Del(20q) Deletion - Detail

Deletions of the long arm of chromosome 20 are found in 4.1% and 1.5% of MDS and AML cases respectively. Del(20q) also occurs in 10% of polycythemia vera patients and other subgroups of MPD^1,2,3. The deletions are predominantly interstitial and the breakpoints usually occur in the region q11.2-q13.1. Often other cytogenetic abnormalities are present such as del(5q), - 7/del(7q), +8, del(18q), +21 and rearrangements of 13q. Due to the relatively small size of the deletion and the lack of banding features on chromosome 20, FISH is particularly useful in detecting this abnormality. The prognosis for MDS cases where del(20q) is the sole abnormality is good. However if secondary abnormalities are present, a poor outcome is indicated. AML patients respond poorly to treatment and have reduced survival rates. The clinical outcome for MPD patients remains unchanged in the presence of the abnormality. The mechanism of leukaemogenesis associated with del(20q) is unknown, however deletion of a tumour supressor gene (TSG) is thought to cause the increased proliferation of the cancer cells². Using RT-PCR analysis, Bench et al identified potential target genes in the region of overlap between the AML/MDS and MPD CDR at band 20q12. Five genes were expressed in both bone marrow and CD34 positive cells. Of the three previously identified genes, h-lmbt regulates chromatin structure during mitosis, SFRS6 encodes a serine rich protein important to regulation of alternative splicing of mRNA and MYBL2, a member of the myb transcription factor family, is involved in cell cycle control^2,4,5.

Reference:/Bibliographie/Literatur/Bibliografia

1. Patsouris et al 2002, Cancer Genetics and Cytogenetics 138 32-37.
2. Bilhou-Nabera 2000 Atlas Genet Cytogenet Oncol Haematol.
3. Bench et al 1998 Genomics 49, 351-362.
4. Li et al 2004, PNAS 101:7341-7346.
5. Wang et al 1999, Genomics 59, 275-281.