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Walsh DJ, Bernard DJ, Fiddler JL, Pangilinan F, Esposito M, Harold D, Field MS, Parle-McDermott A, Brody LC. Vitamin B12 status and folic acid supplementation influence mitochondrial heteroplasmy levels in mice. PNAS NEXUS 2024; 3:pgae116. [PMID: 38560530 PMCID: PMC10978065 DOI: 10.1093/pnasnexus/pgae116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 02/29/2024] [Indexed: 04/04/2024]
Abstract
One-carbon metabolism is a complex network of metabolic reactions that are essential for cellular function including DNA synthesis. Vitamin B12 and folate are micronutrients that are utilized in this pathway and their deficiency can result in the perturbation of one-carbon metabolism and subsequent perturbations in DNA replication and repair. This effect has been well characterized in nuclear DNA but to date, mitochondrial DNA (mtDNA) has not been investigated extensively. Mitochondrial variants have been associated with several inherited and age-related disease states; therefore, the study of factors that impact heteroplasmy are important for advancing our understanding of the mitochondrial genome's impact on human health. Heteroplasmy studies require robust and efficient mitochondrial DNA enrichment to carry out in-depth mtDNA sequencing. Many of the current methods for mtDNA enrichment can introduce biases and false-positive results. Here, we use a method that overcomes these limitations and have applied it to assess mitochondrial heteroplasmy in mouse models of altered one-carbon metabolism. Vitamin B12 deficiency was found to cause increased levels of mitochondrial DNA heteroplasmy across all tissues that were investigated. Folic acid supplementation also contributed to elevated mitochondrial DNA heteroplasmy across all mouse tissues investigated. Heteroplasmy analysis of human data from the Framingham Heart Study suggested a potential sex-specific effect of folate and vitamin B12 status on mitochondrial heteroplasmy. This is a novel relationship that may have broader consequences for our understanding of one-carbon metabolism, mitochondrial-related disease and the influence of nutrients on DNA mutation rates.
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Affiliation(s)
- Darren J Walsh
- Gene and Environment Interaction Section, National Human Genome Research Institute, NIH, Bethesda, MD 20892, USA
- School of Biotechnology, Dublin City University, Dublin 9, Ireland
| | - David J Bernard
- Gene and Environment Interaction Section, National Human Genome Research Institute, NIH, Bethesda, MD 20892, USA
| | - Joanna L Fiddler
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14850, USA
- Department of Food, Nutrition, and Packaging Sciences, Clemson University, Clemson, SC 29634, USA
| | - Faith Pangilinan
- Gene and Environment Interaction Section, National Human Genome Research Institute, NIH, Bethesda, MD 20892, USA
| | - Madison Esposito
- Gene and Environment Interaction Section, National Human Genome Research Institute, NIH, Bethesda, MD 20892, USA
| | - Denise Harold
- School of Biotechnology, Dublin City University, Dublin 9, Ireland
| | - Martha S Field
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14850, USA
| | | | - Lawrence C Brody
- Gene and Environment Interaction Section, National Human Genome Research Institute, NIH, Bethesda, MD 20892, USA
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Ohadian Moghadam S, Momeni SA. Human microbiome and prostate cancer development: current insights into the prevention and treatment. Front Med 2020; 15:11-32. [PMID: 32607819 DOI: 10.1007/s11684-019-0731-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 10/31/2019] [Indexed: 12/14/2022]
Abstract
The huge communities of microorganisms that symbiotically colonize humans are recognized as significant players in health and disease. The human microbiome may influence prostate cancer development. To date, several studies have focused on the effect of prostate infections as well as the composition of the human microbiome in relation to prostate cancer risk. Current studies suggest that the microbiota of men with prostate cancer significantly differs from that of healthy men, demonstrating that certain bacteria could be associated with cancer development as well as altered responses to treatment. In healthy individuals, the microbiome plays a crucial role in the maintenance of homeostasis of body metabolism. Dysbiosis may contribute to the emergence of health problems, including malignancy through affecting systemic immune responses and creating systemic inflammation, and changing serum hormone levels. In this review, we discuss recent data about how the microbes colonizing different parts of the human body including urinary tract, gastrointestinal tract, oral cavity, and skin might affect the risk of developing prostate cancer. Furthermore, we discuss strategies to target the microbiome for risk assessment, prevention, and treatment of prostate cancer.
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Affiliation(s)
| | - Seyed Ali Momeni
- Uro-Oncology Research Center, Tehran University of Medical Sciences, Tehran, Iran
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3
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Lahner E, Capasso M, Carabotti M, Annibale B. Incidence of cancer (other than gastric cancer) in pernicious anaemia: A systematic review with meta-analysis. Dig Liver Dis 2018; 50:780-786. [PMID: 29887343 DOI: 10.1016/j.dld.2018.05.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 05/16/2018] [Accepted: 05/17/2018] [Indexed: 02/08/2023]
Abstract
BACKGROUND Pernicious anaemia (PA) is associated with increased gastric cancer risk, but the evidence is conflicting regarding the associated risk of other cancers. AIM To systematically determine the incidence rates of gastro-intestinal cancers other than gastric cancers (GI-other-than-GC) and non-gastrointestinal cancers (non-GIC) in PA adults, globally and per tumour site, and the risk associated with PA for GI-other than GC and non-GIC. METHODS Studies of PA patients reporting the incidence of GI-other-than-GCs and non-GICs were identified with MEDLINE (PubMed)-EMBASE (from first date available to April 2017). A meta-analysis of annual cancer incidence rates was performed. The outcome was the cumulative incidence of GI-other-than-GCs and non-GICs (ratio between the numbers of new cancer cases identified during the follow-up period and the number of PA patients) and the incidence rate expressed as the rate of events-per-time-unit (person-years). RESULTS Of 82,257 PA patients, the pooled incidence rates/100 person-years for non-GCs and non-GICs of 0.27 (95% CI:0.16-0.42) and 0.23 (95% CI:0.22-0.25) were calculated by meta-analysis. Compared to the GLOBOCAN data for the general population from the countries of the included studies, the meta-analysis showed an overall relative risk (RR) of cancer in PA of 0.68 (95% CI:0.48-0.95). PA patients had a lower RR of colorectal, breast, liver, oesophageal, lung, thyroid, ovary, non-melanoma skin and kidney cancers but had a higher RR of biliary tract cancer (1.81:1.21-2.70), multiple myeloma (2.83:1.76-4.55), Hodgkin's lymphoma (3.0:1.35-6.68), non-Hodgkin's lymphoma (2.08: 1.58-2.75), and leukaemia (1.56:1.16-2.12). CONCLUSION An overall lower RR of cancers-other-than-gastric-cancer in PA patients but an increased RR of biliary tract cancers and haematological malignancies was observed.
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Affiliation(s)
- Edith Lahner
- Medical-Surgical Department of Clinical Sciences and Translational Medicine, Sapienza University of Rome, Italy.
| | - Marina Capasso
- Medical-Surgical Department of Clinical Sciences and Translational Medicine, Sapienza University of Rome, Italy
| | - Marilia Carabotti
- Medical-Surgical Department of Clinical Sciences and Translational Medicine, Sapienza University of Rome, Italy
| | - Bruno Annibale
- Medical-Surgical Department of Clinical Sciences and Translational Medicine, Sapienza University of Rome, Italy
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4
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Wei EK, Wolin KY, Colditz GA. Time course of risk factors in cancer etiology and progression. J Clin Oncol 2010; 28:4052-7. [PMID: 20644083 DOI: 10.1200/jco.2009.26.9324] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Patients with cancer increasingly ask what they can do to change their lifestyles and improve outcomes. Risk factors for onset of cancer may differ substantially from those that modify survival with implications for counseling. This review focuses on recent data derived from population-based studies of causes of cancer and of patients with cancer to contrast risk factors for etiology with those that impact survival. For different cancer sites, the level of information to inform the timing of lifestyle exposures and risk of disease onset or progression after diagnosis is often limited. For breast cancer, timing of some exposures, such as radiation, is particularly important. For other exposures, such as physical activity, higher levels may prevent onset and also improve survival. For colon cancer, study of precursor polyps has provided additional insight to timing. Extensive data indicate that physical activity reduces risk of colon cancer, and more limited data suggest that exposure after diagnosis improves survival. Dietary factors including folate and calcium may also reduce risk of onset. More limited data on prostate cancer point to obesity increasing risk of aggressive or advanced disease. Timing of change in lifestyle for change in risk of onset and for survival is important but understudied among patients with cancer. Counseling patients with cancer to increase physical activity and avoid weight gain may improve outcomes. Advice to family members on lifestyle may become increasingly important for breast and other cancers where family history is a strong risk factor.
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Affiliation(s)
- Esther K Wei
- Washington University, 660 S Euclid Ave, Campus Box 8109, St Louis, MO 63110, USA
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Tisman G, Kutik S, Rainville C. Coexistence of pernicious anemia and prostate cancer - 'an experiment of nature' involving vitamin B(12 )modulation of prostate cancer growth and metabolism: a case report. J Med Case Rep 2009; 3:9295. [PMID: 20062784 PMCID: PMC2803818 DOI: 10.1186/1752-1947-3-9295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Accepted: 11/24/2009] [Indexed: 11/13/2022] Open
Abstract
Introduction This report presents the clinical and laboratory course of a patient with prostate cancer and severe vitamin B12 deficiency undergoing watchful waiting for prostate cancer. The possible interaction between therapy for B12 deficiency and the natural course of prostate cancer is presented. Case presentation We present the case of a 75-year-old Chinese man with prostate cancer and pernicious anemia. His serum vitamin B12 level was 32 pg/ml (300-900 pg/ml) and holotranscobalamin was 0 pg/ml (>70 pg/ml). There was an unexpected rapid progression of Gleason's score during 10 months of watchful waiting. After the diagnosis of pernicious anemia was made, therapeutic injections of vitamin B12 were started. We observed a significant acceleration in prostate-specific antigen and prostatic acid phosphatase and a shortening of prostate-specific antigen doubling time after initiation of B12 therapy. Conclusion We propose that the relatively short period of watchful waiting before histological progression of Gleason's score (GS [3+2] = 5 to GS [3+4] = 7 over 10 months) may have been a result of depleted holotranscobalamin 'active' B12. Replacement of B12 was associated with an initial rapid increase in serum prostate-specific antigen and prostatic acid phosphatase followed by stabilization. The patient represents an 'experiment of nature' involving vitamin B12 metabolism and raises the question as to whether rapid histological progression of Gleason's score was related to absence of serum holotranscobalamin while prostate-specific antigen and prostatic acid phosphatase, markers of cell growth, were accelerated by vitamin B12 replacement. To our knowledge, this is the first report of a possible cellular kinetic interaction between an epithelial malignancy and vitamin B12 metabolism.
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Affiliation(s)
- Glenn Tisman
- Department of Nutrition and Neoplasia, Whittier Cancer Research Building, Bailey Street, Whittier, CA 90601, USA
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Lin J, Lee IM, Cook NR, Selhub J, Manson JE, Buring JE, Zhang SM. Plasma folate, vitamin B-6, vitamin B-12, and risk of breast cancer in women. Am J Clin Nutr 2008; 87:734-43. [PMID: 18326613 DOI: 10.1093/ajcn/87.3.734] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND B vitamins such as folate, vitamin B-6, and vitamin B-12 are coenzymes that are important for DNA integrity and stability. Deficiency in these B vitamins may promote tumor carcinogenesis. OBJECTIVE We prospectively evaluated plasma concentrations of folate, pyridoxal 5-phosphate (PLP; the principal active form of vitamin B-6), and vitamin B-12 in relation to breast cancer risk. DESIGN We included 848 incident cases of invasive breast cancer identified as of 31 March 2004, and 848 individually matched control subjects from 28 345 women in the Women's Health Study aged > or =45 y who provided blood samples and had no history of cancer and cardiovascular disease at baseline in 1993. Logistic regression controlling for matching factors and other risk factors for breast cancer was used to estimate relative risks (RRs) and 95% CIs. All statistical tests were 2 sided. RESULTS Plasma concentrations of folate, PLP, and vitamin B-12 were not associated with overall risk of breast cancer. Women in the highest quintile group relative to those in the lowest quintile had multivariate RRs of 1.42 (95% CI: 1.00, 2.02) for plasma folate (P for trend = 0.21), 0.91 (95% CI: 0.63, 1.30) for plasma PLP (P for trend = 0.48), and 1.29 (95% CI: 0.92, 1.82) for plasma vitamin B-12 (P for trend = 0.18). However, higher plasma folate concentrations were moderately associated with an increased risk of developing premenopausal breast cancer (P for trend = 0.04) and for developing estrogen receptor (ER)-positive or progesterone receptor (PR)-positive breast tumors (P for trend < or = 0.06). Conversely, an inverse association was seen between plasma PLP and postmenopausal breast cancer (P for trend = 0.04). CONCLUSIONS Data from this study suggest that B vitamins, including folate, vitamin B-6, and vitamin B-12, may confer little or no reduction in overall risk of developing breast cancer. The observed positive associations of folate status with risk of developing premenopausal breast cancer and ER-positive or PR-positive tumors are unexpected. Additional research is needed to elucidate the role of folate in breast cancer development.
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Affiliation(s)
- Jennifer Lin
- Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02215, USA
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7
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Branda RF, O'Neill JP, Brooks EM, Powden C, Naud SJ, Nicklas JA. The effect of dietary folic acid deficiency on the cytotoxic and mutagenic responses to methyl methanesulfonate in wild-type and in 3-methyladenine DNA glycosylase-deficient Aag null mice. Mutat Res 2007; 615:12-7. [PMID: 17207504 DOI: 10.1016/j.mrfmmm.2006.09.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 08/22/2006] [Accepted: 09/12/2006] [Indexed: 11/26/2022]
Abstract
Folic acid deficiency (FA-) augments DNA damage caused by alkylating agents. The role of DNA repair in modulating this damage was investigated in mice. Weanling wild-type or 3-methyladenine glycosylase (Aag) null mice were maintained on a FA- diet or the same diet supplemented with folic acid (FA+) for 4 weeks. They were then treated with methyl methanesulfonate (MMS), 100mg/kg i.p. Six weeks later, spleen cells were collected for assays of non-selected and 6-thioguanine (TG) selected cloning efficiency to measure the mutant frequency at the Hprt locus. In wild-type mice, there was no significant effect of either MMS treatment or folate dietary content on splenocyte non-selected cloning efficiency. In contrast, non-selected cloning efficiency was significantly higher in MMS-treated Aag null mice than in saline treated controls (diet-gene interaction variable, p=0.04). The non-selected cloning efficiency was significantly higher in the FA+ diet than in the FA- diet group after MMS treatment of Aag null mice. Mutant frequency after MMS treatment was significantly higher in FA- wild-type and Aag null mice and in FA+ Aag null mice, but not in FA+ wild-type mice. For the Aag null mice, mutant frequency was higher in the FA+ mice than in the FA- mice after either saline or MMS treatment. These studies indicate that in wild-type mice treated with MMS, dietary folate content (FA+ or FA-) had no effect on cytotoxicity, but FA- diet increased DNA mutation frequency compared to FA+ diet. In Aag null mice, FA- diet increased the cytotoxic effects of alkylating agents but decreased the risk of DNA mutation.
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Affiliation(s)
- Richard F Branda
- Department of Medicine, University of Vermont, Burlington, VT 05405, United States.
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8
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Influence of micronutrients and related genes on colorectal cancer risk. CURRENT COLORECTAL CANCER REPORTS 2006. [DOI: 10.1007/s11888-006-0025-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Basten GP, Duthie SJ, Pirie L, Vaughan N, Hill MH, Powers HJ. Sensitivity of markers of DNA stability and DNA repair activity to folate supplementation in healthy volunteers. Br J Cancer 2006; 94:1942-7. [PMID: 16736000 PMCID: PMC2361358 DOI: 10.1038/sj.bjc.6603197] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We have previously reported that supplementation with folic acid (1.2 mg day−1 for 12 week) elicited a significant improvement in the folate status of 61 healthy volunteers. We have examined effects of this supplement on markers of genomic stability. Little is known about the effect of folate supplementation on DNA stability in a cohort, which is not folate deficient. Preintervention, there was a significant inverse association between uracil misincorporation in lymphocyte DNA and red cell folate (P<0.05). In contrast, there were no associations between folate status and DNA strand breakage, global DNA methylation or DNA base excision repair (measured as the capacity of the lymphocyte extract to repair 8-oxoGua ex vivo). Folate supplementation elicited a significant reduction in uracil misincorporation (P<0.05), while DNA strand breakage and global DNA methylation remained unchanged. Increasing folate status significantly decreased the base excision repair capacity in those volunteers with the lowest preintervention folate status (P<0.05). Uracil misincorporation was more sensitive to changes in folate status than other measures of DNA stability and therefore could be considered a specific and functional marker of folate status, which may also be relevant to cancer risk in healthy people.
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Affiliation(s)
- G P Basten
- Human Nutrition Unit, Division of Clinical Sciences (North), The University of Sheffield, Northern General Hospital, Sheffield S5 7AU, UK
| | - S J Duthie
- Rowett Research Institute, Aberdeen AB21 9SB, UK
| | - L Pirie
- Rowett Research Institute, Aberdeen AB21 9SB, UK
| | - N Vaughan
- Rowett Research Institute, Aberdeen AB21 9SB, UK
| | - M H Hill
- Human Nutrition Unit, Division of Clinical Sciences (North), The University of Sheffield, Northern General Hospital, Sheffield S5 7AU, UK
| | - H J Powers
- Human Nutrition Unit, Division of Clinical Sciences (North), The University of Sheffield, Northern General Hospital, Sheffield S5 7AU, UK
- E-mail:
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Powers HJ. Interaction among folate, riboflavin, genotype, and cancer, with reference to colorectal and cervical cancer. J Nutr 2005; 135:2960S-2966S. [PMID: 16317155 DOI: 10.1093/jn/135.12.2960s] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Epidemiological studies have linked low folate intake with an increased risk of epithelial cancers, including colorectal cancer and cervical cancer. Riboflavin has received much less attention, but there is increasing interest in the well-established role that flavins play in folate metabolism and the possible synergy of a protective effect between these 2 vitamins. Folate plays a key role in DNA synthesis, repair, and methylation, and this forms the basis of mechanistic explanations for a putative role for folate in cancer prevention. The role of folate in these processes may be modulated by genotype for the common C677T thermolabile variant of methylene tetrahydrofolate reductase (MTHFR), homozygosity for which is associated with lower enzyme activity, lower plasma and red blood cell folate, and elevated plasma homocysteine. Riboflavin, as FAD, is a cofactor for MTHFR and there is evidently some interaction among riboflavin status, folate status, and genotype in determining plasma homocysteine, a functional marker of folate status. The MTHFR C677T polymorphism appears to interact with folate and riboflavin in modulating cancer risk in a manner that varies according to cancer site. Most evidence points to a protective effect of this polymorphism for risk of colorectal cancer, but the effect on cervical cancer risk is not clear. The effect of this polymorphism on cancer risk seems to be further modulated by other factors, including alcohol and, in the case of cervical cancer, infection with the human papilloma virus. An additional factor determining the effect of diet and genotype interactions on cancer risk may be the stage of cancer development.
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11
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Bollheimer LC, Buettner R, Kullmann A, Kullmann F. Folate and its preventive potential in colorectal carcinogenesis. Crit Rev Oncol Hematol 2005; 55:13-36. [PMID: 15927841 DOI: 10.1016/j.critrevonc.2004.12.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Revised: 12/01/2004] [Accepted: 12/22/2004] [Indexed: 12/31/2022] Open
Abstract
Based on a 15-year old hypothesis, it is believed that an adequate ingestion of folate vitamins decreases, whereas a nutritional depletion of folate increases the risk of colorectal cancer. The present article reviews the efforts to provide biochemical and epidemiological evidence for folate as a chemopreventive agent against colorectal carcinogenesis. BIOLOGICAL EVIDENCE: Tetrahydrofolates govern the intracellular one-carbon metabolism and account for proper DNA biosynthesis and macromolecular modification. Numerous experimental studies traced different molecular pathways and tried to link folate depletion with DNA instability and/or mutagenesis. However, none of the proposed underlying molecular mechanisms appear clearly defined. EPIDEMIOLOGICAL EVIDENCE: Numerous case-control and prospective studies have been conducted on folate and colorectal cancer, which all together miss a clinical bottom line. The recommendation of folate intake to prevent colorectal cancer is therefore not evidence-based.
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12
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Wei EK, Giovannucci E, Selhub J, Fuchs CS, Hankinson SE, Ma J. Plasma vitamin B6 and the risk of colorectal cancer and adenoma in women. J Natl Cancer Inst 2005; 97:684-92. [PMID: 15870439 DOI: 10.1093/jnci/dji116] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Vitamin B6, whose main circulating form is pyridoxal 5'-phosphate (PLP), is important in one-carbon metabolism, which is critical for DNA synthesis and DNA methylation, both of which are potentially involved in colorectal carcinogenesis. However, no previous epidemiologic studies have directly evaluated the association of plasma PLP with risk for colorectal neoplasia. METHODS We conducted a prospective nested case-control study of 32,826 female participants of the Nurses' Health Study who provided blood specimens in 1989-1990. From 1989-1990 to 2000 (1998 for adenoma), a total of 194 incident colorectal cancer cases and 410 incident colorectal adenoma cases were identified from medical records. Multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs) were calculated using logistic regression. All statistical tests were two-sided. RESULTS A suggestive inverse association was observed between plasma PLP concentration and risk for colorectal cancer when comparing the highest quartile versus the lowest (RR = 0.56, 95% CI = 0.31 to 1.01; P(trend) = .07); the association of PLP concentration with colon cancer was statistically significant (RR = 0.42, 95% CI = 0.21 to 0.85; P(trend) = .02). Both associations were statistically significant and stronger after controlling for intakes of folate, of multivitamins, and of methionine (for colorectal cancer, RR = 0.48, 95% CI = 0.25 to 0.92; P(trend) = .03; for colon cancer, RR = 0.38, 95% CI = 0.18 to 0.80; P(trend) = .01). Total vitamin B(6) intake was also statistically significantly inversely associated with colon cancer risk (RR = 0.51, 95% CI = 0.27 to 0.97; P(trend) = .007). There was a suggestive inverse association between plasma PLP concentration and advanced distal colorectal adenoma (RR = 0.65, 95% CI = 0.37 to 1.11; P(trend) = .08), but the association with early-stage adenoma was weaker (RR = 0.85, 95% CI = 0.52 to 1.38; P(trend) = .52). CONCLUSIONS Our results suggest that vitamin B6 may be inversely associated with risk of colorectal neoplasia.
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Affiliation(s)
- Esther K Wei
- Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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13
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Choi SW, Friso S, Ghandour H, Bagley PJ, Selhub J, Mason JB. Vitamin B-12 deficiency induces anomalies of base substitution and methylation in the DNA of rat colonic epithelium. J Nutr 2004; 134:750-5. [PMID: 15051821 DOI: 10.1093/jn/134.4.750] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Derangements of one-carbon metabolism can directly affect the integrity of the genome by producing inappropriate uracil insertion into DNA and by altering patterns of DNA methylation. Vitamin B-12, a one-carbon nutrient, serves as a cofactor in the synthesis of precursors of biological methylation and in nucleotide synthesis. We therefore examined whether vitamin B-12 deficiency can induce these molecular anomalies in the colonic mucosa of rats. Weanling male Sprague-Dawley rats (n = 30) were divided into 2 groups and fed either a vitamin B-12-deficient diet or a similar diet containing adequate amounts of the vitamin. Rats from each group were killed at 6 and 10 wk. Uracil misincorporation into DNA was measured by GC/MS and genomic DNA methylation was measured by LC/MS. Plasma vitamin B-12 concentrations in deficient rats were below detectable limits at 6 and 10 wk; in control rats, concentrations were 0.46 +/- 0.07 and 0.42 +/- 0.10 nmol/L at those times. Although the colon total folate concentration did not differ between the groups, the proportion that was methylfolate was marginally greater in the deficient rats at 10 wk (P = 0.05) compared with control, consistent with the "methylfolate trap" that develops during vitamin B-12 deficiency. After 10 wk, the colonic DNA of the deficient rats displayed a 35% decrease in genomic methylation and a 105% increase in uracil incorporation (P < 0.05). This vitamin B-12-deficient diet, which was of insufficient severity to cause anemia or illness, created aberrations in both base substitution and methylation of colonic DNA, which might increase susceptibility to carcinogenesis.
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Affiliation(s)
- Sang-Woon Choi
- Vitamins and Carcinogenesis Laboratory, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston MA 02111, USA.
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14
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James SJ, Pogribny IP, Pogribna M, Miller BJ, Jernigan S, Melnyk S. Mechanisms of DNA damage, DNA hypomethylation, and tumor progression in the folate/methyl-deficient rat model of hepatocarcinogenesis. J Nutr 2003; 133:3740S-3747S. [PMID: 14608108 DOI: 10.1093/jn/133.11.3740s] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Using the folate/methyl-deficient rat model of hepatocarcinogenesis, we obtained evidence that may provide new insights into a major unresolved paradox in DNA methylation and cancer research: the mechanistic basis for genome-wide hypomethylation despite an increase in DNA methyltransferase activity and gene-specific regional hypermethylation. Previous studies revealed that the methyltransferase binds with higher affinity to DNA strand breaks, gaps, abasic sites, and uracil than it does to its cognate hemimethylated CpG sites, consistent with its ancestral function as a DNA repair enzyme. These same DNA lesions are an early occurrence in models of folate and methyl deficiency and are often present in human preneoplastic cells. We hypothesized that the high-affinity binding of the maintenance DNA methyltransferase to unrepaired lesions in DNA could sequester available enzyme away from the replication fork and promote passive replication-dependent demethylation. In support of this possibility, we found that lesion-containing DNA is less efficiently methylated than lesion-free DNA from folate/methyl-deficient rats and that an increase in DNA strand breaks precedes DNA hypomethylation. Despite an adaptive increase in DNA methyltransferase activity, hemimethylated DNA from folate/methyl-deficient rats is progressively replaced by double-stranded unmethylated DNA that is resistant to remethylation with dietary methyl repletion. In promoter regions, the inappropriate binding of the DNA methyltransferase to unrepaired lesions or mispairs may promote local histone deacetylation, methylation, and regional hypermethylation associated with tumor suppressor gene silencing. These insights in an experimental model are consistent with the possibility that DNA lesions may be a necessary prerequisite for the disruption of normal DNA methylation patterns in preneoplastic and neoplastic cells.
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Affiliation(s)
- S Jill James
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72202, USA.
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Grandics P. Cancer: a single disease with a multitude of manifestions? J Carcinog 2003; 2:9. [PMID: 14624698 PMCID: PMC305362 DOI: 10.1186/1477-3163-2-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2003] [Accepted: 11/18/2003] [Indexed: 02/03/2023] Open
Abstract
The relationships of critical nutrients such as plant phenolics, vitamins, minerals and lipids are considered with respect to the incidence of a variety of cancers, and analyzed in terms of how these nutrient deficiencies alter immune function, DNA integrity and cell proliferation. With a significant correlation found between cancer and these nutrient deficiencies, the hypothesis is presented here that nutrition could provide a unifying perception of cancer and recast it as a single disease. This further suggests that a coordinated administration of specific, critical nutrients to cancer patients could lead to the reversal of the disease. It is also proposed that the concurrent presence of a variety of nutritional deficiencies in cancer patients requires a multilevel, systemic approach to this disease as opposed to the single active therapeutic agent approach that is the cornerstone of contemporary research and pharmacology.
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Affiliation(s)
- Peter Grandics
- A-D Research Foundation, 5922 Farnsworth Ct, Carlsbad, CA 92008 USA.
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Duthie SJ, Narayanan S, Brand GM, Pirie L, Grant G. Impact of folate deficiency on DNA stability. J Nutr 2002; 132:2444S-2449S. [PMID: 12163709 DOI: 10.1093/jn/132.8.2444s] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Convincing evidence links folate deficiency with colorectal cancer incidence. Currently, it is believed that folate deficiency affects DNA stability principally through two potential pathways. 5,10-Methylenetetrahydrofolate donates a methyl group to uracil, converting it to thymine, which is used for DNA synthesis and repair. If folate is limited, imbalances in the DNA precursor pool occur, and uracil may be misincorporated into DNA. Subsequent misincorporation and repair may lead to double strand breaks, chromosomal damage and cancer. Moreover, folate affects gene expression by regulating cellular S-adenosylmethionine (SAM) levels. 5-Methyltetrahydrofolate serves as methyl donor in the remethylation of homocysteine to methionine, which in turn is converted to SAM. SAM methylates specific cytosines in DNA, and this regulates gene transcription. As a consequence of folate deficiency, cellular SAM is depleted, which in turn induces DNA hypomethylation and potentially induces proto-oncogene expression leading to cancer. Data from several model systems supporting these mechanisms are reviewed here. There is convincing evidence that folate modulates both DNA synthesis and repair and DNA hypomethylation with altered gene expression in vitro. The data from in vivo experiments in rodents is more difficult to interpret because of variations in the animal and experimental systems used and the influence of tissue specificity and folate metabolism. Most importantly, the confounding effects of nutrient-gene interactions, together with the identification of polymorphisms in key enzyme systems and the influence that these have on folate metabolism and DNA stability, must be considered when interpreting evidence from human studies.
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17
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Duthie SJ, Narayanan S, Blum S, Pirie L, Brand GM. Folate deficiency in vitro induces uracil misincorporation and DNA hypomethylation and inhibits DNA excision repair in immortalized normal human colon epithelial cells. Nutr Cancer 2001; 37:245-51. [PMID: 11142099 DOI: 10.1207/s15327914nc372_18] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Epidemiological studies have indicated that folic acid protects against a variety of cancers, particularly cancer of the colorectum. Folate is essential for efficient DNA synthesis and repair. Moreover, folate can affect cellular S-adenosylmethionine levels, which regulate DNA methylation and control gene expression. We have investigated the mechanisms through which folate affects DNA stability in immortalized normal human colonocytes (HCEC). DNA strand breakage, uracil misincorporation, and DNA repair, in response to oxidative and alkylation damage, were determined in folate-sufficient and folate-deficient colonocytes by single cell gel electrophoresis. In addition, methyl incorporation into genomic DNA was measured using the bacterial enzyme Sss1 methylase. Cultured human colonocyte DNA contained endogenous strand breaks and uracil. Folate deficiency significantly increased strand breakage and uracil misincorporation in these cells. This negative effect on DNA stability was concentration dependent at levels usually found in human plasma (1-10 ng/ml). DNA methylation was decreased in HCEC grown in the absence of folate. Conversely, hypomethylation was not concentration dependent. Folate deficiency impaired the ability of HCEC to repair oxidative and alkylation damage. These results demonstrate that folic acid modulates DNA repair, DNA strand breakage, and uracil misincorporation in immortalized human colonocytes and that folate deficiency substantially decreases DNA stability in these cells.
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Affiliation(s)
- S J Duthie
- Rowett Research Institute, Bucksburn, Aberdeen AB21 9SB, UK.
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18
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Ryan BM, Weir DG. Relevance of folate metabolism in the pathogenesis of colorectal cancer. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 2001; 138:164-76. [PMID: 11528369 DOI: 10.1067/mlc.2001.117161] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The purpose of this review is to outline the principal mechanisms involved in folate metabolism and how they may relate to the pathogenesis of colorectal cancer (CRC). In recent years, mild folate depletion (low normal level) has been associated with an increased risk of developing certain cancers, in particular colorectal neoplasia. The epidemiologic and mechanistic evidence linking folate deficiency with carcinogenesis is reviewed, with a particular emphasis on colorectal neoplasia. Methylenetetrahydrofolate reductase (MTHFR) is a critical folate metabolizing enzyme, and a functional polymorphic variant of this enzyme, the so-called thermolabile variant, caused by a C677T transition in the MTHFR gene, is common in the general population. This review critically examines the evidence that suggests that carriers of this C677T variant may be at increased risk of developing colorectal neoplasia. Although folate depletion may predispose to the initiation of the neoplastic process, folate supplementation, on the other hand, might potentiate the progression of an already established early neoplastic clone (eg, a colorectal adenoma). This could have potential public health implications, given an increasingly widespread policy of folate supplementation of food staples.
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Affiliation(s)
- B M Ryan
- Department of Clinical Medicine, St James's Hospital and Trinity College, Dublin, Ireland
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19
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Branda RF, O'Neill JP, Brooks EM, Trombley LM, Nicklas JA. The effect of folate deficiency on the cytotoxic and mutagenic responses to ethyl methanesulfonate in human lymphoblastoid cell lines that differ in p53 status. Mutat Res 2001; 473:51-71. [PMID: 11166026 DOI: 10.1016/s0027-5107(00)00138-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Folic acid deficiency acts synergistically with alkylating agents to increase genetic damage at the HPRT locus in Chinese hamster ovary cells in vitro and in rat splenocytes in vivo. The present studies extend these observations to human cells and, in addition, investigate the role of p53 activity on mutation induction. The human lymphoblastoid cell lines TK6 and WTK1 are derived from the same parental cell line (WI-L2), but WTK1 expresses mutant p53. Treatment of folate-replete or deficient WTK1 and TK6 cells with increasing concentrations (0-50microg/ml) of ethyl methanesulfonate (EMS) resulted in significantly different HPRT mutation dose-response relationships (P<0.01), indicating that folate deficiency increased the EMS-induced mutant frequency in both cell lines, but with a greater effect in TK6 cells. Molecular analyses of 152 mutations showed that the predominant mutation (65%) in both cell types grown in the presence or absence of folic acid was a G>A transition on the non-transcribed strand. These transitions were mainly at non-CpG sites, particularly when these bases were flanked 3' by a purine or on both sides by G:C base pairs. A smaller number of G>A transitions occurred on the transcribed strand (C>T=14%), resulting in 79% total G:C>A:T transitions. There were more genomic deletions in folate-deficient (15%) as compared to replete cells (4%) of both cell types. Mutations that altered RNA splicing were common in both cell types and under both folate conditions, representing 33% of the total mutations. These studies indicate that cells expressing p53 activity exhibit a higher rate of mutation induction but are more sensitive to the toxic effects of alkylating agents than those lacking p53 activity. Folate deficiency tends to reduce toxicity but increase mutation induction after EMS treatment. The p53 gene product did not have a major influence on the molecular spectrum after treatment with EMS, while folate deficiency increased the frequency of deletions in both cell types.
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Affiliation(s)
- R F Branda
- Department of Medicine and The Vermont Cancer Center, University of Vermont, Burlington, VT 05405, USA.
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20
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Duthie SJ, Grant G, Narayanan S. Increased uracil misincorporation in lymphocytes from folate-deficient rats. Br J Cancer 2000; 83:1532-7. [PMID: 11076664 PMCID: PMC2363426 DOI: 10.1054/bjoc.2000.1481] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The development of certain human cancers has been linked with inadequate intake of folates. The effects of folate deficiency in vivo on DNA stability (strand breakage, misincorporated uracil and oxidative base damage) in lymphocytes isolated from rats fed a diet deficient in folic acid was determined. Because the metabolic pathways of folate and other methyl donors are closely coupled, the effects of methionine and choline deficiency alone or in combination with folate deficiency were determined. Feeding male Hooded Lister rats a folate-free diet for 10 weeks created a moderate folate deficiency (25-50% (approx.) decrease in plasma, red blood cell and hepatic folate concentrations (P < 0.05) and a 20% rise in plasma homocysteine (P < 0.05)). Lymphocyte DNA strand breakage was increased successively in all groups after 4 weeks and 8 weeks on the diet (50-100% (approx.) after 8 weeks). Only low folate specifically and progressively induced uracil misincorporation throughout the study (100% (approx.) after 8 weeks). Neither folate deficiency nor choline/methionine deficiency altered oxidative DNA base damage. In summary, moderate folate deficiency in vivo is associated with a decrease in DNA stability, measured as increased DNA strand breakage and misincorporated uracil.
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Affiliation(s)
- S J Duthie
- Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK
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21
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Branda RF, Lafayette AR, O'Neill JP, Nicklas JA. The effect of folate deficiency on the hprt mutational spectrum in Chinese hamster ovary cells treated with monofunctional alkylating agents. Mutat Res 1999; 427:79-87. [PMID: 10393262 DOI: 10.1016/s0027-5107(99)00095-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Folic acid deficiency acts synergistically with alkylating agents to increase DNA strand breaks and mutant frequency at the hprt locus in Chinese hamster ovary (CHO) cells. To elucidate the mechanism of this synergy, molecular analyses of hprt mutants were performed. Recently, our laboratory showed that folate deficiency increased the percentage of clones with intragenic deletions after exposure to ethyl methanesulfonate (EMS) but not N-nitroso-N-ethylurea (ENU) compared to clones recovered from folate replete medium. This report describes molecular analyses of the 37 hprt mutant clones obtained that did not contain deletions. Folate deficient cells treated with EMS had a high frequency of G>A transitions at non-CpG sites on the non-transcribed strand, particularly when these bases were flanked on both sides by G:C base pairs. Thirty-three percent of these mutations were in the run of six G's in exon 3. EMS-treated folate replete cells had a slightly (but not significantly) lower percentage of G>A transitions, and the same sequence specificity. Treatment of folate deficient CHO cells with ENU resulted in predominantly T>A transversions and C>T transitions relative to the non-transcribed strand. These findings suggest a model to explain the synergy between folate deficiency and alkylating agents: (1) folate deficiency causes extensive uracil incorporation into DNA; (2) greatly increased utilization of base excision repair to remove uracil and to correct alkylator damage leads to error-prone DNA repair. In the case of EMS, this results in more intragenic deletions and G:C to A:T mutations due to impaired ligation of single-strand breaks generated during base excision repair and a decreased capacity to remove O6-ethylguanine. In the case of ENU additional T>A transversions and C>T transitions are seen, perhaps due to mis-pairing of O2-ethylpyrimidines. Correction of folate deficiency may reduce the frequency of these types of genetic damage during alkylator therapy.
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Affiliation(s)
- R F Branda
- Department of Medicine and the Vermont Cancer Center, University of Vermont, Burlington, VT 05405, USA.
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22
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Folate Deficiency Delays the Onset But Increases the Incidence of Leukemia in Friend Virus-Infected Mice. Blood 1997. [DOI: 10.1182/blood.v90.10.4054] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
AbstractClinical studies have indicated that folate deficiency may enhance the development of various malignancies. In animal studies that examined the effect of folate deficiency on malignancies, conflicting results have been reported. In some studies, folate deficiency increased the development and growth of malignant tumors; in others, it decreased the development and growth of malignancies. We examined the effect of transient folate deficiency on the development of leukemia in mice infected with the anemia-inducing strain of Friend leukemia virus. Friend virus disease can be considered as a model for human acute leukemias that are preceded by a preleukemic period. These include leukemias that develop in patients who received previous chemotherapy and/or radiation therapy, as well as patients with chronic granulocytic leukemia or myelodysplasia. Folate deficiency around the time of Friend virus-infection delayed the onset but increased the incidence of leukemia. The rates of rearrangement of the Spi-1 (PU.1 ) oncogene by provirus integration and alteration of the p53 tumor-suppressor gene were the same in leukemia cell lines derived from folate-deficient mice as they were in cell lines from control mice. These results indicate that folate deficiency did not exert its enhancement of leukemogenesis through changes in either Spi-1 or p53, even though these two genes have been found to be the most frequently altered ones in Friend virus-induced leukemias. Our results suggest that folate deficiency may enhance the development of acute leukemia in patients who are at high risk for this disease.
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23
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Jackson CD, Weis C, Miller BJ, James SJ. Dietary nucleotides: effects on cell proliferation following partial hepatectomy in rats fed NIH-31, AIN-76A, or folate/methyl-deficient diets. J Nutr 1997; 127:834S-837S. [PMID: 9164248 DOI: 10.1093/jn/127.5.834s] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The requirement of a number of tissues for dietary nucleotides could explain some of the differences observed in animals fed natural ingredient diets vs. those fed purified diets lacking a source of dietary nucleotides. Lack of dietary nucleotides is exacerbated in animals fed folate- or methyl-deficient semipurified diets, in which both salvage and folate-dependent de novo synthetic pathways are diminished. We examined hepatocyte proliferation following partial hepatectomy in weanling male Fischer-344 rats fed natural ingredient NIH-31 diet, nucleotide-free purified AIN-76A diet or a basal diet similar to AIN-76A but deficient in the methyl donors folate, choline and methionine. Additional groups were fed AIN-76A or folate/methyl-deficient diets supplemented with 0.25% yeast RNA. Compared with NIH-31, AIN-76A increased dUMP/dTTP ratios, reduced the mitotic index (MI) and increased the ratio of proliferating cell index (PCI) to mitotic cells, an indication that hepatocytes were delayed in S-phase. Addition of yeast RNA to AIN-76A reversed (by approximately 50%) the effects of AIN-76A on dUMP/dTTP and cell proliferation. A folate/methyl-deficient diet also produced an increased dUMP/dTTP ratio and markedly reduced the MI, increasing the PCI/MI, which suggested even further delay of cells in S-phase. Addition of yeast RNA to the folate/methyl-deficient diet was effective in significantly reversing the effects of folate/methyl deficiency.
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Affiliation(s)
- C D Jackson
- Division of Nutritional Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA
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24
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Kunz BA. Inhibitors of thymine nucleotide biosynthesis: antimetabolites that provoke genetic change via primary non-DNA targets. Mutat Res 1996; 355:129-40. [PMID: 8781581 DOI: 10.1016/0027-5107(96)00026-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Folate antagonists and direct-acting inhibitors of thymidylate synthase are potent genotoxic antimetabolites. These agents induce genetic change not by attacking DNA, but by interfering with the control of DNA precursor metabolism. This review surveys the genetic effects attributable to selected representatives of this class of antimetabolites.
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Affiliation(s)
- B A Kunz
- School of Biological and Chemical Sciences, Deakin University, Geelong, Victoria, Australia.
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25
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Abstract
Folate deficiency significantly increases uracil content and chromosome breaks (as measured by micronucleated cells) in human leukocyte DNA. Folate supplementation reduces both the uracil content of DNA and the frequency of micronucleated cells, indicating that uracil misincorporation may play a causative role in folate deficiency-induced chromosome breaks. A calculation is presented to explain how the levels of uracil found in DNA could cause chromosome breaks. Based on this calculation, the frequency of uracil repair events that might result in double-strand DNA breaks increases by 1752-fold. These results are consistent with clinical and epidemiological evidence linking folate deficiency to DNA damage and cancer.
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Affiliation(s)
- B C Blount
- Biomedical Mass Spectrometry Unit, University of New South Wales, Kensington, Australia
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26
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Wickramasinghe SN. Morphology, biology and biochemistry of cobalamin- and folate-deficient bone marrow cells. BAILLIERE'S CLINICAL HAEMATOLOGY 1995; 8:441-59. [PMID: 8534956 DOI: 10.1016/s0950-3536(05)80215-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
B12- or folate-deficient haemopoietic cells display abnormalities in their morphology under both the light and electron microscope, their cell kinetics and their capacity to synthesize protein. These abnormalities are maximal in the last dividing cell class and in non-dividing cells, presumably because B12 and folate uptake is largely confined to the most immature erythroid and granulocyte precursors. In patients with moderate or severe anaemia due to B12 or folate deficiency, erythropoiesis is markedly ineffective; intramedullary cell death occurs mainly in the early and late polychromatic megaloblasts. The damaged erythroblasts appear to display neoantigens or normally-hidden antigens at their cell surface and these react with naturally occurring antibodies. The opsonised erythroblasts are then recognised by macrophages via their IgG-Fc receptors and phagocytosed. Marrow cells from B12- or folate-deficient patients show a subnormal suppression of 3H-thymidine incorporation after pre-incubation with nonradioactive deoxyuridine, suggesting that such cells suffer from an impairment of the 5,10-methylene-THF-dependent methylation of deoxyuridylate to thymidylate. However, the exact mechanism by which B12 deficiency causes a reduced supply of this folate coenzyme is uncertain. Methylcobalamin is required for the 5-methyl-THF-dependent methylation of homocysteine to methionine and an impairment of this reaction will result in both reduced conversion of 5-methyl-THF to THF and in reduced methionine synthesis. There is controversy as to whether the reduced supply of THF or methionine is responsible for the reduced availability of 5,10-methylene-THF. Currently, the balance of evidence favours the hypothesis that the reduced supply of methionine leads to reduced synthesis of formyl-THF and, eventually, of 5,10-methylene-THF. Despite the evidence for impaired thymidylate synthesis, the duration of the S phase of megaloblasts appears to be normal or only modestly increased. Data on rates of DNA strand elongation are inconsistent, with subnormal rates reported in PHA-stimulated B12- or folate-deficient lymphocytes and normal rates in B12- or folate-deficient bone marrow cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- S N Wickramasinghe
- Division of Pathology Sciences, St Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London, UK
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27
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Kunz BA, Kohalmi SE, Kunkel TA, Mathews CK, McIntosh EM, Reidy JA. International Commission for Protection Against Environmental Mutagens and Carcinogens. Deoxyribonucleoside triphosphate levels: a critical factor in the maintenance of genetic stability. Mutat Res 1994; 318:1-64. [PMID: 7519315 DOI: 10.1016/0165-1110(94)90006-x] [Citation(s) in RCA: 185] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
DNA precursor pool imbalances can elicit a variety of genetic effects and modulate the genotoxicity of certain DNA-damaging agents. These and other observations indicate that the control of DNA precursor concentrations is essential for the maintenance of genetic stability, and suggest that factors which offset this control may contribute to environmental mutagenesis and carcinogenesis. In this article, we review the biochemical and genetic mechanisms responsible for regulating the production and relative amounts of intracellular DNA precursors, describe the many outcomes of perturbations in DNA precursor levels, and discuss implications of such imbalances for sensitivity to DNA-damaging agents, population monitoring, and human diseases.
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Affiliation(s)
- B A Kunz
- Microbiology Department, University of Manitoba, Winnipeg, Canada
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28
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James SJ, Miller BJ, McGarrity LJ, Morris SM. The effect of folic acid and/or methionine deficiency on deoxyribonucleotide pools and cell cycle distribution in mitogen-stimulated rat lymphocytes. Cell Prolif 1994. [DOI: 10.1111/j.1365-2184.1994.tb01471.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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29
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Koury MJ, Horne DW. Apoptosis mediates and thymidine prevents erythroblast destruction in folate deficiency anemia. Proc Natl Acad Sci U S A 1994; 91:4067-71. [PMID: 8171036 PMCID: PMC43724 DOI: 10.1073/pnas.91.9.4067] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Deficiency of the vitamin folic acid causes pancytopenia by decreasing the production of new blood cells. Although impaired DNA synthesis and destruction of hematopoietic cells have been implicated, the mechanism by which folate deficiency decreases blood cell production is uncertain. An in vitro model of folate-deficient erythropoiesis was developed by using proerythroblasts isolated from folate-deficient mice that were infected with Friend leukemia virus. Proerythroblasts from folate-deficient mice had one-tenth the total folate as did proerythroblasts from control mice. The folate-deficient proerythroblasts underwent apoptosis, a form of programmed cell death, after 20-32 h in culture in folate-deficient medium. At the time of apoptosis the cells had differentiated into the later erythroblast stages and some had begun hemoglobin synthesis. Addition of either folic acid or thymidine, but not deoxycytidine or inosine, to the folate-deficient medium prevented the apoptosis and permitted proliferation and differentiation of the proerythroblasts into reticulocytes. The prevention of apoptosis by thymidine indicates (i) that decreased thymidylate synthesis plays a role in erythroblast apoptosis and the anemia of folate deficiency and (ii) that DNA cleavage is likely to be a primary event in the apoptosis of folate-deficient erythroblasts. Apoptosis of erythroblasts in the late stages of differentiation leads to decreased erythrocyte production and to anemia. The increased erythropoietin produced in response to the anemia increases the number of erythroid progenitor cells in the differentiation stages preceding those in which the cells undergo apoptosis. This population shift to earlier stage erythroblasts and proerythroblasts is characteristic of bone marrows of individuals with folate deficiency anemia.
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Affiliation(s)
- M J Koury
- Department of Medicine, Vanderbilt University, Nashville, TN 37232
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