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Publications and source records attributed to W Y K Hwang.
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The processes mediating genomic instability and clonal evolution are obscure in multiple myeloma (MM). Acquisition of new chromosomal translocations into the switch region of the immunoglobulin heavy chain (IgH) gene (chromosome 14q32) in MM, often heralds transformation to more aggressive disease. Since the combined effects of CD40 plus interleukin-4 (IL-4) mediate IgH isotype class switch recombination (CSR), and this process involves DNA double strand break repair (DSBR), we hypothesized that CD40 and/or IL-4 activation of MM cells could induce abnormal DNA DSBR and lead to genomic instability and clonal evolution. In this study, we show that MM cell lines that are optimally triggered via CD40 and/or IL-4 demonstrate abnormal decoupling of IL-4 signal transduction from CD40. Specifically, CD40 alone was sufficient to trigger maximal growth of tumor cells. We further demonstrate that CD40 triggering induced both DNA DSBs as well as newly acquired karyotypic abnormalities in MM cell lines. Importantly, these observations were accompanied by induction of activation induced cytidine deaminase expression, but not gross apoptosis. These data support the role of abnormal CD40 signal transduction in mediating genomic instability, suggesting a role for the CD40 pathway and intermediates in myelomagenesis and clonal evolution in vivo.
Based on unusual probe hybridization patterns, two human leukocyte antigen (HLA)-A, five HLA-B, and two HLA-C alleles (A*240208, A*3211Q; B*1822, B*3938Q, B*4606, B*4607N, B*5139; Cw*0321, Cw*0734) were identified in individuals from the Singapore Bone Marrow Donor Program and Singapore Cord Blood Bank. Eight of the nine alleles encode amino acid substitutions altering the antigen-binding region including three alleles with changes altering a cysteine at codon 164 (A*3211Q, B*3938Q, B*4607N). This substitution either eliminates a key disulfide bond or results in a stop codon, both likely affecting the expression of the HLA molecules. Only one allele (A*240208) carries a synonymous substitution.
We initiated a randomized study of amifostine (the organic thiophosphate formerly known as WR-2721) given to patients during myeloablative conditioning therapy for allogeneic bone marrow transplantation. Amifostine was given at a dose of 1000 mg/day of conditioning and was well tolerated if attention was given to serum calcium levels, blood pressure and antiemetics. Since August 1998, 60 patients (30 on each arm) have completed the study. There was no significant difference in the days to neutrophil or platelet engraftment in either arm of the study. Significantly, the duration of grade I-IV mucositis was decreased in the group that received amifostine (P=0.02). Also grade III or IV infections (P=0.008), duration of antibiotic therapy (P=0.03) and duration of fever (P=0.04) were significantly reduced with amifostine. However, there were no differences in the incidence of grade III or IV mucositis, liver toxicity or renal toxicity. There were also no differences in early mortality, relapse and long-term survival. We conclude that amifostine, while reducing the duration of mucositis and infections (possibly through some preservation of gut mucosal integrity), has a modest effect in allogeneic bone marrow transplants given the multiplicity of factors influencing organ toxicity and survival in this setting.
INTRODUCTION: The thrombotic thrombocytopenic purpura-haemolytic uraemic syndromes (TTP-HUS) are uncommon disorders that are fatal if untreated. Therapeutic plasma exchange has resulted in excellent remission and survival rates in this patient population. METHODS: We reviewed our experience of therapeutic plasmapheresis for TTP-HUS syndromes for 11 patients who presented in the last five years. Parameters captured included haemoglobin and platelet counts at presentation as well as the number of plasmapheresis sessions and adjunctive treatment given. RESULTS: We found a response rate of 82 percent to plasma exchange, of whom 55 percent attained complete remission. Responses were excellent in the five patients who presented with primary or idiopathic TTP (100 percent response) among whom 80 percent had sustained long term responses. Responses were poor and often unsustained (only one out of six survived) in patients who presented with thrombotic microangiopathies secondary to underlying disorders such as bone marrow transplantation and metastatic carcinoma. CONCLUSION: Plasmapheresis is mandatory and extremely effective for primary TTP. However, it is at most an adjunct for patients who developed it secondary to an underlying disorder until and if the primary disorder can be successfully treated.
Although haematopoietic stem cell transplantation (HSCT) is a powerful treatment modality, it is a blunt instrument against cancer and diseases of the haematopoietic and immune system. Various techniques have been developed to engineer the haematopoietic stem cell (HSC) graft to enable it to perform its task more effectively. These techniques include the removal of cells which cause graft-versus-host disease (GVHD), the eradication of cells which might cause relapse, the expansion of donor cells when there is an inadequate cell dose, and the addition of selected cells to improve graft function. In this review, we will discuss each of these means of haematopoietic graft manipulation in turn and then touch on some regulatory requirements in the field of haematopoietic graft engineering. While the science is still prepubescent, it has passed its infancy and further developments in the next decade or so should allow it to be taken to a wider scale to benefit more patients.
Allogeneic hematopoietic stem cell transplantation (HSCT) is the only known curative therapy for patients with chronic myeloid leukemia (CML), but is associated with significant morbidity and mortality. The recent introduction of imatinib mesylate (STI-571) and reduced intensity transplant regimens has made the choice of primary treatment for patients with CML increasingly difficult. We have evaluated the outcome of 53 patients who have received allogeneic HSCT from human leukocyte antigen (HLA)-identical sibling donors between October 1985 and March 2002, determined the variables affecting the outcome, and tried to define indications for this aggressive approach. Successful engraftment occurred in 49 (98%) of evaluable patients. Acute graft-versus-host disease (GVHD) of grade II to IV severity was observed in 63% of the evaluable patients whereas the incidence of chronic GVHD was 57.5%. The Kaplan-Meier estimate of survival at 10 years was 54% [95% confidence interval (CI): 38-70%] and 31% (95% CI: 6-56%) for patients with first chronic phase and more advanced diseases, respectively. Multivariate analysis showed that younger age, absence of grade III-IV GVHD, the use of busulphan and cyclophosphamide (BuCy) as preparative regimen, and transplantation performed after January 1992 were factors associated with improved survival. Patients who were 30 years of age or younger who had transplantation done within 1 year after diagnosis during their first chronic phase of disease had a particularly good prognosis, with a probability of surviving 10 years of 72% (95% CI: 52-92%). We conclude that allogeneic HSCT remains a feasible option for Asian patients with CML. The most favorable outcome is observed in younger patients with early phase of the disease.
The main obstacles to successful hematopoietic stem cell transplantation for patients with chronic myeloid leukemia (CML) in blast crisis (BC) are increased post-transplant relapse and high treatment-related mortality. We report a patient with CML in BC who was treated initially with imatinib mesylate and was then concurrently treated with a nonmyeloablative stem cell transplant. Successful engraftment of donor cells followed by complete cytogenetic remission was achieved in the absence of severe therapy-related toxicities. This case demonstrates that imatinib mesylate given through nonmyeloablative transplant is a minimally toxic therapeutic approach, which does not compromise engraftment and may result in a favorable outcome in patients with CML in BC.