and signifies a poor clinical prognosis. Thus, down-regulation of ErbB2 signaling has
emerged as a new anti-cancer strategy. Ubiquitinylation, mediated by the Cbl family of
ubiquitin ligases, has emerged as a physiological mechanism of ErbB receptor down-
regulation, and this mechanism appears to contribute to ErbB2 down-regulation induced by
therapeutic anti-ErbB2 antibodies. Hsp90 inhibitory ansamycin antibiotics such as …