Binding of lactoferrin to IGBP1 triggers apoptosis in a lung adenocarcinoma cell line.

Lactoferrin (Lf), an iron-binding protein present in mammalian secretions, plays important roles in cancer prevention by inducing apoptosis. PC-14 lung adenocarcinoma cells were exposed to bovine Lf (bLf) protein and the expression of caspase-3 and apoptosis protease-activating factor-1 (APAF-1) was assessed. To investigate the molecular mechanism of apoptosis induced by bLf, a major Lf-binding protein was screened using a protein microarray with bLf protein as the probe. Protein interaction was demonstrated by co-immunoprecipitation, immunofluorescence and phosphatase activity assay. Lf directly suppressed the proliferation of the PC-14 cells by triggering their apoptosis. Lf was shown to bind specifically with a 36-kDa protein, immunoglobulin (CD79A)-binding protein 1 (IGBP1). The binding complex interacted with the catalytic subunit of protein phosphatase 2A (PP2A), thus reducing the phosphatase activity of PP2A and triggering apoptosis. Lf binds IGBP1 and promotes the acceleration of cellular apoptosis.