Biomedical subjects

Clayton A Smith

Publications and source records attributed to Clayton A Smith.

13 recordsLinked to original sources

PubMed2006

Philadelphia-negative clonal hematopoiesis following imatinib therapy in patients with chronic myeloid leukemia: a report of nine cases and analysis of predictive factors.

There are increasing reports of Philadelphia-negative (Ph-negative) clonal hematopoiesis developing among patients with chronic myeloid leukemia (CML) treated with imatinib mesylate (IM). To establish the incidence and significance of these chromosomal abnormalities, we analyzed data on 141 consecutive patients with CML treated with IM at the British Columbia Cancer Agency and Vancouver General Hospital from 1999 to 2004. The cumulative incidence of developing a Ph-negative clone three years from the start of IM was 8.7% at a median of 13.3 months. The Ph-negative clonal abnormalities included monosomy 7 and/or trisomy 8 (seven patients), monosomy for chromosomes X and 22 (one patient), and a (12;16) translocation (one patient). Two of the patients presented with the same chromosomal abnormality in both Ph-negative and Ph-positive cells. None of the Ph-negative clonal abnormalities was associated with myelodysplasia. In a multivariate analysis, an interval from diagnosis to initiation of IM of 1 year or less was associated with an increased risk of developing a Ph-negative clone (relative risk = 20.2; P = 0.025). There was no difference, however, in event-free survival between patients who did and did not develop Ph-negative clones. Therefore, while the development of Ph-negative clonal hematopoiesis in patients with CML treated with IM is uncommon, it appears to be more frequent than that previously seen with IFN, but it does not seem to confer a worse prognosis.

Adolescent↗

PubMed2006

Early stem cell transplantation for refractory acute leukemia after salvage therapy with high-dose etoposide and cyclophosphamide.

Primary refractory acute leukemia (AL) has a poor prognosis, although some patients can be salvaged with allogeneic stem cell transplantation (SCT). Induction of complete remission (CR) with conventional chemotherapy before SCT may improve outcome in this patient population. Between March 1991 and October 2003, 59 adults with primary refractory AL were treated with continuous-infusion etoposide (VP) 2.4 to 3.0 g/m(2) followed by cyclophosphamide (Cy) 6.0-7.2 g/m(2) intravenously over 3 to 4 days with the intention of proceeding to SCT in CR1. Forty-two patients had acute myelogenous leukemia (AML), 13 patients had acute lymphoblastic leukemia (ALL), and 4 patients had acute biphenotypic leukemia. The most frequent nonhematologic toxicities were oral mucosal, gastrointestinal, and hepatic toxicities (44%, 20%, and 15% of patients, respectively). Thirty-two (57%) of 56 evaluable patients entered CR1 with a median time to platelet and neutrophil recovery of 22 and 26 days, respectively. CR1 rates were similar in AML (54%) and ALL/acute biphenotypic leukemia (67%; P = .52), and analysis of baseline characteristics did not reveal any predictors of response to VP/Cy. Twenty-nine of 32 CR1 patients subsequently underwent SCT (24 allogeneic and 5 autologous). Estimated 5-year event-free survival (EFS) and overall survival for the entire cohort are 23% and 26%, respectively. In the allogeneic SCT group, 5-year EFS was 52% for AML patients and 14% for ALL patients (P = .04), and only male sex was predictive of a favorable outcome (P = .03). VP/Cy is able to induce CR1 in most patients with primary refractory AL with an acceptable toxicity profile. Subsequent allogeneic SCT can lead to long-term EFS in a significant proportion of patients.

Adolescent↗

PubMed2006

Data standards for flow cytometry.

Flow cytometry (FCM) is an analytical tool widely used for cancer and HIV/AIDS research, and treatment, stem cell manipulation and detecting microorganisms in environmental samples. Current data standards do not capture the full scope of FCM experiments and there is a demand for software tools that can assist in the exploration and analysis of large FCM datasets. We are implementing a standardized approach to capturing, analyzing, and disseminating FCM data that will facilitate both more complex analyses and analysis of datasets that could not previously be efficiently studied. Initial work has focused on developing a community-based guideline for recording and reporting the details of FCM experiments. Open source software tools that implement this standard are being created, with an emphasis on facilitating reproducible and extensible data analyses. As well, tools for electronic collaboration will assist the integrated access and comprehension of experiments to empower users to collaborate on FCM analyses. This coordinated, joint development of bioinformatics standards and software tools for FCM data analysis has the potential to greatly facilitate both basic and clinical research--impacting a notably diverse range of medical and environmental research areas.

Cell Separation↗

PubMed2006

Maintenance of proliferative capacity and retroviral transduction efficiency of human fetal CD38(-)/CD34(++) stem cells.

Methods for the efficient transduction and expansion of fetal hematopoietic stem cells could lead to novel in utero therapies for blood cell disorders and enzymatic deficiencies. Here we describe a new assay to measure rapidly the effects of cytokines on the differentiation or expansion of primitive progenitors and stem cells found among CD38(-)CD34(++) lineage() cells isolated from human midgestation liver. Importantly, conditions that otherwise supported the expansion of clonogenic progenitors reduced their proliferative capacity. A combination of megakaryocyte growth and development factor and granulocyte-macrophage colony-stimulating factor maintained proliferative potential while also yielding an intermediate level of progenitor expansion. Retroviral transduction was achieved using Moloney murine leukemia virus-based vectors. Freshly isolated candidate stem cells could be transduced at almost 17% efficiency by a 1-h exposure to virus with centrifugation to aid transduction. This was increased to a mean 35.5% transduction efficiency after 1 day of culture. Additionally, the transduction efficiency of candidate stem cells isolated from fetal placental blood was 33.0%. These findings encourage further investigation into the feasibility of ex utero gene therapy whereby fetal cells are isolated from the circulation, transduced, and expanded ex utero before being returned to the fetus.

ADP-ribosyl Cyclase 1↗

PubMed2006

Haematopoietic stem cell transplantation as primary therapy of sporadic adult Burkitt lymphoma.

High dose chemoradiotherapy and haematopoietic stem cell transplantation (SCT) is used as primary therapy for patients diagnosed with Burkitt lymphoma (BL). Forty-three adults presented with sporadic BL in British Columbia between 1987 and 2003. Twenty patients had bone marrow involvement. Sixteen patients did not proceed to SCT because of chemorefractory disease (n = 9) or other reasons (n = 7). Twenty-seven patients proceeded to SCT and had a 3-year event-free survival of 51%. In conclusion, approximately 50% of patients with chemosensitive BL who undergo SCT can be cured; however, a significant number of patients will not proceed to SCT because of early resistance or recurrence.

Adolescent↗

PubMed2005

High-dose therapy and autologous hematopoietic stem-cell transplantation does not increase the risk of second neoplasms for patients with Hodgkin's lymphoma: a comparison of conventional therapy alone versus conventional therapy followed by autologous hematopoietic stem-cell transplantation.

PURPOSE: To determine the incidence of second malignancies among patients with Hodgkin's lymphoma (HL) treated with autologous hematopoietic stem cell transplantation (AHSCT) compared with patients receiving conventional therapy alone and to identify potential risk factors for their occurrence. PATIENTS AND METHODS: We analyzed data on 1,732 consecutive patients with HL treated at the British Columbia Cancer Agency from 1976 to 2001, including 202 patients undergoing AHSCT. The median follow-up duration was 9.8 years for the whole cohort, 9.7 years for those patients treated with conventional therapy, and 7.8 years from AHSCT. RESULTS: The cumulative incidence of developing any second malignancy 15 years after therapy for HL was 9% (risk ratio = 3.5; P < .001); however, the incidence did not differ between those patients receiving conventional therapy alone compared with those undergoing AHSCT (10% and 8%, respectively; P = .48). In multivariate analysis, the only factor significantly associated with an increased risk of developing any second neoplasm or solid tumor was age > or = 35 years (P < .0001). An increased risk of therapy-induced acute myeloid leukemia and therapy-induced myelodysplastic syndrome was seen for patients aged > or = 35 years (P = .03) and stage III/IV (P = .04). CONCLUSION: Patients with HL are at increased risk of developing a second neoplasm. However, those patients undergoing AHSCT do not seem to be at greater risk compared with those patients receiving conventional therapy alone, at least during the first decade after therapy.

Adolescent↗

PubMed2005

High-dose chemotherapy and autologous stem cell transplantation for primary refractory or relapsed Hodgkin lymphoma: long-term outcome in the first 100 patients treated in Vancouver.

Beginning in 1985, patients in British Columbia with Hodgkin lymphoma (HL) that was not controlled by conventional chemotherapy routinely underwent high-dose chemotherapy and autologous stem cell transplantation (HD-ASCT). Long-term complications of HD-ASCT have become apparent as more patients survive without recurrence of HL. Data were obtained retrospectively on the first 100 patients that underwent HD-ASCT for HL in Vancouver, focusing on relapse, treatment-related complications, and the occurrence of late events. Fifty-three patients remain alive (median follow-up, 11.4 years [range, 10.0-17.4 years]) with an overall survival (OAS) of 54% at 15 years. OAS was significantly better in patients in first relapse (67%) than in patients with primary refractory-induction failure (39%) and advanced disease (29%) (P = .002). The major cause of death was progression of HL (32% at 15 years). Treatment-related mortality, including death from second malignancy, was 17% at 15 years. Cumulative risk of a second malignancy was 9% at 15 years. Karnofsky performance status was at least 90% in 47 patients although hypogonadism (20 patients), hypothyroidism (12 patients), unusual infections (10 patients), anxiety or depression (7 patients), and cardiac disease (5 patients) were not uncommon in survivors. HD-ASCT can lead to durable remissions in relapsed or refractory HL with acceptable but definite late toxicity. The occurrence of late events necessitates lifelong medical surveillance.

Adolescent↗

PubMed2005

Distinct hematopoietic progenitor compartments are delineated by the expression of aldehyde dehydrogenase and CD34.

A broad range of hematopoietic stem cells and progenitors reside within a fraction of umbilical cord blood (UCB) that exhibits low light scatter properties (SSC(lo)) and high expression of aldehyde dehydrogenase (ALDH(br)). Many SSC(lo) ALDH(br) cells coexpress CD34; however, other cells express either ALDH or CD34. To investigate the developmental potential of these cell subsets, purified ALDH(br) CD34+, ALDH(neg) CD34+, and ALDH(br) CD34(neg) UCB cells were characterized within a variety of in vivo and in vitro assays. Primitive progenitors capable of multilineage development were monitored in long- and short-term repopulation assays performed on nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice, and in primary and secondary long-term culture assays. These progenitors were highly enriched within the ALDH(br) CD34+ fraction. This cell fraction also enriched short-term myeloid progenitors that were detected in vitro. By comparison, ALDH(neg) CD34+ cells contained few primitive progenitors and had diminished short-term myeloid potential but exhibited enhanced short-term natural killer (NK) cell development in vitro. The ALDH(br) CD34(neg) cells were not efficiently supported by any of the assays used. These studies suggested that in particular the expression of ALDH delineated distinct CD34+ stem cell and progenitor compartments. The differential expression of ALDH may provide a means to explore normal and malignant processes associated with myeloid and lymphoid development.

Aldehyde Dehydrogenase↗

PubMed2005

Hypercalcemia due to all trans retinoic acid in the treatment of acute promyelocytic leukemia potentiated by voriconazole.

All-trans-retinoic acid (ATRA) is a new and effective treatment of acute promyelocytic leukemia. It has many side-effects, including the retinoic acid syndrome and Sweet's syndrome. There have been only nine cases of hypercalcemia associated with ATRA described in the literature. We discuss a case of hypercalcemia, which we believe was due to inhibition of cytochrome P450 function by voriconizole when used concomitantly with ATRA.

Adult↗

PubMed2005

Allogeneic haematopoietic stem-cell transplantation for relapsed and refractory aggressive histology non-Hodgkin lymphoma.

Forty-four patients with relapsed or refractory aggressive histology non-Hodgkin lymphoma (NHL) (diffuse large B cell, n = 23; peripheral T cell, n = 5; transformed B cell, n = 16) proceeded to allogeneic stem cell transplant (allo-SCT) between 1987 and 2003. Median age at transplant was 40 years (range 19-56 years). At the time of transplant, 35 were chemosensitive and nine were chemorefractory. Thirty-three patients had matched sibling donors and 11 had unrelated donors. Forty-two patients (95%) received radiation-based conditioning regimens. Event-free survival (EFS) and overall survival (OS) at 5 years was 43% [95% confidence interval (CI): 27-58%] and 48% (95% CI: 32-63%) respectively. Treatment-related mortality was 25% at 1 year. Grade III-IV acute graft-versus-host disease (GVHD) was the only significant variable affecting OS and EFS, and had a negative impact. Chronic GVHD did not influence survival. Lymphoma relapse <12 months after initial therapy predicted for increased risk of relapse post-transplant (P = 0.02). Patients with chemorefractory lymphoma were not at increased risk of relapse (P = 0.20) with four of nine patients remaining alive without disease 12-103 months post-transplant. In conclusion, allo-SCT for relapsed or refractory aggressive histology NHL results in long-term EFS and OS of 40-50%. Patients with chemorefractory disease can have a durable remission post-transplant.

Adolescent↗

PubMed2004

Enhanced long-term survival, but no increase in replicative capacity, following retroviral transduction of human cord blood CD34+ cells with human telomerase reverse transcriptase.

Overexpression of telomerase reverse transcriptase (hTERT) can immortalize some primary human mesenchymal cells. We investigated whether retrovirally-mediated expression of hTERT in CD34+ umbilical cord blood (UCB) cells can extend the replicative lifespan of human hematopoietic progenitor cells. Overexpression of hTERT did not immortalize these cells but did lead to enhanced survival of mature hematopoietic cells.

Antigens, CD34↗

PubMed2003

Bladder cancer facts: accuracy of information on the Internet.

PURPOSE: Patients continually seek information regarding the etiology, diagnosis, management and treatment of bladder cancer. The Internet has a growing number of health web sites and it is a tremendous resource for medical information. We examined the accuracy and completeness of bladder cancer sites on the World Wide Web. MATERIALS AND METHODS: Internet searching was performed by retrieving the first 30 universal resource locators from 8 popular search engines using the search term bladder cancer. A total of 38 independent web sites were evaluated. Other sites were inaccessible, duplicates or only contained linked pages. Two reviewers evaluated the accuracy and completeness of information using a predetermined 41-point checklist rating instrument that evaluated essential information related to bladder cancer. The kappa statistic was used to evaluate interrater variability. RESULTS: The mean kappa statistic for evaluable variables was 0.70. Most nonevaluable variables had excellent agreement, indicating good overall interrater reliability. No rating factor was present on 100% of sites. Eight factors were present and accurate on 80% to 90% of web pages and related to signs/symptoms, risk factors, diagnostic tests and treatment of early stage disease. Six factors were inaccurate on 32% of sites, including incidence (7), staging (3), recurrence (1), and treatment of early invasive (1) and metastatic (1) disease. CONCLUSIONS: Bladder cancer information retrieved from the majority of medical web sites was incomplete. However, general information relating to presentation, diagnosis, staging and treatment of low stage disease was present and accurate on most sites. Although inaccurate information was detected on 32% of the sites, it tended to be related to outdated information. It is reasonable to refer patients to select comprehensive web sites to obtain pertinent information about bladder cancer.

Humans↗

PubMedDate not supplied

Hippocampal overexpression of mutant creb blocks long-term, but not short-term memory for a socially transmitted food preference.

Phosphorylation of the transcription factor CREB on Ser133 is implicated in the establishment of long-term memory for hippocampus-dependent tasks, including spatial learning and contextual fear conditioning. We reported previously that training on a hippocampus-dependent social transmission of food preference (STFP) task increases CREB phosphorylation in the hippocampus of trained rats in comparisons with controls. In the current study, we tested the hypothesis that CREB function is necessary for long-term memory for STFP using herpes simplex viral (HSV) vector-mediated gene transfer. Rats received intrahippocampal infusions of HSV-mCREB (a mutant form of CREB, in which Ser133 has been replaced with Ala), HSV-LacZ, or saline, and were trained 3 d later. Rats were tested for food preference (demonstrated vs. novel foods) immediately (short-term test) and 11 d (long-term test) after training. Rats in all treatment groups showed a significant preference for the demonstrated food at the short-term memory test. At the long-term memory test, however, the percentage of demonstrated food eaten by mCREB-treated rats was significantly less than that eaten by the LacZ- or saline-treated rats. Quantitative Western blotting confirmed that mCREB-infused rats had significantly more hippocampal CREB protein than controls during training. The present results show that hippocampal CREB function is necessary for long-term, but not short-term memory for STFP.

Amino Acid Substitution↗