The 5q- syndrome is a myelodysplastic disorder characterized by refractory macrocytic anemia with dyserythropoiesis, low or low normal WBC counts, hypolobulated megakaryocytes with normal to high platelet counts, and acquired deletion of part of the long arm of chromosome 5 usually as the sole marrow karyotypic abnormality. The majority of patients are female; the median age is 65 years. The three most common deletions are del(5)(q!3q33), del(5)(q!4q33) and del(5)(q!5q33); however, all bands between 5qll.2 and 5q35 have been implicated as breakpoints. The dihydrofolate reductase (DHFR) gene has been mapped to band 5ql 3. We hypothesized that one copy of the DHFR gene may be deleted in some 5q- patients, leaving only an abnormal DHFR allele and causing cytopenias that could potentially be normalized by leucovorin. To test this hypothesis, N1H protocol 98-CC-0101 was designed to study up to 14 patients with transfusion dependent 5qsyndrome. To date, six patients have been enrolled. Patients were treated with 25 mg of leucovorin orally daily for three months. Bone marrow samples were obtained from all patients prior to therapy, and from five of the six patients after treatment. Pretreatment karyotypes were: 46,XX,del(5)(ql5q35.1), 46,XX,del(5)(q13q33)/47,XX,+8, 46.XX,del(5)(q13q33)/46,XX, 46,XX,del(5)(ql5q35)/46,XX, 46.XY,del(5)(q31q35)/46,XY, 46,XX,del(5)(q22q33)/46,XX. Metaphase FISH analysis was performed on bone marrow from patients 2-6 using a reporter probe to 5pl5.2 (D5S23, VYSIS) and a BAC clone, 325J23, for DHFR (gift from Dr. Larry Mesner, PNAS 97(141:7921-6) that we mapped to 5q13.3. DHFR was retained on both the normal and deleted chromosomes 5 in all cases. All patients had a normal sequence of the DHFR gene amplified from bone marrow RNA. Colony assays showed markedly decreased CFUE and moderately decreased CFU-G and CFU-M as compared with controls, with and without leucovorin supplementation of the bone marrow culture media. All patients remained transfusion dependent after 3 months' treatment with leucovorin, with no significant increase in their reticulocyte counts, and no significant change in their marrow morphology or cytogenetics. Although eight additional patients are needed to confirm the preliminary results, these data suggest the DHFR gene does not play a role in the etiology of the 5q- syndrome, and leucovorin does not reverse the refractory anemia of patients with this disorder.
|Original language||English (US)|
|Issue number||11 PART II|
|State||Published - 2000|
ASJC Scopus subject areas
- Cell Biology