Association between folate intake and risk of head and neck squamous cell carcinoma: An overall and dose-response PRISMA meta-analysis

Malnutrition as a Risk Factor in the Development of Oral Cancer: A Systematic Literature Review and Meta-Analyses

This systematic review and meta-analyses aimed to assess whether malnutrition may increase the incidence of oral cancer. Following the PRISMA statement, the research was conducted on PubMed, Scopus, and MEDLINE via OVID without any time restrictions. The risk of bias was assessed, and the quality of evidence for each performed meta-analysis was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. Sixty-one articles met the inclusion criteria and seven studies underwent quantitative evaluation. For our meta-analysis on hypovitaminosis B, three studies with a total of 90,011 patients were included. An odds ratio of 2.22 was found. Our meta-analysis on the correlation between vitamin C and oral cancer included one study with a total of 866 patients and the derived odds ratio was 1.06. Our meta-analysis on the relationship between vitamin D deficiency and the incidence of oral cancer included three studies with a total of 12,087 patients and the odds ratio was -2.58. The GRADE system showed a moderate strength of evidence due to the presence of studies with a high risk of bias and high indirectness of the data given. The present findings suggest that an inadequate intake of vitamins, particularly vitamin D, poses a risk for the onset of oral cancer.

Folic acid: friend or foe in cancer therapy

Folic acid plays a crucial role in diverse biological processes, notably cell maturation and proliferation. Here, we performed a literature review using articles listed in electronic databases, such as PubMed, Scopus, MEDLINE, and Google Scholar. In this review article, we describe contradictory data regarding the role of folic acid in cancer development and progression. While some studies have confirmed its beneficial effects in diminishing the risk of various cancers, others have reported a potential carcinogenic effect. The current narrative review elucidates these conflicting data by highlighting the possible molecular mechanisms explaining each point of view. Further multicenter molecular and genetic studies, in addition to human randomized clinical trials, are necessary to provide a more comprehensive understanding of the relationship between folic acid and cancer.

Correlation of several forms of folic acid with endometrial cancer: cross-sectional data from the National Health and Nutrition Examination Surveys (NHANES) 2011-2018

OBJECTIVE

Endometrial cancer (EC) is a common malignancy of the female reproductive system and although most patients have a good prognosis, 20-30% of patients with advanced disease have a poor prognosis. There are currently no reliable biomarkers for early diagnosis and effective prognostic improvement of the disease. The purpose of this study was to explore the correlation between different forms of folic acid and endometrial cancer.

METHODS

This study included 8809 female subjects aged ≥ 20 years in the NHANES database from 2011 to 2018, including 8738 non-oncology patients and 71 EC patients. Selection bias was reduced using 1:1 propensity score matching (PSM) method. Restricted cubic spline (RCS) was plotted to explore the non-linear relationship between different forms of folic acid and EC.

RESULT

Using data from the NHANES database from 2011 to 2018, the association between folic acid and the risk of developing EC was assessed. The results of the 1:1 ratio propensity score matching (PSM) showed 68 each for EC patients and non-oncology participants. Total serum folate, 5-methyltetrahydrofolate (5-methylTHF), 5-formyltetrahydrofolate (5-formylTHF), tetrahydrofolate (THF) and 5,10-methylenetetrahydrofolate (5,10-methenylTHF) were significantly correlated with EC (p < 0.05). In addition, the RCS showed a significant non-linear correlation between THF and 5,10-formyl THF and the risk of developing EC.

CONCLUSION

The results of this study showed that changes in serum total folate, 5-methylTHF, 5-formylTHF, THF and 5,10-methenylTHF were related to EC.

Folate Intake and Risk of Pancreatic Cancer: A Systematic Review and Updated Meta-Analysis of Epidemiological Studies

INTRODUCTION

Pancreatic cancer is one of the most fatal malignancies and primary prevention strategies are limited. Epidemiological studies focusing on the association between folate intake and pancreatic cancer risk have reported inconsistent findings.

METHODS

A systematic search of the literature was conducted using the PubMed and EMBASE databases. A systematic review and meta-analysis of eligible studies was performed to assess the association between folate intake and risk of pancreatic cancer.

RESULTS

A total of 16 studies involving 5654 cases and 1,009,374 individuals were included. The result showed a significant association of folate intake with a decreased risk of pancreatic cancer, with a pooled OR of 0.82 (95% CI: 0.69-0.97, P = 0.019) for the highest category of intake vs. the lowest. The data suggested that high intake of folate may contribute to the prevention of pancreatic cancer. However, the association was observed only in case-control studies (OR = 0.78, 95% CI: 0.65-0.93, P = 0.006), but not in cohort studies (RR = 0.85, 95% CI: 0.66-1.09, P = 0.244). Dose-response meta-analysis showed that an increment of folate intake (100 μg/day) was marginally associated with the risk of pancreatic cancer, with a pooled OR of 0.97 (95% CI: 0.93-1.00, P = 0.053).

CONCLUSION

High folate intake might be inversely associated with pancreatic cancer risk, which needs to be confirmed.

The Concept of Folic Acid in Health and Disease

Folates have a pterine core structure and high metabolic activity due to their ability to accept electrons and react with O-, S-, N-, C-bounds. Folates play a role as cofactors in essential one-carbon pathways donating methyl-groups to choline phospholipids, creatine, epinephrine, DNA. Compounds similar to folates are ubiquitous and have been found in different animals, plants, and microorganisms. Folates enter the body from the diet and are also synthesized by intestinal bacteria with consequent adsorption from the colon. Three types of folate and antifolate cellular transporters have been found, differing in tissue localization, substrate affinity, type of transferring, and optimal pH for function. Laboratory criteria of folate deficiency are accepted by WHO. Severe folate deficiencies, manifesting in early life, are seen in hereditary folate malabsorption and cerebral folate deficiency. Acquired folate deficiency is quite common and is associated with poor diet and malabsorption, alcohol consumption, obesity, and kidney failure. Given the observational data that folates have a protective effect against neural tube defects, ischemic events, and cancer, food folic acid fortification was introduced in many countries. However, high physiological folate concentrations and folate overload may increase the risk of impaired brain development in embryogenesis and possess a growth advantage for precancerous altered cells.

Association Between Folate and Health Outcomes: An Umbrella Review of Meta-Analyses

Background: There is no study that has systematically investigated the breadth and validity of the associations of folate and multiple health outcomes. We aimed to evaluate the quantity, validity, and credibility of evidence regarding associations between folate and multiple health outcomes by using umbrella review of meta-analysis. Methods: We searched the MEDLINE, EMBASE, and Cochrane Library databases from inception to May 20, 2018, to identify potential meta-analyses that examined the association of folate with any health outcome. For each included meta-analysis, we estimated the summary effect size and their 95% confidence interval using the DerSimonian and Laird random-effects model. We used the AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews) to assess methodological quality and the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation working group classification) to assess the quality of evidence for each outcome included in the umbrella review. Results: Overall, 108 articles reporting 133 meta-analyses of observational studies and 154 meta-analyses of randomized controlled trials (RCTs) were included in the study. Among them, 108 unique exposure-outcome-population triplets (referred to as unique meta-analyses hereafter) of RCTs and 87 unique meta-analyses of observational studies were reanalyzed. Beneficial effects of folate were observed in the all-cause mortality rate and in a number of chronic diseases, including several birth/pregnancy outcomes, several cancers, cardiovascular disease and metabolic-related outcomes, neurological conditions, and several other diseases. However, adverse effects of folate were observed for prostate cancer, colorectal adenomatous lesions, asthma or wheezing, and wheezing as an isolated symptom and depression. Conclusions: Current evidence allows for the conclusion that folate is associated with decreased risk of all-cause mortality and a wide range of chronic diseases. However, folate may be associated with an increased risk of prostate cancer. Further research is warranted to improve the certainty of the estimates.

Gene Polymorphisms Involved in Folate Metabolism and DNA Methylation with the Risk of Head and Neck Cancer

BACKGROUND

Folate is essential for DNA synthesis, repair, and methylation. Polymorphisms in genes associated with folate metabolism may alter these processes and, consequently, modulate cancer development.

AIM

We aimed to assess DNMT3B -149C/T (rs2424913), DNMT3B -283T/C (rs6087990), DNMT3B -579G/T (rs2424909), DHFR 19-pb ins/del (rs70991108), SHMT1 1420C/T (rs1979277), and TYMS 28-bp tandem repeat (rs34743033) polymorphisms with risk of head and neck cancer.

METHODS

A case-control study was conducted in 1,086 Brazilian individuals. Real-time and conventional polymerase chain reactions-PCR were performed for genotyping the polymorphisms.

RESULTS

The single nucleotide polymorphism (SNP), DNMT3B -283T/C, revealed a higher risk of head and neck squamous cell carcinoma (HNSCC) when compared with the C group in the codominant (p < 0.001), dominant (p <0.001), and overdominant (p= 0.001) models for T/C and C/C genotypes. DNMT3B -149C/T and DNMT3B -579G/T revealed no association between groups in any model. The DHFR 19-pb ins/del polymorphism protected against HNSCC development compared to the C group by the codominant (p < 0.001), dominant (p < 0.001), and overdominant (p < 0.001) models. In the TYMS, the 3R/3R genotype had a protective effect against HNSCC development compared with the C group by the recessive models (p= 0.009). In contrast, SHMT1 1420 C/T presented no association between the HNSCC and C groups. DHFR 19-pb ins/del polymorphisms protected against oral cavity cancer (p= 0.003), and only TYMS-28 3R/3R decreased the risk of tumor progression (p= 0.023). In the Kaplan-Meier curve, an association was found between DHFR ins/ins and TYMS -28 3R carriers with respect to relapse-free time; further, DNMT3B -579 T and TYMS-28 2R/2R carriers had longer survival times.

CONCLUSION

DNMT3B -283T/C is associated with higher risk, whereas DHFR 19-pb ins/del and TYMS 28 3R/3R protect against head and neck cancer. We also highlighted the association of TYMS 3R/3R genotype carriers with relapse-free cancer protection and survival time.

Folate and Its Impact on Cancer Risk

PURPOSE OF REVIEW

Research has evaluated the potential impact of folate on cancer risk with conflicting findings. Studies have demonstrated increased risk, no effect, and decreased risk. This review summarizes findings of mixed results between folate intake, serum levels, gene polymorphisms, and cancer risk based on meta-analyses from the past five years.

RECENT FINDING

Low or deficient folate status is associated with increased risk of many cancers. Folic acid supplementation and higher serum levels are associated with increased risk of prostate cancer. Gene polymorphisms may impact risk in certain ethnic groups. Folate has been studied extensively due to its role in methylation and nucleotide synthesis. Further prospective studies are needed to clarify optimal levels for nutrient remediation and risk reduction in those at risk, as well as elucidate the association between high intake, high serum levels, and prostate cancer risk. Future considerations for cancer risk may include gene interactions with nutrients and environmental factors.

Decreased expression of folate transport proteins in oral cancer

OBJECTIVES

The purpose of this study was to assess the expression of the 3 major folate transporters-folate receptors (FRs), reduced folate carrier (RFC), and proton-coupled folate transporter (PCFT)-in oral squamous cell carcinoma (OSCC). We hypothesized that patterns of expression of folate transporters would be different in OSCC compared with normal oral epithelium.

STUDY DESIGN

We used immunohistochemistry to examine the expression of FR, RFC, and PCFT in 15 primary specimens collected from patients with OSCC, 2 human cadaveric samples of OSCC, and 12 normal human cadaveric oral tissues from a medical gross anatomy laboratory. Possible correlations between the expression of each folate transporter and patients' clinical data were determined.

RESULTS

All 3 folate transporters were highly expressed in normal oral epithelium. In contrast, OSCC samples generally demonstrated low expression of FR, RFC, and PCFT, with wide distribution in the invading cancer cells. There were no differences in folate transporter expression between OSCC samples collected from patients and from human cadavers. The lowest expression of FR and PCFT characterized less-differentiated tumors, and the lowest expression of RFC correlated with higher lymph node involvement.

CONCLUSIONS

Human oral cancer samples expressed decreased amounts of all 3 major folate transport proteins compared with controls from normal cadaveric oral tissues.

Folate Repletion after Deficiency Induces Irreversible Genomic and Transcriptional Changes in Human Papillomavirus Type 16 (HPV16)-Immortalized Human Keratinocytes

Supplementation of micronutrients like folate is a double-edged sword in terms of their ambivalent role in cell metabolism. Although several epidemiological studies support a protective role of folate in carcinogenesis, there are also data arguing for an opposite effect. To address this issue in the context of human papillomavirus (HPV)-induced transformation, the molecular events of different folate availability on human keratinocytes immortalized by HPV16 E6 and E7 oncoproteins were examined. Several sublines were established: Control (4.5 µM folate), folate deficient (0.002 µM folate), and repleted cells (4.5 µM folate). Cells were analyzed in terms of oncogene expression, DNA damage and repair, karyotype changes, whole-genome sequencing, and transcriptomics. Here we show that folate depletion irreversibly induces DNA damage, impairment of DNA repair fidelity, and unique chromosomal alterations. Repleted cells additionally underwent growth advantage and enhanced clonogenicity, while the above mentioned impaired molecular properties became even more pronounced. Overall, it appears that a period of folate deficiency followed by repletion can shape immortalized cells toward an anomalous phenotype, thereby potentially contributing to carcinogenesis. These observations should elicit questions and inquiries for broader additional studies regarding folate fortification programs, especially in developing countries with micronutrient deficiencies and high HPV prevalence.

Flavonoids intake and risk of type 2 diabetes mellitus: A meta-analysis of prospective cohort studies

Epidemiological studies exploring the role of flavonoids intake in preventing type 2 diabetes mellitus (T2DM) showed inconsistent results. Therefore, we performed a meta-analysis of relevant studies to examine the relationship between flavonoids intake and risk of T2DM. We hypothesized that flavonoids intake may decrease the risk of developing T2DM.A systematical search in PubMed and Embase until September 2017 was performed to identify eligible prospective cohort studies. The summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random-effect models. Dose-response pattern between total flavonoids intake and T2DM risk was also estimated.Eight prospective studies were included with 312,015 participants, of whom 19,953 developed T2DM during the follow-up periods of 4 to 28 years. Compared with lower consumption, high intake of total flavonoids was associated with a decreased risk of T2DM (RR: 0.89, 95% CI: 0.82-0.96). Among flavonoid subclasses, inverse correlations with T2DM were achieved for intakes of anthocyanidins, flavan-3-ols, flavonols, and isoflavones. Dose-response meta-analysis indicated a curvilinear relationship between total flavonoids intake and incident T2DM (P for nonlinearity = .042), with a significant risk reduction at an intake of ≥550 mg/day. When assuming a linear pattern, the risk of T2DM was decreased by 5% for each 300-mg/day increment in total flavonoids intake (RR: 0.95, 95% CI: 0.93-0.97).Our study suggests that higher intakes of total flavonoids and subclasses (anthocyanidins, flavan-3-ols, flavonols, and isoflavones) are associated with lower risk of T2DM.