large deletions. Among these deletion mutants, 33% were total gene deletions, 22% affected multiple exons, and 42% involved a single exon, of which most (9/15) were exon 1. The majority (63%) of ADR-induced AS52 mutants had a total deletion of the gpt gene. These observations indicate that ADR induces large deletions as a major type of gene mutation in mammalian cells, suggesting the involvement of reactive oxygen species as one mutagenic pathway in the mutagenesis of ADR.

Adriamycin promotes neurite outgrowth in the "neurite-minus" N1A-103 mouse neuroblastoma cell line

Adriamycin, an anticancer agent acting on topoisomerase II, promotes the arrest of cell division and neurite extension in a "neurite-minus" murine neuroblastoma cell line, N1A-103. This morphological differentiation is accompanied by a blockade in the S phase of the cell cycle, modification of the amount of peripherin, and appearance of the beta 7-tubulin isoform. Yet, adriamycin-induced N1A-103 cells fail to express other neuronal markers, such as long-lasting Ca2+ channels, synaptophysin, and the shift in the proportion of the beta'1 tubulin isoform to the beta'2 isoform, whose appearance parallels the terminal differentiation of the wild type neuroblastoma cell line N1E-115. Hence, a comparison of the behavior of these two cell lines leads to the proposal that there are two programs of neuroblastoma differentiation: one where expression is triggered by the arrest of cell division and which is observed in adriamycin-induced N1A-103 variant cells, and the other, presumably occurring further downstream, which would involve further changes in morphogenesis and acquisition of new electrophysiological properties.