L5178Y sublines: a look back from 40 years. Part 1: General characteristics

The lower alkyl methacrylates: Genotoxic profile of non-carcinogenic compounds

All of the lower alkyl methacrylates are high production chemicals with potential for human exposure. The genotoxicity of seven mono-functional alkyl esters of methacrylic acid, i.e. methyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, n-, i- and t-butyl methacrylate and 2 ethyl hexyl methacrylate, as well as methacrylic acid itself, the acyl component common to all, is reviewed and compared with the lack of carcinogenicity of methyl methacrylate, the representative member of the series so evaluated. Also reviewed are the similarity of structure, chemical and biological reactivity, metabolism and common metabolic products of this group of compounds which allows a category approach for assessing genotoxicity. As a class, the lower alkyl methacrylates are universally negative for gene mutations in prokaryotes but do exhibit high dose clastogenicity in mammalian cells in vitro. There is no convincing evidence that these compounds induce genotoxic effects in vivo in either sub-mammalian or mammalian species. This dichotomy of effects can be explained by the potential genotoxic intermediates generated in vitro. This genotoxic profile of the lower alkyl methacrylates is consistent with the lack of carcinogenicity of methyl methacrylate.

The contribution of women to radiobiology: Marie Curie and beyond

Marie Sklodowska-Curie, an extraordinary woman, a Polish scientist who lived and worked in France, led to the development of nuclear energy and the treatment of cancer. She was the laureate of two Nobel Prizes, the first woman in Europe who obtained the degree of Doctor of Science and opened the way for women to enter fields which had been previously reserved for men only. As a result of her determination and her love of freedom, she has become an icon for many female scientists active in radiation sciences. They are successors of Maria Curie and without the results of their work, improvement in radiation oncology will not be possible. Many of them shared some elements of Maria Curie's biography, like high ethical and moral standards, passionate dedication to work, strong family values, and scientific collaboration with their husbands. The significance of Tikvah Alper, Alma Howard, Shirley Hornsey, Juliana Denekamp, Helen Evans, Eleanor Blakely, Elizabeth L. Travis, Fiona Stewart, Andree Dutreix, Catharine West, Peggy Olive, Ingela Turesson, Penny Jeggo, Irena Szumiel, Eleonor Blakely, Sara Rockwell and Carmel Mothersill contribution to radiation oncology is presented. All the above mentioned ladies made significant contribution to the development of radiotherapy (RT) and more efficient cancer treatment. Due to their studies, new schedules of RT and new types of ionizing radiation have been applied, lowering the incidence of normal tissue toxicity. Their achievements herald a future of personalized medicine.

From radioresistance to radiosensitivity: In vitro evolution of L5178Y lymphoma

PURPOSE

To discuss the possible reasons for the loss of tumourigenicity and the acquisition of new phenotypic features (among them, sensitivity to X and UVC radiations) as a result of in vitro cultivation of L5178Y lymphoma cells.

RESULTS

Ten years ago the phenotypic differences between LY-R (original L5178Y maintained in vivo and examined in vitro) and LY-S lines were reviewed in detail by the author. The loss of tumourigenicity of LY-R cells upon in vitro cultivation accompanying the acquirement of the LY-S phenotype had been described earlier by Beer et al. (1983). In spite of their common origin, the sublines were shown to differ in their relative sensitivity to a number of DNA damaging agents and in numerous other features. Here, selected differences between LY-R and LY-S lines are briefly reviewed. It is proposed that Wallace's concept (2010a) that mitochondria are the interface between environmental conditions and the genome may explain the LY-R-LY-S conversion under prolonged in vitro cultivation.

CONCLUSION

The differences between the LY lines were probably of epigenetic rather than genetic character. The properties of LY-R cells changed as a result of exposure to an oxic in vitro milieu. The changes could be preconditioned by heteroplasmy and the selection of cells endowed with mitochondria best fitted to a high oxygen-low carbon dioxide environment.

Role of immunogenic fetuin A on L5178Y-R lymphoma tumorigenesis

In the present study, we report the detection of immunogenic fetuin-A on L5178Y-R (LY-R) lymphoma cells. Fetuin-A was recognized by antibodies present in the serum of LY-R tumor-bearing and immunized mice, but not by sera of mice immunized with the non-tumorigenic variant LY-S or by healthy mouse sera. However, according with Western blot analysis with commercial anti-fetuin antibodies, fetuin-A is present in both cell types which suggests that the fetuin recognized by anti-LY-R antibodies is an immunogenic form associated only with the tumorigenic LY-R cells and might be involved in tumor progression in this lymphoma.

The photo comet assay—A fast screening assay for the determination of photogenotoxicity in vitro

Different classes of chemicals can induce a phototoxic effect by absorbing light energy within the wavelength range of sunlight. The assessment of photo-safety is therefore an obligatory part of the development of new drugs. Ten UV-vis (280-800nm)-absorbing compounds (ketoprofen, promazine, chlorpromazine, dacarbazine, acridine, lomefloxacin, 8-methoxypsoralen, chlorhexidine, titanium dioxide, octylmethoxycinnamate) were tested for their photogenotoxic potential in the alkaline comet assay in the presence and absence of UV-vis. In order to establish an easy and timesaving protocol for a photo comet assay screening test, the application of 96-well plates was essential. The use of mouse lymphoma L5178Y cells, a cell line growing in suspension, allowed the determination of photocytotoxicity with the Alamar Blue assay and of photogenotoxicity with the alkaline comet assay in parallel. L5178Y cells were incubated with the test compounds for 20min and irradiated with simulated sunlight in the wavelength range from 280 to 800nm. The applied UV dose was 600mJ/cm(2) UV-A and 30mJ/cm(2) UV-B. After a post-incubation of 10min, the Alamar Blue assay and the alkaline comet assay were performed. All of the compounds which are known to be photogenotoxic (8-methoxypsoralen, acridine, chlorpromazine, dacarbazine, ketoprofen, lomefloxacin) showed a positive effect under our assay conditions. Furthermore, four UV-vis absorbing chemicals which are known to be not photogenotoxic (promazine, chlorhexidine, titanium dioxide, octylmethoxycinnamate) were analysed. For none of them an increase of the DNA damage following irradiation was observed in this study. In conclusion, all of the chemical compounds tested were classified in agreement with published data. From the data presented it is concluded that the photo comet assay with L5178Y mouse lymphoma cells is a reliable model to assess photochemical genotoxicity in vitro.