CD49d, the α-chain of the integrin heterodimer α4β1 (CD49d/CD29) is expressed on cell surface of ~40% of chronic lymphocytic leukemia (CLL) cases. It mediates both cell–cell and cell–matrix adhesion through binding to the vascular cell adhesion molecule-1 (VCAM-1) and fibronectin (FN), respectively. These interactions regulate CLL cell recirculation from the blood stream to tissue sites, as well as the transmission to CLL cells of signals of pro-survival and resistance to drug-induced apoptosis.1 Consistent with this functional role in CLL, a recent worldwide meta-analysis carried out on a large patient cohort, definitely demonstrated the independent prognostic relevance of CD49d in this disease
