-7/del(7q) in adults

1999-06-01 François Desangles Affiliation

Clinics and Pathology

Disease

myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML); they may occur de novo, or be secondary to an exposure to chemical mutagens or to chemotherapy treatments with alkylating agents; may probably also be secondary to immunosuppressive therapy for severe aplastic anemia

Phenotype stem cell origin

MDS cases : found in 30% of RAEB/RAEB-T, 20% of CMML, and only 5% of RA with an abnormal karyotype;

AML most often M4 or M6 ;

Monosomy 7 and these deletions does not seem a specific feature of the dysplastic clone in the MDS, they are secondary events contributing to the leucogenesis

Epidemiology

-7 is the most frequent abnormality in secondary myeloid disorders, found in 51% of the cases in a series of 246 cases, while del(7q) was found in 7%, and a partial monosomy 7 as a result of an unbalanced translocation in 8% of cases; in contrast, -7/del(7q) is found in 10% of de novo myeloid disorders; the sex ratio is 1.5 male for 1 female; the proportion of adults with a -7 myeloid disorder grows dramatically after 60 years

Clinics

characterized by infectious susceptibility, quick aggravation, and treatment resistance

Prognosis

monosomy 7 is classified as a poor prognostic criterium by the International Prognostic Scoring System; the actuarial relapse rate at one year is 82 %, and the 7-yr actuarial event-free survival is 6 %; after an allogeneic bone marrow transplantation, -7 is predictive of an unfavorable outcome

Cytogenetics

Cytogenetics morphological

deletion (7q) is always interstitial; cluster of breakpoints in 7q11 to 7q36, is a with two common minimal zones in q22 and in q32-34

Cytogenetics molecular

using loss of heterogygocity (LOH) studies and YAC libraries, a 2 to 3 Mb segment in 7q22 has been designated as the proximal common deleted area; the 7q33-34 zone is the consensual area for the distal deletion; LOH studies suggest that a specific mechanism, such as mitotic recombination in bone marrow stem cell leading to homozygosity in both granulocytes and lymphocytes, may be implicated

Additional anomalies

-5/del(5q), found in 40 to 60 % of the secondary MDS cases; trisomy 8

Variants

the balanced translocation t(1;7)(q10;p10), and many unbalanced translocation, having for consequence a partial monosomy 7 of the 7q22 to 7q34 bands may, in a way, be considered as variants

Genes Involved and Proteins

Note

-7/del(7q) is not only frequent in secondary MDS or AML, but also in leukemias occurring in individuals with constitutional syndromes including predisposition to myeloid disorders; these findings suggest the presence of a putative myeloid leukemia suppressor gene in the commonly deleted genomic segment 7q22 and even multiple genes in 7q22 -31.1 that are playing a role in leukemogenesis;

candidate genes are :

ASNS (asparagine synthetase gene) in 7q21.3-q22.1;

ACHE (acetyl cholinesterase),

EPO (erythropoietin),

PLANH1 (plasminogen activator inhibitor 1) in 7q22; and

MET in 7q31.2-31.3

Bibliography

Pubmed ID	Last Year	Title	Authors
8445946	1993	Cytokine modulation of the susceptibility of acute T-lymphoblastic leukemia cell lines to LAK activity.	Cesano A et al
9058725	1997	Molecular cytogenetic delineation of deletions and translocations involving chromosome band 7q22 in myeloid leukemias.	Fischer K et al
7093525	1982	Correlation of occupation and karyotype in adults with acute nonlymphocytic leukemia.	Golomb HM et al
10374851	1999	Neutrophil dysplasia is not a specific feature of the abnormal chromosomal clone in myelodysplastic syndromes.	Hast R et al
1868912	1991	Cytogenetics of secondary myelodysplasia (sMDS) and acute nonlymphocytic leukemia (sANLL).	Johansson B et al
9218106	1997	Monosomy 7 and 7q--associated with myeloid malignancy.	Johnson E et al
8611680	1996	Molecular definition of a narrow interval at 7q22.1 associated with myelodysplasia.	Johnson EJ et al
9447826	1997	Evidence for two molecular steps in the pathogenesis of myeloid disorders associated with deletion of chromosome 7 long arm.	Kiuru-Kuhlefelt S et al
10071086	1999	Allelotyping of acute myelogenous leukemia: loss of heterozygosity at 7q31.1 (D7S486) and q33-34 (D7S498, D7S505).	Koike M et al
8822909	1996	Cytogenetic and molecular delineation of a region of chromosome 7 commonly deleted in malignant myeloid diseases.	Le Beau MM et al
9520444	1998	Molecular anatomy of chromosome 7q deletions in myeloid neoplasms: evidence for multiple critical loci.	Liang H et al
7718870	1995	Childhood monosomy 7: epidemiology, biology, and mechanistic implications.	Luna-Fineman S et al
9731047	1998	Cytogenetic abnormalities in primary myelodysplastic syndrome are highly predictive of outcome after allogeneic bone marrow transplantation.	Nevill TJ et al
8637218	1996	Deletion of the acetylcholinesterase locus at 7q22 associated with myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML).	Stephenson J et al
7475268	1995	Cytogenetic clonality analysis in myelodysplastic syndrome: monosomy 7 can be demonstrated in the myeloid and in the lymphoid lineage.	van Lom K et al

Summary

Note

-7/del(7q) in childhood blood malignancies exhibits a specific pattern of pathogenesis; chromosome 7 anomalies are not rare in acute lymphocytic leukaemia (ALL); they occur in balanced translocations involving 7p15 or 7q34 in T lineage and 7q22 or 7q32 in B proliferations; monosomy 7 is present in 5 to 6 % of ALL, most often as a secondary anomaly of the t(9;22); the association t(9;22), -7 is present in 16 % of the Ph1+ ALL, i.e. in 3% of ALL as a whole; we will hereunder focuse on -7/del(7q) in adult myeloproliferations

del(7q) Figure 1: Partial karyotypes with 7q deletions (A). Fluorescence in situ hybridization with Vysis D7S486 (7q31)/CEP 7 probe (Abbott moleculars, US) showing 2 green and 2 red signals on normal and one red signal in abnormal metaphases indicating 7q deletion of various sizes (C-H) u2013 Courtesy Adriana Zamecnikova. Figure 2: del(7q) G- banding - Courtesy Jean-Luc Lai and Alain Vanderhaegen; Hybridization with Vysis D7S486 (7q31)/CEP 7 probe (Abbott moleculars, US) showing 1 green and 1 red signal confirming monosomy 7on metaphase and interphase cells u2013 Courtesy Adriana Zamecnikova.

Citation

François Desangles

-7/del(7q) in adults

Atlas Genet Cytogenet Oncol Haematol. 1999-06-01

Online version: http://atlasgeneticsoncology.org/haematological/1093/del7qid1093