The causal roles of vitamin B 12 and transcobalamin in prostate cancer: Can Mendelian randomization analysis provide definitive answers?

Simon M. Collin, Chris Metcalfe, Tom M. Palmer, Helga Refsum, Sarah J. Lewis, George Davey Smith, Angela Cox, Michael Davis, Gemma Marsden, Carole Johnston, J. Athene Lane, Jenny L. Donovan, David E. Neal, Freddie C. Hamdy, A. David Smith, Richard M. Martin

Research output: Contribution to journalArticle (Academic Journal)peer-review

10 Citations (Scopus)

Abstract

Circulating vitamin B 12 (cobalamin/B 12) and total transcobalamin (tTC) have been associated with increased and reduced risk, respectively, of prostate cancer. Mendelian randomization has the potential to determine whether these are causal associations. We estimated associations of single nucleotide polymorphisms in B 12-related genes (MTR, MTRR, FUT2, TCN2, TCN1, CUBN, and MUT) with plasma concentrations of B 12, tTC, holo-transcobalamin, holohaptocorrin, folate, and homocysteine and with prostate cancer risk in a case-control study (913 cases, 895 controls) nested within the UK-wide population-based ProtecT study of prostate cancer in men age 45-69 years. Instrumental variable (IV) analysis was used to estimate odds ratios for effects of B 12 and tTC on prostate cancer. We observed that B 12 was lower in men with FUT2 204G>A (rs492602), CUBN 758C>T (rs1801222) and MUT 1595G>A (rs1141321) alleles (P trend<0.001); tTC was lower in men with the TCN2 776C>G (rs1801198) allele (P trend<0.001). FUT2 204G>A and CUBN 758C>T were selected as instruments for B 12; TCN2 776C>G for tTC. Conventional and IV estimates for the association of log e (B 12) with prostate cancer were: OR=1.17 (95% CI 0.90-1.51), P=0.2 and OR=0.60 (0.16-2.15), P=0.4, respectively. Conventional and IV estimates for the association of log e (tTC) with prostate cancer were: OR=0.81 (0.54-1.20), P=0.3 and OR=0.41 (0.13-1.32), P=0.1, respectively. Confidence intervals around the IV estimates in our study were too wide to allow robust inference. Sample size estimates based on our data indicated that Mendelian randomization in this context requires much larger studies or multiple genetic variants that explain all of the variance in the intermediate phenotype.

Original languageEnglish
Pages (from-to)316-327
Number of pages12
JournalInternational journal of molecular epidemiology and genetics
Volume2
Issue number4
Publication statusPublished - 21 Dec 2011

Structured keywords

  • BTC (Bristol Trials Centre)

Keywords

  • Mendelian randomization
  • Prostate cancer
  • Transcobalamin
  • Vitamin B /cobalamin

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