Interestingly, in the HER2+ SK-BR-3 tumor line, neither SN-38 nor IMMU-132 mediated the up-regulation of p21WAF1/Cip1 above constitutive levels in the first 24 h, but as seen in MDA-MB-468 cells after 48-h exposure to SN-38 or IMMU-132, the amount of p21WAF1/Cip1 decreased > 57%. Here, ERBB2 is linked to neoplasm.