Analysis of differentially expressed novel post-translational modifications of plasma apolipoprotein E in Taiwanese females with breast cancer

Yih Huei Uen, Chen Chung Liao, Jung Chun Lin, Yi Hsuan Pan, Yi Chung Liu, You Chia Chen, Wei Jung Chen, Chih Chun Tai, Kuan Wei Lee, Yun Ru Liu, Hung Tse Lin, Ching Yu Lin

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Abstract

APOE ε2 or ε4 alleles being used as indicators of breast cancer risk are controversial in Taiwanese females. We provide a concept for relative comparisons of post-translational modifications (PTMs) of plasma apolipoprotein E (ApoE) between normal controls and breast cancer patients to investigate the association of ApoE with breast cancer risk. APOE polymorphisms (ApoE isoforms) were not assessed in this study. The relative modification ratio (%) of 15 targeted and 21 modified peptides were evaluated by 1D SDS-PAGE, in-gel digestion, and label-free nano-LC/MS to compare normal controls with breast cancer patients. Plasma levels of the ApoE protein did not significantly differ between normal controls and breast cancer patients. Eleven sites with novel PTMs were identified from 7 pairs of differentially expressed targeted and modified peptides according to the relative modification ratio including methylation at the E3 (↑1.45-fold), E7 (↑1.45-fold), E11 (↑1.19-fold), E77 (↑2.02-fold), E87 (↑2.02-fold), and Q98 (↑1.62-fold) residues; dimethylation at the Q187 (↑1.44-fold) residue; dihydroxylation at the R92 (↑1.25-fold), K95 (↑1.25-fold), and R103 (↑1.25-fold) residues; and glycosylation at the S129 (↑1.14-fold) residue. The clustered methylation and dihydroxylation of plasma ApoE proteins may play a role in breast cancer.

Original languageEnglish
Pages (from-to)252-262
Number of pages11
JournalJournal of Proteomics
Volume126
DOIs
Publication statusPublished - Aug 3 2015

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Keywords

  • Apolipoprotein E
  • Breast cancer
  • Extracted ion chromatogram
  • Label-free relative quantification
  • Plasma
  • Post-translational modification

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics

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