Vitamin B12 and its binding proteins in patients with non-small cell lung cancer referred to fast-track diagnostic work-up for lung cancer.

High cobalamin levels have previously been associated with short-term cancer risk, including lung cancer. We explored whether levels of cobalamin and/or its binding proteins are useful as a diagnostic tool in patients suspected of non-small cell lung cancer. We included 889 patients referred for fast-track diagnosis of lung cancer to Aarhus University Hospital, Denmark. We analyzed plasma concentrations of cobalamin, transcobalamin, holotranscobalamin and haptocorrin. Information on lung cancer diagnosis was retrieved from a national database. The study cohort showed levels above reference intervals for cobalamin 12%, holotranscobalamin 25%, transcobalamin 9% and haptocorrin 36% (all p-values <.05). We observed no difference in cobalamin or holotranscobalamin levels when comparing patients diagnosed with non-small cell lung cancer (n = 161, 18%) to patients without lung cancer (n = 742, 80%), while transcobalamin showed minor differences. Haptocorrin was significantly higher in those with cancer, mainly among patients with adenocarcinoma (n = 94). A comparison of patients with the highest vs. lowest quartile levels of haptocorrin yielded an adjusted odds ratio for adenocarcinoma of 2.39 (95% confidence interval: 1.26-4.55). However, ROC curve analyzes showed haptocorrin (AUC = 0.55) and total transcobalamin (AUC = 0.56) to be poor diagnostic markers for lung cancer. A high proportion of patients suspected for non-small cell lung cancer showed increased levels of cobalamin-binding proteins. We thereby confirm the association between non-small cell lung cancer and high cobalamin levels and found that haptocorrin was the major underlying factor causing high cobalamin levels. However, none of these biomarkers were of diagnostic use among patients referred for suspected lung cancer.

Diagnostic and Therapeutic Perspectives Associated to Cobalamin-Dependent Metabolism and Transcobalamins' Synthesis in Solid Cancers.

Cobalamin or vitamin B12 (B12) is a cofactor for methionine synthase and methylmalonyl-CoA mutase, two enzymes implicated in key pathways for cell proliferation: methylation, purine synthesis, succinylation and ATP production. Ensuring these functions in cancer cells therefore requires important cobalamin needs and its uptake through the transcobalamin II receptor (TCII-R). Thus, both the TCII-R and the cobalamin-dependent metabolic pathways constitute promising therapeutic targets to inhibit cancer development. However, the link between cobalamin and solid cancers is not limited to cellular metabolism, as it also involves the circulating transcobalamins I and II (TCI or haptocorrin and TCII) carrier proteins, encoded by TCN1 and TCN2, respectively. In this respect, elevations of B12, TCI and TCII concentrations in plasma are associated with cancer onset and relapse, and with the presence of metastases and worse prognosis. In addition, TCN1 and TCN2 overexpressions are associated with chemoresistance and a proliferative phenotype, respectively. Here we review the involvement of cobalamin and transcobalamins in cancer diagnosis and prognosis, and as potential therapeutic targets. We further detail the relationship between cobalamin-dependent metabolic pathways in cancer cells and the transcobalamins' abundancies in plasma and tumors, to ultimately hypothesize screening and therapeutic strategies linking these aspects.

Early changes in vitamin B12 uptake and biomarker status following Roux-en-Y gastric bypass and sleeve gastrectomy.

BACKGROUND & AIMS: Bariatric surgery increases the risk of micronutrient deficiencies, including vitamin B12 (B12) deficiency. We analysed early changes in biomarkers of B12 status following bariatric surgery. METHODS: We prospectively included adult patients (n = 27) referred for either Roux-en-Y Gastric Bypass (RYGB) (n = 19) or Sleeve Gastrectomy (SG) (n = 8). Blood samples were drawn before surgery and 2 and 6 months following surgery for measurement of B12, holotranscobalamin (holoTC), and methylmalonic acid (MMA). The B12 absorption capacity was estimated from the increase in plasma holoTC two days after a standardised oral B12 challenge. RESULTS: B12 status decreased following both RYBG and SG. While a decrease in plasma B12 was not evident until 6 months postoperatively, we observed a statistically significant decrease in plasma holoTC and increase in MMA already 2 months postoperatively. These changes were more pronounced at 6 months post surgery. Correspondingly, the B12 absorption capacity was decreased following surgery. CONCLUSIONS: HoloTC and MMA were superior to B12 to detect early changes in B12 status following bariatric surgery. Our data challenge the current concept that liver B12 stores secure long-term maintenance of B12 status. They indicate that B12 treatment in pharmacological doses may be warranted immediately after surgery.

A80G polymorphism of reduced folate carrier 1 (RFC1) and C776G polymorphism of transcobalamin 2 (TC2) genes in Down's syndrome etiology / Polimorfismos do gene carregador de folato reduzido (RFC1) A80G e transcobalamina 2 (TC2) C776G na etiologia da síndrome de Down

CONTEXT AND OBJECTIVE: There is evidence that polymorphisms of genes involved in folate metabolism may be associated with higher risk that mothers may bear a Down's syndrome (DS) child. This study therefore had the objective of investigating the A80G polymorphism of the reduced folate carrier 1 (RFC1) gene and the C776G polymorphism of the transcobalamin 2 (TC2) gene as maternal risk factors for DS among Brazilian women. DESIGN AND SETTING: Analytical cross-sectional study with control group, at Faculdade de Medicina de São José do Rio Preto (Famerp). METHODS: Sixty-seven mothers of DS individuals with free trisomy 21, and 113 control mothers, were studied. Molecular analysis of the polymorphisms was performed by means of the polymerase chain reaction with restriction fragment length polymorphism (PCR-RFLP), followed by electrophoresis on 2 percent agarose gel. RESULTS: The frequencies of the polymorphic alleles were 0.51 and 0.52 for RFC1 80G, and 0.34 and 0.34 for TC2 776G, in the case and control groups, respectively. Thus, there were no differences between the groups in relation to either the allele or the genotype frequency, for both polymorphisms (P = 0.696 for RFC1 A80G; P = 0.166 for TC2 C776G; P = 0.268 for combined genotypes). CONCLUSION: There was no evidence of any association between the RFC1 A80G and TC2 C776G polymorphisms and the maternal risk of DS in the sample evaluated.

CONTEXTO E OBJETIVO: Considerando as evidências de que polimorfismos em genes envolvidos no metabolismo do folato podem estar associados ao risco materno elevado para a síndrome de Down (SD), o objetivo deste estudo foi investigar os polimorfismos A80G do gene carregador de folato reduzido 1 (RFC1) e C776G do gene transcobalamina 2 (TC2) como fatores de risco maternos para a SD em mulheres brasileiras. TIPO E ESTUDO LOCAL: Estudo transversal analítico com grupo controle, realizado na Faculdade de Medicina de São José do Rio Preto (Famerp). MÉTODOS: Foram avaliadas 67 mães de indivíduos com trissomia livre do 21 e 113 mães de indivíduos sem a síndrome. A análise molecular dos polimorfismos foi realizada pela técnica de reação em cadeia da polimerase/polimorfismo de comprimento fragmentos de restrição (PCR-RFLP), seguida por eletroforese em gel de agarose 2 por cento. RESULTADOS: As freqüências dos alelos polimórficos foram de 0,51 e 0,52 para RFC1 80G e 0,34 e 0,34 para TC2 776G nos grupos caso e controle, respectivamente. Assim, não houve diferença nas freqüências alélicas e genotípicas para ambos os polimorfismos entre os grupos (P = 0,696 para RFC1 A80G; P = 0,166 para TC2 C776G; p = 0,268 para genótipos combinados). CONCLUSÃO: Não há evidência de associação entre os polimorfismos RFC1 A80G e TC2 C776G e o risco materno para a SD na casuística avaliada.