Immunoglobulin and T-cell receptor delta gene rearrangements are rarely found in myelodysplastic syndromes in chronic phase

Clinical observations on chemotherapy curable malignancies: unique genetic events, frozen development and enduring apoptotic potential

BACKGROUND

A select number of relatively rare metastatic malignancies comprising trophoblast tumours, the rare childhood cancers, germ cells tumours, leukemias and lymphomas have been routinely curable with chemotherapy for more than 30 years. However for the more common metastatic malignancies chemotherapy treatment frequently brings clinical benefits but cure is not expected. Clinically this clear divide in outcome between the tumour types can appear at odds with the classical theories of chemotherapy sensitivity and resistance that include rates of proliferation, genetic development of drug resistance and drug efflux pumps. We have looked at the clinical characteristics of the chemotherapy curable malignancies to see if they have any common factors that could explain this extreme differential sensitivity to chemotherapy.

DISCUSSION

It has previously been noted how the onset of malignancy can leave malignant cells fixed with some key cellular functions remaining frozen at the point in development at which malignant transformation occurred. In the chemotherapy curable malignancies the onset of malignancy is in each case closely linked to one of the unique genetic events of; nuclear fusion for molar pregnancies, choriocarcinoma and placental site trophoblast tumours, gastrulation for the childhood cancers, meiosis for testicular cancer and ovarian germ cell tumours and VDJ rearrangement and somatic hypermutation for acute leukemia and lymphoma. These processes are all linked to natural periods of supra-physiological apoptotic potential and it appears that the malignant cells arising from them usually retain this heightened sensitivity to DNA damage. To investigate this hypothesis we have examined the natural history of the healthy cells during these processes and the chemotherapy sensitivity of malignancies arising before, during and after the events. To add to the debate on chemotherapy resistance and sensitivity, we would argue that malignancies can be functionally divided into 2 groups. Firstly those that arise in cells with naturally heightened apoptotic potential as a result of their proximity to the unique genetic events, where the malignancies are generally chemotherapy curable and then the more common malignancies that arise in cells of standard apoptotic potential that are not curable with classical cytotoxic drugs.

Treatment of myelodysplastic syndrome with cyclosporin A

A multicenter prospective study was carried out to evaluate the efficacy of cyclosporin A (CsA) in 32 patients with myelodysplastic syndromes. The FAB subtypes of the patients included refractory anemia, refractory anemia with ringed sideroblasts, and refractory anemia with excess blasts. The dosage of CsA was 3 to 6 mg/kg per day and was adjusted according to the blood concentration of CsA and the responses of patients. The drug was administered twice a day for more than 3 months. After 3 months of treatment, hematological improvement was observed in 18 of 32 patients (56.3%) by the criteria of the International Working Group. At the end of the follow-up (median time, 14 months), 4 patients showed alteration of disease progression, including 1 complete remission and 3 partial remissions, and 16 patients showed hematological improvement. There were a total of 20 responders. The response rate was 62.5% (20/32). It was shown that the CsA therapy was effective in patients with refractory anemia or refractory anemia with excess blasts and both hypo- and hyperplastic bone marrows might respond to the therapy. The survival time was significantly longer in responders than in nonresponders. The study shows that CsA therapy is potentially the most effective therapy for myelodysplastic syndromes.

Protein aggregation as a cause for disease

The ability of proteins to fold into a defined and functional conformation is one of the most fundamental processes in biology. Certain conditions, however, initiate misfolding or unfolding of proteins. This leads to the loss of functional protein or it can result in a wide range of diseases. One group of diseases, which includes Alzheimer's, Parkinson's, Huntington's disease, and the transmissible spongiform encephalopathies (prion diseases), involves deposition of aggregated proteins. Normally, such protein aggregates are not found in properly functioning biological systems, because a variety of mechanisms inhibit their formation. Understanding the nature of these protective mechanisms together with the understanding of factors reducing or deactivating the natural protection machinery will be crucial for developing strategies to prevent and treat these disastrous diseases.

Determination of T-cell receptors of clonal CD8-positive T-cells in myelodysplastic syndrome with erythroid hypoplasia

We determined T-cell receptor alpha-chain variable (TCRAV) and T-cell receptor beta-chain variable (TCRBV) region repertoires in peripheral bloods from patients with myelodysplastic syndrome (MDS) with erythroid hypoplasia. T-cells bearing TCR ADV14S1/BV5S2, AV21S1/BV21S4, and AV2S2/BV7S2 segments were markedly increased in three of four MDS patients, respectively. In addition, there was a positive relationship between the increase in the number of CD8-positive T-cells and the expression levels of these TCR transcripts. These findings suggest that CD8-positive T-cells monoclonally or oligoclonally expanded in the peripheral blood. We also determined the nucleotide and amino acid sequences of the complementarity-determining region 3 (CDR3) of TCR alpha- and beta-chains of the expanded T-cells. Unique sequences were detected in a high percentage of the respective CDR3 clones. The gene segment of the variable and joining regions, however, varied among the patients. The deduced amino acid sequences of CDR3 were heterogeneous among the patients, and there was no common motif. These results indicate there is monoclonal or oligoclonal proliferation of CD8-positive T-cells in MDS patients with erythroid hypoplasia, and suggest that these proliferating T-cells are responsible for the pathogenesis of the MDS entity.

Immunosuppressive treatments for myelodysplastic syndromes

The myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal hematopoietic stem cell disorders, while, immunological abnormalities are frequently observed in patients with MDS. Several reports revealed that about 10% of MDS patients have clinical autoimmune disorders like skin vasculitis, rheumatic disease, or autoimmune hemolytic anemia. Furthermore, serological immunological abnormalities like hyper- or hypogammaglobulinemia, positivities of antinuclear antibody, positivities of direct Coombs test, or inverted CD4/8 ratios were found in 18-65% of patients with MDS. Recently immunosuppressive therapies including prednisolone, antithymocyte globulin, and cyclosporin A (CsA) are used to treat cytopenia in some patients with MDS. We examined the efficacy of CsA in 50 patients with MDS. Hematologic improvement was observed in 30 (60%) patients especially for erythroid lineage. There were significantly more responders with good karyotype or DRB1*1501 than with intermediate/poor karyotypes or with other HLA types. MDS with erythroid hypoplasia is a rare form of MDS, and has not yet been clearly defined. We reported four patients with MDS with erythroid hypoplasia who had morphological evidence of myelodysplasia and low percentage of erythroid precursors. Rearrangements of the TCR-beta and -gamma genes were seen in these patients using Southern blot and PCR analysis. Also they had skewed TCR usages using TCR repertoire analysis. Their anemia drastically improved with CsA therapy. We have to establish the clinical usefulness of immunosuppressive therapy in MDS patients and simple tools for revealing T-cell mediated myelosuppression in the individual patients for decision-making.

Successful treatment with cyclosporin A for myelodysplastic syndrome with erythroid hypoplasia associated with T-cell receptor gene rearrangements

Myelodysplastic syndrome (MDS) with erythroid hypoplasia, a rare form of MDS, has not yet been clearly defined. We report four patients with MDS with erythroid hypoplasia who received immunosuppressive therapy. All were elderly, had severe transfusion-dependent anaemia, morphological evidence of myelodysplasia and a low percentage (3.2-13.6%) of erythroid precursors. Administration of cyclosporin A (CsA) improved their anaemia; all transfusion-dependent patients achieved transfusion-independence. An inverted CD4/8 ratio was seen in three patients who also demonstrated T-cell receptor (TCR)-beta and -gamma gene rearrangements by Southern blotting and clonality by polymerase chain reaction. Treatment with CsA can be an attractive alternative treatment for patients with MDS with erythroid hypoplasia, which may be associated with a clonal abnormality in T cells.

Clonality in the myelodysplastic syndromes

The myelodysplastic syndromes (MDSs) comprise a heterogeneous group of stem cell disorders involving cytopenia and dysplastic changes in 3 hematopoietic lineages. Although it is accepted that MDS is a clonal disorder, the exact nature of the involvement of multipotent stem cells and progenitor cells has not been resolved. Most clonality studies of MDS support the proposal that the primary neoplastic event occurs, in most patients, at the level of a committed myeloid progenitor cell, capable of differentiation into multiple myeloid lineages. The extent of the involvement of T and B lymphocytes in MDS remains controversial. Much of the variation reported may result from disease heterogeneity and technical issues such as skewed methylation patterns occurring in studies analyzing X-chromosome inactivation patterns (XCIP) and possible impurities in lymphocyte preparation. A great deal of the evidence in support of T-lymphocyte involvement in MDS has been generated by XCIP studies, and some of these data need to be treated with caution, especially data from studies in which appropriate controls were omitted. In contrast, B-lymphocyte involvement in some patients with MDS is based on studies using more robust technology including combined immunophenotyping and fluorescence in situ hybridization. Clonality studies involving myeloid and lymphoid cells in MDS have yielded discrepant results with regard to the potential involvement of multipotent (lympho-myeloid) hematopoietic stem cells (HSCs). However, failure to detect a clonal marker in all cells of all lineages does not preclude multipotent-HSC involvement. Some recent studies have produced compelling evidence to show that, in some patients with MDS, the multipotent HSC is the target of the primary neoplastic event. It now seems probable that MDS arises in multipotent HSCs more commonly than previously recognized. Such data not only provide important new insights into the biology of MDS but also may have therapeutic implications. The determination of whether multipotent HSCs are involved in the MDS clone may be important for the use of autologous stem cell transplantation in these patients.