C3 and neoplasm: Immunohistochemical staining of the xenograft tumor sections showed that FOXO3a had repressed the expression of the ER target genes pS2, complement C3, cathepsin-D, and PgR (Figure 7a), and upregulated the expression of p21Cip1, p27Kip1, and p57Kip2 in tumors derived from MCF7-FO cells relative to tumors derived from control MCF7-C cells (Figure 7b).