Development of a monomeric recombinant Butea monosperma agglutinin as a diagnostic and prognostic biomarker for cholangiocarcinoma

Native Butea monosperma agglutinin (nBMA), is a lectin isolated from the seeds of the Butea monosperma plant, which binds specifically to galactose, N-acetylgalactosamine, and lactose. This study developed a recombinant β-chain of BMA (rBMA) expressed in Escherichia coli. The rBMA exists in a monomeric form, retains native structure and sugar-binding capacity without exhibiting hemagglutination activity. The binding activity of rBMA was evaluated through lectin-cytofluorescent staining of CCA cell lines. Similar to nBMA, rBMA exhibited a positive signal to CCA cell lines but displayed a strong signal in different cell lines. Sodium periodate treatment abolished rBMA binding in CCA tissues and serum dot blots, confirming carbohydrate-dependent interactions. The neutralizing activity for sugar binding specificity indicated that rBMA binds to the complex glycosylated glycans rather than mono- and di-saccharides. Elevated levels of rBMA binding glycans in serum dot blots were found to differentiate CCA patients from healthy individuals, achieving a diagnostic sensitivity of 92.9%, specificity of 36%, and overall accuracy of 74%. High levels of serum rBMA-binding glycans were associated with poorer survival in CCA patients, and directly correlated with serum alkaline phosphatase levels. No correlation was found with carcinoembryonic antigen and CA19–9 levels. These findings position serum rBMA-binding glycans as potential biomarkers reflecting CCA progression. The monomeric nature and retained glycan specificity of rBMA, coupled with its absence of hemagglutination activity, make it a superior candidate to nBMA for diagnostic applications and a promising platform for targeted therapeutic development for CCA.