The Role of Adhesion Molecules and Chemokine Receptor CXCR4 (CD184) in Small Cell Lung Cancer

Small-cell lung cancer (SCLC) is a particularly aggressive form of lung cancer. Responsible for this highly malignant phenotype is an early and widespread metastasis with a high propensity of SCLC cells for bone marrow involvement and the ability to develop resistance against chemotherapeutic agents. Tumor cell migration and metastasis share many similarities with leukocyte trafficking, which is critically regulated by chemokines and adhesion molecules. There is growing evidence that the chemokine stromal derived factor-1 (SDF-1/CXCL12) and its receptor CXCR4 (CD184) regulate migration and metastasis of a variety of cancers including SCLC. SCLC cells express high levels of functional CXCR4 receptors. Engagement of CXCR4 by CXCL12 leads to an upregulation of integrin-mediated adhesion in SCLC and other tumor cells. Activation of CXCR4 chemokine receptors and integrins on SCLC cells promotes adhesion to accessory cells (such as stromal cells) and extracellular matrix molecules within the tumor microenvironment. These adhesive interactions result in an increased resistance of SCLC cells to chemotherapy. As such, inhibitors of the CXCR4/CXCL12 axis and/or integrin activation may increase the chemosensitivity of SCLC cells and lead to new therapeutic avenues for patients with SCLC.