Quantification by affinity perfusion chromatography of phosphorylated BRCAl and BRCA2 proteins from tumor cells after lycopene treatment

Abstract

A new procedure for the quantification of phosphorylated BRCA1 (P-BRCA1) and BRCA2 (P-BRCA2) proteins in breast cell lines after different treatments was carried out. Cells were cultivated with [ 35S]-methionine and extracts subjected to three perfusion chromatographies. First heparin affinity chromatography purified cellular DNA-binding proteins. Subsequent specific immunoprecipitation of BRCA1 and BRCA2 proteins was performed with antibodies raised against BRCA1 or BRCA2. The immune complexes were isolated by protein A affinity chromatography. Phosphorylated BRCA1 or BRCA2 proteins were then purified with a Poros 20 AL column where anti-phosphothreonine and anti-phosphoserine antibodies were previously bound. The percentage of phosphorylated BRCA1 or BRCA2 proteins was calculated as follows: 100 × dpm of P-BRCA1 or P-BRCA2 eluted from the POROS ® 20AL column/total dpm eluted from POROS ® 20AL column. Treatment with 10 μM lycopene increased P-BRCA1 and P-BRCA2 in the breast tumor cell line MCF7 but not in MDA-MB-231 or MCF-10a, breast tumor or fibrocystic cell lines, respectively.