[Effects of the addition of conditioned media on the response of Fanconi anemia lymphocytes to mitomycin C].

It has been shown that the addition of normal plasma to Fanconi anemia (FA) lymphocyte cultures significantly decreases the frequency of mitomycin C (MMC) induced chromosome aberrations, suggesting that normal plasma contains a diffusible correction factor (CF) which is able to partially complement FA lymphocytes. On the other hand, there is evidence suggesting that FA cells are defective in the DNA postreplicative repair. CF could then be involved in DNA repair processes and in possible inducible mechanisms. In the present study MMC-treated FA lymphocytes were grown during the last 24 hours of culture, in conditioned media obtained from untreated and MMC-treated normal cells. The purpose was to investigate if MMC-stressed normal cells were induced to produce CF in vitro. The results failed to show a constant decrease of FA cells chromosome aberrations when plasma-free conditioned media from MMC-stressed normal cells were added (experiments 2 and 3). However, when the conditioned media were supplemented with normal plasma (experiments 1 and 4) a partial repair of MMC-induced damage of the FA cells was observed. The results suggest the presence of CF in normal plasma and two possible mechanisms of action are suggested: CF is involved in DNA repair of MMC-damaged FA cells or it induces cellular division selecting the less damaged cell population through mitosis.