Frequent allelic loss of the RB, D13S319 and D13S25 locus in myeloid malignancies with deletion/translocation at 13q14 of chromosome 13, but not in lymphoid malignancies

In order to identify a commonly deleted region of 13q14 on chromosome 13, w e performed fluorescence in situ hybridization (FISH) on 17 patients with m yeloid malignancies and 12 patients with lymphoid leukemia/lymphoma who exh ibited either deletion or translocation at 13q14. Three cosmid probes (RB, D13S319 and D13S25) hybridizing to sequences on 13q14 were used. Fourteen o f the 17 patients with myeloid malignancies (82.4%) exhibited allelic loss at the RE, D13S319 and D13S25 locus, whereas only three of the 12 patients with lymphoid malignancies (25.0%) exhibited loss within these loci. These three patients had chronic lymphocytic leukemia (CLL). Six, two and one of the remaining nine lymphoid leukemia/lymphoma patients had breakpoints cent romeric to the RE gene, telomeric to D13S25 and within the D13S319 locus, r espectively. A high frequency of allelic loss was found using these probes in patients with myeloid malignancies, compared to in patients with leukemi a in the lymphoid origin, except CLL patients. These results indicate that loss of the RE gene itself or a region between RE and D13S319, which includ es commonly deleted loci, may play an important role in myeloid leukemogene sis.