Monosomy X as the sole cytogenetic abnormality in acute lymphoblastic leukemia: a report of two new patients

Sex chromosome loss after allogeneic hematopoietic stem cell transplant in patients with hematologic neoplasms: a diagnostic dilemma for clinical cytogeneticists

BACKGROUND

Sex chromosome loss (SCL), including loss of an X chromosome (-X) in females and loss of the Y chromosome (-Y) in males, resulting in a karyotype of 45,X, rarely occurs in patients post an allogeneic hematopoietic stem cell transplant (alloHSCT). However, origin of this abnormal clone and its clinical significance remains unknown.

RESULTS

We present 12 cases with SCL who underwent alloHSCT; 9 patients (4 men and 5 women with a median age of 56 years) developed isolated SCL after alloHSCT (Group I), and 3 patients (all women with a median age of 58 years) had a SCL before undergoing alloHSCT after which SCL disappeared (Group II). The primary neoplasms included chronic lymphocytic leukemia (n = 5), acute myeloid leukemia (n = 5), chronic myelogenous leukemia with nodal marginal zone lymphoma (n = 1) and Hodgkin lymphoma (n = 1). According to the donor/recipient relationship, their alloHSCT can be divided into sex-matched, HLA-matched, unrelated donors (n = 2); sex-mismatched, HLA-matched, unrelated donors (n = 4); sex-mismatched, HLA-matched, related donors (2 HLA-identical and 2 HLA-haploidentical cases) and sex-matched, HLA-matched, related donors (2 HLA-haploidentical cases). In Group I, isolated SCL was first detected with a median interval of 3 months (range 1 to 42 months) after the alloHSCT. By the end of clinical follow-up in patients in Group I, 7 patients expired with a median overall survival of 45 months (range 3 to 108 months) after alloHSCT and 33 months (range 0 to 66 months) after SCL detection. In Group II, 1 patient expired with a survival time of 54 months after the alloHSCT. Detection of SCL after alloHSCT can be transient, intermittent or persistent.

CONCLUSIONS

Interpretation of SCL is challenging in the context of alloHSCT. Chimerism testing is useful in determining the origin of SCL. In the case of SCL with donor/recipient chimerism, deduction of the SCL origin by all means and use of "-?X" or "-?Y" in the ISCN nomenclature are recommended. Clinical follow-up with closely monitoring the SCL by both cytogenetic and molecular analyses is needed.

Cytogenetic analysis of CpG-oligonucleotide DSP30 plus Interleukin-2-Stimulated canine B-Cell lymphoma cells reveals the loss of one X Chromosome as the sole abnormality

Human and canine lymphoid neoplasms are characterized by non-random cytogenetic abnormalities. However, due to the low mitotic activity of the B cells, cytogenetic analyses of B-cell lymphoid proliferations are difficult to perform. In the present study we stimulated canine B-cell lymphoma cells with the immunostimulatory CpG-oligonucleotide DSP30 in combination with interleukin-2 (IL-2) and obtained an adequate number of metaphases. Cytogenetic analyses revealed the loss of one X chromosome as the sole cytogenetic aberration. Chromosome analysis of the corresponding blood showed a normal female karyotype. Monosomy X as the sole clonal chromosomal abnormality is found in human hematopoietic malignancies as well, thus the dog may serve as a promising animal model.

Constitutional chromosome aberrations as pathogenetic events in hematologic malignancies

A predisposition to tumor development is associated with some constitutional chromosomal abnormalities. Investigations of families with an apparent hereditary cancer and constitutional chromosome rearrangements have led to the molecular identification of tumor suppressor genes. Under the somatic mutation theory for the development of cancer, two mutational events are required. The first step may be a constitutional event and the second an acquired genetic mutation. Cytogenetic studies were performed on 5633 bone marrow specimens from patients with hematologic malignancies from a single institution. Fifty cases of constitutional chromosome aberrations were detected. Data collected from the literature and from our series are reviewed and compared with the incidence of specific constitutional chromosome aberrations in the newborn population. Possible mechanisms that may predispose individuals with constitutional chromosome aberrations to the development of a hematologic malignancy are reviewed.

Loss of X chromosome in childhood acute lymphoblastic leukemia

We present six cases of childhood acute lymphoblastic leukemia (ALL) in which an acquired loss of the X chromosome was detected. The cases derive from a consecutive series of 178 childhood ALL, consisting of 80 girls and 98 boys. In five cases the presence of the TEL-AML1, t(12;21), fusion product was detected by FISH. The single negative case had an unusual t(1;19)(p13;q13). In addition, this was the only case that did not have a cytogenetically visible rearrangement involving one of the chromosome regions 6q, 9p, or 12p. The six cases showed the typical presentation features of an ALL of FAB type L1, a common ALL immunophenotype with myeloid marker co-expression, and a median presenting age of 7 years. We, therefore, conclude that loss of chromosome X may be a secondary event in older girls with TEL-AML1-positive ALL.