Fragile sites: overview, occurrence in acute nonlymphocytic leukemia and effects of caffeine on expression.

Interest has recently grown in the possible role of chromosomal fragile sites as factors predisposing to chromosome rearrangements characteristic of specific human cancers. Data from two series of experiments relating to this hypothesis are presented. First, the effects of caffeine and theophylline on expression of the fragile X and common fragile sites was studied in lymphocytes from three subjects. Caffeine and theophylline did not enhance fragile X expression under the conditions employed but did greatly enhance expression of the common fragile sites. Second, three patients with acute nonlymphocytic leukemia-M4 and inv(16)(p13q22) in leukemic cells were tested for the presence of fra(16)(q22) in normal cells. The fragile site was not seen in any of the patients in this study.