Prediagnostic circulating metabolites in female breast cancer cases with low and high mammographic breast density

Abstract

Mammographic breast density (MBD) is a strong independent risk factor for breast cancer (BC). We designed a matched case-case study in the EPIC Florence cohort, to evaluate possible associations between the pre-diagnostic metabolomic profile and the risk of BC in high- versus low-MBD women who developed BC during the follow-up. A case-case design with 100 low-MBD (MBD ≤ 25%) and 100 high-MDB BC cases (MBD > 50%) was performed. Matching variables included age, year and type of mammographic examination. ¹H NMR metabolomic spectra were available for 87 complete case-case sets. The conditional logistic analyses showed an inverse association between serum levels of alanine, leucine, tyrosine, valine, lactic acid, pyruvic acid, triglycerides lipid main fraction and 11 VLDL lipid subfractions and high-MBD cases. Acetic acid was directly associated with high-MBD cases. In models adjusted for confounding variables, tyrosine remained inversely associated with high-MBD cases while 3 VLDL subfractions of free cholesterol emerged as directly associated with high-MBD cases. A pathway analysis showed that the "phenylalanine, tyrosine and tryptophan pathway" emerged and persisted after applying the FDR procedure. The supervised OPLS-DA analysis revealed a slight but significant separation between high- and low-MBD cases. This case-case study suggested a possible role for pre-diagnostic levels of tyrosine in modulating the risk of BC in high- versus low-MBD women. Moreover, some differences emerged in the pre-diagnostic concentration of other metabolites as well in the metabolomic fingerprints among the two groups of patients.

Figure 1

(A) Summary of pathways analysis using MetaboAnalyst (https://www.metaboanalyst.ca): (1) phenylalanine, tyrosine and tryptophan biosynthesis; (2) pyruvate metabolism. (B) Detailed results of pathway analysis. Total Cmpd is the total number of compounds in the pathway; Hits is the actually matched number of compounds from the user uploaded data; Raw p is the original p value calculated from the enrichment analysis; Holm is the p value adjusted by Holm-Bonferroni method; FDR is the p value adjusted using False Discovery Rate; Impact is the pathway impact value calculated from pathway topology analysis (EPIC Florence, low- vs high-MBD BC case–case study).

Figure 2

OPLS-DA score plot and confusion matrix for the comparison of low (red spheres) and high (cyan spheres) mammographic density breast cancer patients. The results are reported for the three kind of NMR spectra acquired: (A) NOESY, for low and high molecular mass molecules; (B) CPMG, for low molecular mass molecules; (C) Diffusion, for high molecular mass molecules. (EPIC Florence, low- vs high-MBD BC case–case study).