STUB1 and breast cancer: CHIP has also been found to mediate ERBB2 degradation induced by the flavonoid Quercetin (3, 5, 7, 30, 40-pentahydroxyflavone) in a study of BC cell lines.[19] Quercetin appears to enhance the binding activity of CHIP, encouraging ERBB2 ubiquitination and proteasomal degradation.