Proteomic Analysis of Serum Biomarkers in Early-Stage Breast Cancer Among Women in Ibadan, Oyo State

Early detection of breast cancer in Nigerian women through biochemical biomarker identification remains a critical research priority, as the majority of Nigerian breast cancer diagnoses occur at late stages when treatment options are limited. This study applies proteomic methods to identify and characterise serum protein biomarker panels for early-stage breast cancer detection in women attending the University College Hospital Ibadan, Oyo State. Serum samples from sixty women with histologically confirmed stage I and II breast cancer, sixty women with benign breast conditions, and sixty healthy age-matched controls were collected before any surgical or chemotherapy intervention. Label-free quantitative proteomics was performed using nano-liquid chromatography-tandem mass spectrometry after depletion of the twelve most abundant serum proteins. Differentially expressed proteins were identified by statistical analysis with false discovery rate correction. Candidate biomarkers were validated by enzyme-linked immunosorbent assay in the full cohort. Proteomic analysis identified forty-three significantly upregulated and twenty-nine significantly downregulated proteins in early breast cancer versus healthy controls. The most diagnostically promising proteins, lipocalin-2, clusterin, apolipoprotein C-III, and complement factor D, were validated by ELISA. A three-protein panel of lipocalin-2, clusterin, and apolipoprotein C-III achieved an area under the receiver operating characteristic curve of 0.89 for early-stage breast cancer discrimination from healthy controls and 0.81 for discrimination from benign conditions. The study identifies a candidate serum protein panel for early breast cancer detection in Nigerian women pending larger multi-centre validation. Keywords: proteomics, breast cancer biomarkers, serum proteins, early detection, Ibadan.