Comparison of bivalent chemical Herceptin/rGel conjugate and monovalent rITs in two directions including 4D5/rGel (rGel is fused to 4D5 by VH) and rGel/4D5 (rGel is fused to 4D5 by VL) showed that they all have the same affinity for Her2-expressing cancer cells, although their antitumor activity is different [79]. This evidence concerns the gene ERBB2 and cancer.