ERBB4 and breast cancer: T-47D human breast cancer cells that naturally express the cleavable JM-a isoforms of ErbB4 (data not shown) were injected into the mammary fat pads of SCID mice and the mice were treated for three weeks with the JM-a isoform-specific anti-ErbB4 mAb 1479 or with a control IgG AK990/02 that does not recognize antigens in T-47D cells (data not shown).