Loss of a whole chromosome S or a deletion of its long arm (5q) is a recurring abnormality in malignant myeloid neoplasms. To determine the location of genes on Sq that may be involved in leukemogenesis, we examined the deleted chromosome 5 homologs in a series of 135 patients with malignant myeloid diseases. By comparing the breakpoints, we identified a small segment of 5q, consisting of band 5q31, that was deleted in each patient. This segment has been termed the critical region. Distal Sq contains a number of genes encoding growth factors, hormone receptors, and proteins involved in signal transduction or transcriptional regulation. These include several genes that are good candidates for a tumorsuppressor gene, as well as the genes encoding five hematopoietic growth factors (CSF2, IL3, IL4, IL5, and IL9). By using fluorescence in situ hybridization, we have refrned the localization of these genes to 5q31.1 and have determined the order of these genes and of other markers within 5q31. By hybridizing probes to metaphase cells with overlapping deletions involving 5q31, we have narrowed the critical region to a smail segment of 5q31 containing the EGRI gene. The five hematopoietic growth factor genes and seven other genes are excluded from this region. The EGRI gene was not deleted in nine other patients with acute myeloid leukemia who did not have abnormalities of chromosome 5. By physical mapping, the minimum size of the critical region was estimated to be 2.8 megabases. This cytogenetic map of 5q31, together with the molecular characterization of the critical region, will facilitate the identification of a putative tumor-suppressor gene in this band.Recurring chromosomal rearrangements are characteristic of human malignant diseases, particularly the leukemias and lymphomas (1) (93%o) had a clonal chromosomal abnormality and 97 (75%) had loss or deletion of chromosome 5 and/or 7. Among these 97 patients, 21 had loss of chromosome 5, 26 had a del(5q), 8 had loss of 5q following unbalanced translocations, 51 had loss of chromosome 7, 11 had a del(7q), and 12 had loss of 7q as a result of an unbalanced translocation. Thirty-one patients had abnormalities of both chromosomes 5 and 7. Overall, 55 patients (43%) had abnormalities of chromosome 5. A del(5q) was the most common structural aberration in our series.In addition to t-MDS/t-AML, a -5/del(Sq) has also been observed in the malignant cells of 10%o ofpatients with AML de novo and in 15% ofpatients who have MDS arising de novo (8). Many of these patients have had significant occupational exposure to potential environmental carcinogens, suggesting that abnormalities of chromosome 5 or 7 may be a marker of mutagen-induced leukemia. A distinct clinical syndrome associated with a del(5q) is seen in a subset ofpatients with MDS de novo. Clinically, this disorder, termed the "5q-syndrome," is characterized by refractory anemia (RA). These patients having a del(Sq) as the sole abnormality tend to have a relatively mild course that usually does not progress to ...

Chronic myelogeneous leukemia (CML) is genetically characterized by fusion of the bcr and abl genes on chromosomes 22 and 9, respectively. In most cases, the fusion involves a reciprocal translocation t(9;22)(q34;q11), which produces the cytogenetically distinctive Philadelphia chromosome (Ph1). Fusion can be detected by Southern (DNA) analysis or by in vitro amplification of the messenger RNA from the fusion gene with polymerase chain reaction (PCR). These techniques are sensitive but cannot be applied to single cells. Two-color fluorescence in situ hybridization (FISH) was used with probes from portions of the bcr and abl genes to detect the bcr-abl fusion in individual blood and bone marrow cells from six patients. The fusion event was detected in all samples analyzed, of which three were cytogenetically Ph1-negative. One of the Ph1-negative samples was also PCR-negative. This approach is fast and sensitive, and provides potential for determining the frequency of the abnormality in different cell lineages.

By in situ chromosomal hybridization, the GM-CSF and FMS genes were localized to human chromosome 5 at bands q23 to q31, and at band 5q33, respectively. These genes encode proteins involved in the regulation of hematopoiesis, and are located within a chromosome region frequently deleted in patients with neoplastic myeloid disorders. Both genes were deleted in the 5q-chromosome from bone marrow cells of two patients with refractory anemia and a del(5)(q15q33.3). The GM-CSF gene alone was deleted in a third patient with acute nonlymphocytic leukemia (ANLL) who has a smaller deletion, del(5)(q22q33.1). Leukemia cells from a fourth patient who has ANLL and does not have a del(5q), but who has a rearranged chromosome 5 that is missing bands q31.3 to q33.1 [ins(21;5)(q22;q31.3q33.1)] were used to sublocalize these genes; both genes were present on the rearranged chromosome 5. Thus, the deletion of one or both of these genes may be important in the pathogenesis of myelodysplastic syndromes or of ANLL.

The Philadelphia (Ph1) chromosome, or its molecular counterpart, the BCR-ABL fusion gene, is a rare but important prognostic indicator in childhood acute lymphoblastic leukemia (ALL), but its impact on adult ALL has not been well ascertained. A prospective study of the BCR-ABL fusion gene was begun on patients entered on clinical trials conducted by the Cancer and Leukemia Group B (CALGB). All patients received intensive, multiagent chemotherapy that included daunorubicin. Over 2 years, 56 patients were studied for molecular evidence of a BCR-ABL gene using Southern blot and pulsed-field gel hybridization analysis. Results were compared with cytogenetic detection of a Ph1 chromosome, and clinical features were compared for the BCR-ABL-positive and - negative groups. Molecular methods detected the BCR-ABL gene in 30% of cases compared with cytogenetic detection of the Ph1 chromosome in only 23%. The majority of cases (76%) showed the p190 gene subtype similar to pediatric ALL; the BCR-ABL-positive cases displayed a more homogeneous immunophenotype than the BCR-ABL-negative cases and were predominantly CALLA positive (86%) and B-cell surface antigen positive (82%). The rate of achieving complete remission was similar in the BCR- ABL-positive and -negative groups (71% and 77%, respectively, P = .72). There were more early relapses in the BCR-ABL-positive group, resulting in a shorter remission duration that was especially marked in the CALLA- positive and B-cell antigen-positive populations. These preliminary data suggest that the impact of the BCR-ABL gene on clinical outcome in ALL may be on maintenance of complete remission (CR) rather than achievement of CR when aggressive, multiagent chemotherapy is used. This study identifies the BCR-ABL gene as an important factor in adult ALL and demonstrates the utility of molecular methods for its accurate diagnosis.

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