We detected about 10.9 (shRb-1) or 14.1 (shRb-2) CD44-positive circulating cancer cells/clusters per ml of blood, suggesting that the majority of CCC released from Rb knockdown tumors express CD44 while the control released only 2.5 CD44-positive CCC per ml of blood (Figure 6D). This evidence concerns the gene CD44 and cancer.