NBR1(named as next toBRCA1) was originally cloned as a candidate gene for the ovarian cancer antigen CA125, using expression cloning with the anti-CA125 Ig, has been of interest due to its position close toBRCA1, although no involvement in breast or ovarian cancer has been demonstrated. Recently, the antigen CA125 has been cloned, and identi®ed as a new mucin, MUC16, entirely di erent from NBR1.