Immunogen sequence: PYPGMSNHEA FLRVDAGYRM PCPLECPPSV HKLMLTCWCR DPEQRPCFKA LRERLSSFTS YENPT. Breast tumor kinase (Brk) is a non-receptor protein tyrosine kinase expressed in over 60% of breast carcinoma tissue samples and breast tumor cell lines. Brk is