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Biomedical subjects

Kim Robien

Publications and source records attributed to Kim Robien.

10 recordsLinked to original sources
PubMed2006

Methylenetetrahydrofolate reductase and thymidylate synthase genotypes and risk of acute graft-versus-host disease following hematopoietic cell transplantation for chronic myelogenous leukemia.

Methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TS) play key roles in intracellular folate metabolism. Polymorphisms in these enzymes have been shown to modify toxicity of methotrexate (MTX) after hematopoietic cell transplantation. In this study, we evaluated the risk of acute graft-versus-host disease (GVHD) associated with genetic variation in recipient and donor MTHFR and TS genotypes to assess whether genotype alters the efficacy of MTX in acute GVHD prophylaxis. Data on the transplantation course were abstracted from medical records for 304 adults who received allogeneic hematopoietic cell transplants. MTHFR (C677T and A1298C) and TS (enhancer-region 28-base pair repeat, TSER, and 1494del6) genotypes were determined using polymerase chain reaction/restriction fragment length polymorphism and TaqMan assays. Multivariable logistic regression was used to assess the associations between genotypes and risk of acute GVHD. Compared with recipients with the wild-type MTHFR 677CC genotype, those with the variant 677T allele showed a decreased risk of detectable acute GVHD (677CT: odds ratio, 0.8; 95% confidence interval, 0.4-1.6; 677TT: odds ratio, 0.4; 95% confidence interval, 0.2-0.8; P for trend = .01). The variant MTHFR 1298C allele in recipients was associated with an increased risk of acute GVHD compared with the wild-type MTHFR 1298AA genotype (1298AC: odds ratio, 2.0; 95% confidence interval, 1.1-3.9; 1298CC: odds ratio, 3.6; 95% confidence interval, 1.0-12.7; P for trend < .01). No association with risk of acute GVHD was observed for donor MTHFR genotypes or for recipient or donor TS genotypes, with the exception of an increase in acute GVHD among recipients whose donors had the TSER 3R/2R genotype (odds ratio, 3.0; 95% confidence interval, 1.3-7.2). These findings indicate that host, but not donor, MTHFR genotypes modify the risk of acute GVHD in recipients receiving MTX, in a manner consistent with our previously reported associations between MTHFR genotypes and MTX toxicity. A direct trade-off between drug toxicity and drug efficacy may play a role. Alternatively, the systemic folate environment, regulated by host tissues, might influence donor T-cell growth and activity.

Acute Disease↗
PubMed2006

American Dietetic Association: standards of practice and standards of professional performance for registered dietitians (generalist, specialty, and advanced) in oncology nutrition care.

The Standards of Practice and Standards of Professional Performance in Oncology Nutrition Care serve as a professional resource for self-evaluation and professional development for RDs specializing in oncology nutrition practice. Application of these documents in clinical practice presents the opportunity for quality improvement in oncology nutrition services provided by the RD. Just as the professional self-evaluation and continuing education process is an ongoing cycle, these standards are also a work in progress, and will be reviewed and updated on a regular basis. The Standards of Practice and Standards of Professional Performance are a quality initiative of the ADA and ON DPG that reflect a commitment to improving the quality of nutrition services provided by RDs in oncology settings.

Certification↗
PubMed2005

Folate during antifolate chemotherapy: what we know... and do not know.

The nutrient folate is essential for normal cell growth and development. Enzymes that require folate as a cofactor have been common targets for chemotherapeutic agents. Limited clinical guidance is available regarding optimal levels of dietary or supplemental folate intake during antifolate chemotherapy to meet the goals of minimizing treatment-related toxicity yet preserving treatment effectiveness. Patients with higher folate intake may experience less treatment-related toxicities; however, the concern is that folate may interfere with the effectiveness of the antifolate treatment and possibly support tumor growth. This article will review folate and antifolate metabolism and review the current body of knowledge regarding the interactions between folates and antifolates. Future research in this area should include evaluation of pretreatment folate status and dietary and supplemental folate intake before, during, and after treatment.

Antimetabolites, Antineoplastic↗
PubMed2005

Pharmacogenetics of folate-related drug targets in cancer treatment.

Folate metabolism is the target of two major drug groups: folate antagonists (for example, methotrexate) and thymidylate synthase inhibitors (for example, 5-fluorouracil). These agents are used in the treatment of cancer, as well as for other conditions, such as rheumatoid arthritis. High-dose cancer treatment protocols can induce a state of acute folate depletion which may lead to significant treatment-related toxicity. Polymorphisms in folate-metabolizing enzymes may modify the therapeutic effectiveness and toxicity of these drugs. This review briefly summarizes the drugs targeting the folate pathway and describes common polymorphisms in folate-metabolizing enzymes and transport proteins. Pharmacogenetic studies investigating folate-related drug targets in the treatment of colorectal cancers and hematologic malignancies will subsequently be discussed. Findings to date illustrate a potential for targeting therapy based on patients' genotypes, in order to improve outcomes and reduce toxicity. However, larger, well-designed studies are needed to confirm these early findings.

Animals↗
PubMed2004

Methylenetetrahydrofolate reductase genotype affects risk of relapse after hematopoietic cell transplantation for chronic myelogenous leukemia.

PURPOSE: Methylenetetrahydrofolate reductase (MTHFR) directs intracellular folate toward homocysteine metabolism and away from nucleotide synthesis. Two common MTHFR polymorphisms, C677T and A1298C, are associated with reduced enzyme activity. We evaluated the association of these polymorphisms with risk of relapse and bcr-abl mRNA transcript detection among 336 Caucasian patients who underwent allogeneic hematopoietic cell transplantation for chronic myelogenous leukemia. EXPERIMENTAL DESIGN: Data on the transplant course and folate-related exposures were abstracted from medical records. MTHFR C677T and A1298C genotypes were determined using polymerase chain reaction/restriction fragment length polymorphism and TaqMan assays. Qualitative bcr-abl mRNA testing was conducted using a two-step reverse transcription-polymerase chain reaction assay. Cox regression analysis was used to assess the association between MTHFR genotypes and time to relapse and bcr-abl mRNA detection. RESULTS: A statistically significant decreased risk of relapse was observed in patients with the variant A1298C genotype [1298AC, hazard ratio (HR)=0.48 and 95% confidence interval (CI)=0.26-0.88; 1298CC, HR=0.28 and 95% CI=0.09-0.84; P-trend <0.01). For the joint C677T/A1298C genotype, variant genotypes were associated with a decreased risk of relapse when compared with the wild-type 677CC/1298AA genotype. This risk was lowest for the 677CC/1298CC genotype (HR, 0.23; 95% CI, 0.08-0.72). MTHFR genotypes were not associated with bcr-abl transcript detection. CONCLUSIONS: These findings suggest that individuals with the 677CC/1298AA genotype are at higher risk of relapse after hematopoietic cell transplantation and that the balance of intracellular folate metabolites available for nucleotide synthesis (regulated by the relative activity of the MTHFR enzyme) may affect the progression from bcr-abl positivity to clinical relapse.

Adolescent↗
PubMed2004

Predictors of oral mucositis in patients receiving hematopoietic cell transplants for chronic myelogenous leukemia.

PURPOSE: Oral mucositis is a nearly universal and often severe complication following hematopoietic cell transplantation (HCT). The objective of this study was to evaluate factors predicting oral mucositis severity among 133 patients undergoing allogeneic HCT for chronic myelogenous leukemia. PATIENTS AND METHODS: All patients were transplanted between 1992 and 1999, were >or= 18 years of age, received either cyclophosphamide/total-body irradiation (TBI) or busulfan/cyclophosphamide conditioning regimens, and received four doses of methotrexate for graft-versus-host disease prophylaxis post-transplant. Oral mucositis was measured by a trained examiner every 2 to 3 days using the Oral Mucositis Index (OMI). Multiple linear regression analysis was used to identify predictors of mean OMI during days 6 to 12, 1 to 18, and the maximum OMI score between days 1 to 18. RESULTS: TBI containing conditioning regimens, body mass index >or= 25, and methylenetetrahydrofolate reductase 677 TT genotype were found to be predictive of higher mean OMI scores (P <.05). Pretransplant multivitamin supplement use was associated with lower mean OMI scores compared to those who did not use supplements. Smoking status, race, pretransplant treatment with interferon-alfa or hydroxyurea, and patient/donor ABO compatibility were not associated with mean OMI scores. CONCLUSION: Patients who are scheduled to receive conditioning regimens containing TBI, have a pretransplant body mass index >or= 25, or carry the methylenetetrahydrofolate reductase 677 TT genotype should be considered at greater risk of developing oral mucositis following HCT. Future studies should investigate whether multivitamin supplementation before HCT could reduce mucositis severity.

Adolescent↗
PubMed2003

5,10-Methylenetetrahydrofolate reductase polymorphisms and leukemia risk: a HuGE minireview.

Leukemias commonly arise as a result of DNA translocations, inversions, or deletions in genes regulating blood cell development or homeostasis. Folate deficiency has been associated with uracil misincorporation into DNA and DNA double strand breaks during uracil excision repair, thus increasing the risk of chromosomal aberrations. Methylenetetrahydrofolate reductase (MTHFR) directs 5,10-methylenetetrahydrofolate toward methionine synthesis at the expense of DNA synthesis. Two MTHFR polymorphisms, C677T and A1298C, have been associated with reduced enzyme activity and C677T with altered distribution of intracellular folate metabolites. Rapidly replicating cell types, such as hematopoietic cells, may be especially sensitive to changes in the availability of intracellular folate. Three case-control studies have evaluated the association between MTHFR polymorphisms and the risk of acute leukemia, and they suggest that both adults and children with the variant forms of MTHFR have a decreased risk of lymphoid leukemias. However, no modification in risk has been observed for myeloid leukemias, suggesting that differences in folate requirements or susceptibility to chromosomal damage may exist between myeloid and lymphoid cells. Further investigation into the association between MTHFR polymorphisms and the risk of leukemia is warranted. It should include larger sample sizes and other polymorphisms in folate metabolism and address interactions with folate status.

Adolescent↗
PubMed2002

Pharmacogenetics and folate metabolism -- a promising direction.

Folate metabolism is the target of two major drug groups: folate antagonists (e.g., methotrexate) and thymidylate synthase inhibitors (for example, 5-fluorouracil). These agents are widely used in cancer chemotherapy, as treatment for rheumatoid arthritis, and for other conditions. The administration of these drugs in cancer chemotherapy can induce a state of acute folate depletion with sometimes life-threatening toxic sequelae. Recent studies suggest that polymorphisms in folate-metabolizing enzymes may modify the therapeutic effectiveness and toxicity of drugs targeting folate metabolism. This review briefly summarizes major drugs targeting the folate pathway and describes common polymorphisms in folate-metabolizing enzymes and transport proteins. Pharmacogenetic studies investigating the relevance of these polymorphisms with respect to patients' response to antifolate chemotherapeutic agents are discussed. Investigating genetic variability in folate metabolism in the framework of pharmacogenetics is a promising field. Findings to date illustrate the potential for targeting therapy based on patients' genotypes with improved outcomes and reduced toxicity.

Animals↗